The Power Within - Morehead Planetarium and Science Center

Transcription

Developers of The Power Within
Sherri Andrews, PhD
Betty Brown, MS
Lenis Chen, MEd
Stefanie Hartmann, PhD
Crystal McDowell, BS
Nathan Nicely, PhD
Lisa Pierce, MEd
Cathy Pike, MEd
Todd Vision, PhD
Amber Vogel, PhD
Jane Wright, MEd
John Zhu, BA
Additional Contributors to The Power Within
Jon Herron, PhD
Stephenie McLean, MS
Jennifer Murphy, MA
The DESTINY Traveling Science Learning Program developed The Power Within: Endosymbiosis and the Origin of
Eukaryotes with support from the National Science Foundation (Fed. Grant # 0227314) to Dr. Todd Vision, Associate
Professor of Biology at the University of North Carolina at Chapel Hill, and from the National Center for Research
Resources of the National Institutes of Health through a Science Education Partnership Award (Fed. Grant #1 R25
RR016306) to Dr. Amber Vogel, Director of Widening Horizons in Science Education (WHISE) at the University of
North Carolina at Chapel Hill. The contents of this module are the responsibility of the authors, and do not necessarily
represent the official views of NCRR or NIH. The DESTINY Traveling Science Learning Program (moreheadplanetarium.org/go/destiny) is a science education outreach initiative of Morehead Planetarium and Science Center at
UNC-Chapel Hill that serves pre-college teachers and schools
across North Carolina. DESTINY develops and delivers a standards-based, hands-on curriculum and teacher professional development with a team of educators and a fleet of vehicles that travel throughout the state.
DESTINY has been supported in part by the State of North
Carolina; grants from GlaxoSmithKline, the Howard Hughes
Medical Institute, and the National Aeronautics and Space Administration; and a Science Education Partnership Award from
the National Center of Research Resources, part of the National Institutes of Health. Additional support has come from
Bio-Rad, IBM, Medtronic, and New England BioLabs. In particular, development and dissemination of The Power Within
have benefitted from the participation of the Renaissance Computing Institute.
© 2007, 2008 The University of North Carolina at Chapel Hill,
through its Morehead Planetarium and Science Center. The
University of North Carolina at Chapel Hill grants teachers
permission to reproduce materials from this curriculum guide
for classroom use only, without alteration, provided all copies
contain the following statement: “© The University of North
Carolina at Chapel Hill, through its Morehead Planetarium and
Science Center. This work is reproduced solely for classroom
use with the permission of The University of North Carolina
at Chapel Hill, through its Morehead Planetarium and Science
Center. No other use is permitted without the express prior written permission of Morehead Planetarium and Science Center of
The University of North Carolina at Chapel Hill. To request
permission, contact The DESTINY Program (Morehead Planetarium and Science Center’s outreach initiative at UNC-Chapel
Hill), CB# 7448, Morehead Planetarium and Science Center
Annex, UNC-Chapel Hill, Chapel Hill, NC 27599-7448.”
© DESTINY • UNC-Chapel Hill • CB #7448, MPSC Annex • Chapel Hill, NC 27599 • moreheadplanetarium.org/go/destiny
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TABLE OF CONTENTS
KEY TERMS ..........................................................5
ALIGNMENTS .................................................... 11
The Key Components of the 5E Model ................. 11
North Carolina Standard Course of Study
for Biology — Grades 9-12 ...................................12
Correlation to the National Science Education
Standards: The Teaching Standards .......................16
Correlation to the National Science Education
Standards: The Content Standards ......................... 17
INTRODUCTION................................................19
The Cell: An Overview ..........................................19
Prokaryotes vs. Eukaryotes ....................................19
Organelles ..............................................................19
Figure 1: Mitochondrion ........................................20
Figure 2: Chloroplast .............................................21
Figure 3: Comparing Eukaryotes and Prokaryotes ....22
Figure 4: Different Ribosomes in Eukaryotic Cells...23
Symbiosis ...............................................................24
Endosymbiosis vs. Ectosymbiosis .........................25
Lynn Margulis and the Endosymbiotic Theory......25
Cooperation, Not Competition ...............................27
Pre-lab Activities....................................................28
Wet-Lab Activities .................................................28
Post-Lab Activities .................................................28
Additional Activities ..............................................28
Connection to Other DESTINY Modules ..............31
PRE-LAB ..............................................................33
Utilizing The 5E Model .........................................34
Engagement Activity..............................................36
Power Trip: Engage Students in the Concept
of Biological Relationships ................................36
Power Trip: Teacher’s Script ..............................37
Power Trip: Work Sheet .....................................40
KEY Power Trip: Work Sheet ............................. 42
Power Trip: Students’ Scripts ............................. 44
The Power Within Data Observation Sheet........49
Station P: Parts of the Cell .....................................51
Exploration Activity ...........................................53
Parts of the Cell Crossword ............................55
KEY Parts of the Cell Crossword .................... 56
Construct a Plant Cell Model ..........................57
Construct an Animal Cell Model ....................59
Explanation/Elaboration Activity .......................63
Figure 5: How a Bacterium Might
Become a Mitochondrion ...............................63
Figure 6: Different Ribosomes in
Eukaryotic Cells..............................................64
Station O: Organism Classification ........................65
Organism Classification ..................................68
KEY Organism Classification..........................69
Organism Classification Chart ........................70
KEY Organism Classification Chart................ 71
Discussion of the Three Domains ...................72
Figure 7: Timeline of Life on Earth ................73
Figure 8: The Three Domains .........................74
Station W: Who Am I? ...........................................75
Station W: Who Am I? Worksheet ..................78
Student Instructions ........................................78
Who Am I? Charles Darwin ...........................79
Who Am I? Carl Linnaeus .............................. 80
Who Am I? Lynn Margulis ............................81
Who Am I? Constantin Mereschkowsky ........ 82
Who Am I? Carl Woese ................................. 83
Station E: Evolutionary Relationships ...................85
Create Your Own Cladogram ..........................89
KEY Create Your Own Cladogram ................. 90
KEY Explanation/Elaboration Activity............... 92
Station R: Biological Relationships .......................97
KEY Exploration Activity ................................. 101
Explanation/Elaboration Activities...................103
Biology Vocabulary Hand-out ..........................105
Evaluation Activity ..............................................106
WET-LAB ...........................................................107
POST-LAB ..........................................................109
Review Questions ................................................ 110
KEY Review Questions ........................................ 111
Using Databases to Obtain Real Amino Acid
Sequence Data to Create Cladograms .................. 113
KEY Using Databases to Obtain Real Amino Acid
Sequence Data to Create Cladograms .................. 117
Quick Guide to Blast Searching........................... 118
Blast-Searching Questions ................................... 119
KEY Blast-Searching Questions........................... 120
Tree Analysis........................................................121
KEY Tree Analysis ............................................... 123
The Power Within Quiz Game Questions ............124
KEY The Power Within Quiz Game Answers ...... 125
ADDITIONAL ACTIVITIES ...........................127
A Fishy Family Tree.............................................128
KEY A Fishy Family Tree .................................... 130
Symbiotic Concentration .....................................131
KEY Symbiotic Concentration: Additional
Information for the Teacher .................................137
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Reading Guide: “SAR11 clade dominates ocean
surface bacterioplankton communities” ...............140
KEY Reading Guide: “SAR11 clade dominates
ocean surface bacterioplankton communities” ....141
INTERDISCIPLINARY BRIDGES .................143
Picture This ..........................................................144
Picture This Worksheet ........................................146
Darwin, the Writer ...............................................147
Discussion Questions, Guided Reading,
and Activities for Charles Darwin’s
On the Origin of Species ..................................149
Handout: The last paragraph of Charles Darwin’s
On the Origin of Species ..................................152
Additional Activities
for English Classrooms ....................................153
A Discovery-Based Approach to Understanding
Clinical Trials: With a Focus on Symbiosis and Bacteria ......................................................................155
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KEY TERMS
amino acid: any of 20 basic building blocks of proteins, composed of a free amino (NH2) end, a free
carboxyl (COOH) end, and a side group (R).
initiation and elongation factors, and their transcription involves TATA-binding proteins and TFIIB as in
eukaryotes.
aerobic: living or occurring in the presence of oxygen.
bacteria: one of the three domains of life. Bacteria
(singular – bacterium) are a major group of living
organisms. They are microscopic and mostly unicellular
and lack a cell nucleus, cytoskeleton, and organelles
such as mitochondria and chloroplasts. Bacteria are
the most abundant of all organisms, and many of them
are pathogens. Bacteria reproduce only asexually, not
sexually. Specifically, they reproduce by binary fission, or simple cell division. During this process, one cell
divides into two daughter cells with the development of
a transverse cell wall.
alga: usually single-celled, predominantly aquatic
organisms that contain chlorophyll and can therefore
carry out photosynthesis. They lack true roots, stems,
and leaves. Plural is algae.
alignment: the comparison of related DNA or protein sequences that reveals the location of accumulated changes
since their divergence from a common ancestor.
algorithm: a procedure consisting of a sequence of
algebraic formulas and/or logical steps to calculate or
determine a given task.
amoeba: or ameba (plural – amoebae) is a genus of
protozoa that moves by means of temporary projections
called pseudopods, and is considered to be a unicellular
organism. The word amoeba or ameba is variously used
to refer to it and its close relatives, now grouped as the
Amoebozoa, or to all protozoa that move using pseudopods, otherwise termed amoeboids.
ancestor: a person, organism, or sequence from whom
another person, organism, or sequence is descended (e.g., a
parent, grandparent, or great-grandparent).
antibiotic: any of various substances (e.g., penicillin)
that can destroy or inhibit the growth of microorganisms.
alpha-proteobacteria: a major group of bacteria, many
of which are pathogens. The precursors of the eukaryotic mitochondria have originated from this bacterial
group.
archaea: one of the three domains of life (the others
are bacteria and eukarya). Archaea are single-celled
organisms that live under extreme environmental conditions. Like bacteria, they are all prokaryotes and lack a
nucleus. Archaea are similar to other bacteria in most
aspects of cell structure and metabolism. However, their
transcription and translation – the two central processes
in molecular biology – do not show typical bacterial
features, but are extremely similar to those of eukaryotes. For instance, archaean translation uses eukaryotic
bioinformatics: the development and application of
computer and statistical methods to analyze biological
data, and the development of databases for storage and
management of biological data.
chloroplast: any organelle found in plant cells and
eukaryotic algae in which photosynthesis is carried out.
Chloroplasts are surrounded by a double membrane
with an intermembrane space and have their own DNA.
Chloroplasts are one type of plastid. Plastids are derived
from endosymbiotic cyanobacteria. The plastid genome
is considerably reduced compared to that of free-living
cyanobacteria, but the regions that are still present show
clear similarities.
cladogram: a philosophy of classification that arranges organisms only by their order of branching in an evolutionary tree and not by their morphological similarity.
Modern systematic research is likely to be based on a
wide variety of information, including DNA-sequences
(so-called “molecular data”), biochemical data and morphological data. In a cladogram, all organisms lie at the
leaves, and each inner node is ideally binary (two-way).
The two taxa on either side of a split are called sister taxa
or sister groups. Each subtree, whether it contains one
item or a hundred thousand items, is called a clade.
chromosome: a continuous piece of DNA, which
contains many genes, regulatory elements and other
intervening nucleotide sequences. In eukaryotes, the
chromosome is the DNA-protein complex. eukaryotes
possess multiple linear chromosomes contained in the
cell’s nucleus. Bacterial chromosomes are not within
nuclei and are often circular but sometimes linear.
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compartmentalization, compartments: refers to the
fact that the cell contains different organelles, allowing
it to carry out different metabolic activities at the same
time.
are organelles of eukaryotic cells. According to this
theory, these organelles originated as separate prokaryotic organisms that were taken inside the cell as
endosymbionts.
Cyanobacteria: a group of bacteria that obtain their energy through photosynthesis. Fossil traces of cyanobacteria from around 3.8 billion years ago are the oldest known
organisms. They were previously called blue-green algae,
even though they are not related to any of the other algal
groups, which are all eukaryotes.
Eubacteria: see bacteria, one of the domains of life.
cycloheximide: an antibacterial and antifungal antibiotic.
cytoplasm: semi-fluid matter within the cell and surrounding the nucleus, in which organelles are suspended.
dichotomy: a division or split into two entities.
DNA: deoxyribonucleic acid – the molecule that stores
genetic information, codes for RNA and proteins, and
is stably transmitted from generation to generation.
domains of life: the highest category in the taxonomy
of organisms. There are three such domains: Archaea,
Bacteria, and Eukarya.
endoplasmic reticulum (or ER): is an organelle found
in all eukaryotic cells that is an interconnected network
of tubules, vesicles and cisternae that is responsible
for several specialized functions: Protein translation,
folding, and transport of proteins to be used in the
cell membrane (e.g., transmembrane receptors and
other integral membrane proteins), or to be secreted
(exocytosed) from the cell (e.g., digestive enzymes);
sequestration of calcium; and production and storage
of glycogen, steroids, and other macromolecules. The
endoplasmic reticulum is part of the endomembrane
system.
endosymbiosis: an endosymbiont is an organism that
lives within another organism, i.e., forming an endosymbiosis (Greek: endo = inner and biosis = living).
Many examples of endosymbiosis are obligate, where
neither the endosymbiont nor the host can survive
without the other. The theory that eukaryotic chloroplasts and mitochondria originated as bacterial endosymbionts is known as the endosymbiotic theory.
endosymbiotic theory: developed and popularized
by Lynn Margulis, this theory concerns the origins of
mitochondria and plastids (e.g., chloroplasts), which
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Eukarya: one of the three domains of life. Eukaryotes
are organisms whose cells are organized into complex
structures by internal membranes and a cytoskeleton.
The most characteristic membrane bound structure is
the nucleus. This feature gives them their name, also
spelled “eucaryote,” which comes from the Greek ευ, meaning good/true, and κάρυον, meaning nut, referring to the nucleus. Many eukaryotic cells also contain
membrane-bound organelles such as mitochondria,
chloroplasts and Golgi bodies.
evolution: is any process of change over time. In biology, it refers to the change in the genetic, developmental, morphological, physiological, or behavioral traits
over the course of multiple generations.
Fungi: a kingdom of eukaryotic organisms. The fungi
(singular – fungus) are heterotrophic organisms characterized by a chitinous cell wall, and in the majority
of species, filamentous growth as multicellular hyphae forming a mycelium; some fungal species also grow
as single cells. Sexual and asexual reproduction is via
spores, often produced on specialized structures or
in fruiting bodies. Yeasts, molds, and mushrooms are
examples of fungi. The discipline of biology devoted
to the study of fungi is known as mycology.
GenBank: an open access, annotated collection of
all publicly available nucleotide sequences and their
protein translations. This database is produced at National Center for Biotechnology Information (NCBI)
as part of the International Nucleotide Sequence
Database Collaboration, or INSDC. GenBank and its
collaborators receive sequences – produced in laboratories throughout the world – from more than 100,000
distinct organisms.
genes: units of inheritance; encode information essential for the construction and regulation of proteins that
determine the growth and functioning of the organism.
genome: the entire genetic complement of an organism, which includes both genes and non-coding
sequences.
histones: proteins that serve to package eukaryotic
nuclear DNA.
hyperthermophilic: referring to bacteria that live in
hot water environments, including hot springs and geysers in volcanically active regions.
hypothesis: a testable prediction or suggested explanation for a phenomenon, or a reasoned argument for a
possible correlation between multiple phenomena.
insertion/deletion (genetic): in a pairwise or multiple
sequence alignment, a segment that has been inserted in
one sequence or deleted in another. Genetic insertion is
the addition of one or more nucleotide base pair into a
genetic sequence. This can often happen in microsatellite regions due to the DNA polymerase slipping. On a
chromosome level, an insertion refers to the insertion of
a larger sequence into a chromosome. In genetics, a deletion (also called gene deletion, deficiency, or deletion mutation) is a mutation (genetic aberration) in which a
part of a chromosome or a sequence of DNA is missing. Any number of nucleotides can be deleted, from a
single base to an entire piece of chromosome. Deletions
can be caused by errors in chromosomal crossover during meiosis and can cause serious genetic diseases.
lineage: a group of organisms that trace their descent
from one common ancestor.
Margulis, Lynn (1938-): an American biologist
best known for her theory of the origin of eukaryotic
organelles, and her contributions to the endosymbiotic
theory—which is now generally accepted for how
certain organelles were formed. Margulis put forward
the hypothesis that mitochondria originated as separate
organisms that long ago entered a symbiotic relationship with eukaryotic cells through endosymbiosis.
According to this theory, organelles such as chloroplasts and mitochondria are the descendants of bacteria
that evolved into an intracellular symbiosis with early
eukaryotic cells.
Mereschkowsky, Constantin (1855-1921): a Russian
botanist who was the first to argue that the chloroplast and the nucleus originated through endosymbiosis. He
based his argument for the chloroplast on the observed
fact of symbiosis and on prior work that showed the
organelles reproduce themselves even when separated
from the nucleus. Mereschkowsky’s research on lichens
led him to propose that larger, more complex cells
evolved from the symbiotic relationship between less
complex ones. His ideas of symbiogenesis are reflected in the modern endosymbiotic theory developed and
popularized by Lynn Margulis.
mitochondria: the energy factory of cells. It is the
organelle in most eukaryotic cells, including those of
plants, animals, fungi, and protists, in which the Krebs
cycle and the electron transport chain occur to generate
ATP. Like chloroplasts, they are surrounded by a double
membrane with an intermembrane space and have their
own DNA. Mitochondria are derived from endosymbiotic alpha-proteobacteria. The mitochondrial genome
is considerably reduced compared to that of free-living
alpha-proteobacteria, but the regions that are still present show clear similarities; singular is “mitochondrion.”
molecular evolution: The study of evolutionary
changes to the structure and function of DNA, protein,
and other biological macromolecules.
Monera: an obsolete biological kingdom of the five-
kingdom system of biological classification. It comprised most organisms with a prokaryotic cell organization. For this reason, the kingdom was sometimes called
Prokaryota or Prokaryotae.
morphological: relates to physical properties (size,
shape, color, etc) of organisms. In this module, morphological is contrasted with characters or traits that are
molecular characters. (DNA or protein sequence)
multiple alignment: the comparison of three or more
related DNA or protein sequences that reveals the
location of accumulated changes since their divergence
from a common ancestor.
node: is used in this module in the context of a phylogenetic tree; a node in a phylogeny represents the
hypothetical ancestors that split into two (or more)
descendants.
nucleotides: the basic building blocks of DNA and
RNA molecules. They consist of a 5-carbon sugar
(DNA — deoxyribose; RNA – ribose), a phosphate
group, and a nitrogen-containing base (DNA – adenine,
thymine, cytosine, and guanine; RNA – adenine, uracil,
cytosine, guanine).
nucleus: a membrane-enclosed organelle (compartment) found in most eukaryotic cells. It contains most
of the cell’s genetic material, organized as multiple long
linear DNA molecules in connection with a large variety of proteins, such as histones, to form chromosomes.
The function of the nucleus is to maintain the integrity
of these genes and to control the activities of the cell by
regulating gene expression.
organelle: compartment within eukaryotic cell in which
specialized functions are carried out (e.g. mitochondria,
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nucleus, and chloroplasts). In cell biology, an organelle is a discrete structure of a cell having specialized
functions, and is separately enclosed in its own lipid
membrane.
organ: a group of tissues that constitute a morphologically
and functionally distinct part of an organism.
pairwise alignment: the comparison of two related
DNA or protein sequences that reveals the location of
accumulated changes since their divergence from a
common ancestor.
paulinella: rhizopod amoeba that contains cyanelles
most closely resembling free-living cyanobacteria.
photosynthesis: the biochemical process in which
plants, algae, and some bacteria convert light, water,
and carbon dioxide into food (complex carbohydrates)
and oxygen.
phylogeny: the patterns of ancestry among a group of
organisms, typically represented by a tree structure;
the evolutionary relationship of a group of species or
populations.
plastid: a membrane-bound organelle found in plant
and algal cells. In plants, plastids may differentiate
into several forms, depending upon which function
they need to play in the cell. Undifferentiated plastids
(proplastids) may develop into any of the following
plastids: amyloplasts – for starch storage; chloroplasts
– for photosynthesis; etioplasts – chloroplasts that have
not been exposed to light; elaioplasts – for storing fat;
chromoplasts – for pigment synthesis and storage; and
leucoplasts – for monoterpene synthesis. Plastids are
derived from endosymbiotic cyanobacteria. The plastid
genome is considerably reduced compared to that of
free-living cyanobacteria, but the regions that are still
present show clear similarities.
porphyra: a red alga that is a commonly eaten seaweed
(also called nori).
prokaryotes: are usually unicellular organisms that
lack a nucleus. They also lack cytoskeletons and
membrane-bound cell compartments such as vacuoles,
endoplasmic reticulum, mitochondria, and chloroplasts.
This is in contrast to eukaryotes, organisms that have
cell nuclei and may be variously unicellular or multicellular. Prokaryotes are divided into Bacteria and Archaea
(also Eubacteria and Archaebacteria). Also spelled
“procaryotes.”
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protein: a macromolecule that consists of amino acids
joined by covalent peptide bonds. Proteins are the
workhorses of the cell – they have enzymatic functions (e.g., they are enzymes or subunits of enzymes) or
structural functions (e.g., cytoskeletal protein).
Protista: a kingdom of diverse organisms, comprising
those eukaryotes that cannot be classified in any of the other kingdoms as fungi, animals, or plants. Protists
were traditionally subdivided into several groups based
on similarities to the higher kingdoms: the animal-like
protozoa, the plant-like algae, and the fungus-like slime
molds and water molds.
respiration (cellular): the process in which the chemical bonds of molecules such as glucose are converted
into energy usable for life processes. In cellular respiration, this process is broken down into two basic
metabolic pathways: glycolysis (anaerobic respiration)
or aerobic respiration.
ribosomes: complexes made up of proteins and ribosomal RNA; they are the site of protein synthesis and
can occur as free ribosomes in the cytoplasm or associated with the endoplasmatic reticulum. Each ribosome
consists of a large and a small subunit.
sequence database: a large collection of DNA, protein,
or other sequences stored on a computer. A database can
include sequences from only one organism, or it can
include sequences from all organisms whose DNA has
been sequenced.
small subunit RNA: a small molecule of RNA that is
found only in the nucleus of eukaryotes and responsible for splicing of mRNA. May also be called “small
nuclear RNA.”
streptomycin: an antibiotic that stops bacterial growth
by damaging cell membranes and inhibiting protein
synthesis. Specifically, it binds to the 16S rRNA of the bacterial ribosome, which prevents the release of the
growing protein (polypeptide chain).
symbiosis: a term used by scientists to describe a
relationship between organisms, very often of different species. A symbiotic relationship can either benefit, harm, or have no effect on one or both of the organisms
involved. It can be used to describe relationships where
one organism lives on or in another, or cases in which
two otherwise unrelated organisms are connected by
behaviors and environment.
topology: in this module, topology refers to the branching order of a polygenetic tree (e.g., as a tree’s branches
can be divided into additional branches, which may also
branch in turn).
transcription: the process by which RNA polymerase
synthesizes a single-stranded RNA molecule complementary to a single-stranded DNA sequence.
translation: the process by which RNA is used as a
template to synthesize a sequence of amino acids according to the rules specified by the genetic code.
Tree of Life: (also known as “evolutionary tree” and
“phylogenetic tree”) describes the relationships of all
life on Earth in an evolutionary context as in a branched
diagram that is very tree-like.
SOURCES
Brett, C.J. (1989). The dictionary of cell biology. Boston, MA: Harcourt Brace Jovanovich.
Clark, D.P. (2005). Molecular biology made simple and
fun. St. Louis, MO: Cache River Press.
Konstantin Mereschkowski. Retrieved November 12,
2007, from Wikipedia Web site: http://en.wikipedia.
org/wiki/Konstantin_Mereschkowsky
Lynn Margulis. In UXL Encyclopedia of World Biography [Web]. Retrieved November 12, 2007, from
FindArticles Web site from http://findarticles.com/p/articles/mi_gx5229/is_2003/ai_n19148497
Medical dictionary online. Retrieved November 12,
2007, from Medical Dictionary Online Web site: http://
www.online-medical-dictionary.org/
Properzio, J. di (2004, February 1). Lynn Margulis:
Full speed ahead. University of Chicago Magazine.
Retrieved November 12, 2007, from Mindfully.org Web
site: http://www.mindfully.org/Heritage/2004/LynnMargulis-Gaia1feb04.htm
Taber’s Cyclopedic Medical Dictionary. FA Davis Company: Philadelphia, PA.
Weisstein, E.W., et al. (2007). Wolfram mathworld: The
web’s most extensive mathematics resource. Retrieved
November 12, 2007, from Wolfram MathWorld Web
site: http://mathworld.wolfram.com/
Wikipedia: The free encyclopedia. Retrieved November
12, 2007, from Wikipedia Web site: http://en.wikipedia.
org
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The Key Components of the 5E Model
WHAT THE TEACHER DOES THAT IS
PHASE
ENGAGE
EXPLORE
EXPLAIN
ELABORATE
EVALUATE
Consistent with the 5E Model
•
•
•
•
Creates interest
Generates curiosity
Raises questions
Elicits responses that uncover what students know
or think about the concept/subject
Inconsistent with the 5E Model
•
•
•
•
•
Explains concepts
Provides definitions and answers
States conclusions
Provides premature answers to students’ questions
Lectures
• Encourages students to work together without direct
instruction from teacher
• Observes and listens to students as they interact
• Asks probing questions to redirect students’ investigations when necessary
• Provides time for students to puzzle through problems
• Acts as a consultant for students
• Provides answers
• Tells or explains how to work through the problem
• Tells students they are wrong
• Gives information or facts that solve the problem
• Leads students step-by-step to a solution
• Encourages students to explain concepts and definitions in their own words
• Asks for justification (evidence) and clarification
from students
• Formally provides definitions, explanations, and
new labels
• Uses students’ previous experiences as the basis for
explaining concepts
• Accepts explanations that have no justification
• Neglects to solicit students’ explanations
• Introduces unrelated concepts or skills
• Expects students to use formal labels, definitions
and explanations provided previously
• Encourages students to apply or extend concepts
and skills in new situations
• Reminds students of alternative explanations
• Refers students to existing data and evidence and asks
“What do you already know?”“Why do you think…?”
• Provides definitive answers
• Tells students they are wrong
• Lectures
• Leads students step-by-step to a solution
• Explains how to work through the problem
• Observes students as they apply new concepts and
skills
• Assesses students’ knowledge and/or skills
• Looks for evidence that students have changed their
thinking or behaviors
• Allows students to assess their own learning and
group process skills
• Asks open-ended questions, such as “Why do you
think . . . ?”“What evidence do you have?”“What do
you know about x?”“How would you explain x?”
• Tests vocabulary words, terms, and isolated facts
• Introduces new ideas or concepts
• Creates ambiguity
• Promotes open-ended discussion unrelated to
concept or skill
(Trowbridge & Bybee, 1990), adapted by Biological Sciences Curriculum Study
Available online at http://science.education.nih.gov/supplements/nih1/diseases/guide/module3.htm
11
North Carolina Standard Course of Study for Biology — Grades 9-12
Highlighted sections are objectives addressed in the The Power Within module
Strands: Nature of Science, Science as Inquiry, Science and Technology, Science in Personal and
Social Perspectives. The strands provide the context for teaching of the content Goals and Objectives.
Competency Goal 1:
The learner will develop abilities necessary to do and understand scientific inquiry.
Objectives
1.01 Identify biological questions and problems that can be answered through scientific investigations.
1.02 Design and conduct scientific investigations to answer biological questions.
• Create testable hypotheses
• Identify variables.
• Use a control or comparison group when appropriate.
• Select and use appropriate measurement tools.
• Collect and record data.
• Organize data into charts and graphs.
• Analyze and interpret data.
• Communicate findings.
• Students will compare different phylogenies that
represent different hypotheses regarding the evolution of eukaryotic organelles
• Students will learn that molecular data can be used
to generate multiple sequence alignments and to
reconstruct phylogenies, and why/how these tools
are appropriate for the question of organelle origin
• Students will “carry out” sequence alignments and
phylogeny reconstruction and will interpret the
resulting phylogeny
• Students will be asked to describe and discuss their
results
1.03 Formulate and revise scientific explanations and models of biological phenomena using logic and
evidence to:
• Explain observations
• Make inferences and predictions
• Explain the relationship between evidence and
explanation
• Students will use evidence (given to them) to confirm and correct hypotheses that were published in a 1905 study.
1.04 Apply safety procedures in the laboratory and in field studies: • Recognize and avoid potential hazards
•Safely manipulate materials and equipment needed for scientific investigations
1.05 Analyze reports of scientific investigations from an informed, scientifically literate viewpoint including considerations of:
• Appropriate sample
• Adequacy of experimental controls
• Replication of findings
•Alternative interpretations of the data
12
• Students will use evidence (given to them) to confirm and correct hypotheses that were published in a 1905 study.
Competency Goal 2:
The learner will develop an understanding of the physical, chemical and cellular basis of life.
Objectives
2.01 Compare and contrast the structure and functions of the following organic molecules:
• Carbohydrates
• Proteins
• Lipids
• Nucleic acids
2.02 Investigate and describe the structure and functions of cells including:
• Cell organelles
• Cell specialization
• Communication among cells within an organism.
• Students will use ribosomal DNA sequences for the
sequence alignment and phylogeny reconstruction
in the computer lab. DNA, ribosomes, translation
are topics that this is related to and that can be
reviewed in the pre-lab or post-lab.
• The focus of this module is the evolutionary origin
of chloroplasts and mitochondria. Properties of
the organelles are part of the computer lab. The
structure and function of these organelles can be
reviewed in the pre-lab or the post-lab.
2.03 Investigate and analyze the cell as a living system including:
• Maintenance of homeostasis
• Movement of materials into and out of cells
• Energy use and release in biochemical reactions
2.04 Investigate and describe the structure and function of enzymes and explain their importance in biological
systems.
2.05 Investigate and analyze the bioenergetic reactions:
• Aerobic respiration
• Anaerobic respiration
• Photosynthesis
• The focus of this module is the evolutionary origin
of chloroplasts and mitochondria. Aerobic respiration (partly carried out in the mitochondrion) and
photosynthesis (carried out in the chloroplast) can
be reviewed in the pre-lab or the post-lab.
Competency Goal 3:
The learner will develop an understanding of the continuity of life and the changes of organisms over time.
Objectives
3.01 Analyze the molecular basis of heredity including:
• DNA replication
• Protein synthesis (transcription, translation)
• Gene regulation
• Students will use small subunit ribosomal RNA sequences for the sequence alignment and phylogeny
reconstruction. The function of the ribosomes and
the process of translation can be reviewed in the
pre-lab or the post-lab.
3.02 Compare and contrast the characteristics of asexual and sexual reproduction.
3.03 Interpret and predict patterns of inheritance.
• Dominant, recessive and intermediate traits
• Multiple alleles
• Polygenic inheritance
• Sex-linked traits
• Independent assortment
• Test cross
• Pedigrees
• Punnett squares
13
3.04 Assess the impact of advances in genomics on
individuals and society.
• Human genome project
• Applications of biotechnology
3.05 Examine the development of the theory of evolution by natural selection, including:
• Development of the theory
• The origin and history of life
• Fossil and biochemical evidence
• Mechanisms of evolution
• Applications (pesticide and antibiotic resistance)
• Students are going to learn about the evolutionary
origin of chloroplasts and mitochondria, and how
these primary endosymbioses have shaped the history of all eukaryotic life throughout the module.
• Mechanisms of evolution can be covered in a postlab activity
• The origin of the eukaryotic nucleus can be covered
in a post-lab activity
Competency Goal 4:
The learner will develop an understanding of the unity and diversity of life.
Objectives
4.01 Analyze the classification of organisms according to their evolutionary relationships.
• The historical development and changing nature of classification systems
• Similarities and differences between eukaryotic
and prokaryotic organisms
• Similarities and differences among the eukaryotic kingdoms: protists, fungi, plants, animals
• Classify organisms using keys
• Eukaryotic and prokaryotic organisms are going to
be used in the computer-lab, and their evolutionary
relationships are of central importance in the prelab and the computer-lab.
• Similarities and differences among the eukaryotic
kingdoms are not the focus of any exercise but can
be covered in a post-lab activity.
4.02 Analyze the processes by which organisms representative of the following groups accomplish essential life
functions including:
• Unicellular protists, annelid worms, insects, amphibians, mammals, non vascular plants, gymnosperms
and angiosperms
• Transport, excretion, respiration, regulation, nutrition, synthesis, reproduction, and growth and development
4.03 Assess, describe and explain adaptations affecting survival and reproductive success.
• Structural adaptations in plants and animals (form to function)
• Disease-causing viruses and microorganisms
• Co-evolution
4.04 Analyze and explain the interactive role of internal and external factors in health and disease:
• Genetics
• Immune response
• Nutrition
• Parasites
• Toxins
4.05 Analyze the broad patterns of animal behavior as adaptations to the environment.
• Innate behavior
• Learned behavior
• Social behavior
14
Competency Goal 5:
The learner will develop an understanding of the ecological relationships among organisms.
Objectives
5.01 Investigate and analyze the interrelationships among organisms, populations, communities, and ecosystems.
• Techniques of field ecology
• Abiotic and biotic factors
• Carrying capacity
5.02 Analyze the flow of energy and the cycling of matter in the ecosystem.
• Relationship of the carbon cycle to photosynthesis and respiration
• Trophic levels — direction and efficiency of energy transfer
5.03 Assess human population and its impact on local ecosystems and global environments.
• Historic and potential changes in population
• Factors associated with those changes
• Climate change
• Resource use
• Sustainable practices/stewardship
15
The Power Within
Correlation to the National Science Education Standards
The Teaching Standards
The Power Within Correlation
Each activity in the module provides short-term objectives for students. There
is a conceptual flow of activities that help teachers plan a timeline for teaching
the module.
Use of this module helps teachers to update their curriculum in response to
student interest in the topic.
Standard A: Teachers of science plan an inquiry-based science program
for their students. In doing this, teachers
• develop a framework of yearlong and short-term goals for students.
• select science content and adapt and design curriculum to meet the interests, knowledge, understanding, abilities, and experiences of students.
• select teaching and assessment strategies that support the development of
student understanding and nurture a community of science learners.
The module’s focus is active, collaborative, and inquiry-based learning.
Student inquiry is encouraged by all activities in the module.
The module promotes discourse among students, and challenges students to
accept responsibility for their learning.
The use of the 5E instructional model with collaborative learning is an effective way of responding to diversity in student backgrounds and learning styles.
There are a variety of assessment components provided in module.
Answers are provided to help teachers analyze student feedback.
The answers provided for teachers model respect for the diverse ideas, skills,
and experiences of all students.
Students work collaboratively in teams to complete activities in the module.
Discussion activities in this module model the rules of scientific discourse.
16
Standard B: Teachers of science guide and facilitate learning. In doing
this, teachers
• focus and support inquiries while interacting with students.
• orchestrate discourse among students about scientific ideas.
• challenge students to accept and share responsibility for their own learning.
• recognize and respond to student diversity and encourage all students to
participate fully in science learning.
• encourage and model the skills of scientific inquiry, as well as the curiosity,
openness to new ideas and data, and skepticism that characterize science.
Standard C: Teachers of science engage in ongoing assessment of their
teaching and of student learning. In doing this, teachers
• use multiple methods and systematically gather data about student
understanding and ability.
• analyze assessment data to guide teaching.
Standard E: Teachers of science develop communities of science learners
that reflect the intellectual rigor of scientific inquiry and the attitudes
and social values conducive to science learning. In doing this, teachers
• display and demand respect for the diverse ideas, skills, and experiences of
all students.
• structure and facilitate ongoing formal and informal discussion based on a
shared understanding of rules of scientific discourse.
• model and emphasize the skills, attitudes, and values of scientific inquiry.
The Power Within
Correlation to the National Science Education Standards
The Content Standards
The Power Within
activity
Pre-lab Activities
Wet-lab Activities
Introduction
Pre-lab Activities
Explanation
Elaboration
Wet-lab Activities
Pre-lab Activities
Wet-lab Activities
Post-lab Activities
Post-lab Activities
Quiz Game
All
Standard A (Science as Inquiry) : As a result of activities in grades 9-12, all students should develop
1. abilities necessary to do scientific inquiry.
• Identify questions and concepts that guide scientific investigations
• Use technology and mathematics to improve investigations and communications
• Formulate and revise scientific explanations and models using logic and evidence
• Recognize and analyze alternative explanations and models
• Communicate and defend a scientific argument
2. understanding about scientific inquiry.
Standard C (Life Science): As a result of their activities in grades 9-12, all students should develop understanding of
1. the cell.
• Cells store and use information to guide their functions.
• Cells can differentiate, and complex multicellular organisms are formed as a highly organized arrangement of differentiated cells
2. molecular basis of heredity.
• In organisms, the instructions for specifying the characteristics of the organism are carried in the DNA.
• Changes in DNA occur spontaneously at low rates
3. biological evolution.
• Species evolve over time.
• The great diversity of organisms is the result of more than 3.5 billion years of evolution
• Biological classifications are based on how organisms are related. Organisms are classified into a hierarchy of groups and
subgroups based on similarities which reflect their evolutionary relationships
Standard E (Science and Technology): As a result of activities in grades 9-12, all students should develop understanding of
1. abilities of technological design.
2. science and technology.
• Scientists in different disciplines, ask questions, use different methods of investigation, and accept different types of evidence
to support these explanations.
• Science often advances with the introduction of new technologies.
• Creativity, imagination, and good knowledge base are all required in the work of science and engineering.
• Science and technology are pursued for different purposes.
Standard F (Science in Personal and Social Perspectives): As a result of activities in grades 9-12, all students should
develop understanding of
6. science and technology in local, national, and global challenges.
• Science and technology are essential social enterprises, but alone they can only indicate what can happen, not what should happen
• Individuals and society must decide on proposals involving new research and the introduction of new technologies into society
Standard G (History and Nature of Science): As a result of activities in grades 9-12, all students should develop
understanding of
1. science as a human endeavor.
• Individuals and teams have contributed and will continue to contribute to the scientific enterprise.
2. nature of scientific knowledge.
• Because all scientific ideas depend on experimental and observational confirmation, all scientific knowledge is, in principle,
subject to change as new evidence becomes available.
3. historical perspectives.
• The historical perspective of scientific explanations demonstrates how scientific knowledge changes by evolving over time,
almost always building on earlier knowledge.
17
18
INTRODUCTION
The Power Within has several key learning
objectives related to the concepts of cellular
structure, taxonomy, and genetic evolution:
1. To differentiate between prokaryotes and
eukaryotes in structure and function;
2. To describe the structure and function of
cell organelles, including the nucleus, mitochondrion, and chloroplast;
3. To identify characteristic features of organisms from different kingdoms and to classify
specific organisms accordingly;;
4. To define symbiosis, and to identify general and specific examples of parasitic, commensalist, and mutualistic relationships;
5. To explain Lynn Margulis’s endosymbiotic theory, particularly in relation to cellular
compartmentalization;
6. To interpret a cladogram in the context of
phylogeny and evolutionary theory; and
7. To recognize the relationship between organisms’ genetic sequences and their respective positions on an evolutionary tree.
THE CELL: AN OVERVIEW
The human cell is a marvel of complexity
despite its miniature size. The average diameter of one human cell is so small that several
such cells, lined end to end, would approximate the width of a human hair.
Cells vary widely in their structure and function.
The human body alone contains over 200 kinds,
from a large neuron a meter in length to a tiny
sperm cell, whose length can be measured in
micrometers. Yet despite this degree of variation, cells also contribute to the consistency and
unity of life on Earth. Every living creature, no
matter if it lives in deep hydrothermal vents at
the bottom of the ocean, preys on gazelles in the
savannah, or reaches its branches upward in a
rainforest, is made of one or more cells. Animals,
plants, bacteria, fungi, and protists all rely on
Endothelial cells under the microscope.
their constituent cells for functions such as nutrition, reproduction, motility, protein production,
and the generation and processing of energy.
PROKARYOTES vs. EUKARYOTES
Cells differ in their fundamental structure depending on the nature of their genetic material,
as well as the lack or presence of specialized,
membrane-bound structures called organelles. Prokaryotic cells usually contain their
genetic material in the form of a single circular
chromosome and lack a defined nucleus, or
control center of the cell. Prokaryotes do not
contain any organelles. Typically, prokaryotic
cells are single, small cells, with a width ranging from 1 to 10 micrometers.
Alternatively, eukaryotic cells have a
membrane-bound nucleus as well as membrane-bound organelles. The nucleus contains
genetic information in the form of chromosomes, which vary in number according to
species (but whose numbers do not, perhaps
surprisingly, reflect the complexity of the organism). Typically, multicellular organisms are eukaryotes, and their cells are often
greater than 10 micrometers in width.
ORGANELLES
A distinguishing characteristic of eukaryotes
is the presence of membrane-bound organelles, structures within the cell that perform
specific functions. For example, the mitochondrion, often known as the “powerhouse”
of a cell, is responsible for converting oxygen
and glucose into energy in the form of ATP
and carbon dioxide as a by-product.
In a complementary process, the chloroplast
takes oxygen and energy in the form of sunlight
to make glucose and an oxygen by-product.
19
FIGURE 1: MITOCHONDRION
Inner membrane
Outer membrane
Cristae
Matrix
20
FIGURE 2: CHLOROPLAST
Outer membrane
Inner membrane
Granum
(stack of thylakoids)
Thylakoid
Stroma
(the fluid between the grana)
21
FIGURE 3: COMPARING EUKARYOTES AND PROKARYOTES
Prokayrotes
Cell division
without mitosis
Eukayrotes
Ribosomes in
cytoplasm
Chromosome
(singular circular
in prokaryotes,
multiple linear in
eukaryotes)
Nuclear envelope
Membrane-enclosed
organelles
Cellulose in cell walls
Ribosomes in mitochondria and chloroplast
Cell division with
mitosis
KINGDOMS
The lack or presence of particular membrane-bound organelles is a useful feature for
classifying organisms into their representative kingdoms. Prokaryotes dominate the
kingdoms of Archaebacteria and Eubacteria. These kingdoms include organisms such
as Streptococcus, a bacterium responsible for
causing strep throat, and blue-green algae,
which grow in water.
Conversely, eukaryotes are found in the
Kingdoms Protista, Fungi, Plantae, and Animalia, and include organisms such as molds,
mushrooms, hardwood trees, and humans,
respectively. Multicellular eukaryotes’ cells
typically contain a nucleus and mitochondria,
and chloroplasts are commonly found in the
plant kingdom.
RIBOSOMES
Both prokaryotes and eukaryotes have
ribosomes, which are responsible for protein
22
synthesis via the translation of mRNA into
an amino acid sequence. The fact that both
prokaryotes and eukaryotes have ribosomes
is a testament to the need for all organisms to
make protein. Additionally, because all living
things make protein, the structure and genetic
composition of the ribosome tends to evolve
more slowly than other cell structures.
Ribosomes have two parts, known as a small
and a large subunit. Each subunit contains the
label “S” (for “Svedberg unit”), which correlates
with its size. In prokaryotes, ribosomes have a
30S and a 50S subunit; in eukaryotes, ribosomes
have a 40S and a 60S subunit. Another difference
between prokaryotic and eukaryotic ribosomes is
where they are found. Prokaryotes typically contain ribosomes found free-floating in the cytosol, whereas eukaryotes have ribosomes that are attached to an intricate membrane network within
the cell known as the endoplasmic reticulum, or
ER. The ER provides a structure for transport of
proteins made on ribosomes. ER with ribosomes
attached is known as “rough ER”; ER without
FIGURE 4: DIFFERENT RIBOSOMES IN EUKARYOTIC CELLS
Animal cell
Ribosomes on rough ER
Mitochondrial ribosomes
Chloroplast ribosomes
Cytoplasmic ribosomes
Plant cell
23
ribosomes is “smooth ER.” Small ribosomes are
also located inside the mitochondria and chloroplast of eukaryotic cells.
RIBOSOMES AND EVOLUTION
When comparing evolutionary relationships
between different kinds of organisms, it is
helpful to pick a structure common to all
organisms. It also helps to find a structure that changes very slowly over evolutionary time,
because it is easier to track changes in relationships between organisms over long periods
of time. The ribosome is an ideal choice. It
is common to all organisms because of the
universal need for organisms to make protein.
It also evolves slowly over time, which allows
scientists to relate the gradual accumulation of
ribosomal changes to different species along
an evolutionary line. It is particularly advantageous to use ribosomal RNA because only the
DNA that codes for the RNA is needed for
comparisons between organisms. Additionally,
the organisms do not need to be intact or alive
for the harvesting of such DNA.
Organisms in different kingdoms differ not
only in the presence of types of organelles,
but also differ in the nature of the DNA that
code for their ribosomal RNA. The more
dissimilar two strands of such DNA, the
farther apart these two organisms will be
on an evolutionary tree, or cladogram. A
cladogram is a visual representation of how
different organisms are related. The oldest ancestors are represented near the bottom of the
diagram, whereas relatively recent organisms
are found near the top.
DNA that codes for ribosomal RNA has
provided evidence that mitochondria and
chloroplasts, although found in a variety of
multicellular organisms, actually have more
in common with Eubacteria than they do with
organisms in other kingdoms. Consider the
following hypothetical DNA sequences:
AGTCCCTGAGAGCTCACAG
— from Eubacteria
AGTCCCTGTGAGCTCACAG
— from mitochondria
AGTCCGTGCGAGCAGACAG
— from the nucleus of an animal cell
24
Notice that the DNA sequences in Eubacteria
and mitochondria differ only by one nucleotide;
an adenine (A) in the Eubacteria is changed
to thymine (T, in blue) in mitochondria. These
sequence alignments suggest a more remote
evolutionary relationship between the Eubacteria and the animal, since the animal DNA has
four different nucleotide bases (the red G, C, A,
and G) compared to that of the Eubacteria.
To explain the phenomenon of molecular
similarity between Eubacteria and mitochondria, we need to first focus on a broader, more organismal concept of relationships.
SYMBIOSIS
Scientists use the word symbiosis to describe
a relationship between organisms, very often
of different species. Just as human relationships can be positive or negative, so too can a
symbiotic relationship either benefit, harm, or have no effect on the organisms involved.
On one end of the symbiotic spectrum is
parasitism. Parasites depend on their hosts
for food and sustenance at the expense of
their hosts. Therefore, one species benefits in the relationship, while the other is harmed.
Examples of parasites include viruses, as well
as certain bacteria, fungi, insects, and worms.
In commensalism, one species benefits while the other is unaffected. A classic example of
commensalism is that of the remora suckerfish and the shark. The remora has an appendage modified into a kind of sucker that helps it attach to the shark. As it moves along with
the shark, the remora feeds on food carried
to it by ocean currents or dropped as scraps
by the shark. The remora thus benefits from being on the shark because of the food it gets;
the shark, on the other hand, neither benefits nor is harmed by the remora.
In mutualism, both organisms benefit from the relationship. In the case of a yucca plant
and yucca moth, these different species serve
essential functions to benefit each other. Yucca moth caterpillars feed on the seeds of the
yucca plant. In return, the yucca moths can
fly from plant to plant to help pollinate the plants. Over time, the relationship between
yucca moths and yucca plants has become
DAVID BURDICK | NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION/DEPARTMENT OF COMMERCE
In an example of commensalism, a remora attaches itself close to the gills of a nurse shark. The remora benefits by getting
food, while the relationship neither helps nor hurts the shark.
necessary. Each organism is codependent on
the other and would face a dramatic decrease
in population without its obligate, or necessary, partner. The adaptations developed
over time by the yucca moth in response to
changes over time in the yucca plant provide
an example of co-evolution.
ENDOSYMBIOSIS vs. ECTOSYMBIOSIS
Symbiotic relationships can be classified as endosymbiotic or ectosymbiotic. In endosymbiosis, one organism lives inside of another (in
Greek, “endo” refers to “within” or “inside”).
For example, in one example of endosymbiotic mutualism, green algae live inside the
digestive cells of green hydra, which are very
small aquatic organisms. The photosynthetic
algae are useful to the hydra in times of starvation and oxygen deprivation, and the hydra
provide protection and additional materials
for the algae. In contrast to endosymbiosis,
ectosymbiosis (in Greek, “ecto” refers to
“outside”) relates to one organism living on
the outside of another organism or on the
outside of an organism’s cells. For example,
cows and other ruminants have bacteria in the
gut that can digest the polysaccharide cellulose
into its constituent sugars. The by-products
of these digestive processes provide the cow
with energy. Although these microorganisms
live inside the animal, they live extracellularly
(outside the cells) in the digestive tract and
thereby form an ectosymbiotic relationship
with their hosts.
LYNN MARGULIS AND THE
ENDOSYMBIOTIC THEORY
In 1970, female scientist Lynn Margulis combined the concepts of mutualism, endosym-
25
J.S. PETERSON | USDA-NRCS PLANTS DATABASE
The yucca plant (above) and the yucca moth (right) have come
to depend on each other for survival.
BILL MAY | USDA FOREST SERVICE
biosis, and evolutionary theory to generate a
powerful explanation for eukaryote structure
and function known as the endosymbiotic
theory. According to this theory, free-living
bacteria of ancient times generated their own
energy by way of anaerobic (non-oxygen-requiring) processes such as fermentation. The
presence of oxygen would have actually been
toxic to such cells. In such an oxygen-poor
environment, primitive forms of photosynthesis did not involve the production of oxygen.
This model of primitive oxygen-independent
photosynthesis stands in stark contrast to the
reality of photosynthesis today, in which photosynthetic organisms such as trees and grass
naturally produce oxygen as a by-product.
More recently, photosynthesis in bacteria
developed into the form with which we are
familiar today. An increase in the bacteria’s
photosynthetic activity led to the production
of oxygen, causing the death of many organisms that were not used to living in such an
environment. Some bacteria adapted over
evolutionary time to handle oxygen through
26
HYDRA PHOTO BY RALF WAGNER
Photosynthetic green algae (left) live inside the digestive
cells of green hydra (right) in a demonstration of endosymbiotic mutualism.
processes such as aerobic cell respiration.
Other bacteria continued to produce energy
anaerobically; such bacteria belong to the
present-day kingdom of Archaebacteria and
survive in remote locations, such as hydrothermal vents deep in the ocean.
Another way in which prokaryotes cope with
an oxygen-rich environment is by taking in
aerobic bacteria as endosymbionts. In this
way, the prokaryotic host cell that cannot
JAVIER PEDREIRA
Lynn Margulis
Constantin
Mereschkowsky
handle oxygen on its own will be able to
do so with the help of the bacteria that can
conduct cellular respiration inside of it. Margulis initially proposed the idea of anaerobic
and aerobic bacteria living together in the
context of a parasitic relationship—that is,
the aerobic bacteria preyed upon host cells,
to the host cells’ detriment. However, she
contends that the originally parasitic relationship became mutualistic as evolutionary
forces came into play. Over time, the host
cell came to provide the aerobic bacteria with
protection and additional food sources, such
as the sugars needed to power the process
of cellular respiration. In this way, both the
host cell and the aerobic bacteria benefitted in their relationship with one another.
How does the endosymbiotic theory relate to
the structure and function of the modern-day
eukaryote? Evidence suggests that mitochondria, which serve as energy powerhouses
of cells in all organisms, evolved from the
aerobic bacteria of long ago. Furthermore, the
host cells that played such a key role in the
endosymbiotic theory are believed to be the
precursors of the modern eukaryotic cell.
What evidence supports the idea that mitochondria once existed as free-living bacteria?
First, mitochondria have their own DNA that
is distinctly different from the nuclear DNA
of eukaryotic cells; such a difference suggests
that the mitochondria and the eukaryotic cell
have different origins. Second, the shape and
size of mitochondria is very similar to the
shape and size of present-day bacteria. Finally, both mitochondria and bacteria divide
in a similar way.
Mitochondria are not the only organelles
that are believed to have developed by way
of endosymbiosis. As early as 1905, even
before Margulis’s groundbreaking work,
Russian scientist Constantin Mereschkowsky
used endosymbiosis to explain the origin of
chloroplasts. Chloroplasts, too, contain many
of the characteristics of bacteria, and they are
believed to have evolved in a way akin to the
evolution of mitochondria. The way in which
green pigments are distributed in chloroplasts
approximates the way in which they are distributed in cyanobacteria. Additionally, both
chloroplasts and cyanobacteria use carbon
dioxide from the atmosphere to make energy
molecules such as glucose. Like mitochondria, chloroplasts reproduce in a manner similar to bacterial replication.
Recent evidence supports the theories of
Mereschkowsky and Margulis. Lab studies
conducted by Kwang W. Jeon showed that although bacteria introduced into amoebas led
to their initial death, the relationship between
amoebas and bacteria evolved in a relatively
short period of time into a mutually beneficial one. After time passed, not only could the
amoebas coexist with the bacteria, but they
also developed a need for the bacteria and
could not live without them. The bacteria that
were once harmful to the amoeba became
indispensable. Even at the molecular level,
genetic changes occur to reflect the nature of a symbiotic relationship; the bacteria will
actually begin to exert genetic control over
their host cells.
COOPERATION, NOT COMPETITION
Endosymbiosis differs from evolutionary
theory in that it concentrates not so much on
competition, but more on how organisms contribute to each other’s survival. In some ways,
Darwin’s evolutionary theory aligns with the
endosymbiotic theory: organisms undergo
a variety of changes, some enabling them
to adapt to another organism’s needs, to the
benefit of both partners. The concept of coevolution illustrates this concept. The structures
of some plants are particularly well suited in
length, shape, size, scent, and/or color to draw
pollinators in and to provide easy access. A
bumblebee’s weight, for instance, provides
just the right amount of force to open a snapdragon. This is beneficial to the snapdragon because the bee serves as a pollinator, and it is
beneficial to the bee, which will receive nectar from the snapdragon. The ability to provide
access to some organisms and not to others
also confers protection to the host.
Evolution of life as we know it may have
required teamwork, the kind of teamwork
evident in endosymbiosis. This leads us to the
question, How did endosymbiosis affect the
evolution of eukaryotes and thereby affect the
branching patterns of life?
27
PRE-LAB ACTIVITIES
Initially, students are engaged to think about
biological relationships by way of a TV reality show skit. They then visit five stations to gain the knowledge that provides the power
to help them understand how bioinformatics can be used as a tool to test the prediction
that endosymbiosis played a role in the evolution of eukaryotic cells. The five stations are as follows:
P—Parts of the cell
O—Organism classification
W—Who am I? (contributions of scientists)
E—Evolutionary relationships (how to read
cladograms)
R—Relationships between organisms (types
of Symbiosis)
WET-LAB ACTIVITIES
A new tool, bioinformatics, allows scientists to better understand the role played by
endosymbiosis in the evolution of eukaryotes.
Biologists are now using computers to compare gene sequences of different organisms.
Generally, the more similar two organisms’
genes, the more recent their two — lineages
split apart from one another. Students will
test the prediction based on similar gene
sequences that chloroplasts and mitochondria
are closely related to the bacteria.
ADDITIONAL ACTIVITIES
Additional activities include the “Fishy Family Tree” activity, which allows students to
use structural differences to make a cladogram. Students find their symbiotic partner in “Symbiotic Connections.” Students are
able to understand the importance of bioinformatics in our world today as they read an
article from Nature entitled “SAR11 clade
dominates ocean surface bacterioplankton
communities.”
INTERDISCIPLINARY ACTIVITIES
“Picture This” is a writing and listening exercise that can be used as a starting point for an
evolution unit in a biology or language arts
class. Working individually or cooperatively,
science and non-science teachers can use the
reading and discussion activities suggested
in “Darwin the Writer” or assign one of the
literary works described in “Additional Activities for English Classrooms.” An activity
for Social Studies and other classrooms takes
a discovery-based approach to understanding
clinical trials.
POST-LAB ACTIVITIES
The post-lab activities include a review of
the wet-lab activity, plus another opportunity
for students to use a data base to obtain real
amino acid sequence data to create a cladogram. Included in the post-lab activities is a
Power Within quiz game. A tree analysis activity provides students additional assistance
in reading cladograms.
28
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Kansas Naturalist Web site: http://www.emporia.edu/
30
CONNECTION TO OTHER DESTINY MODULES
THE POWER WITHIN
Students focus on endosymbiosis
and its role in the evolutionary
origin of the mitochondrion and
the chloroplast—two eukaryotic
organelles. Students learn about
the science of bioinformatics
as they use molecular data to
generate sequence alignments
which can be used to construct
phylogenetic trees. In the process
they learn that the computer can be used as a tool for
scientific investigation. Students learn how to read and compare phylogenetic trees.
FROM FISHES TO FINCHES
Students compare protein from
the muscle cells of fish to determine which fish are most closely related. Since DNA determines
protein, those fish which have the most similar proteins would
be expected to have similar DNA
and similar origins.
SEQUENCE OF MODULES
A sequence relating the three modules is summarized
below:
1. EXPLORING NEW ENVIRONMENTS — Students learn fundamental concepts of relationships
between organisms and their environment. In both modules students examine the vital relationship of bacteria
to all living organisms.
2. FROM FISHES TO FINCHES — Students use
molecular data to determine which fish are most closely related. In The Power Within students also use molecular data to compare the evolutionary origin of organisms, and in each module they learn how to read and
draw phylogenetic trees.
3. THE POWER WITHIN — Students are introduced
to the science of bioinformatics which uses molecular
data to generate sequence alignments. This data can
then be used to construct phylogenetic trees. Bioinformatics, which allows students to compare sequence
alignments, would be considered a more advanced
method of comparing organisms than comparing morphological differences or differences in protein banding.
EXPLORING NEW ENVIRONMENTS
Students examine complex relationships between organisms and
the physical and biological environment as well as the movement
of energy and materials within an
ecosystem.
31
32
THE POWER WITHIN IMPLEMENTATION PLAN — PRE-LAB
Activity
Estimated
Time
Engagement Activity:
“Power Trip” skit
15 Minutes
Exploration Activity:
P–Parts of the Cell
O–Organism Classification
W–Who am I?
E–Evolutionary Relationships
R–Biological Relationships
45 Minutes
Explanation/
Elaboration Activity
15 Minutes
Evaluation
10 Minutes
Materials/Equipment
Copies of script
Copies of worksheet
Data Sheet for Stations
P: Cell Poster/Station Sheets/Cell
models/Crossword Puzzle
O: Magnetic Diagram Station
Sheets and Labels
W: Station Sheets
E: Magnetic White Boards/Pens,
Station Sheets
R: Station Sheets and Stickers
Alphabet Rubber Stamp Set
Ink pads
Diagrams
• How a bacterium might
become a mitochondrion
• Different ribosomes in
eukaryotes
• Geological time scale
• Domains of life
• Pictures of cladograms
• Tree analysis picture
Purpose/Objectives/
Essential Question
Purpose
To help students understand the evolutionary origin of certain eukaryotic organelles—chloroplasts and mitochondria.
Objectives
P: Students will review the structure and
function of cellular organelles.
O: Students will analyze the classification of organisms according to their
evolutionary relationships.
W: Students will become familiar with the
contribution of various scientists to the
theory of endosymbiosis.
E: Students will learn how to draw and
interpret cladograms.
R: Students will analyze and explain the
interactive role of organisms in nature.
Essential Question
How did endosymbiosis lead to the origin
of eukaryotic cells?
Writing Activity
Alignment with NC Competency Goals
Biology
Goal 1
Objectives 1.01, 1. 02, 1.03, 1.05
Goal 2
Objectives 2.01, 2.02
Goal 3
Goal 4
33
THE POWER WITHIN PRE-LAB ACTIVITIES:
UTILIZING THE 5E MODEL
PURPOSE
To help students understand the evolutionary origin of
two eukaryotic organelles—the chloroplast and mitochondrion.
OBJECTIVES:
• Students will review the structure and function of cellular organelles.
• Students will analyze the classification of organisms according to their evolutionary relationships.
• Students will analyze and explain the interactive role
of organisms in nature.
• Students will learn how to analyze sequence alignments and draw and interpret cladograms.
• Students will examine scientists’ explanations for the
evolutionary origin of eukaryotic organelles.
ESSENTIAL QUESTION
“What role did endosymbiosis play in the evolution of
the eukaryotic cell?”
MATERIALS NEEDED
FOR THE POWER STATIONS:
• Timer – one per class
• 5 stamps P, O, W, E and R
• 5 ink pads
ENGAGEMENT
Based on a reality-TV format, this skit introduces students to four types of relationships in nature. This activity takes
15 minutes.
EXPLORATION
Teacher will set up the five POWER Stations
(Allow students 8-10 minutes for each station.)
Instruct students to make observations
and gather information from each of the
five stations, P, O, W, E, and R, and to answer the essential question: What role
did endosymbiosis play in the evolution of the eukaryotic cell?
34
Instructions: All group members are responsible for
everyone in the group as well as themselves in learning
the assigned materials at each station. The group leader
for each station will stamp the individual data sheets for
group members if they feel everyone in the group has
learned the assigned material.
All student groups will visit each of the 5 Exploration
stations, P, O, W, E, and R. Use a timer to “move” the
groups along to all of the 5 stations.
Randomly assign a different group to explain each of
the 5 stations. For example:
Only one group will be asked to explain the Scientist station via the questions they have written. That
one student group will ask the class their revealing
questions to assess the class’s understanding of the
scientists and their contributions.
Group members should divide up the tasks and share in
the responsibility equally. All group members will be
involved in the Explanation that is brought back to the
class.
STATION P: PARTS OF THE CELL
MATERIALS NEEDED
Station Sheets, Cell Poster, Cell Model, Crossword
Puzzle
PROCEDURE
1. Review the Background Information for Cellular
Organization.
2. Using your knowledge gained in step #1 above,
complete the Crossword Puzzle.
3. Assemble the plant and animal cells using the provided materials.
STATION O: ORGANISM CLASSIFICATION
MATERIALS NEEDED
Station Sheets and Magnetic Diagrams with labels
PROCEDURE
1. Students will complete the table that summarizes the
main points used in classifying organisms into the
major taxonomic categories.
DIRECTIONS
There are five “baggies of information” used to distinguish each group of organisms. Divide the baggies
among the members of your group and take turns
placing the correct information onto the magnetic game
board. Consult with your group to make sure all the information is in the correct category. When everyone in
your group is finished, answer the following questions to determine to which kingdom the mystery organism
belongs.
STATION W: WHO AM I?
MATERIALS NEEDED
Station sheets and charts
PROCEDURE
1. Each member of your group needs to choose a different scientist from the 5 scientist sheets provided
at your station.
2. Students will read the information about each scientist and introduce their scientist to group members.
3. Formulate specific clues that will reveal your scientist without telling who your scientist is. Example:
Which scientist came up with the formula, E=mc2?
Answer: Albert Einstein.
EXPLANATION/ ELABORATION
1. Student groups will be selected
randomly to present information from
each of the five stations.
2. Teachers will guide students by using
questioning techniques to ensure
essential information is presented at
each station.
3. More in depth topics related to each
station will be discussed by the
teacher.
EVALUATION
Endosymbiosis Quiz Game — Jeopardy
style quiz game
or
Writing Activity — Students are asked
to write a paragraph which describes a
diagram illustrating the endosymbiosis theory.
STATION E: EVOLUTIONARY RELATIONSHIPS
MATERIALS NEEDED
Magnetic white boards, pens, station sheets
PROCEDURE
1. Read the information on the station sheets.
2. Use the example provided to draw your own cladogram on the white board provided at the station.
STATION R: RELATIONSHIPS THAT EXIST BETWEEN
ORGANISMS
MATERIALS NEEDED
Station sheets, Tic Tac Toe Grid; stickers
PROCEDURE
1. Examples of parasitism, commensalism, and mutualism are required to complete the Tic Tac Toe chart.
2. Each example corresponds to a sticker on the next
sheet of labels.
3. Match each label to its corresponding symbiotic
description above, and place the sticker in its appropriate space.
35
ENGAGEMENT ACTIVITY
POWER TRIP: ENGAGE STUDENTS IN THE CONCEPT
OF BIOLOGICAL RELATIONSHIPS
Based on a reality-TV format, this skit introduces students to four types of relationships occurring between organisms in nature. Depending upon time taken for discussion, this activity lasts 15-20 minutes.
MATERIALS NEEDED
• Copies of the “Power Trip” script for students playing parts. The announcer will need a copy of the entire script.
Each pair of actors will need only copies of their own scene.
• Copies of the “Power Trip” worksheet and script: one worksheet and one full script (or one scene) for each student
group.
DIRECTIONS FOR THE TEACHER
1. The teacher selects nine students to play parts in the skit: one announcer and eight contestants in the “Power
Trip” reality show on TV.
2. The students act out the scenes in this week’s episode of “Power Trip” in front of the class.
3. The teacher may choose to have the class vote on their favorite character—the character they most want to stay
on the show (Madison, Mike, Tina, Antonio, Rose, Trey, Lara, or Theta). The character with the least votes is off
the show!
4. The teacher then divides the class into groups of five or six students. Each group will have a copy of the script and a copy of the “Power Trip” worksheet. (As an alternative, shorter version of this activity, the teacher may ask
each group to analyze a different scene and report their conclusion to the rest of class.)
5. The teacher will explain that, all around us in nature, living things are involved in a kind of reality show of their
own – with many relationships and associations between different species occurring. Some of these relationships
are beneficial to both organisms;; some are beneficial or harmful to one partner in the relationship and not to the other;; and some associations do not benefit either partner, and in fact may be harmful to one or both of them.
6. The teacher provides the following instruction to the groups: “Using clues provided in the ‘Power Trip’ script,
identify which scenes correspond to each of these four types of biological relationships described on your worksheet: commensal, competitive, mutualistic, and parasitic.”
7. When the groups complete their worksheets, the teacher brings the class together to discuss their answers. In addition to matching each scene with a type of relationship, the class should compare the clues they gathered from
each scene. These clues can be listed on the board in front of the class.
8. Finally, now that the students know which organisms are related to the “Power Trip” characters, the teacher may
choose to have the class take another vote. Which organism (cockroach, mite, human toe, fungus, flower, tree, human large intestine, or bacterium) do they want to stay on the show?
36
POWER TRIP: TEACHER’S SCRIPT
SCENE 1
Announcer: In this week’s episode of the hit reality show “Power Trip,” the relationships between the remaining
contestants are really being tested. While they try to make their big break in the entertainment industry, they have
to endure the everyday struggles of young adults just starting out their lives in the big city. They have to make ends
meet, discover who their real friends are, and perhaps even find true love that will last long after this TV show has ended.
Let’s check in on what happened to the Power Trippers this week …
While they wait for their big break, good friends Madison and Michael are sharing an apartment.
[Madison and Michael take center stage.]
Madison: Um … can I talk to you about something, Mike?
Michael: Sure, I’m just kind of hanging out. Going to have something to eat in a moment.
Madison: Uh … well, I don’t mind about this myself—I mean, it doesn’t bother me personally—but some people
on the show are saying that you take advantage of me.
Michael: What?! Who said that?! Wow! I can’t believe that they would say that!
Madison: Hey, now, don’t get all upset! It’s just that you’re sleeping on my couch, and eating all your meals over
here, and giving nothing back. Some people think that’s not right.
Michael: Wow! It’s not like I’m in anyone’s way. I take up very little space around here, and I just eat leftovers.
Cold pizza and flat Pepsi for breakfast. Yeah, that’s my big gourmet feast! That’s taking advantage?!
Madison: OK, I’m sorry I brought this up. I really don’t care one way or the other.
[Madison and Michael exit.]
SCENE 2
Announcer: Meanwhile, the show’s hot couple, Antonio and Tina, are also having difficulties.
[Antonio and Tina take center stage.]
Antonio: Tina, I … I want to take a break from our relationship.
Tina: No way! What are you saying?! I thought we were going to the beach together this weekend!
Antonio: I’m sorry, Tina. I … I need to stay in the city. I have an audition coming up. I need to focus on that. I … I
need some space.
Tina: What did I do, Antonio? We were getting along fine. I thought you really liked me!
37
Antonio: Yeah, I did … I mean, sort of … Uh, I don’t know. It’s just too much for me. You’re too much for me. It’s
irritating!
Tina: I’m irritating? I’m irritating?! Do you think you’re some sort of dream date? It’s not like you’re good looking
or anything!
Antonio: Yeah, well, don’t you think I know you’ve just been hanging out with me because I’m a free meal ticket.
Well, that’s over!
Tina: Yeah, well, this stinks!
[Antonio and Tina exit.]
SCENE 3
Announcer: Rose and Trey are clashing again. They just cannot seem to be in the same space together without getting in each other’s way.
[Rose and Trey take center stage]
Rose: I am sick and tired of this, Trey! Stop spreading rumors about me! I have not had cosmetic surgery! As if I
even need it!
Trey: Hey, now, simmer down! What are you talking about?
Rose: You know what I’m talking about! You’re telling everyone I’m basically plastic! And I’m not!
Trey: Well, now, I’m not saying I did or I didn’t. People talk. Anyway, you’re not going to win votes just because
the viewers think you have a pretty face.
Rose: If you think you’re going to win votes just because … because you’re the biggest oaf on the show.… Well,
two can play that game, Trey! I can start rumors about you and steroids!
Trey: Hey, now, that hurts. You’re just throwing accusations around without any proof. You really need to stop being
so petalant.
Rose: It’s pet-u-lant! Not pet-a-lant! Do you even know what the word means?!
[Trey and Rose exit.]
SCENE 4
Announcer: The only contestants who haven’t been involved in a big controversy this season are Lara and Theta.
[Lara and Theta take center stage.]
Lara: Did you hear Mad and Mike arguing? Can you believe it? They never argue!
Theta: Yeah, it’s not like Rose and Trey. Those two have never gotten along.
Lara: I know. And did you hear that Antonio and Tina are breaking up?
38
Theta: Yeah, they were getting along all right until … I don’t know … I think sometimes things just get out of balance. One side wants more than the other can give. You know what I mean?
Lara: Yeah, I hope that doesn’t happen with us. We’re so different, but we’re really good friends. You’ve helped me
get this far on the show.
Theta: From the moment I arrived here, you made me feel like one of the group.
Lara: Well, not everyone’s like you, Theta. It’s give-and-take with you—not just take, take, take. You’re one of the
good ones.
Theta: Why, thank you, Lara! I think you’re OK, too.
[Lara and Theta exit.]
Announcer: Tune in to see what happens next and who gets voted off the show. All we can say now is … IT’S A
TRIP!
39
POWER TRIP: WORK SHEET
Using clues provided in the script, identify which scenes in this episode of “Power Trip” correspond to each of these
four types of biological relationship described below. Also identify which character corresponds to which organism
in each “Power Trip” relationship.
A. Commensalism [ ]: In this biological relationship, one organism benefits. The other organism does not benefit, but neither is it harmed.
Example: The Madagascar hissing cockroach and the hissing-cockroach mite.
This cockroach (which really does hiss!) plays host to the mite, which feeds on saliva and scraps of food it finds on the roach’s body. The mite, which neither harms nor benefits the roach, cannot survive apart from this host.
“Power”ful Connections: This commensal relationship corresponds to this scene in “Power Trip” (choose scene 1,
2, 3, or 4): ______.
This organism (_________________) corresponds to this character (_______________) in the scene.
These are some of the clues provided in the scene: ____________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
B. Competition [ ]: In this biological relationship, both organisms are annoyed by the other’s pushy behavior.
By the way, it’s not always a fair fight.
Example: Plants such as flowers and trees may compete with each other for the same resources available in an area—moisture and nutrients in the soil, space in which to grow, and sunlight.
“Power”ful Connections: This competitive relationship corresponds to this scene in “Power Trip” (choose scene 1,
2, 3, or 4): ______.
_____________________________________________________________________________________________
_____________________________________________________________________________________________
C. Mutualism [
]: In this biological relationship, both organisms benefit.
Example: The human large intestine and some species of gut flora (bacteria that make the intestines their home). Bacterioides thetaiotamicron is one species of bacteria that can be found in the healthy human intestine, where it
40
helps stimulate development of the blood vessels.
“Power”ful Connections: This mutualistic relationship corresponds to this scene in “Power Trip” (choose scene 1,
2, 3, or 4): ______
_____________________________________________________________________________________________
_____________________________________________________________________________________________
D. Parasitism [ ]: In this biological relationship, one partner benefits, while the other organism is taken advantage of and even harmed.
Example: The human toe and Trichophyton rubrum, one of the species of fungi that cause Tinea pedis, the infection
known as Athlete’s Foot.
The human toe can supply a menu of nutritious items (like dead skin and nails) for certain kinds of fungi to dine on.
Normally, the human toe is fine with this. But sometimes (in damp conditions, for instance) the fungi overgrow and become very irritating.
“Power”ful Connections: This parasitic relationship corresponds to this scene in “Power Trip” (choose scene 1, 2,
3, or 4): ______.
_____________________________________________________________________________________________
_____________________________________________________________________________________________
41
POWER TRIP: WORK SHEET
Using clues provided in the script, identify which scenes in this episode of “Power Trip” correspond to each of these
four types of biological relationship described below. Also identify which character corresponds to which organism
in each “Power Trip” relationship.
A. Commensalism [ ]: In this biological relationship, one organism benefits. The other organism does not benefit, but neither is it harmed.
Example: The Madagascar hissing cockroach and the hissing-cockroach mite.
This cockroach (which really does hiss!) plays host to the mite, which feeds on saliva and scraps of food it finds on the roach’s body. The mite, which neither harms nor benefits the roach, cannot survive apart from this host.
“Power”ful Connections: This commensal relationship corresponds to this scene in “Power Trip” (choose scene 1,
2, 3, or 4): 1 .
This organism (Madagascar hissing cockroach) corresponds to this character (Madison) in the scene.
This organism (hissing-cockroach mite) corresponds to this character (Michael) in the scene.
These are some of the clues provided in the scene: Michael/Mite is “just kind of hanging out,” eating leftovers, and
sleeping on the couch. He’s not in the way. And Madison/Roach really doesn’t mind; he says that “it doesn’t bother
me personally.”
B. Competition [ ]: In this biological relationship, both organisms are annoyed by the other’s pushy behavior.
By the way, it’s not always a fair fight.
Example: Plants such as flowers and trees may compete with each other for the same resources available in an area—moisture and nutrients in the soil, space in which to grow, and sunlight.
“Power”ful Connections: This competitive relationship corresponds to this scene in “Power Trip” (choose scene 1,
2, 3, or 4): 3
.
This organism (flower) corresponds to this character (Rose) in the scene.
This organism (tree) corresponds to this character (Trey) in the scene.
These are some of the clues provided in the scene: The announcer says it best: “They just cannot seem to be in the
same space together without getting in each other’s way.”
C. Mutualism [ ]: In this biological relationship, both organisms benefit.
Example: The human large intestine and some species of gut flora (bacteria that make the intestines their home). Bacterioides thetaiotamicron is one species of bacteria that can be found in the healthy human intestine, where it
helps stimulate development of the blood vessels.
“Power”ful Connections: This mutualistic relationship corresponds to this scene in “Power Trip” (choose scene 1,
2, 3, or 4): 4 .
42
KEY
This organism (human large intestine) corresponds to this character (Lara) in the scene.
This organism (B. thetaiotamicron) corresponds to this character (Theta) in the scene.
These are some of the clues provided in the scene: Lara/large intestine tells her friend Theta/B. thetaiotamicron,
“We’re so different, but we’re really good friends. You’ve helped me get this far on the show” and “It’s give-andtake with you – not just take, take, take.” Theta agrees with Lara; and she says, “From the moment I arrived here,
you made me feel like one of the group” (i.e., provided shelter) and “I think you’re OK, too.”
D. Parasitism [ ]: In this biological relationship, one partner benefits, while the other organism is taken advantage of and even harmed.
Example: The human toe and Trichophyton rubrum, one of the species of fungi that cause Tinea pedis, the infection
known as Athlete’s Foot.
The human toe can supply a menu of nutritious items (like dead skin and nails) for certain kinds of fungi to dine on.
Normally, the human toe is fine with this. But sometimes (in damp conditions, for instance) the fungi overgrow and become very irritating.
“Power”ful Connections: This parasitic relationship corresponds to this scene in “Power Trip” (choose scene 1, 2,
3, or 4): 2 .
This organism (human toe) corresponds to this character (Antonio) in the scene.
This organism (T. rubrum) corresponds to this character (Tina) in the scene.
These are some of the clues provided in the scene: Antonio/human toe needs a break because Tina/fungus has
become “irritating”; he says she sees him as “a free meal ticket.” Tina was looking forward to going to the beach
(fungi like damp environments!).
43
POWER TRIP: STUDENTS’ SCRIPTS
POWER TRIP: ANNOUNCER’S SCRIPT
SCENE 1
[Madison and Michael take center stage, act out their scene, and exit.]
SCENE 2
[Antonio and Tina take center stage, act out their scene, and exit.]
SCENE 3
[Rose and Trey take center stage, act out their scene, and exit.]
SCENE 4
[Lara and Theta take center stage, act out their scene, and exit.]
Announcer: Tune in to see what happens next and who gets voted off the show. All we can say now is … IT’S A
TRIP!
44
POWER TRIP: MICHAEL AND MADISON’S SCRIPT
SCENE 1
[Madison and Michael take center stage.]
Madison: Um … can I talk to you about something, Mike?
Michael: Sure, I’m just kind of hanging out. Going to have something to eat in a moment.
Madison: Uh … well, I don’t mind about this myself—I mean, it doesn’t bother me personally—but some people
on the show are saying that you take advantage of me.
Michael: What?! Who said that?! Wow! I can’t believe that they would say that!
Madison: Hey, now, don’t get all upset! It’s just that you’re sleeping on my couch, and eating all your meals over
here, and giving nothing back. Some people think that’s not right.
Michael: Wow! It’s not like I’m in anyone’s way. I take up very little space around here, and I just eat leftovers.
Cold pizza and flat Pepsi for breakfast. Yeah, that’s my big gourmet feast! That’s taking advantage?!
Madison: OK, I’m sorry I brought this up. I really don’t care one way or the other.
[Madison and Michael exit.]
45
POWER TRIP: ANTONIO AND TINA’S SCRIPT
SCENE 2
[Antonio and Tina take center stage.]
Antonio: Tina, I … I want to take a break from our relationship.
Tina: No way! What are you saying?! I thought we were going to the beach together this weekend!
Antonio: I’m sorry, Tina. I … I need to stay in the city. I have an audition coming up. I need to focus on that. I … I
need some space.
Tina: What did I do, Antonio? We were getting along fine. I thought you really liked me!
Antonio: Yeah, I did … I mean, sort of … Uh, I don’t know. It’s just too much for me. You’re too much for me. It’s
irritating!
Tina: I’m irritating? I’m irritating?! Do you think you’re some sort of dream date? It’s not like you’re good looking
or anything!
Antonio: Yeah, well, don’t you think I know you’ve just been hanging out with me because I’m a free meal ticket.
Well, that’s over!
Tina: Yeah, well, this stinks!
[Antonio and Tina exit.]
46
POWER TRIP: ROSE AND TREY’S SCRIPT
SCENE 3
[Rose and Trey take center stage]
Rose: I am sick and tired of this, Trey! Stop spreading rumors about me! I have not had cosmetic surgery! As if I
even need it!
Trey: Hey, now, simmer down! What are you talking about?
Rose: You know what I’m talking about! You’re telling everyone I’m basically plastic! And I’m not!
Trey: Well, now, I’m not saying I did or I didn’t. People talk. Anyway, you’re not going to win votes just because
the viewers think you have a pretty face.
Rose: If you think you’re going to win votes just because … because you’re the biggest oaf on the show.… Well,
two can play that game, Trey! I can start rumors about you and steroids!
Trey: Hey, now, that hurts. You’re just throwing accusations around without any proof. You really need to stop being
so petalant.
Rose: It’s pet-u-lant! Not pet-a-lant! Do you even know what the word means?!
[Trey and Rose exit.]
47
POWER TRIP: LARA AND THETA’S SCRIPT
SCENE 4
[Lara and Theta take center stage.]
Lara: Did you hear Mad and Mike arguing? Can you believe it? They never argue!
Theta: Yeah, it’s not like Rose and Trey. Those two have never gotten along.
Lara: I know. And did you hear that Antonio and Tina are breaking up?
Theta: Yeah, they were getting along all right until … I don’t know … I think sometimes things just get out of balance. One side wants more than the other can give. You know what I mean?
Lara: Yeah, I hope that doesn’t happen with us. We’re so different, but we’re really good friends. You’ve helped me
get this far on the show.
Theta: From the moment I arrived here, you made me feel like one of the group.
Lara: Well, not everyone’s like you, Theta. It’s give-and-take with you—not just take, take, take. You’re one of the
good ones.
Theta: Why, thank you, Lara! I think you’re OK, too.
[Lara and Theta exit.]
48
THE POWER WITHIN
DATA OBSERVATION SHEET
STATION P
1
2
3
4
5
6
7
8
STATION O
Based on the information given to you from the completed table and these questions, in what
kingdom does your mystery organism belong?
_______________________________________
In what domain is this kingdom found?
_______________________________________
List some possible examples of this kingdom.
_______________________________________
49
STATION W
Write your clue questions below.
1. ______________________________________________________________________________
2. ______________________________________________________________________________
3. ______________________________________________________________________________
4. ______________________________________________________________________________
5. ______________________________________________________________________________
STATION E
Copy the cladogram your group has drawn on the marker board onto your data sheet.
STATION R
Place stickers on the blocks to indicate which organisms your team has selected for
each space below.
Species A +
Parasitism
Species A benefits and Species B is
harmed.
Commensalism
Species A benefits and
Species B is unaffected.
Mutualism
Both species benefit.
Species A 0
FREE SPACE
Neutralism
Both species unaffected
NO STICKER NEEDED
Commensalism
Species A is unaffected
while Species B benefits.
Species A –
Competition
Neither species benefits
NO STICKER NEEDED
FREE SPACE
Parasitism
Species B benefits at the expense of
Species A.
Species B -
50
Species B 0
Species B +
P
STATION
PARTS OF THE CELL
51
52
EXPLORATION ACTIVITY
OBJECTIVE
Student will gain knowledge about the structure and function of the cell.
MATERIAL NEEDED
•
•
•
•
Background Information Sheet
Parts of the Cell Crossword Puzzle
Pre-printed magnetic sheets for plant and animal cell organelles
Pre-printed magnetic sheets for plant and animal cells
PROCEDURE
1. Review the Background Information for Cellular Organization.
2. Using your knowledge gained in step #1 above, complete the Crossword Puzzle.
3. Construct the plant and animal cells using the magnetic sheets provided.
After teacher review and evaluation of your models, please disassemble both the plant and animal cell models.
53
PARTS OF THE CELL: (Cellular Organization)
BACKGROUND INFORMATION
COMPARTMENT
DESCRIPTION
FUNCTION
Plasma Membrane
Semi-permeable lipid bilayer on outside of cell
Controls movement of substances into and out of cell
Cytoplasm
Consists of a semifluid medium called cytosol, where the
organelles are located
Site where most cellular activities are performed
Mitochondria
• Kidney bean-shaped
• Contains inner and outer membranes composed of phospholipid bilayers and proteins
• Contains cristae (formed by infoldings of the inner
membrane), and the matrix (space within the inner
membrane)
• Mitochondria possess their own genetic material, and
the machinery to manufacture their own RNAs and
proteins
• Mitochondria contain ribosomes
• Generate most of the cell’s supply of ATP
• Source of energy
• The matrix is important in the production of ATP with
the aid of the ATP synthase contained in the inner
membrane. Of the enzymes, the major functions
include oxidation of pyruvate and fatty acids, and the
citric acid cycle.
• Mitochondria have the ability to manufacture their
own RNAs and proteins
Chloroplast
• Looks like a green sack
• Found only in plants and protista
• The chloroplast is surrounded by a double-layered
composite membrane with an intermembrane space
• Chloroplasts often surround vacuoles, which are fluid
cavities surrounded by a single membrane
• The chloroplast has its own DNA
• The chloroplast is the site of photosynthesis
• The material within the chloroplast is called the
stroma
• Within the stroma are stacks of thylakoids, the suborganelles which are the site of photosynthesis
• The thylakoids are arranged in stacks called grana
(singular: granum)
• Photosynthesis takes place on the thylakoid
membrane
• The chloroplast contains ribosomes
ONLY IN PLANT CELLS
Responsible for conducting photosynthesis (captures
light energy from the sun, using water and carbon
dioxide, producing sugar and oxygen)
Ribosomes
• A small, dense, functional structure found in all known
cells that assembles proteins
• Free ribosomes are suspended in the cytosol (the semifluid portion of the cytoplasm) or bound to the rough
endoplasmic reticulum, or to the nuclear envelope
• Ribosomes are also found within the mitochondria and
chloroplast
Builds proteins with the assistance of mRNA & tRNA
Endoplasmic reticulum
• An extensive membrane network of cisternae (sac-like
structures), tubules, and vesicles held together by the
cytoskeleton
• Looks like a stack of pancakes with syrup dripping off
• If contains ribosomes is known as “rough ER”
• If ribosomes are not present is known as “smooth ER”
Responsible for several specialized functions:
• Protein translation
• Protein folding
• Transport of proteins to be used in the cell membrane
54
ORGANELLE
PARTS OF THE CELL CROSSWORD
1
2
3
4
5
6
7
8
ACROSS
4.
6.
7.
8.
Structural and functional unit of life
Powerhouses of the cell (plural)
Control center for the cell
Fluid portion of the cytoplasm
DOWN
1.
2.
3.
5.
In a plant cell: fluid-filled cavity surrounded by a membrane
Endoplasmic _____________ (ER)
Responsible for photosynthesis in plant cells (singular)
These may be attached to the ER or free in the cytoplasm
55
KEY
PARTS OF THE CELL CROSSWORD
1
2
3
R
E
6
7
M
I
N
T
O
C
E
L
L
5
U
L
C
H
O
N
D
R
R
I
R
L
B
U
O
E
O
L
P
C
M
56
4
C
U
8
A
C
H
T
V
C
Y
L
S
E
U
O
S
A
M
S
E
T
A
O
S
O
L
S
CONSTRUCT A PLANT CELL MODEL
57
58
CONSTRUCT AN ANIMAL CELL MODEL
59
60
61
62
EXPLANATION/ELABORATION ACTIVITY
FIGURE 5: HOW A BACTERIUM MIGHT BECOME A MITOCHONDRION
1.
A bacterium encounters an
eukaryotic cell membrane.
Eukaryotic cell
membrane
Bacterial
cell membrane
Bacterial DNA
Nucleus
Cytoplasm
Bacterium
Bacterial
ribosomes
2.
The bacterium is enveloped by
the eukaryotic cell membrane
Eukaryotic cell
membrane
Bacterial
cell membrane
3.
The bacterium develops a double
membrane and remains inside
the cell.
DNA
Ribosomes
Mitochondrion
Inner mitochondrial membrane
(from the bacterial cell membrane)
Outer mitochondrial membrane
(from the eukaryotic cell membrane)
63
FIGURE 6: DIFFERENT RIBOSOMES IN EUKARYOTIC CELLS
Animal cell
Chloroplast ribosomes
Plant cell
64
O
STATION
ORGANISM CLASSIFICATION
65
66
OBJECTIVES
Student will gain knowledge about the classification of organisms and complete a chart that summarizes the main points used in classifying organisms into the current major taxonomic categories.
MATERIAL NEEDED
• Magnetic Game Board
• Magnetic Game Board Pieces contained in five bags, labeled with the headings from the game board
• Station sheets for each student
• Teacher Answer Sheet
TEACHER PREPARATION
1. Prior to the lab, cut the game board pieces out and place in the appropriate size baggies, labeled with the headings
from the game board.
2. Magnetic Game Board and game pieces should be placed at the station.
3. There are five “baggies of information” used to distinguish each group of organisms. Have the students divide the baggies among the members of the group and take turns placing the correct information onto the magnetic
game board. Students should consult with the group to make sure all the information is in the correct category.
When all students in the group are finished, they should answer the questions to determine which kingdom the mystery organism belongs in.
4. When students have completed this activity, the group leader should check their answers so that they can receive
the stamp of completion.
5. Instruct the students to place all the game pieces back into the correct baggie for the next group to use. Make
sure they do not share their findings with the other groups of students until asked to do so.
6. Teachers can vary the difficulty of the chart by adding or deleting blocks on the game board.
67
At this station, you will complete the table that summarizes the main points used in classifying organisms
into the major taxonomic categories.
DIRECTIONS
There are five “baggies of information” used to distinguish each group of organisms. Divide the baggies among the members of your group and take turns placing the correct information onto the magnetic game board. Consult with
your group to make sure all the information is in the correct category. When everyone in your group is finished, answer the following questions to determine which kingdom the mystery organism belongs in.
MYSTERY ORGANISM
List the possible choices at each question until you have narrowed down the organism to one kingdom.
1. This organism is eukaryotic:
_________________________________________________________________
2. This organism has cell walls:
_________________________________________________________________
3. This organism has membrane bound organelles:
_________________________________________________________________
4. This organism belongs to a group of organisms which could be unicellular or multicellular:
_________________________________________________________________
5. This organism is heterotrophic:
_________________________________________________________________
6. This organism does not carry out photosynthesis, but obtains its nourishment from dead or decaying organic matter:
_________________________________________________________________
SUMMARIZE
Based on the information given to you from the completed table and these questions, in what kingdom does your
mystery organism belong?
__________________________________
In what domain is this kingdom found? __________________________________
List some possible examples of this kingdom. __________________________________
CHECK
When you have completed this activity, have your teacher check your answers so that you can receive your stamp of
completion.
CLEAN UP
Place all the game pieces back into the correct baggie for the next group to use. Do not share your findings with the other groups of students until asked to do so.
68
At this station, you will complete the table that summarizes the main points used in classifying organisms into the
major taxonomic categories.
DIRECTIONS
There are five “baggies of information” used to distinguish each group of organisms. Divide the baggies among the members of your group and take turns placing the correct information onto the magnetic game board. Consult with
your group to make sure all the information is in the correct category. When everyone in your group is finished, answer the following questions to determine which kingdom the mystery organism belongs in.
MYSTERY ORGANISM
List the possible choices at each question until you have narrowed down the organism to one kingdom.
1. This organism is eukaryotic:
Protista, Fungi, Plantae, Animalia
2. This organism has cell walls:
Protista, Fungi, Plantae
3. This organism has membrane bound organelles:
Protista, Fungi, Plantae, Animal
4. This organism belongs to a group of organisms which could be unicellular or multicellular:
Protista, Fungi
5. This organism is heterotrophic:
Protista, Fungi
6. This organism does not carry out photosynthesis, but obtains its nourishment from dead or decaying organic matter:
Fungi
SUMMARIZE
Based on the information given to you from the completed table and these questions, in what kingdom does your
mystery organism belong?
Fungi
In what domain is this kingdom found?
Eukarya
List some possible examples of this kingdom.
Mushrooms, Yeast, Penicillium
CHECK
When you have completed this activity, have your group leader check your answers so that you can receive your
stamp of completion.
CLEAN UP
Place all the game pieces back into the correct baggie for the next group to use. Do not share your findings with the other groups of students until asked to do so.
69
KEY
Domain
Bacteria
Archaea
Eukarya
KINGDOM
Fungi
CELL TYPE
Prokaryote
NUMBER OF
CELLS
MODE OF
NUTRITION
CELL
STRUCTURES
GENERAL
CHARACTERISTICS
Multicellular
Autotroph or
Heterotroph
Membranebound organelles. Cell walls
composed of
cellulose for
some. Chloroplasts found in
some.
Very diverse
group of
organisms
that can move
about at least
for some part
of their life
cycle
EXAMPLES
70
KEY
Domain
Bacteria
Archaea
Eukarya
KINGDOM
Eubacteria
Archaebacteria
Protista
Fungi
Plantae
Animalia
CELL TYPE
Prokaryote
Prokaryote
Eukaryote
Eukaryote
Eukaryote
Eukaryote
NUMBER OF
CELLS
Unicellular
Unicellular
Typically unicellular. Some
colonial. Some
are multicellular
Most are multicellular. Some
are unicellular
Multicellular
Multicellular
MODE OF
NUTRITION
Autotroph or
Heterotroph
Autotroph or
Heterotroph
Autotroph or
Heterotroph
Heterotroph
Autotroph
Heterotroph
CELL
STRUCTURES
Cell walls with
peptidoglycan
(a polymer of
sugars crosslinked by short
polypeptides)
Cell walls
without peptidoglycan
composed of
cellulose for
some. Chloroplasts found in
some.
composed of
chitin.
composed
of cellulose.
Chloroplasts
present.
Membranebound
organelles. No
cell walls. No
chloroplasts.
GENERAL
CHARACTERISTICS
Ecologically
diverse; some
are free-living
soil organisms
and others
are deadly
parasites
Found in the
most extreme
environments
like volcanoes,
brine pools,
and the guts
of cows. Cell
membranes
contain unique
lipids.
Some share
characteristics
with plants,
such as being
photosynthesizers while
others share
characteristics
with animals,
such as being
heterotrophic.
Most feed on
dead or decaying organic
matter. Also
secrete digestive enzymes
into their food
source
Photosynthetic
autotrophs,
which means
they can
manufacture
their own food
by the energy
from sun.
Very diverse
group of
organisms
that can move
about at least
for some part
of their life
cycle
EXAMPLES
Escherichia coli,
Cyanobacteria
Extreme
halophiles,
Methanogens
Amoeba,
Paramecium,
Slime molds
Mushrooms,
Yeast, Penicillium
Mosses, Ferns,
Maple trees
Sponges,
worms, insects,
fishes, birds,
and mammals
71
DISCUSSION OF THE THREE DOMAINS
Discuss the Geological Time Scale relating several major biological events to the history of the earth. Use the diagram provided.
In this calendar 4.6 billion years of the earth’s history are compressed into one year. Each day on the calendar is
equal to almost 13 million years on the earth.
It is estimated that the solar system is about 6 billion years old. The Earth formed approximately 4.6 billion years
ago. Moon rocks and meteorites indirectly confirm this information, with moon rocks dating around 4.6 billion years old and meteorites dating 4.5 billion years old. There was no oxygen present. Scientists have worked out a chronology of Earth’s history based on the evidence in its rocks, using radiometric dating methods. Fossils, the preserved
remnants left by organisms that lived in the past, are historical documents of biology. The fossil record is the way in
which fossils appear within the layers of sedimentary rocks that mark the passing of geological time. The first cells appeared 3.5 billion years ago. Stromatolites contain layered mats of prokaryotic cells similar to modern bacteria.
The first Eukaryotic cells evolved 1.5 billion years ago. Endosymbiosis suggests that cellular organelles may have originated from engulfed prokaryotes. The theory of enfolding suggests inner membranes of organelles originated
from the enfolding of the cell membrane. Autotrophs evolved with the ability to carry out photosynthesis. Oxygen
was first released into the water and then the atmosphere, making possible aerobic respiration, a more efficient form of respiration .
Ask students to use the geological time scale to place the following events on a time line:
• Formation of the Earth (no oxygen present)
• The first cells (prokaryotes, stromatolites, heterotrophs)
• First eukaryotic cells (organelles, oxygen, enfolding hypothesis, endosymbiosis)
• Formation of the solar system
Billions of years ago
6
4.5
3.5
1.5
Discuss how the information in parentheses relates to the event.
72
FIGURE 7: TIMELINE OF LIFE ON EARTH
JANUARY 1
4500 Million Years Ago (M.Y.A.)
Origin of Earth
Precambrian
3700 M.Y.A.
Oldest Earth rocks
3500 M.Y.A.
Oldest stromatolites and
prokaryotic microfossils
MARCH 25
2000 M.Y.A.
Significant levels of O2 in
the atmosphere
1400 M.Y.A.
Oldest eukaryotic fossils
Paleozoic
580 M.Y.A.
NOVEMBER 27
500 M.Y.A.
First vertebrates appear
430 M.Y.A.
First land plants appear
395 M.Y.A.
First amphibians and
insects appear
Mesozoic
225 M.Y.A.
Mammal-like reptiles appear
135 M.Y.A.
Flowering plants appear
66 M.Y.A.
Dinosaurs become extinct
Cenozoic
245 M.Y.A.
38 M.Y.A.
Origin of modern mammals
7 M.Y.A.
Ape-like ancestors of
humans appear
10
9
8
11 12 1
7 6 5
2
3
4
DECEMBER 26
9 p.m.
10
9
8
11 12 1
7 6 5
2
3
4
DECEMBER 31
10 p.m.
73
Animalia
Plantae
Cyanobacteria
Proteobacteria
Thermoproteus
Eubacteria
Archaebacteria
Methanosarcina
Eucarya
Extreme halophiles
Protista
Fungi
FIGURE 8: THE THREE DOMAINS
74
W
STATION
WHO AM I?
Scientists and the Theory of Endosymbiosis
75
76
STATION W: WHO AM I?
SCIENTISTS AND THE THEORY OF ENDOSYMBIOSIS
OVERVIEW
Students will read about five scientists who have contributed to our knowledge of the origin of various organelles within the eukaryotic cell such as the mitochondria and chloroplast. They will become familiar with the types of
evidence used by each scientist that helped formulate their ideas regarding evolution of these cellular structures.
GOAL
How did each of the five scientists contribute to the theory of endosymbiosis?
OBJECTIVES
Students will be able to:
• Identify the important contributions of each scientist.
• Identify how each scientist’s contribution(s) relate(s) to the endosymbiosis theory.
• Write specific questions giving clues about each of the scientists without revealing the scientist via the evidence used, published books, and theories in use today.
STUDENT INSTRUCTIONS
Student Instructions: You have a limited time to earn your ‘W’ stamp of completion. The timer will tell you to move
to the next station.
1. Each member of your group needs to choose a different scientist from the 5 scientist sheets provided at your station.
2. Read the information about your chosen scientist, then introduce your scientist to other members of your group.
3. Formulate specific clues that will reveal your scientist without telling who your scientist is. Example: Which scientist came up with the formula, E=mc2? Answer: Albert Einstein.
MATERIALS NEEDED
• One station sheet with instructions for students
• One copy of each of the five Scientist sheets laminated or placed into sheet protectors and then placed into one of the five different folders.
• Carl Linnaeus
• Charles Darwin
• Lynn Margulis
• Constantin Mereschkowsky
• Carl Woese
77
STATION W: WHO AM I? WORKSHEET
NAME __________________________________________________________________ CLASS _____________
DATE _____________________
Student Instructions: You have a limited time to earn your ‘W’ stamp of completion. The timer will tell you to move
to the next station.
1. Each member of your group needs to choose a different scientist from the 5 scientist sheets provided at your station.
2. Read the information about your chosen scientist, then introduce your scientist to other members of your group.
3. Formulate specific clues that will reveal your scientist without telling who your scientist is. Example: Which scientist came up with the formula, E=mc2? Answer: Albert Einstein.
Scientist
Name
Contributions
Year Presented
Reception by Scientific
Community
Connections to Evolution
78
WHO AM I?
CHARLES DARWIN
Scientist
Name
Charles Darwin (1809-82)
Contributions
Proposed the theory of natural selection to explain how evolution occurs; used the phrase “descent
with modification” instead of evolved in the first edition of his book. Collected thousands of fossils
and living organisms both plant and animal during his voyage aboard the HMS Beagle which began in 1831 and ended in 1836; noted that animals were unique to their specific habitat, i.e. fossils
of South America were more similar to modern South American species than fossils from other
continents. His perception was a unity among species with organisms related through a common
ancestor that lived in the remote past.
Year Presented
Early 1840s — wrote long essay describing the major features of his theory of evolution
1859 — published book, On the Origin of the Species by Means of Natural Selection
Community
Only a few scientists in the 1700s questioned the accepted ideas of that time, that species were
fixed and unchanging; Darwin observed similarities between fossils and living organisms.
His theory of natural selection was an explanation of how evolution occurs.
79
WHO AM I?
CARL LINNAEUS
Scientist
Name
Carl Linnaeus (1707-1778)
Contributions
Father of Taxonomy – Linnaeus successfully introduced the system of classifying organisms, a system that now includes kingdom, phylum, class, order, family, genus and species; only 2 kingdoms,
Plantae and Animalia; admitted this was an “artificial classification.” Collected and studied plants;
plant taxonomy based solely on number and arrangement of plants’ reproductive organs.
Year Presented
1735 — published the first edition of his classification of living things, Systema Naturae.
Community
Linnaeus provided a workable system for naming organisms which was necessary due to the large
number of plants and animals being brought back from Asia, Africa, and the Americas. He simplified the naming of organisms by designating one Latin name to designate the genus and one as
a shorthand name for the species. His binomial naming system became the standard for naming
species. Linnaeus also published that plants reproduce sexually.
In his early years Linnaeus believed species were unchangeable, but altered this to suggest some
species in a genus arose from hybridization. He also felt some species of plants could be altered
through acclimatization.
80
WHO AM I?
LYNN MARGULIS
Scientist
Name
Lynn Margulis (1938- )
Contributions
Margulis hypothesized in the 1960s that symbiosis was a major force in the evolution of cells. Her
theory was known as symbiogenesis and argues that inherited variation does not come mainly
from random mutation but does evolve from fusion of genomes in symbioses followed by natural
selection; Ancestors of all life are bacteria which are fused into protists (algae, amoebas) which
fused into multicellular organisms. Not all DNA is contained in the nucleus of the cell; mitochondria contain their own DNA which is similar to the bacterium that causes typhus; chloroplasts
contain their own DNA which is cyanobacterial DNA and dissimilar to the nuclear DNA.
Year Presented
1970 — published The Origin of Eukaryotic Cells
1981 — published Symbiosis in Cell Evolution
Community
Her theory challenged Darwin’s theory of evolution by natural selection. Their ideas were at odds
and could not be discussed at respectable scientific meetings.
Theory is now taught to high school students. Endosymbiosis is the best explanation for the evolution of the eukaryotic cell.
81
WHO AM I?
CONSTANTIN MERESCHKOWSKY
Scientist
Name
Constantin Mereschkowsky (1855-1921)
Contributions
He hypothesized that a free living bacterium was engulfed, but not digested, by an early plant cell
and that modern-day chloroplasts descended from that original bacterium.
Year Presented
1905
Community
His papers were not translated and did not catch on in the Western world. The idea was accepted
for two decades of the 20th century, but it was dismissed by a text writer, which led to a dismissal
of any endosymbiotic origins of cellular structures for the next 50 years.
Did not believe that Darwin’s theory of natural selection could explain the biological diversity of
living organisms. He explained the diversity among eukaryotes by the acquisition and inheritance
of microbes.
82
WHO AM I?
CARL WOESE
Scientist
Name
Carl Woese (1928- )
Woese redrew the tree of life based on three domains: eukaryotes, bacteria, and archaea.
Contributions
He suggested this is based on genetic relationships rather than morphological similarities. Archaea
include many species adapted to life in extreme environments without oxygen, such as hot springs
and salt ponds.
He felt that instead of one primordial form, there were initially at least three types of loosely constructed organisms swimming in a pool of genes, and that these three evolved through horizontal
gene transfer into three distinct types of cells.
Year Presented
1977
Community
He challenged the Darwinian assumption known as the doctrine of common descent, which stated
that all life descended from a common ancestor. Famous scientists objected to the division of
prokaryotes; archaea were once thought to be extreme organisms that evolved from organisms
more familiar to us.
Archaea accepted by mid 1980s due to supporting data; very significant in terms of search for life
on other planets that have extreme environmental conditions.
83
84
E
STATION
EVOLUTIONARY RELATIONSHIPS
85
86
OBJECTIVES
To understand how DNA sequence alignments can be used to draw cladograms.
MATERIALS NEEDED
Station Sheets/Student Instructions
White Magnetic Boards
PROCEDURE
1. Read the information on the station sheets.
2. Use the example provided to draw your own cladogram on the white board provided at this station.
To better understand how the first endosymbiont got inside the host cell, it would be beneficial to know which species of bacteria came together to make the original eukaryotic cell.
A new tool, bioinformatics, allows scientists to address these kinds of questions. Bioinformatics is the application
of computer and statistical methods to analyze biological data.
Biologists are now using bioinformatics to compare gene sequences of different organisms. Generally the more similar two organisms’ genes, the more recent their two lineages split apart from one another.
Consider the following hypothetical DNA sequences that code for ribosomal RNA in aardvarks, bats, cockroaches,
and dung beetles, respectively:
GTGGACTAC
GTGGACTAT
GACCACTAC
CACCACTAC
— Aardvark
— Bat
— Cockroach
— Dung beetle
Notice that the DNA sequences in aardvark and bat differ only by one nucleotide, while the DNA sequences in
the aardvark and the cockroach differ by 3 nucleotide sequences and the aardvark and the dung beetle differ by 4
nucleotides.
Two organisms evolving slowly over a long period of time, and having a distant common ancestor, are likely to have
evolved lots of differences between their gene sequences.
Biologists use this kind of information to make a cladogram, like the one below, which is a dichotomous (a separation into two divisions that differ widely from each other) phylogenetic tree that branches repeatedly, suggesting a
classification of organisms based on the time sequence in which the evolutionary branches arise.
87
The following chart represents differences in nucleotide sequences of the aardvark, bat, cockroach, and the dung beetle.
This information can be used to create a cladogram showing the evolutionary relationships between organisms.
Aardvark
GTGGACTAC
GTGGACTAT
Bat
Cockroach
Dung beetle
Aardvark
0
1
3
4
Bat
1
0
4
5
Cockroach
3
4
0
1
Dung beetle
4
5
1
0
GTGGACTAC
GTGGACTAT
GACCACTAC
CACCACTAC
GACCACTAC
CACCACTAC
First, find two species that have the least numbers of differences in their sequences.
Aardvark and bat. These would be placed at the tips of corresponding branches representing sister species,
which are descendants of a common ancestor.
Now find another two species that differ by only one nucleotide sequence.
Cockroaches and dung beetles differ by one nucleotide also. These two organisms would be placed at the tips of
another set of corresponding branches, representing sister species, which are descendants of a common ancestor.
The aardvark and the bat differ from the cockroach and the dung beetle by 3, 4, or 5 nucleotides. In this case,
a difference of this magnitude (considering only 9 nucleotides) would indicate they are on two completely
separate branches of a cladogram and they had a common ancestor in the distant past.
Bat
Aardvark
88
Cockroach
Dung beetle
CREATE YOUR OWN CLADOGRAM
Observe the differences in the gene sequences represented in each organism below. Use this data to make your own
cladogram for organisms W, X, Y, and Z. Use the magnets and the erasable whiteboard and markers to complete this
activity. Copy onto your data sheet the cladogram that your group draws on the whiteboard.
Species W
Species X
Species Y
Species Z
Species W
0
1
5
6
Species X
1
0
6
5
Species Y
5
6
0
1
Species Z
6
5
1
0
Find two organisms that have the least number of differences in their sequences. These would be placed at the tips of
corresponding branches, representing sister species, which are the descendants of a common ancestor.
Now find another two species that have the next smallest differences in their nucleotide sequences. These two organisms would be placed at the tips of another set of corresponding branches representing sister species, which are
descendants of a common ancestor.
89
KEY
CREATE YOUR OWN CLADOGRAM
X
W
90
Y
Z
For questions 1-3, use these sequence alignments:
Plant mitochondrial DNA:
Plant chloroplast DNA:
Plant nuclear DNA:
Cyanobacterial DNA:
Proteobacterial DNA:
CTTAGCGATCATTA
CTTAGCGATCATTA
CTTAAGGATCATTC
CTTAGCGATCATTA
CTTAGCGATCATTA
1. Is the DNA from the nucleus of the plant like the DNA found in the mitochondria or chloroplast?
2. How do the DNA sequences from the cyanobacteria and proteobacteria compare with the DNA from the plant
mitochondria and chloroplast?
3. What might this kind of evidence indicate?
4. Is there a major difference between the following terms: phylogeny, evolutionary tree, phylogenic tree, and cladogram?
5. Using the figure below, come up with your own definition of what an “outgroup” is.
A and B are sister groups
taxon A
C is the outgroup to A and B
taxon B
taxon C
Common ancestor
of A and B
91
Is the DNA from the nucleus of the plant like the DNA found in the mitochondria or chloroplast?
No, not exactly. There is a difference of three nitrogen bases.
Plant mitochondrial DNA:
Plant chloroplast DNA:
CTTAGCGATCATTA
CTTAGCGATCATTA
Plant nuclear DNA:
CTTAAGGATCATTC
How do the DNA sequences from the cyanobacteria and proteobacteria compare with the DNA from the plant mitochondria and chloroplast?
The sequences are exactly the same.
What might this kind of evidence indicate?
This evidence suggests a closer relationship between the mitochondria, chloroplast, cyanobacteria, proteobacteria and a more remote ancestor for the nuclear DNA.
Is there a major difference between the following terms: phylogeny, evolutionary tree, phylogenic tree, and cladogram?
For general purposes, there is not much difference. Biologists use the terms interchangeably. All represent the
evolutionary relationships between groups of organisms.
An evolutionary tree, which is also called a phylogeny, represents the evolutionary relationships between groups
of organisms called taxa. The tips of the trees represent groups that are descendent taxa called species. The node
on a tree represents the common ancestors of descendent taxa. If two groups descend from the same node, they
are called sister groups and would be considered close relatives.
Come up with your own definition of what an “outgroup” is.
An outgroup is a taxon outside the group of interest. It would stem from the base of a tree, because an outgroup
is not related to the group of interest. An outgroup is helpful in constructing evolutionary trees because it gives
you a sense of where on the bigger tree of life the main group of organisms falls.
92
KEY
KEEP THE FOLLOWING IN MIND WHEN READING A PHYLOGENETIC TREE
If organisms are positioned at the branches of a tree, they may not
simply be written sequentially along the same tree line.
amoeba (nucleus)
amoeba (nucleus)
plant (nucleus)
plant (nucleus)
fungus (nucleus)
Incorrect
is NOT the same as
fungus (nucleus)
Correct
human (nucleus)
human (nucleus)
In a phylogenetic tree, what is important is not the position of organisms along the tree, but rather the number of nodes (common ancestors) they have between them. In these trees, the human nucleus and
the plant nucleus are still two nodes apart.
amoeba (nucleus)
plant (nucleus)
fungus (nucleus)
amoeba (nucleus)
fungus (nucleus)
IS the same as
human (nucleus)
human (nucleus)
plant (nucleus)
amoeba (nucleus)
Amoebas and plants are NOT
more complex than humans.
plant (nucleus)
fungus (nucleus)
The placement of one organism above another organism in
the phylogenetic tree does not mean that the organism is more
complex than the organisms below it.
human (nucleus)
93
USE THE DIAGRAM PROVIDED TO DISCUSS THESE QUESTIONS
1. Does the horizontal proximity indicate similarity or closeness of relationship? (Yes or No)
2 Do deeper nodes represent organisms that have lived before more shallow nodes? (Yes or No)
3. Are species which are located at the tips of longer and /or deeper branches more ancient or primitive? (Yes or No)
4. Could one extinct species at a terminal node be the ancestor of another species? (Yes or No)
94
Species G
Species F
Species E
Species D
Species C
Species B
Species A
5. Could criteria other than branching (such as the shape or horizontal closeness) define a tree? (Yes or No)
USE THE DIAGRAM PROVIDED TO DISCUSS THESE QUESTIONS
KEY
1. Does the horizontal proximity indicate similarity or closeness of relationship?
No
2 Do deeper nodes represent organisms that have lived before more shallow nodes?
Yes
3. Are species which are located at the tips of longer and /or deeper branches more ancient or primitive?
No
4. Could one extinct species at a terminal node be the ancestor of another species?
No
Species G
Species F
Species E
Species D
Species C
Species B
Species A
5. Could criteria other than branching (such as the shape or horizontal closeness) define a tree?
No
95
Sources consulted for pages 93-95 of The Power Within
Eernisse, D.J. (2000-2003). Introduction to phylogeny:
how to interpret cladograms. Retrieved February 20,
2008, from CSU Fullerton Biology 402 Web site: http://
biology.fullerton.edu/bio1402/phylolab_new.html.
Tree Thinking Group, (2004). A brief introduction to
tree thinking. Retrieved February 20, 2008, from Tree
Thinking Group Web Site: http://www.tree-thinking.
org/intro.html
University of California Museum of Paleontology,
Berkeley, and the Regents of the University of California, (2006). Trees, not ladders. Retrieved February 20,
2008, from Understanding Evolution for Teachers Web
site: http://evolution.berkeley.edu/evosite/evo101/IIB2Notladders.shtml
—. Understanding phylogenies. Retrieved February 20,
2008, from Understanding Evolution for Teachers Web
site: http://evolution.berkeley.edu/evosite/evo101/IIBPhylogenies.shtml
96
R
STATION
BIOLOGICAL RELATIONSHIPS
97
98
STATION R: BIOLOGICAL RELATIONSHIPS
OBJECTIVES
Students will be able to identify different types of biological and symbiotic relationships, and they will be able to
determine if such relationships are positive, negative, or neutral for the organisms involved.
MATERIALS NEEDED
Worksheet with Parasitism, Commensalism, Mutualism, Neutralism, and Competition vocabulary
Stickers with the names of organisms in various biological relationships
PROCEDURE
Just as two people can have a positive or a negative relationship, so too can relationships between organisms be
positive or negative. These relationships often occur between organisms of different species. In certain biological
relationships, known as symbiotic relationships, one organism might benefit at the expense of another, or two organisms may depend on one another for survival.
The table on the next page includes examples of different kinds of biological relationships. Some of these examples
include symbiotic relationships, such as parasitism, commensalism, and mutualism. In another type of biological
relationship, competition, organisms may compete for various needs, such as food resources or a mate. Competition
is not a symbiotic relationship; rather, it represents a type of organismal behavior.
The positive (+), neutral (0), and negative (-) signs represent the benefit, absence of benefit or harm, or harm (respectively) of a particular organism. For example, in the upper left corner, Species A has a positive (+) sign, while
Species B has a negative (-) sign. Therefore, the relationship between Species A and Species B is one of parasitism:
Species A benefits, but Species B is harmed.
Follow the instructions below the table to match your sticker labels to the proper spaces on the table. Place the stickers directly on their corresponding spaces on the table.
99
Species A +
Parasitism
harmed.
Commensalism
Mutualism
Species A 0
FREE SPACE
Neutralism
NO STICKER NEEDED
Commensalism
Species A –
Competition
NO STICKER NEEDED
FREE SPACE
Parasitism
Species A.
Species B -
Species B 0
Species B +
The following examples are representative of Parasitism, Commensalism, or Mutualism. Each example corresponds
to a sticker on the next sheet of labels. Match each label to its corresponding symbiotic description above, and place
the sticker in its appropriate space.
1. Ticks feed on the blood of deer, and the deer are harmed as a result.
2. The remora suckerfish is an organism that attaches itself to a shark and eats the leftover scraps of a shark’s meal. The shark does not harm the remora, nor is it harmed in the process.
3. A human becomes infected with hookworm, and his symptoms include abdominal pain, bloody diarrhea, and
asthma type symptoms. The hookworm is a roundworm that gains nutrients from its host.
4. Barnacles are crustaceans that latch onto the jaws of whales. As the whale moves through the water, currents
bring food to the barnacles. The whale is not hurt by the barnacle.
5. Lichens are composed of two different organisms in relationship with one another, algae and fungi; the algae
make food for the fungi using the sun’s energy via photosynthesis; and the fungi provide moisture and minerals
for the algae, providing it with a protective habitat.
100
Species A +
Parasitism
harmed.
1. A) Tick and B) Deer
Commensalism
2. A) Remora and B) Shark
Mutualism
5. Lichens:
A) Algae + B) Fungi
Species A 0
FREE SPACE
Neutralism
NO STICKER NEEDED
Commensalism
4. A) Whale and B) Barnacle
Species A –
Competition
NO STICKER NEEDED
FREE SPACE
Parasitism
Species A.
3. A) Human and B) Hookworm
Species B -
Species B 0
KEY
Species B +
The following examples are representative of Parasitism, Commensalism, or Mutualism. Each example corresponds
to a sticker on the next sheet of labels. Match each label to its corresponding symbiotic description above, and place
the sticker in its appropriate space.
1. Ticks feed on the blood of deer, and the deer are harmed as a result.
2. The remora suckerfish is an organism that attaches itself to a shark and eats the leftover scraps of a shark’s meal. The shark does not harm the remora, nor is it harmed in the process.
3. A human becomes infected with hookworm, and his symptoms include abdominal pain, bloody diarrhea, and
asthma type symptoms. The hookworm is a roundworm that gains nutrients from its host.
4. Barnacles are crustaceans that latch onto the jaws of whales. As the whale moves through the water, currents
bring food to the barnacles. The whale is not hurt by the barnacle.
5. Lichens are composed of two different organisms in relationship with one another, algae and fungi; the algae
make food for the fungi using the sun’s energy via photosynthesis; and the fungi provide moisture and minerals
for the algae, providing it with a protective habitat.
101
102
2. A) Remora Suckerfish and B) Shark
5. Lichens:
A) Algae + B) Fungi
5. Lichens:
A) Algae + B) Fungi
5. Lichens:
A) Algae + B) Fungi
5. Lichens:
A) Algae + B) Fungi
5. Lichens:
A) Algae + B) Fungi
STATION R: BIOLOGICAL RELATIONSHIPS
EXPLANATION/ELABORATION ACTIVITIES
A GUIDE FOR THE TEACHER
BIOLOGY VOCABULARY
ELABORATION ON ENDOSYMBIOSIS VS. ECTOSYMBIOSIS
Often, the key to successfully explaining difficult scientific concepts to students is making sure that they understand the language and vocabulary of science.
The handout provided at the end of this teacher’s guide
(“Biology Vocabulary: A Sample of Words with the
Prefixes Endo-, Ecto-, and Exo-”) is designed to help
address this need.
Sometimes, the concept of ectosymbiosis is a bit tricky.
Although one organism might live inside of another,
their relationship would be considered an ectosymbiotic
one if the organism lived outside the cell of the host. If
an organism lives on the interior lining of its host’s digestive tract, but not inside the cells of the host’s digestive tract, then the relationship is actually an example of
ectosymbiosis.
The handout contains a sample of words that include
the prefix endo-, which refers to processes within a cell or inside an organism; and a sample of words
that contain the prefixes ecto- or exo-, which refer to outward processes or activities that occur outside of an
organism.
There are several ways in which the “Biology Vocabulary” handout may serve as a useful teaching tool:
• As a reference guide. Whenever a scientific concept is taught with the prefixes “endo” or “ecto,” the teacher can refer students to this table, or to sample
words in this table, to underline the similarities
between the new vocabulary word and the words that
are provided.
Here is a suggested discussion question with which to
engage students:
Q. Explain why having a symbiotic relationship
between a host cell and a bacterial cell inside the host
cell would be defined as endosymbiosis.
A. Answers will vary. One possible answer is that
the bacteria are living intracellularly; in other words,
they are living inside the host cell. Therefore, the
relationship is an endosymbiotic one.
ELABORATION ON ENDOSYMBIOTIC THEORY
• As a review sheet of various biology concepts. The
words in the table cover a spectrum of topics, from
molecular biology and cell development to homeostasis.
Reminding students of the symbiotic relationships of
parasitism, commensalism, and mutualism is a good
way to introduce Lynn Margulis’s endosymbiotic
theory to students. The endosymbiotic theory suggests that today’s modern-day mitochondria were once
bacteria that entered into a symbiotic relationship with
their host cells.
• As a homework assignment or quiz. A teacher could
eliminate certain words, definitions, or sections of text in the table, and ask the student to fill in the blanks.
Once you have introduced the endosymbiotic theory to
students, it will be important for them to apply the concept of a symbiotic relationship between a bacterium
and a host cell.
• As a way to introduce the concepts of endoparasitism vs. ectoparasitism. Definitions of these concepts reinforce the ideas of symbiotic relationships in the
The Power Within module, and highlight the idea that
parasites can be classified according to where they live respective to their host.
Some possible questions to ask students include:
• As a way to introduce the concepts of endosymbiosis vs. ectosymbiosis. The introduction of the prefixes endo- and ecto- naturally leads to the definition and use of vocabulary related to the concept of symbiosis.
Q. Some ancient bacteria were able to make energy
using oxygen, while their host cells were not. How
could such an adaptation be beneficial to a host cell?
A: Bacteria could generate their own energy not only
for themselves, but also for their host cells.
Q. What kind of benefits could the host cell in turn provide to the bacteria?
103
A. The host cell could offer the bacteria shelter and
protection.
Q. In a situation where a bacterium generates energy
for its host cell, and the host cell provides shelter and
protection for the bacterium, what type of symbiotic
relationship is represented by this type of interaction?
A. Mutualism describes the given relationship
between a bacterium and its host cell, which is a
relationship that served as a precursor to the presentday mitochondrion.
SUPPLEMENTAL/OPTIONAL ADDITIONAL ACTIVITY
As an additional activity to highlight the endosymbiotic theory, your students can watch a YouTube video
on endosymbiosis titled “Only The Strong Survive:
The Story of the Oxygen Revolution” (made by Nikki
Bitsack and Alexandria Walker). See if your students
can identify the endosymbiont (the organism inside the
host cell), the host cell, and the reasons why they ended
up so “happy together.”
SOURCES
Arenstein, S., Jaffe, C., Ott, S., & Zack, L. SymbioticConnections.com. Retrieved November 21,
2007, from YouTube Web site: http://youtube.com/
watch?v=NDuSuvTzwiw
Bitsack, N., & Walker, A. Only the strong survive: the
story of the oxygen revolution. Retrieved November 8,
2007, from YouTube Web site: http://youtube.com/
watch?v=dSjg_uYS_QY
Ectosymbiosis. Retrieved November 6, 2007, from
Babylon Web site: http://www.babylon.com/definition/
Ectosymbiosis/English
Tea for two. Retrieved November 6, 2007, from
University of Regina Biology Dept. Web site: www.
uregina.ca/biology/courses/Bio265/PowerPoint/
Tea%20for%20Two%20-%20Assignment%20Two.ppt
http://youtube.com/watch?v=dSjg_uYS_QY
Students may also enjoy a YouTube video on symbiotic
relationships titled “SymbioticConnections.com” (made
by Sarah Arenstein, Claire Jaffe, Stephan Ott, and Liz
Zack). See if your students can identify the different
types of organisms identified in the video, as well as how the organisms benefit from one another.
http://youtube.com/watch?v=NDuSuvTzwiw
Both videos can be used as supplemental teaching
material, or may be assigned as part of a homework
assignment with one or two accompanying thought
questions.
104
BIOLOGY VOCABULARY
A Sample of Words with the Prefixes Endo-, Ecto-, and ExoENDO-
ECTO-, EXO-
Endoderm: The innermost layer of cells of a developing
embryo. These cells develop into parts of the body such
as the gastrointestinal tract and glands of the digestive
system.
Ectoderm: The outermost layer of cells of a developing
embryo. These cells develop into parts of the body such as
hair, skin, and the lens of the eye.
Endotherm: An animal that is able to make its own energy
and maintain its own internal body temperature; warmblooded.
Ectotherm: An animal whose body temperature depends
on the temperature of its surroundings and gets its energy
from the environment; cold-blooded.
Endoskeleton: A skeleton that is found entirely within
some animals, such as the human skeleton.
Exoskeleton: A hard protective covering found on the
outside of some animals.
Endocytosis: The process by which a cell membrane
encloses a substance and brings it into the cell.
Exocytosis: The process by which a vesicle with a substance fuses with a cell membrane, leading to its transport
out of the cell .
Endonuclease: An enzyme, such as a restriction enzyme,
that cuts within a nucleotide sequence at a specific site.
Exonuclease: An enzyme that works on breaking down
the ends of nucleotide sequences.
Endoparasite: A parasite that lives on the inside of its
host.
Ectoparasite: A parasite that lives on the outside of its
host.
Endosymbiosis: A relationship between two organisms
in which one organism lives inside the other or inside the
cell(s) of the other.
Ectosymbiosis: A relationship between organisms in
which one organism lives on the outside of its host or on
the outside of its host’s cells.
Definitions Adapted from Oxford Dictionary of Science and Encyclopedia Britannica Online
105
Plants, Fungi, Animals
EVALUATION ACTIVITY
Fungi
Animals
Protists
Plants
Prokaryotes
Mitochondria-containing protist
Photosynthetic bacteria
Aerobic bacteria
Prokaryotic host
Using the words provided in the diagram and other information that you learned in the pre- lab activities, write a
paragraph that describes what is happening in the picture.
Examples of other information that can be added:
• Endosymbiosis theory
• Eukaryotic cells
• Conditions of early atmosphere
106
• Ancient anaerobic cells
• Age of the earth/age of the solar
system
• First prokaryotes
• First eukaryotes
THE POWER WITHIN IMPLEMENTATION PLAN — WET-LAB
Activity
Estimated
Time
Materials/Equipment
Purpose/Objectives/
Essential Questions
Purpose:
To understand how endosymbiosis
led to the evolutionary origin of
certain eukaryotic organelles: chloroplasts and mitochondria.
Objectives:
Bioinformatics Activity:
“The Power Within” interactive CD
45 minutes
Copy of “The Power Within” CD
Computer
• To use molecular data to generate
sequence alignments which can be
used to construct a phylogenetic
tree.
• To recognize how the computer
can be used as a tool for scientific
investigations.
• To apply scientific methods.
• To demonstrate the ability to read
and compare phylogenetic trees.
Biology
Goal 1
Objectives 1.01, 1. 02, 1.03, 1.05
Goal 2
Goal 3
Goal 4
107
108
THE POWER WITHIN IMPLEMENTATION PLAN — POST-LAB
Activity
Review Questions from the
Wet Lab Activity
Using Data Bases to Obtain
Real Amino Acid Sequence
Data to Create Cladograms
Tree Analysis Activity
Estimated
Time
20 minutes
Materials/Equipment
Copies of Review Questions
Purpose/Objectives/
Essential Questions
Purpose:
To help students better understand
the evolutionary origin of certain
eukaryotic organelles: chloroplasts
and mitochondria.
45 minutes
Copies of Activity
30 minutes
Copies of the Activity
Objectives:
• To use structural data to construct
a phylogenetic tree.
Power Within Quiz Game
30 Minutes
CD containing the Power Within quiz
game or Transparency of the game
• To understand how scientists use
bioinformatics to construct evolutionary trees.
• To analyze and interpret data.
Essential Question:
• What is the evolutionary origin of
chloroplasts and mitochondria?
Biology
Goal 1
Objectives 1.01, 1. 02, 1.03, 1.05
Goal 2
Goal 3
Goal 4
109
Name ___________________
REVIEW QUESTIONS
1. What was Constantin Mereschkowsky’s theory regarding the origin of chloroplasts?
2. Did the molecular data support the phylogenic trees drawn by Constantin Mereschkowsky?
Green algae
Land plants
Red algae
Invertebrate and vertebrate animals
Bacteria
Fungi (basidiomycetes)
Fungi (ascomycetes)
3. How did eukaryotic cells evolve to be dependent on sophisticated internal machines like chloroplasts and mitochondria?
4. How can computers be used to solve the mystery of where cellular organelles like mitochondria and chloroplasts
might have come from?
5. How did Lynn Margulis’s work support Mereschkowsky’s theory?
6. Describe the structure of ribosomes and explain how the presence of ribosomes in various cellular organelles was
used to test Mereschkowsky’s theory.
7. Explain how similarities in sequence alignments indicate evolutionary similarities.
8. According to the sequence alignments for small ribosomal subunits, what type of bacteria would be most closely
related to chloroplasts?
related to mitochondrial ribosomes?
10. Why do scientists need to examine multiple data sets before determining evolutionary relatedness?
110
REVIEW QUESTIONS
KEY
1. What was Constantin Mereschkowsky’s theory regarding the origin of chloroplasts?
Mereschkowsky hypothesized that a free-living bacterium was engulfed, but not digested, by an early plant cell
and that modern chloroplasts have descended from that original bacterium.
2. Did the molecular data support the phylogenic trees drawn by Constantin Mereschkowsky?
Green algae
Land plants
Red algae
Mereschkowsky’s tree indicates there were
two independent origins of life. He made no
reference to the origin of mitochondria; he was
way ahead of his time in hypothesizing the
endosymbiotic origin of chloroplasts.
Invertebrate and vertebrate animals
Bacteria
Fungi (basidiomycetes)
Fungi (ascomycetes)
3. How did eukaryotic cells evolve to be dependent on sophisticated internal machines like chloroplasts and mitochondria?
Chloroplasts allowed cells to capture light energy and transform it into chemical bond energy which could be
used directly by the cell to carry out activities. The by product of photosynthesis, oxygen, changed the composition of the atmosphere and made possible aerobic respiration, a more efficient form of respiration. The mitochondria evolved to carry out this more efficient form of cellular respiration.
4. How can computers be used to solve the mystery of where cellular organelles like mitochondria and chloroplasts
might have come from?
The development and application of computers and statistical methods can be used to analyze biological data.
The development of databases allows scientists to store and manage biological data.
5. How did Lynn Margulis’s work support Mereschkowsky’s theory?
In 1967, Lynn Margulis proposed the hypothesis which became the endosymbiotic theory. She proposed that
mitochondria originated from separate organisms that entered cells by endosymbiosis long ago and formed a
symbiotic relationship with a eukaryotic cell.
6. Describe the structure of ribosomes and explain how the presence of ribosomes in various cellular organelles was
used to test Mereschkowsky’s theory.
Ribosomes are complexes of proteins and ribosomal RNA; they are the site of protein synthesis and can occur
in the cytoplasm, attached to the endoplasmic reticulum. They are also located in the chloroplast and the mitochondrion. Each ribosome consists of a large and small subunit.
The ribosome is ideal for this test because of the universal need for organisms to make proteins. It evolves
slowly over time, which allows scientists to relate the gradual accumulation of ribosomal changes to different
species along an evolutionary line. It is particularly advantageous to use ribosomal RNA because only the DNA
that codes for the RNA is needed for comparisons between two organisms. Additionally the organisms do not
need to be intact or alive for the harvesting of such DNA.
7. Explain how similarities in sequence alignments indicate evolutionary similarities.
The more similar the sequence alignments between two organisms, the more likely they have had the same
common ancestor.
111
related to chloroplasts?
The phylogeny makes it clear that the photosynthetic cyanobacteria contain the small ribosomal RNA sequence
most closely related to that found in chloroplasts.
related to mitochondrial ribosomes?
Evidence indicates that α proteobacteria contain small ribosomal RNA sequence most closely related to those found in mitochondrial ribosomes.
10. Why do scientists need to examine multiple data sets before determining evolutionary relatedness?
The statistical relevance of data grows as the size of the data sets increase. Also, different molecules provide different answers because scientists can look at different cellular compartments.
112
USING DATABASES TO OBTAIN REAL AMINO ACID SEQUENCE DATA TO CREATE CLADOGRAMS
From Bio-Rad’s Comparative Proteomics Kit I: Protein Profiler Module
In order to determine how closely related species are,
scientists often will study amino acid sequences of
essential proteins. Any difference in the amino acid
sequence is noted and a phylogenetic tree is constructed
based on the number of differences. More closely related species have fewer differences (i.e., they have more
amino acid sequence in common) than more distantly
related species.
There are many tools scientists can use to compare
amino acid sequences of muscle protein. One such tool
is the National Center for Biotechnology Information
protein databases (http://www.ncbi.nlm.nih.gov/). By
entering the amino acid sequence of a protein you are
interested in, the BLAST search tool compares that sequence to all others in its database. The data generated
provides enough information to construct cladograms.
The purpose of this activity is to use data obtained from
NCBI to construct an evolutionary tree based on the
amino acid sequences of the myosin heavy chain. In
this example we have input a 60 amino acid sequence
from myosin heavy chain of rainbow trout and then
pulled out matching sequences using BLAST, which
include chum salmon, zebra fish, common carp, and bluefin tuna, and then compared each of these sequences with each other.
You may either use the data provided below or have
your class go online and obtain their data directly by
performing BLAST searches. A quick guide to performing BLAST searches is given at the end of this activity.
The data below was obtained by entering a 60 amino
acid sequence from the heavy myosin chain of rainbow
trout. The database search tool returned all sequences
that were a close match. The results are formatted as
such:
gi|755771|emb|CAA88724.1 myosin heavy chain [Oncorhynchus mykiss]
Length=698
Score = 119 bits (299), Expect = 2e-26
Identities = 60/60 (100%), Positives = 60/60 (100%), Gaps = 0/60 (0%)
Query 1
VAKAKGNLEKMCRTLEDQLSELKTKNDENVRQVNDISGQRARLLTENGEFGRQLEEKEAL 60
VAKAKGNLEKMCRTLEDQLSELKTKNDENVRQVNDISGQRARLLTENGEFGRQLEEKEAL
Sbjct 1
The value for “identities” is the number of amino
acids exactly in common, the value for “positives”
is the number of amino acids that are similar to each
other (such as serine and threonine), and the value for
‘gaps’ is the number of amino acid positions that are
absent one of the sequences. “Query” is the original
trout sequence, “Sbjct” is the aligned sequence, and the
middle sequence shows the mismatches: a “+” indicates
a positive and a space indicates a mismatch that is not
a positive. There are resources on the NCBI website
to help you understand more about the information a
BLAST search generates.
The data on the following pages compares rainbow
trout to salmon, zebra fish, carp, and tuna, and then compares salmon to zebra fish, carp, and tuna, then zebra fish to carp and tuna, and finally carp to tuna.
Use the data provided to determine how many amino
acid differences exist between the organisms. Organize
your data in charts.
113
Rainbow trout compared to chum salmon
Chum salmon compared to common carp
gi|806515|dbj|BAA09069.1| myosin heavy chain [Cyprinus carpio]
gi|21623523|dbj|BAC00871.1| myosin heavy chain [Oncorhynchus keta]
Length=955
Length=1937
Query 1
AKAKGNLEKMCRTLEDQLSELKTKNDENVRQVNDISGQRARLLTENGEFGRQLEEKEAL 60
Query 1
VAKAK NLEKMCRTLEDQLSE+KTK+DENVRQ+ND++ QRARL TENGEF RQLEEKEAL
Sbjct 1240
Sbjct 259
VAKAKANLEKMCRTLEDQLSEIKTKSDENVRQLNDMNAQRARLQTENGEFSRQLEEKEAL 318
Chum salmon compared to zebra fish
Rainbow trout compared to zebra fish
gi|68360600|ref|XP_708916.1| PREDICTED: myosin, heavy polypeptide 1,
gi|68360600|ref|XP_708916.1| PREDICTED: myosin, heavy polypeptide 1,
skeletal muscle [Danio rerio]
skeletal muscle [Danio rerio]
Length=2505
Length=2505
Query 1
VAKAK NLEKMCRTLEDQLSE+K+KNDEN+RQ+ND+S QRARL TENGEFGRQLEEKEAL
Query 1
VAKAK NLEKMCRTLEDQLSE+K+KNDEN+RQ+ND+S QRARL TENGEFGRQLEEKEAL
Sbjct 1240
VAKAKANLEKMCRTLEDQLSEIKSKNDENLRQINDLSAQRARLQTENGEFGRQLEEKEAL 1299
Sbjct 1240
Chum salmon compared to bluefin tuna
Rainbow trout compared to common carp
gi|1339977|dbj|BAA12730.1| skeletal myosin heavy chain [Thunnus thynnus]
Length=786
Length=955
Query 1
VAKAK NLEKMCRTLEDQLSE+KTK+DENVRQ+ND++ QRARL TENGEF RQLEEKEAL
Query 1
VAK+KGNLEKMCRT+EDQLSELK KNDE+VRQ+ND++GQRARL TENGEF RQ+EEK+AL
Sbjct 259
Sbjct 88
VAKSKGNLEKMCRTIEDQLSELKAKNDEHVRQLNDLNGQRARLQTENGEFSRQIEEKDAL
147
Zebra fish compared to common carp
Rainbow trout compared to bluefin tuna
Length=955
Length=786
Query 1
VAK+KGNLEKMCRT+EDQLSELK KNDE+VRQ+ND++GQRARL TENGEF RQ+EEK+AL
Query 1
VAKAKANLEKMCRTLEDQLSEIK+K+DEN+RQ+ND++AQRARLQTENGEF RQLEEKEAL
Sbjct 88
Sbjct 259
114
147
Zebra fish compared to bluefin tuna
Common carp compared to bluefin tuna
Length=786
Length=786
Query 1
VAK+K NLEKMCRT+EDQLSE+K+KNDE++RQ+NDL+ QRARLQTENGEF RQ+EEK+AL
Query 1
VAK+K NLEKMCRT+EDQLSE+K K+DE+VRQLND+N QRARLQTENGEFSRQ+EEK+AL
Sbjct 88
Sbjct 88
147
147
Construct a table of your data containing the number of amino acid differences between each of the different fish.
Rainbow trout
Chum salmon
Zebra fish
Common carp
Bluefin tuna
Rainbow trout
Chum salmon
Zebra fish
Common carp
Bluefin tuna
Which two fish share the most amino acids in their myosin heavy chains based on your data?
Which two fish share the fewest amino acids?
Are there any fish that share more amino acids with each other than each does with the two fish in question one? If yes, which fish?
115
Construct a cladogram based on this data:
The myosin heavy chain of white croaker (Pennahia argentata) (BAB12571) has the following amino acid differences with the five fish above.
White croaker
Rainbow trout
4
Chum salmon
4
Zebra fish
11
Common carp
9
Bluefin tuna
11
Add this fish to your cladogram and explain why you placed it where you did.
116
Construct a table of your data containing the number of amino acid differences between each of the different fish.
Rainbow trout
Chum salmon
Zebra fish
Common carp
Bluefin tuna
Rainbow trout
0
Chum salmon
0
0
Zebra fish
8
8
0
Common carp
9
9
7
0
Bluefin tuna
11
11
13
11
0
Which two fish share the most amino acids in their myosin heavy chains based on your data?
Trout and salmon
Which two fish share the fewest amino acids?
Tuna and zebra fish
Are there any fish that share more amino acids with each other than each does with the two fish in question one? If yes, which fish?
Yes, carp and zebra fish
Construct a cladogram based on this data:
tuna
carp zebrafish
croaker
salmon
trout
117
KEY
Taxonomic data can be derived from many sources:
DNA sequences, protein sequences, morphology, and
paleontology. Classification of organisms derives from these sources. Inconsistencies in the phylogenetic trees
generated between molecular and taxonomic data emphasize why data from different sources is required to
generate phylogenetic trees and why there is still much
dispute in the field of phylogenetics on the correct placement of organisms within phylogenetic trees. The
amount of work required to process the small amount
of data provided here also emphasizes the need for
skilled bioinformaticists to process and analyze the vast
amount of data generated by genomic and proteomic
research.
Examine the taxonomic classification of the fishes below and construct a phylogenetic tree based on that
data. The large phylogenetic tree figure will be useful for this exercise.
Rainbow Trout (Oncorhynchus mykiss) Vertebrata;
Euteleostomi; Actinopterygii; Neopterygii; Teleostei;
Euteleostei; Protacanthopterygii; Salmoniformes; Salmonidae; Oncorhynchus.
Chum Salmon (Oncorhynchus keta) Vertebrata; Euteleostomi; Actinopterygii; Neopterygii; Teleostei; Euteleostei; Protacanthopterygii; Salmoniformes; Salmonidae;
Oncorhynchus.
Zebra Fish (Danio rerio) Vertebrata; Euteleostomi;
Actinopterygii; Neopterygii; Teleostei; Ostariophysi;
Cypriniformes; Cyprinidae; Danio.
Carp (Cyprinus carpio) Vertebrata; Euteleostomi;
Actinopterygii; Neopterygii; Teleostei; Ostariophysi;
Cypriniformes; Cyprinidae; Cyprinus.
Bluefin Tuna (Thunnus thynnus) Vertebrata; Euteleostomi; ctinopterygii; Neopterygii; Teleostei; Euteleostei;
Neoteleostei; Acanthomorpha; Acanthopterygii; Percomorpha; Perciformes; Scombroidei; Scombridae; Thunnus.
White Croaker (Pennahia argentata) Vertebrata; Euteleostomi; ctinopterygii; Neopterygii; Teleostei; Euteleostei;
Neoteleostei; canthomorpha; Acanthopterygii; Percomorpha; Perciformes; Percoidei; Sciaenidae; Pennahia.
Does the taxonomic classification support the molecular data?
Why do scientists need to examine multiple data sets
before determining evolutionary relatedness?
QUICK GUIDE TO BLAST SEARCHING
Please note, this is a quick guide to obtain a list of fish myosin sequences, there are many refinements you can make to your search and many different ways to use
BLAST searches.
Further information can be found on the NCBI website.
1) Go to http://www.ncbi.nlm.nih.gov/ and choose
BLAST.
2) Choose Protein-Protein BLAST.
3) Enter your myosin sequence into the search box.
Rainbow Trout Myosin Heavy Chain Protein Sequence
(CAA88724):
4) Leave the other fields as found and hit the BLAST button.
5) A new window should pop up. Hit the Format button.
118
6) After a short wait the BLAST results window will
come up and may well be hundreds of pages long
— don’t worry. There should be a long list of sequences
that produced significant alignments. Although the search may pick up hundreds of sequences, they are in
order of homology, so the ones you are interested in
should be in the first 25 or so.
7) Further down the BLAST results page, after the list
of sequences, each sequence will be aligned with the
original trout sequence (as shown in the example) so
that you can see how the two compare.
8) To compare your second fish, say bluefin tuna, with the other fish, you must perform a second BLAST search with the tuna sequence to obtain the protein
alignments of tuna with the other fish. Alternatively, you can align 5 protein sequences yourself from your
original search in a word processing document (use
Courier font, this aligns sequences because all the letters are the same width) and have your students manually compare them.
BLAST-SEARCHING QUESTIONS
Construct a simple phylogenetic tree based on the taxonomic data.
Does the taxonomic data support the molecular data? Please explain your answer.
Why do scientists need to examine multiple data sets before determining evolutionary relatedness?
119
BLAST-SEARCHING QUESTIONS
Construct a simple phylogenetic tree based on the taxonomic data (the large phylogenetic tree figure will be useful here).
carp
zebra fish
tuna
croaker
salmon
Perciformes
Acanthopterygii
trout
Salmoniformes
Protacanthoptrygii
Cypriniformes
Ostariphysi
Euteleostei
Teleosti
Does the taxonomic data support the molecular data? Please explain your answer.
The trees do not entirely match. Both trees show a close relationship between salmon and trout and zebra fish and carp. However, tuna is in the same sub-phylum (Euteleostei) as salmon and trout, yet this does not concur
with the molecular data and croaker is in the same order as tuna (Perciformes) and yet the amino acid sequence
of croaker’s myosin is much closer to salmon than tuna.
Why do scientists need to examine multiple data sets before determining evolutionary relatedness?
The statistical relevance of data grows as the size of the data set increases. The 60 amino acid segment of myosin
heavy chain constitutes just 3% of the myosin heavy chain molecule, which is around 1,900 amino acids long.
Performing a BLAST search with a larger portion of the molecule generates a cladogram with different relationships, demonstrating that the 60 amino acid piece is not large enough to provide a full picture of relatedness.
However, even if the full-length myosin were compared, that is just a single protein out of the thousands generated by the organism. The data would be much stronger if the sequences of multiple proteins were compared, and
stronger still if molecular data were used with other types of classification data such as morphological data.
120
KEY
TREE ANALYSIS
Human
2
Fly
Yeast (Fungi)
4
Chlorella (Green algae)
1
Maize (corn)
Tomato
Porphyra (Red algae)
3
Rickettsia
Nostoc
Thermococcus
1. Is the tomato more closely related to the red algae (Porphyra) or to maiza (corn)?
2. Which node represents the ancestor of the red and green algae?
3. Which node represents the ancestor of all life?
4. Which node represents the ancestor of eukaryotes?
5. Which node represents the ancestor of animals and fungi?
6. Did #1 live before #4 or vice versa?
7. Did # 4 live before #3 or vice versa?
8. Which organism shown on the tree is most closely related to the human?
121
9. Mereschkowsky thought that different bacteria gave rise to different plant lineages. Which of the trees below is
most consistent with Mereschkowsky’s hypothesis?
10. How do you think Mereschkowsky’s hypothesis can be tested?
11. Briefly summarize the three main differences between the three phylogenetic trees shown below.
1
Green alga cp
2
Green plant cp
Plant cp
Green alga cp
Red alga cp
Bacterium A
Bacterium B
Bacterium B
Bacterium A
Bacterium C
Red alga cp
Bacterium C
3
Green plant cp
Green alga cp
Red alga cp
Bacterium A
Bacterium B
Bacterium C
122
TREE ANALYSIS
KEY
1. Is the tomato more closely related to the red algae (Porphyra) or to maiza (corn)?
The tomato is most closely related to corn
2. Which node represents the ancestor of the red and green algae?
#1
3. Which node represents the ancestor of all life?
#3
4. Which node represents the ancestor of eukaryotes?
#4
5. Which node represents the ancestor of animals and fungi?
#2
6. Did #1 live before #4 or vice versa?
#4 lived before #1
7. Did # 4 live before #3 or vice versa?
#3 lived before #4
8. Which organism shown on the tree is most closely related to the human?
Fly
9. Mereschkowsky thought that different bacteria gave rise to different plant lineages. Which of the trees below is
most consistent with Mereschkowsky’s hypothesis?
Tree #1
10. How do you think Mereschkowsky’s hypothesis can be tested?
Mereschkowsky’s hypothesis can be tested using alignments of DNA that encodes very conserved genes from
eukaryotes, bacteria, and arachaea, as well as DNA from the chloroplast.
11. Briefly summarize the three main differences between the three phylogenetic trees shown below.
Tree # 1
Different bacteria gave rise to chloroplasts in different lineages of plants and algae.
Tree #2
One bacterium (A) gave rise to all chloroplasts that are found in plants and algae.
Tree #3
Chloroplasts are not derived from bacteria at all.
123
The Power Within Quiz Game Questions
Parts of a Cell
— Structure
and Function
Organism
Classification
Relationships
between
Organisms
Name the three domains
for the classification of
organisms.
My theory of “natural
selection” was an explanation of how evolution
occurs. Who am I?
Name the branch of science
that allows biologists to
compare gene sequences
of different organisms
using the computer and
statistical analysis to
analyze the data.
True or False: In a parasitic relationship, both
organisms benefit.
What acts as the control
center of the cell?
What are the six
kingdoms of organisms
as they are currently
identified?
I was the first to argue for
endosymbiotic origin of the
nucleus and the chloroplast
because organelles such
as the chloroplast could
reproduce themselves even
when separated from the
nucleus. Who am I?
A ______________
represents the evolutionary relationship between
organisms.
Remoras, or “sharksuckers,”
attach to sharks and feed
on food that the shark
leaves behind. Sharks are
not harmed but do not
experience any advantage.
Is this an example of
mutualism, commensalism,
or parasitism?
Which part of the cell
generates most of the
cell’s supply of energy?
Why are the organisms belonging to the
Kingdom Protista so hard
to classify?
My binomial system of
classification made me
the Father of Taxonomy.
Who am I and what are
the 2 names given for
every organism?
Similarities in two
organisms’ genes indicate
_____________ .
In the tropics, orchids called
epiphytes can grow on
top of other plants. The
orchids do this to get more
sun. The orchid, however,
does not prey on its host
plant. What kind of symbiotic relationship is this?
Chloroplasts in plant
cells capture light energy
through a process called
__________ .
What characteristics
differentiate the kingdom
Fungi from the kingdom
Plantae?
When I noticed the nonnuclear DNA contained in
the mitochondria of the
cells was similar to the
bacterium that causes
typhus, I suggested the
theory of symbiogenesis.
Who am I and what does
symbiogenesis theory
suggest about the variation of organisms?
The point where an
organism branches
from the root is called a
___________ .
Give an example of a
mutualistic relationship.
Explain why this relationship between two organisms is better than if the
two organisms were to
live independently of one
another.
What are the 4 locations
where ribosomes may be
found within the cell?
Explain the reasoning
scientists have used
in separating Bacteria
from Archaea to develop
the six kingdom, three
domain system of classification.
I redrew the tree of life
based on three domains
using evidence that certain
species are adapted to
extree environments such
as hydrothermal vents, and
salt ponds. Name me and
the three domains.
To better understand how
the first symbiont got
inside a host cell, it would
be beneficial to know
which species of bacteria
came together to make
the first type of these cells,
________ , which have
a membrane-enclosed
nucleus and other membrane-enclosed organelles.
A scientist discovers, through genetic
sequencing, that the
mitochondrial DNA of a
fruit fly is more similar to
the DNA of a bacterial cell
than it is to the DNA of
the fly’s cell nucleus. Use
the endosymbiont theory
and mutualism to explain
this finding.
400
600
800
124
Evolutionary
History
What is the structural and
functional unit of all life?
200
1000
Who Am I?
Scientists and
their Theories
KEY
The Power Within Quiz Game Answers
Parts of a
Cell —
Structure
and
Function
Organism
Classification
Who Am I?
Scientists
and their
Theories
Evolutionary
History
Cell
Bacteria, Archaea, Eukarya
Charles Darwin
Bioinformatics
False. In a parasitic relationship, one
organism benefits and one is harmed.
In a mutualistic relationship, both organisms benefit from one another.
Nucleus
Eubacteria, Archaebacteria, Protista, Fungi, Plantae, Animalia
Constantin Mereschkowsky
Cladogram
The relationship between remoras and
sharks is one of commensalism, because
one organism benefits while the other
neither benefits nor is harmed.
Mitochondria
Some share characteristics with
plants, such as being photosynthesizers while others share
characteristics with animals, such
as being heterotrophic.
Carl Linnaeus
— Genus and
species.
Similar origins
The relationship between the orchid and
the other plant is a commensalist one.
The tropical orchid benefits, but the orchid
does not positively or negatively affect the
host plant.
Photosynthesis
In the kingdom Fungi, most organisms
feed on dead or decaying organic
matter. They also secrete digestive
enzymes into their food source. The
organisms in the kingdom Plantae
are photosynthetic autotrophs, which
mean they can manufacture their own
food by the energy from sun.
Lynn Margulis
— Symbiogenesis says variation
comes from fusion of genomes
in symbioses followed by natural
selection.
Node
Answers will vary. In mutualism, each
organism benefits from a function that
the other organism can provide. For example, bees get their food from plants,
but they also help to pollinate plants
and facilitate plant reproduction. Without this relationship, bees would lack
a food supply, and plants would not
experience the number or frequency of
genetic combinations made possible by
the bees’ cross-fertilization.
Cytoplasm, Endoplasmic reticulum,
Chloroplast,
Mitochondria
Originally, scientists grouped all bacteria into the kingdom Monera, because
these organisms did not contain a nucleus and are referred to as Prokaryotic.
All the other kingdoms, Protist, Fungi,
Plant, and Animal do contain a nucleus,
and are called eukaryotic. However, as
evidence about microorganisms has
continued to be discovered, scientists
realized that the Monera were very
different. As a result, the kingdom
Monera was further divided into two
kingdoms, Eubacteria and Archaebacteria. Eubacteria belong to the domain,
Bacteria, while Archaebacteria belong
to the domain, Archaea, and one of the
major distinctions between the groups
is the structure of the cell wall.
Carl Woese — The
three domains are
Eukarya, Bacteria,
and Archaea.
Eukaryotic cell
According to the endosymbiont
theory, free-living bacteria entered
into a mutualistic relationship with
a host cell long ago. The engulfed
bacteria provided energy for the
host cell, and the host cell provided
the bacteria with protection and
food. Over time, the bacteria lost
the ability to live independently.
These bacteria were the ancestors of
today’s mitochondria. Since bacteria
and mitochondria are evolutionarily
related, the fly’s mitochondria share
more genetic material with bacteria
than they do with the nucleus of the
fruit fly cell.
200
400
600
800
1000
Relationships
between Organisms
125
126
THE POWER WITHIN IMPLEMENTATION PLAN — ADDITIONAL ACTIVITIES & RESOURCES
Activity
Estimated Time
Materials/Equipment
A Fishy Family Tree
15 minutes
Copies of the activity
Symbiotic Connections
45 minutes
Copies of the activity
SAR 11 clade dominates ocean bacterioplankton communities
45 minutes
Computer access to Nature article
Copies of the discussion questions
Additional Resources
AAAS, (2006). Cells 1: Make a model cell. Retrieved November 12, 2007, from Science NetLinks Web site: http://www.sciencenetlinks.com/lessons.
cfm?DocID=101
The Futures Channel, (2007). The futures channel. Retrieved November 12, 2007, from The Futures Channel Web site: http://www.thefutureschannel.
com/index.php
Morris, R.M., Rappe, M.S., Connon, S.A., Vergin, K.L., Siebold, W.A., Carlson, C.A., & Giovannoni, S.J. (2002). SAR11 clade dominates ocean surface
bacterioplankton communities. Nature. 420, 806-810. Retrieved November 12, 2007 from Nature Web site: http://www.nature.com/nature/journal/
v420/n6917/abs/nature01240.html
WGBH Educational Foundation, (2007). Lesson plan: Molecular evidence for evolutionary relationships. Retrieved November 12, 2007, from Teachers’
domain Web site: http://www.teachersdomain.org/resources/tdc02/sci/life/gen/lp_cytoc/index.html
WGBH Educational Foundation, (2007). Teachers’ domain. Retrieved November 12, 2007, from Teachers’ domain Web site: http://www.teachersdomain.org
Whitman, W.B., Coleman, D.C., & Wiebe, W.J. (1998). Prokaryotes: The unseen majority. PNAS. 95, 6578-6583. Retrieved November 12, 2007, from
PNAS Web site: http://www.pnas.org/cgi/content/abstract/95/12/6578
127
A FISHY FAMILY TREE
We know that catfish, tuna, and swordfish are all fish and that all three share an ancestor. But which two of these fish share a more recent ancestor? In other words, which two of these fish are most closely related?
To find out, examine the illustrations of these three fish and of their scales. Then fill out the data chart below. Kind of Fish
Tail Fin Shape
(fan shaped vs. lobed)
Presence of Barbels
(“whiskers” present
vs. absent)
Scale Type
(cycloid, ctenoid, etc.)
Catfish
Tuna
Swordfish
1. Which two fish do you think are most closely related?
2. Please explain your reasoning.
3. Label the evolutionary tree below to show your hypothesis.
(Write the name of one kind of fish in each of the three boxes.)
128
FISH WITH SCALES
Channel catfish
Ictalurus albidus
Scaleless
Bluefin tuna
Thunnus thynnus
Ctenoid scales
Have a toothed edge
Swordfish
Xiphias gladius
Ctenoid scales
Have a toothed edge
129
A FISHY FAMILY TREE
We know that catfish, tuna, and swordfish are all fish and that all three share an ancestor. But which two of these fish share a more recent ancestor? In other words, which two of these fish are most closely related?
To find out, examine the illustrations of these three fish and of their scales. Then fill out the data chart below. Kind of Fish
Tail Fin Shape
(fan shaped vs. lobed)
Presence of Barbels
(“whiskers” present
vs. absent)
Scale Type
(cycloid, ctenoid, etc.)
Catfish
Lobed
Present
Scaleless
Tuna
Fan shaped
Absent
Ctenoid
Swordfish
Fan shaped
Absent
Ctenoid
1. Which two fish do you think are most closely related?
Tuna and swordfish.
2. Please explain your reasoning.
Similar traits.
3. Label the evolutionary tree below to show your hypothesis.
(Write the name of one kind of fish in each of the three boxes.)
Catfish
130
Tuna
Swordfish
KEY
SYMBIOTIC CONCENTRATION
Instructions for the Teacher
OBJECTIVES
Students will gain understanding of symbiosis, parasitism, mutualism and commensalism AND be able to explain/
recognize symbiotic relationships that may exist within the intricate web of interdependence in which all plants and
animals live.
MATERIALS NEEDED (for a group of 4 students)
•
•
•
•
Copies of cards
Master Animal List
Research materials
Additional Information for the Teacher
BACKGROUND INFORMATION
When two or more organisms (whether from same or different species) live in close physical contact with one another, a symbiotic relationship exists. In this type of relationship, at least one of the organisms will directly benefit from the other organism. There are three main types of symbiotic relationships:
1. One organism that gains benefit (e.g., food or shelter) from the other organism with causing harm to that organism or providing benefit to that organism is known as commensalism.
2. Two organisms (from different species) benefit and are dependent upon one another is called mutualism.
3. One organism in the relationship benefits at the expense of another organism (whether same or different species) is parasitism. The organism that benefits is the “parasite” while the one harmed is the “host.”
TEACHER INSTRUCTIONS
1. Make copies of several decks of cards (master copies provided) with each deck containing 15 card pairs illustrating symbiotic relationships. There should also be one “NO MATCH” card totaling 31 cards for each deck.
2. Give each student one card (not the “NO MATCH” card). Each student is to find his or her “match” by using the “Master Animal List.”
3. Each pair of matches should research and find out why they are a match answering the following questions:
• Why do we live together?
• What advantages do we give to one another?
• What disadvantages do we give to one another?
• What would happen if one of us were not here in this relationship?
4. Each match of students is to give a short report to the class explaining about their relationship.
5. Divide the class into groups of 4-6 students depending on the class size. Give each group a deck of cards. Give
all students instructions for the game.
6. To end the game, begin a discussion of the definitions for commensalism, mutualism, and parasitism.
7. Have students (each group) decide to which classification each pair belongs. © DESTINY • UNC-Chapel Hill • CB #7448, MPSC Annex • Chapel Hill, NC 27599 • moreheadplanetarium.org/go/destiny
131
NAME__________________________________
SYMBIOTIC CONCENTRATION
1. Deal out all cards in the deck.
2. Play starts to the left of the dealer and will move in a clockwise direction.
3. Each player draws one card from the player to his or her left.
4. After the player draws a card, he or she may lay down all cards in his or her hand which form symbiotic pairs.
5. When a player has NO cards remaining, the game is over.
6. The player with the largest number of pairs at the end of the game is the winner.
7. Only one player will be left holding the “NO MATCH” card at the end of the game.
FINAL EVALUATION
1. Define the following terms: symbiosis, commensalism, mutualism, parasitism.
2. Give at least 2 examples of each symbiotic relationship used in this activity:
• Commensalism
• Mutualism
• Parasitism
3. Explain how competition and “survival of the fittest” fits into this activity.
132
OSTRICH
WARBLER
YUCCA MOTH
GAZELLE
CUCKOO
YUCCA
WHALE
SPRUCE
RHINOCEROS
133
134
BARNACLE
MISTLETOE
OXPECKER
SHARK
HONEYGUIDE BIRD
ANTS
REMORA
BADGER
SILVERFISH
MARIBOU STORK
HERMIT CRAB
DEER
BEE
SHELL
TICK
FLEA
COWBIRD
BASS
135
MOUSE
BISON
WRASSE FISH
NO MATCH
136
SYMBIOTIC CONCENTRATION: ADDITIONAL INFORMATION FOR THE TEACHER
ORGANISMS
RELATIONSHIP
KEY
COMMENTS
Barnacle/
whale
Commensalism
Barnacles create home sites by attaching themselves to whales and neither
harm nor benefit the whale.
Remora/
shark
Commensalism
Remoras attach themselves to a shark’s body and travel with the shark
to feed on the left over food scraps from the shark’s meals. The shark is
neither harmed nor benefited.
Bee/
marabou
stork
Commensalism
The stork uses its saw-like bill to cut up the dead animal it eats and
therefore, will provide a dead animal carcass for the bees as food and for
egg laying.
Silverfish/
army ants
Commensalism
Silverfish live and hunt with army ants and end up sharing their prey. The
silverfish benefit; while the ants are neither harmed nor benefitted.
Hermit
crab/
snail shell
Commensalism
Hermit crabs live in shells made and eventually abandoned by the snail.
The snail is neither harmed nor benefited.
Jan Roletto/NOAA/Department of Commerce
David Burdick/NOAA/Department of Commerce
Stork photo by Steven G. Johnson
Silverfish photo by Sebastian Stabinger
Army ants photo by Mehmet Karatay
NOAA/Department of Commerce
137
ORGANISMS
RELATIONSHIP
COMMENTS
Cowbird/
buffalo
Commensalism
As buffaloes walk through grass, insects will become active, and therefore
can be seen and eaten by the cowbird. The buffalo is neither harmed nor
benefited.
Yucca
plant/
yucca
moth
Mutualism
Yucca flowers are pollinated by yucca moths. The moths will lay their eggs
in the flowers where the larvae will hatch and eat some of the developing
seeds. Both organisms will benefit.
Honeyguide bird/
honey
badger
Mutualism
Honey guide birds alert and direct the badger to bee hives where the
badger will expose the hives and feed on the honey first. The honey guide
bird will eat second. Both organisms will benefit.
U.S. Fish and Wildlife Service
Cowbird photo by Lee Karney
Buffalo photo by Jesse Achtenberg
Yucca plant photo by J.S. Peterson/
USDA-NRCS PLANTS Database
Yucca moth photo by Bill May | USDA Forest Service
Ostrich/
gazelle
Mutualism
Oxpecker/
rhinoceros
Mutualism
Ostriches and gazelles feed next to each other, watch out for predators,
and then will alert the other of danger. Their difference in visual abilities
provides one another with threats the other animal would not otherwise be
able to see. Both animals will benefit.
Ostrich photo by Beth Jackson/
U.S. Fish & Wildlife Service
Oxpeckers feed on the ticks found on the rhinoceros. Both organisms will
benefit.
Oxpecker photo by Lee R. Berger
Rhino photo by Gary M. Stolz/
138
ORGANISMS
RELATIONSHIP
COMMENTS
Wrasse
fish/black
sea bass
Mutualism
Wrasse fish feed on the parasites found on the body of the black sea bass.
Both organisms will benefit.
Mistletoe/
spruce tree
Parasitism
Mistletoe extracts water and nutrients from the spruce tree. The mistletoe
(parasite) will benefit and the spruce (host) and will be harmed.
Cuckoo/
warbler
Parasitism
A cuckoo may lay its eggs in a warbler’s nest. Later in development, the
cuckoo’s young will displace the warbler’s young and will be eventually
raised by the warbler.
Mouse/
flea
Parasitism
A flea feeds on a mouse’s blood. The flea benefits while the mouse is
harmed.
Deer/tick
Parasitism
A tick feeds on the blood of the deer. The tick benefits while the deer is
harmed.
Wrasse fish photo by Tibor Marcinek
Black sea bass photo from NOAA/
Department of Commerce
Photos by R.A. Howard/
USDA-NRCS PLANTS Database
Warbler photo by Ivan Petrov
Mouse photo by Daniela Baack
Tick photo from the CDC
Deer photo by Steve Hillebrand/
Tick photo by Scott Bauer | USDA
139
READING GUIDE:
SAR11 CLADE DOMINATES OCEAN SURFACE BACTERIOPLANKTON COMMUNITIES
http://www.nature.com/nature/journal/v420/n6917/abs/nature01240.html
http://www.pnas.org/cgi/content/abstract/95/12/6578
1. To what bacterial clade does the SAR11 group belong?
2. Other than their presence in seawater, what is known about these organisms?
3. On an average what percentage does the SAR11 clade account for in the cells present in surface waters?
4. Do the results of this study rule out the possibility that other microorganisms may grow more rapidly than SAR11
but may be less abundant because of grazing, viral predation or other sources of removal?
5. What methods were used in this study?
140
READING GUIDE:
SAR11 CLADE DOMINATES OCEAN SURFACE BACTERIOPLANKTON COMMUNITIES
KEY
http://www.nature.com/nature/journal/v420/n6917/abs/nature01240.html
http://www.pnas.org/cgi/content/abstract/95/12/6578
1. To what bacterial clade does the SAR11 group belong?
SAR11 belong to the α-proteobacterial clade
2. Other than their presence in seawater, what is known about these organisms?
Little is known about these organisms
3. On an average what percentage does the SAR11 clade account for in the cells present in surface waters?
It accounts for 33% of cells present in surface waters.
4. Do the results of this study rule out the possibility that other microorganisms may grow more rapidly than SAR11
but may be less abundant because of grazing, viral predation or other sources of removal?
No.
5. What methods were used in this study?
Sample collection
Probe analysis
Fish- hybridization reaction
Florescent microscopy
Bulk nucleic acid hybridization
141
142
Science
Social Studies
X
X
X
Picture This handout
Darwin, the Writer
X
X
X
Darwin, the Writer handout
Additional Activities for
English Classrooms
X
X
X
Additional Activities for English Classrooms
A Discovery-Based Approach
to Understanding Clinical
Trials
X
X
X
Teacher’s guide, student instructions, glossary
Picture This: A Writing and
Listening Exercise for Science
and Non-Science Classrooms
X
Math
English
X
Activity
Health
Arts
THE POWER WITHIN IMPLEMENTATION PLAN — INTERDISCIPLINARY BRIDGES
Provided materials
143
PICTURE THIS
A Writing and Listening Exercise for
Science and Non-Science Classrooms
Subjects: English, Science, Social Studies
B
iological evolution — or, indeed, any complicated or controversial topic—can present an opportunity for teachers to help students develop
skills as critical thinkers, thoughtful writers, and good
listeners. Perhaps this last set of skills is the most vital
of the three — as throughout their lives students will
benefit from an ability to listen respectfully and mindfully when other people express views and ideas that
may seem to differ from their own.
“Picture This” serves several functions. This activity
calls upon students to stretch linguistically and imaginatively — to use a range of vocabulary that typical
class discussion might not require of them, and to make
creative connections between what they already feel,
think, and know and what they are about to learn. As
its name suggests, “Picture This” enables students who
are more visually oriented to relate images to ideas.
And, like other activities recommended by DESTINY,
it encourages active participation by all the students in
the classroom.
We recommend this activity as a starting point for
your evolution unit in a biology class. If you are a
non-science teacher, you may find “Picture This” to be useful at the beginning of a unit involving an evolution-themed literary work (such as Inherit the Wind,
The Time Machine, or Cosmicomics) or argumentative
communication (such as an editorial, speech, or letter).
However, “Picture This” can be adapted for a number
of classroom uses. Though biological evolution is the
topic described here, this writing and listening exercise
will work well to engage students in many other topics
and assignments.
RESOURCES
• A large selection of photographs you have cut from
magazines or catalogues. Almost any weekly or monthly magazine (Time, People, Sports Illustrated, Smithsonian, etc.) and many catalogues (particularly those that
are related to travel or gardening) will yield images that
are useful for “Picture This.”
144
So that your students will have a number of images
from which to choose, provide two or three photographs
per student (e.g., fifty or sixty photographs for a class of twenty-five students). The photographs should offer a range of images: landscapes, cityscapes, animals, machinery, objects, abstractions, and ordinary people (not
celebrities or other people your students will recognize)
in interesting situations or against interesting backdrops. These should be images your students can invest
with their own thoughts and feelings.
• “Picture This” handout: enough copies so that each
student has one to write on. (If you are unable to make
copies of the “Picture This” handout, you can write
the questions on your blackboard or on a transparency.
Students can write their answers and glue their pictures
on loose sheets of blank paper or in their journals.)
• Glue sticks: five or six for the class to share, so that your students can affix the photographs they select to their “Picture This” handouts.
ACTIVITIES/PROCEDURES
WHAT YOU DO
Display all the photographs on a large surface (a counter, several empty student desks, or even the floor will work). Invite your students to come forward and survey
the photographs. Ask each student to select the photograph that best illustrates or symbolizes her feelings or
ideas about evolution. Give your students time to look
at the pictures and to give some thought to their selection process. Each student selects one photograph.
Variation: Group Work. Divide your class into groups
of five or six students. Give each group ten or twelve photographs. Ask the group to choose a photograph that
represents the group’s views. Have each group report to
the class on its answers to the “Picture This” handout.
WHAT YOUR STUDENTS DO
This activity is divided into Writing and Listening
phases that enable all students to participate equally and
simultaneously.
Writing (10-15 minutes). Give your students the
following instructions: “From the photographs on
display, select the one that best illustrates or symbolizes
your feelings or ideas about evolution. Look at the
pictures and give some thought to the selection
process. After selecting a photograph, return to your
desk and write down your answers to the following
questions (listed on the ‘Picture This’ handout). Use a
glue stick to attach the photograph to your handout.”
Questions from “Picture This” Handout
1. Every picture deserves a title. Select a title, or a caption, for the picture you’ve chosen.
2. There were many pictures from which to choose.
Why did this picture appeal to you? (Please write at
least two sentences.)
3. How does the picture you’ve chosen reflect or symbolize your thoughts about evolution? (Please write at
least three sentences.)
Listening. Now comes the opportunity for everyone’s
voice to be heard—and for everyone to listen to their
classmates’ ideas and opinions. Move around the class,
asking every student to briefly describe the picture they selected and to read one of their answers aloud — any
answer they feel most comfortable reading. Acknowledge each student positively — with a smile, or a
“Thank you,” or “Good work.” A simple, friendly, and
non-judgmental acknowledgement of each student’s effort to express herself is what you will aim for.
Remember that this is a chance for your students to
articulate ideas that may be rather difficult to express. Most students will be at the beginning of the process of
learning about this complicated scientific concept;; they are engaging the topic and readying themselves to learn
about it. At the end, you may need to gently correct any
of your students’ misunderstandings about the science
and its history that were revealed during the exercise;
but do this in a general way, without pinpointing a particular student’s error. At the very end, praise all your
students for their good listening.
145
PICTURE THIS: EVOLUTION
Paste or tape your picture here.
If your picture is large, you can
place it on the back of this paper.
1. Every picture deserves a title. Select a title, or a caption, for the picture you’ve
chosen.
2. There were many pictures from which to choose. Why did this picture appeal to
you? (Please write at least two sentences.)
3. How does the picture you’ve chosen reflect or symbolize your thoughts about evolution? (Please write at least three sentences.)
146
Darwin, the Writer
W
e cannot overestimate the importance of
the written word to the development of the
science of evolution and to its dissemination
among a wide public of scientists and non-scientists
that continues to grow. The first edition — 1,250 copies — of On the Origin of Species sold out entirely in 1859.
New editions quickly followed. In the years since, the
rhetorical style in which Darwin made his groundbreaking arguments has been an important reason for
this book’s continuing interest and influence.
That Darwin’s work as a writer is entwined with his
work as a scientist is important to know. The long list
of his works published in his lifetime, beginning with
his account of the five-year voyage that took him to the Galapagos Islands off South America (Voyage of the Beagle, 1839), attests to his productivity as a writer.
The nature of many of his publications suggests his
wish to convey news
of his findings and to describe his life as a
scientist in language
that could be understood
and appreciated by both
expert and lay audiences.
A letter to his publisher
indicates the breadth of
the audience Darwin envisioned for On the Origin
of Species. He wrote: “My
volume cannot be mere
light reading, & some parts
must be dry & some rather
abstruse; yet as far I can
judge perhaps very falsely, it will be interesting to all
(& they are many) who care for the curious problem of
the origin of all animate forms” (Darwin, 1859, April 2).
While some parts may indeed be heavy going, Darwin’s
book as a whole is written to engage and inform a fairly
wide audience (who might be interested and knowledgeable, but not necessarily expert in the field). On the Origin
of Species was, in some senses, in its time, a work of
popular science not unlike those we may find at Amazon.
com or frequently on best-seller lists today.
In his autobiography, Darwin describes in some detail
the creation and reception of a number of his publications, including his magnum opus:
In September 1858 I set to work by the strong advice of
[Charles] Lyell and [Joseph Dalton] Hooker to prepare
a volume on the transmutation of species, but was often
interrupted by ill-health. [...] It cost me thirteen months
and ten days’ hard labour. It was published under the title of the Origin of Species, in November 1859. Though
considerably added to and corrected in the later editions, it has remained substantially the same book.
It is no doubt the chief work of my life. It was from the
first highly successful. The first small edition of 1250 copies was sold on the day of publication, and a second
edition of 3000 copies soon afterwards. Sixteen thousand copies have now (1876) been sold in England and
considering how stiff a book it is, this is a large sale. It
has been translated into almost every European tongue,
even into such languages as Spanish, Bohemian,
Polish, and Russian. […] Even
an essay in Hebrew has appeared
on it, showing that the theory is
contained in the Old Testament!
The reviews were very numerous;
for a time I collected all that appeared on the Origin and on my
related books, and these amount
(excluding newspaper reviews)
to 265;; but after a time I gave up the attempt in despair. (Darwin, 1993, pp. 122-123)
Though Darwin was modest in
his assessment of his facility as a writer, he nonetheless cared to do his best. It is
clear that he worked hard to be a good writer. English
teachers in particular will appreciate Darwin’s methods:
his use of outlines at the “pre-writing” stage, his quick
roughing in of early drafts, and his subsequent work to
pare, correct, and polish.
I have as much difficulty as ever in expressing myself clearly and concisely;; and this difficulty has caused me a very great loss of time; but it has had the compensating advantage of forcing me to think long and intently
about every sentence, and thus I have been often led to
see errors in reasoning and in my own observations or
those of others.
There seems to be a sort of fatality in my mind leading
147
me to put at first my statement and proposition in a wrong or awkward form. Formerly I used to think about
my sentences before writing them down; but for several
years I have found that it saves time to scribble in a vile
hand whole pages as quickly as I possibly can, contracting half the words; and then correct deliberately.
Sentences thus scribbled down are often better ones
than I could have written deliberately.
The result of Darwin’s effort is prose that is typically
lucid and sometimes beautiful. In A Short History of
English Literature, Ifor Evans writes, “Charles Darwin
would have disclaimed any right to be considered as a
literary artist, yet the clarity of his style, and the very
quietness with which he presents his profound conclusions, give to much of his work the qualities of art”
(Evans, 1940, 1961, p. 220).
Having said this much about my manner of writing, I
will add that with my larger books I spend a good deal
of time over the general arrangement of the matter. I
first make the rudest outline in two or three pages, and then a larger one in several pages, a few words or one
word standing for a whole discussion or series of facts.
Each of these headings is again enlarged and often
transformed before I begin to write in extenso [“at full
length”]. (Darwin, 1993, p. 137)
Because Darwin took pains with his writing, even the
paragraph that ends the first edition of On the Origin of
Species — a passage considered by many a reader to be
both graceful and effective — did not escape modification. Darwin continued to tweak the text in subsequent
editions: “an entangled bank” thus became “a tangled
bank,” for instance, and “external” was deleted before
“conditions of life.” He also made the significant addition of the phrase “by the Creator” in the second edition.
TEXTS OF THE LAST PARAGRAPHS IN THE FIRST AND SECOND EDITIONS
First edition (published on November 24th, 1859)
Second edition (published on January 7th, 1860)
It is interesting to contemplate an entangled bank,
clothed with many plants of many kinds, with birds
singing on the bushes, with various insects flitting about, and with worms crawling through the damp
earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent
upon each other in so complex a manner, have all
been produced by laws acting around us. These laws,
taken in the largest sense, being Growth with Reproduction; Inheritance, which is almost implied by
reproduction; Variability from the indirect and direct
action of the external conditions of life, and from use
and disuse; a Ratio of Increase so high as to lead to
a Struggle for Life, and as a consequence to Natural
Selection, entailing Divergence of Character and
the Extinction of less-improved forms. Thus, from
the war of nature, from famine and death, the most
exalted object which we are capable of conceiving,
namely, the production of the higher animals, directly
follows. There is grandeur in this view of life, with its
several powers, having been originally breathed into
a few forms or into one; and that, whilst this planet
has gone cycling on according to the fixed laws of gravity, from so simple a beginning endless forms
most beautiful and most wonderful have been, and
are being, evolved.
follows. There is grandeur in this view of life, with
its several powers, having been originally breathed
by the Creator into a few forms or into one; and that,
whilst this planet has gone cycling on according to
the fixed laws of gravity, from so simple a beginning endless forms most beautiful and most wonderful
have been, and are being, evolved.
148
DISCUSSION QUESTIONS, GUIDED READING, AND ACTIVITIES
FOR CHARLES DARWIN’S ON THE ORIGIN OF SPECIES
Subjects: English, Science, Social Studies
OVERVIEW
Teachers want their students to develop the patience
and focus needed to carry out tasks that take place in
more than one class period, such as following all the
steps in a lengthy experimental process or attentively
reading a whole novel. But asking students to pay very
close attention while reading a short piece of writing—a
poem, a newspaper article, or a passage from a longer
work—can in a manageable time frame help them to
develop their analytical skills, their understanding of
how language works, and their appreciation for what
makes writing compelling and useful. If the passage
they are asked to read with close attention is written
well, is rich in ideas, and has historical or literary significance, so much the better! Depending upon the teacher’s guiding questions, the
well-known last paragraph of Charles Darwin’s On the
Origin of Species can provide a focus for analytical
reading in a biology class or an English class.
RESOURCES
• Handout — The last paragraph of Charles Darwin’s
On the Origin of Species
• Optional — On the Origin of Species by Charles
Darwin
CLASS DISCUSSION
Listed below are a number of questions that you can use
to guide your students’ reading and analysis of this passage. Some questions may be more suitable for use in
your lesson plan than others. Choose the questions that
will meet the needs of your class.
• If you are a biology teacher, you may wish to ask
questions that will encourage your students to draw on
knowledge they have gained in your class or in their
previous science courses. While introducing them to
a significant work in the scientific literature, such a discussion will also help your students see the centrality
of biological evolution to any understanding of modern
biology.
• If you are an English teacher, you may wish to focus
on questions that call on your students to think of
the style of the passage, its vocabulary, the rhetorical
techniques employed, and the literary period in which it
An 1871 caricature in Hornet magazine portraying Darwin as an ape.
was written. Discussion of this passage would fit into a unit on Victorian literature; as an introduction to a study
of an evolution-themed literary work (see “Additional
Activities for English Classrooms”); or as a model for
analysis of rhetorical strategies in other works. If your
students can also connect the passage with what they
have learned in their science classes, you will have
helped them build a useful bridge from discipline to
discipline.
GUIDED READING
You can lead the whole class in a discussion of the
questions you have selected. Or you can divide your
class into four groups. Assign one sentence to each
group. Ask each group to answer all or some of the
questions about the sentence assigned to them. Each
group then reports their answers to the class as a whole.
1. The First Sentence
singing on the bushes, with various insects flitting about, and with worms crawling through the
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damp earth, and to reflect that these elaborately constructed forms, so different from each other, and
dependent upon each other in so complex a manner,
have all been produced by laws acting around us.
• Darwin begins his concluding paragraph with a very
long sentence in which he describes “an entangled
bank.” Have you been on the bank of a river or beside a
creek? What did you see there? What would you expect
to see there?
• List the organisms Darwin describes as inhabiting the
entangled bank. (He mentions “plants” and “bushes,”
“birds,” and “insects” and “worms.” Perhaps we can also
include the people contemplating the bank — the “us” at
the end of the sentence — in the list of organisms.)
• What verbs does Darwin use to describe the organisms
on the bank? (The plants “clothe” the bank, the birds
“sing,” the insects “flit,” and the worms “crawl.”) What would the sentence be like if you removed those verbs?
Would the sentence be a good one? What would the
sentence be like if you removed the organisms? Why
does Darwin include all of these organisms?
• Can you envision the environment or ecosystem that
Darwin describes in this sentence?
• Can you draw or find a picture that matches Darwin’s description of this bank?
• Why does Darwin include these words in this sentence: “entangled,” “elaborately,” “complex”? (Perhaps
they reflect the complexities of the world around us, the interconnections among organisms and their environments, or the complexity of the ideas Darwin’s book
has discussed.)
• What have you learned in biology that helps you
understand what Darwin is referring to when he uses
these phrases:
a. “elaborately constructed forms” (biological
development);
b. “dependent upon each other” (interrelationships
among organisms and their environments);
c. “produced by laws” (genetics, biological evolution; also see the second sentence of the paragraph)?
• Why does Darwin include these words in the opening
sentence of this paragraph: “interesting,” “contemplate,”
and “reflect”? What is he asking his reader to do? Is Darwin saying something about his own thought processes?
150
• Why do you suppose Darwin chose to begin this
important paragraph—the final impression he is leaving with his readers—with a somewhat detailed description
of the “entangled bank”?
• Why does this sentence end with the words “around
us”?
2. The Second Sentence
These laws, taken in the largest sense, being
Growth with Reproduction; Inheritance, which is
almost implied by reproduction;; Variability from the indirect and direct action of the external conditions of life, and from use and disuse; a Ratio of
Increase so high as to lead to a Struggle for Life,
and as a consequence to Natural Selection, entailing Divergence of Character and the Extinction of
less-improved forms.
• What does Darwin do in this long second sentence? Is
he writing a summary of his book’s main points?
• How does Darwin punctuate the sentence? (There are
three semi-colons, which serve to connect four independent clauses. A semi-colon is also used in the fourth
sentence. You might ask your students to try to use this
punctuation mark in their next writing assignment, or to
look for it in their next reading assignment.)
• What have you learned in biology that helps you know
something about the processes that Darwin briefly mentions in this sentence?
a. “Growth with Reproduction” (biological development);
b. “Inheritance, which is almost implied by reproduction” (genetic inheritance);
c. “Variability from the indirect and direct action of
the external conditions of life, and from use and
disuse.” (biological adaptation);
d. “A Ratio of Increase so high as to lead to a
Struggle for Life, and as a consequence to Natural Selection, entailing Divergence of Character
and the Extinction of less-improved forms.”
(biological adaptation).
3. The Third Sentence
Thus, from the war of nature, from famine and
death, the most exalted object which we are
capable of conceiving, namely, the production
of the higher animals, directly follows.
• This is the shortest sentence in the paragraph, and yet
it is very powerful. What do you think of Darwin’s use
of these dramatic words: “war,” “famine,” “death,” and
“exalted”? When you read or hear these words, what
specific things do you personally think about? What meaning do these words have for you?
• To what is Darwin referring when he uses the phrases
“war of nature” and “famine and death”? (A brief description of the inspiration Darwin drew from Malthus’s
writing on population may be useful here. Thomas
Robert Malthus [1766-1834] posited that, through calamitous events such as famine or outbreak of disease,
populations were stabilized so that they would not
outpace available resources.)
• To what is Darwin referring when he uses the phrases
“exalted object” and “higher animals”? Could he be
referring to his readers—to us?
• What have you learned in biology that helps you
understand this sentence?
4. The Fourth Sentence of the Paragraph — and the
Last Sentence of the Book
There is grandeur in this view of life, with its
several powers, having been originally breathed
by the Creator into a few forms or into one; and
that, whilst this planet has gone cycling on according to the fixed laws of gravity, from so simple a beginning endless forms most beautiful and most
wonderful have been, and are being, evolved.
changing in form. Further we must suppose that
there is a power always intently watching each
slight accidental alteration in the transparent layers; and carefully selecting each alteration which,
under varied circumstances, may in any way, or
in any degree, tend to produce a distincter image.
We must suppose each new state of the instrument
to be multiplied by the million; and each to be
preserved till a better be produced, and then the
old ones to be destroyed. In living bodies, variation will cause the slight alterations, generation
will multiply them almost infinitely, and natural selection will pick out with unerring skill each
improvement. Let this process go on for millions on
millions of years; and during each year on millions of individuals of many kinds; and may we not
believe that a living optical instrument might thus
be formed as superior to one of glass, as the works
of the Creator are to those of man?
A search of the many on-line texts of On the Origin of
Species will reveal other instances of Darwin’s use of
the word “Creator.”)
• What contrast is Darwin drawing in the first and last sentences of this paragraph? In the last sentence he
mentions “so simple a beginning.” How does this relate
to the first sentence of the paragraph, in which he used the words “entangled,” “elaborately,” and “complex”?
Is he referring to changes occurring in nature over time?
Is Darwin contrasting the entangled bank in the present
with a primordial scene in the long-distant past?
• Which three words did not appear in the first edition, but were added to the second edition? (“by the Creator”). Why might Darwin have included these words?
• Why does Darwin include these words in the final sentence of his book: “grandeur,” “beautiful,” and “wonderful”? What is he asking his reader to think about?
Is Darwin saying something about his own thought
processes?
• Did references to a “Creator” appear in other parts of
the first edition? (Yes. For example, in Chapter 6, in the section entitled “Organs of extreme perfection and
complication,” Darwin writes about the development of
the eye:
• What does Darwin mean by the phrase “this view
of life”? Can you put his view of life into your own
words?
Have we any right to assume that the Creator
works by intellectual powers like those of man? If
we must compare the eye to an optical instrument,
we ought in imagination to take a thick layer of
transparent tissue, with a nerve sensitive to light
beneath, and then suppose every part of this layer
to be continually changing slowly in density, so as
to separate into layers of different densities and
thicknesses, placed at different distances from each
other, and with the surfaces of each layer slowly
• What is your opinion of the last sentence of On the
Origin of Species?
• What is your opinion of the final paragraph of On the
Origin of Species? What did you learn from it that you
did not know before? (Answers might include opinions
about Darwin himself, about the book, or about the science of biological evolution.)
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THE LAST PARAGRAPH OF CHARLES DARWIN’S ON THE ORIGIN OF SPECIES
First edition (published on November 24th, 1859)
Second edition (published on January 7th, 1860)
follows. There is grandeur in this view of life, with its
several powers, having been originally breathed into
a few forms or into one; and that, whilst this planet
has gone cycling on according to the fixed laws of gravity, from so simple a beginning endless forms
most beautiful and most wonderful have been, and
are being, evolved.
follows. There is grandeur in this view of life, with
its several powers, having been originally breathed
by the Creator into a few forms or into one; and that,
whilst this planet has gone cycling on according to
the fixed laws of gravity, from so simple a beginning endless forms most beautiful and most wonderful
have been, and are being, evolved.
Bibliography
Darwin, C. (2003). On the origin of species: A facsimile of the first edition. Cambridge, Mass.: Harvard University
Press.
Darwin, C. (1998). The origin of species. New York, N.Y.: Oxford University Press.
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ADDITIONAL ACTIVITIES FOR ENGLISH CLASSROOMS
RHETORICAL ANALYSIS
• After your class analyzes the last paragraph of On the
Origin of Species, ask each student to find another short passage of non-fiction writing that has also had an important impact on humankind (e.g., the Preamble to the
United States Constitution or a portion of Martin Luther
King Jr.’s “I Have a Dream” speech). Ask each student
to consider where the passage’s power lies: the beauty
of the language, the strength of the argument, the historical moment it addressed, or other factors. You might
wish to limit the assignment by genre, time frame, or
nationality. Ask your students to explain their choices.
• Alternatively, you may wish to ask your students to
find and analyze a short passage of writing that has had a powerful or important impact on them personally (e.g., the passage from a book they like, part of a
letter or message they may have received, the lyrics of a
song). Ask your students to explain their choices. Why
has the author of each piece of writing succeeded in
reaching his or her audience?
PRINT AND NON-PRINT TEXTS
• Discussion of the last paragraph of On the Origin of
Species would serve as a useful introduction to a unit on
other evolution-themed literary works. We suggest several
texts that we know work well in secondary classrooms:
Charles Darwin’s Autobiography. Darwin’s Autobiography, published several years after his
death, was written primarily for a readership of family members — his children
and grandchildren. It is an accessible book
that, with surprising openness and charm,
provides insights into Darwin’s youth and
gradual development from unfocused student (more interested in outdoor sport, he was considered
“a very ordinary boy, rather below the common standard
in intellect”) to influential scientist. Readers seeking to understand more about Darwin’s childhood, family, and
marriage, his life aboard the Beagle, his religious beliefs,
and his career will find information about these topics in this short book. While the whole book has been assigned
successfully to secondary students, you may prefer to
make selections among the chapters, or perhaps assign
chapters to groups of students. Selections from this book
may be assigned as readings in an upper-level biology
class, or they may be assigned during a unit on autobiography or memoir in an upper-level English class.
The Time Machine. A pioneer of the “scientific romance,” or science fiction, H. G. Wells
established the fictional concept of a time machine in this book, which he
referred to as “my first scientific fantasia.” As a former student of T. H. Huxley
(a vocal defender of evolution, Huxley
was known as “Darwin’s Bulldog”) and
teacher of biology, Wells was positioned
to explore the “what ifs?” suggested by the swirl of
ideas around evolutionary biology in the Victorian Age.
The Time Machine (1895) follows the adventures of
a scientist and inventor (called “The Time Traveller”)
who builds a device that hurtles him forward along
evolution’s time line. Arriving in the year 802,701, he
encounters the strange life ways of the Eloi and the
Morlocks, species that are humans’ evolutionary descendents. The Time Machine is a novella, and therefore
short enough for a manageable reading assignment. In
addition, a number of film versions have been made. We recommend the most recent, which starred Guy
Pearce and Samantha Mumba in 2002. This version
was directed by Wells’s great-grandson Simon. Though
there are some changes to the plot, an emphasis on
science, including evolution, remains. There is even a
futuristic librarian who discusses time travel as a theme
in literature. The special effects in this version will
probably be more plausible to high school audiences today than those of George Pal’s generally well-regarded
effort of 1960.
Inherit the Wind. Though it takes some liberties
with the facts (adding a love story, for
instance), this drama by Jerome Lawrence and Robert E. Lee is recognizably
based on the Scopes “Monkey Trial.”
The play is set in a small Southern town
patterned on Dayton, Tennessee, where
John T. Scopes (Bertram T. Cates in the
play), was charged with breaking a law
recently enacted to prohibit the teaching of evolution
in the state’s public schools. Though the Scopes trial
was short-lived (lasting July 10-21, 1925), it generated
national interest at the time, in large part because of the
famous men representing each side in the dispute. Clarence Darrow (Henry Drummond) was a famed criminal attorney who stepped in for the defense; William
Jennings Bryan (Matthew Harrison Brady), a leading
politician, represented the prosecution. Both men were
outstanding orators, and their dramatized rhetorical
tangle ranges over science’s impact on many facets of
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society: education, law, religion, politics, the press. Inherit the Wind was first produced in 1955 on Broadway. Several film versions have been made, with the best considered to be the 1961 production, featuring Spencer
Tracy as Drummond.
Cosmicomics. Italo Calvino’s Cosmicomics (1965) is
rather more abstract than the other works
mentioned here. First published in Italian,
this collection of short stories follows the
adventures of beings in deep time — well
before language, before dinosaurs, before
vertebrae, before colors. While the whole
book has been assigned successfully to
secondary students, selected stories may serve as more
accessible assignments. In particular, we recommend
“The Aquatic Uncle,” which tells of the coelacanth,
who prefers to stay in the water while his fellows move
to the land. This story can be accompanied by information about the surprising discovery of a coelacanth
off the coast of southern Africa in 1938, though this
fish had been assumed to have become extinct tens of millions of years before. Students can even go online
to view photographs and video clips of living coelacanths—large (reaching five feet in length), blue fish that existed in the time of the dinosaurs and exist in our
time, too.
BIBLIOGRAPHY
Barlow, N. (Ed.), & C. Darwin (1993). The autobiography of Charles Darwin. New York, NY: W. W. Norton.
Darwin, C. (2003). On the origin of species: A facsimile
of the first edition. Cambridge, Mass.: Harvard University Press.
Darwin, C. (1998). The origin of species. New York,
N.Y.: Oxford University Press.
Darwin, C. (1859, April 2). To John Murray [Letter].
The Darwin Correspondence Online Database.
Retrieved May 2, 2006, from http://darwin.lib.cam.
ac.uk/per;/nav?pclass=letter;pkey=2445.
Evans, I. (1961). A short history of English literature.
Harmondsworth, Middlesex: Penguin Books.
Wells, H. G. (1934). Experiment in biography. New
York: MacMillan.
Evolution in the news. Because biological evolution
continues to spur discussion in public forums, any number of news stories, opinion-editorials, letters to editors,
and web-site content related to this topic may serve as
current, useful for texts for analysis. Students can even
consider such a text in light of what they have discovered through analysis of the last paragraph of On the
Origin of Species or one of the texts mentioned here.
154
A Discovery-Based Approach
to Understanding Clinical Trials
With a Focus on Symbiosis and Bacteria
Subjects: English, Health, Science, Social Studies
Engagement Activity; “Beneficial Bacteria to Prevent Malnutrition and Diarrhea in Pakistani
Infants,” Question sheet, FAQ, and Glossary for
the Exploration Activity.
OVERVIEW
Many of us—perhaps when listening to the radio
or browsing the Internet—will hear or read notices
recruiting people with heart disease, depression, myopia, or some other ailment or condition to participate
in clinical trials. People without such conditions,
but who have other needed characteristics (e.g., they
fall into a particular age range or live in a particular
region), are also often invited to be involved in clinical trials. In modern society, the drugs we take and
the medical procedures we undergo are the result of
extensive research. And clinical trials, along with the
individuals who volunteer to participate in them, play
a vital role in this research.
According to the U.S. National Institutes of Health
clinical trials website (ClinicalTrials.gov), clinical
research is the “fastest and safest way to find treatments that work in people and ways to improve
health.” This lesson plan, designed to be covered in
one class period (or at the end and beginning of two
successive classes), will help students to learn about
the make-up of clinical research and the provisions in
place to ensure the safety of the human participants.
Alternatively, teachers may choose to assign only
parts of this lesson.
The activities described here will also be useful in
teaching critical reading and informational writing
skills. Social Studies teachers may wish to expand
on the content provided by focusing on the history,
ethics, and regulations of clinical trials. General
information may be found online at “The history of
clinical testing and its regulation” (www.roche.com/
pages/facets/18/histclinte.htm).
Objectives: Students think critically about the ways
in which scientific researchers approach health problems, while also learning to analyze texts and write
informational, science-based compositions.
RESOURCES
•
Handouts: “Introducing Clinical Trials” for the
•
Students and teachers may also wish to consult
the ClinicalTrials.gov website
ENGAGEMENT ACTIVITY
(15 minutes)
a. At the beginning of class, provide students individually or in groups with a copy of the attached
“Introducing Clinical Trials” handout, which lists
four different clinical trials. (Alternatively, place the
handout on an overhead projector.)
b. Ask the students individually or in groups to look
over the handout and jot down answers to the following questions:
1. What is the purpose of each of these trials?
2. Would you consider participating in one of
these trials, if you met the requirements? Why?
3. Would you do it if you got paid?
4. What questions would you want to ask the
researchers before you agreed to participate?
5. Would you be interested in the results of any of
these trials? Why?
6. Who else would be interested in the results of
these trials?
c. Groups can report out to the class, or the teacher
may engage the class in a quick discussion based on
the questions provided.
This activity may also be assigned as individual or
group homework. (30 minutes)
a. Divide students into small groups and provide
each group with copies of the example clinical trial
(“Beneficial Bacteria to Prevent Malnutrition and Diarrhea in Pakistani Infants”), Question sheet, FAQ,
and Glossary.
155
b. Ask each group to answer the questions on the
“Questions about ‘Beneficial Bacteria to Prevent Malnutrition and Diarrhea in Pakistani Infants” handout.
EVALUATION ACTIVITY
Teachers may choose to evaluate students based on class
participation and completion of the Elaboration activity.
EXPLANATION ACTIVITY
(15 minutes)
a. Groups share and discuss their answers to the
“Questions about ‘Beneficial Bacteria to Prevent Malnutrition and Diarrhea in Pakistani Infants’” with
the entire class.
ELABORATION ACTIVITY
This writing activity can be assigned as homework to
be done by individual students, or it can be an in-class
group project. Choose a or b:
a. Students may locate an additional clinical trial
description that interests them on either the unchealthcare.org website (clinical trials are listed under
“Health & Patient Care”) or the ClinicalTrials.gov
website, and use the descriptions to answer the questions on the “Introducing Clinical Trials” handout.
b. Using “Beneficial Bacteria to Prevent Malnutrition and Diarrhea in Pakistani Infants” as a model, students
individually or in groups devise their own proposed
clinical trials. They, of course, will not conduct this trial
but will describe their proposed trials, outlining the protocol, exclusion/inclusion criteria, measurements, and
time-line. Suggestions for possible trials:
i. The effect of video games on violence in
teenagers
ii. The effect of fast food advertising on teenage
food purchases
iii. The correlations between wearing sandals and
blistered and calloused feet
156
INTRODUCING CLINICAL TRIALS
Questions for Students
Below are brief descriptions of four different clinical trials. Use this information and your own understanding to answer the following questions:
1. What is the purpose of each of these trials?
2. Would you consider participating in one of these trials, if you met the requirements? Why?
3. Would you do it if you got paid?
4. What questions would you want to ask the researchers before you agreed to participate?
5. Would you be interested in the results of any of these trials? Why?
6. Who else would be interested in the results of these trials?
Think You Might Have Gum Disease?
Lung study
RESEARCH PATIENTS NEEDED
Do you currently smoke cigarettes?
UNC Center for Inflammatory Disorders
-andUNC Center for Oral and Systemic Diseases
Have you quit smoking, but smoked for at least 10 years?
Male and female subjects with periodontal (gum) disease are
needed for a clinical research study. This study will assess the
effect of gum treatments on general health. Eligible subjects
will receive certain treatments at reduced fees or no charge.
The Center of Environmental Medicine at UNC is looking for
individuals for a research study. This study involves 1 visit and
a total of 1½ hours of your time.
For information please call or e-mail the
UNC School of Dentistry GO Health Center.
You will be reimbursed for completion of the study.
If you participate, you will have a breathing test and
learn more about your lungs. Participants that are
interested in quitting smoking will be given
information and guidance to help them quit.
Genetic Study of
Anorexia Nervosa in Families
African American Couples
Needed for a Research Study
We are seeking families with at least two members who
have or had anorexia nervosa, and who would be willing to
participate. Experts from around the world are working to
help identify the genes that might predispose individuals to
develop anorexia nervosa.
If you have been living with your partner for at least 9 months,
are not taking anti-hypertensive or anti-depressant medications, are between the ages of 18 and 50, and are willing to
have blood samples and blood pressure taken, then you may
qualify for a study about the benefits of partner relationships.
UNC Eating Disorders Program
Receive up to $200 per couple for completion of 2 lab visits.
If interested, please call the UNC
Stress and Health Research Program.
All advertisements on this page were retrieved on April 27, 2005, from unchealthcare.org
157
FAQ: ABOUT CLINICAL TRIALS
WHAT IS A CLINICAL TRIAL?
A clinical trial is an experimental research study that
evaluates the effect of a new drug or medical device
on human beings. Clinical research is a process of
discovery that is intended to improve medical care.
Researchers attempt to answer questions such as
“Which medication works better?” or “What is the
best way to treat a medical problem?”
WHO CAN PARTICIPATE IN A CLINICAL TRIAL?
All participants in a clinical trial are volunteers
who have agreed to take part in a particular study.
Some volunteers seek out clinical trials, and some
are referred to clinical trial opportunities by their
physicians. There are opportunities to be involved in
clinical trials for persons with specific diseases and conditions and for persons in generally good health.
Participants in a study are referred to as “subjects” or
“participants.” They can leave a study at any time for
any reason.
WHAT ARE THE BENEFITS AND RISKS
OF PARTICIPATING IN A CLINICAL TRIAL?
Benefits
• Play an active role in personal health care.
• Gain access to new research treatments before they
are widely available.
• Obtain expert medical care at leading health care
facilities during the trial.
• Help others by contributing to medical research.
Risks
• There may be unpleasant, serious or even lifethreatening side effects to experimental treatment.
• The experimental treatment may not work for the
participant.
• The trial may require more time and attention than
standard treatment, including trips to the study site,
more treatments, hospital stays or complex requirements.
• The participant may be placed in the “placebo”
group
HOW IS THE SAFETY OF THE PARTICIPANT
PROTECTED?
The ethical and legal codes that govern medical
practice also apply to clinical trials. In addition,
most clinical research is federally regulated with
built in safeguards to protect the participants. Each
trial follows a carefully controlled protocol, a plan
that details what researchers will do in the study. As
a clinical trial progresses, researchers report their
results at scientific meetings, to medical journals, and to various government agencies. Individual participants’ names remain secret and are not mentioned in
these reports.
Every clinical trial in the U.S. must be approved and
monitored by an Institutional Review Board (IRB)
to make sure the risks are as low as possible and are
worth any potential benefits. An IRB is an independent committee of physicians, statisticians, community advocates, and others that ensures that a clinical
trial is ethical and the rights of study participants are
protected.
WHAT SHOULD PEOPLE CONSIDER
BEFORE PARTICIPATING IN A TRIAL?
People should know as much as possible about the
clinical trial and feel comfortable asking the members
of the health care team questions about it. The following questions might be helpful for the participant
to discuss with the health care team:
• What is the purpose of the study?
• Who is going to be in the study?
• Why do researchers believe the experimental treatment being tested may be effective? Has it been
tested before?
• What kinds of tests and experimental treatments are
involved?
• How do the possible risks, side effects, and benefits in the study compare with my current treatment?
• How might this trial affect my daily life?
• How long will the trial last?
• Will hospitalization be required?
• Who will pay for the experimental treatment?
• Will I be reimbursed for other expenses?
• What type of long-term follow-up care is part of this
study?
• How will I know that the experimental treatment is
working?
• Will results of the trials be provided to me?
• Who will be in charge of my care?
• What happens if I’m injured because of the study?
INFORMATION ON THIS PAGE WAS ADAPTED FROM UNIVERSITY OF MARYLAND’S BROCHURE “THINKING ABOUT ENROLLING IN A CLINICAL TRIAL?” AND FROM CLINICALTRIALS.GOV.
158
CLINICAL TRIALS GLOSSARY
Baseline—1. Information gathered at the beginning
of a study from which variations found in the study
are measured. 2. A known value or quantity with
which an unknown is compared when measured or
assessed. 3. The initial time point in a clinical trial,
just before a participant starts to receive the experimental treatment being tested.
Blind — A clinical trial is “blind” if participants are
unaware of whether they are in the experimental or
control arm of the study.
Control group — In many clinical trials, one group
of patients will be given an experimental drug or
treatment, while the control group is given either a
standard treatment for the illness or a placebo.
Double-blind study — A clinical trial design in
which neither the participating individuals nor the
study staff know which participants are receiving the
experimental drug and which are receiving a placebo
(or another therapy). Double-blind trials are thought
to produce objective results, since the expectations of
the doctor and the participant about the experimental
drug do not affect the outcome.
Efficacy — The maximum ability of a drug or treatment to produce a result regardless of dosage. A drug
passes efficacy trials if it is effective at the dose tested and against the illness for which it is prescribed.
Eligibility Criteria—Summary criteria for participant selection; includes Inclusion and Exclusion
criteria.
Expanded access — Refers to any of the FDA
procedures that distribute experimental drugs to
participants who are failing on currently available
treatments for their condition and also are unable to
participate in ongoing clinical trials.
Hypothesis—A supposition or assumption advanced
as a basis for reasoning or argument, or as a guide to
experimental investigation.
Inclusion/exclusion Criteria — The medical or
social standards determining whether a person may
or may not be allowed to enter a clinical trial. Often
based on age, gender, the type and stage of a disease,
previous treatment history, and other medical conditions. These criteria are not used to reject people personally, but rather to identify appropriate participants
and keep them safe.
Informed consent — The process of learning the key
facts about a clinical trial before deciding whether
or not to participate. It is also a continuing process
throughout the study to provide information for
participants.
Interventions—Primary interventions being studied;
types of interventions are Drug, Gene Transfer, Vaccine, Behavior, Device, or Procedure.
Open-label trial—a clinical trial in which doctors
and participants know which drug or vaccine is being
administered.
Peer review — Review of a clinical trial by experts
chosen by the study sponsor. These experts review
the trials for scientific merit, participant safety, and ethical considerations.
Placebo — An inactive pill, liquid, or powder that
has no treatment value. In clinical trials, experimental
treatments are often compared with placebos to assess
the treatment’s effectiveness. In some studies, the
participants in the control group will receive a placebo
instead of an active drug or treatment. No sick participant receives a placebo if there is a known beneficial treatment.
Prevention Trials—Refers to trials to find better ways to prevent disease in people who have never
had the disease or to prevent a disease from returning.
These approaches may include medicines, vitamins,
vaccines, minerals, or lifestyle changes.
Protocol — A study plan carefully designed by the
researcher(s) to safeguard the health of the participants in a clinical trial as well as answer specific research questions. A protocol describes what types
of people may participate; the schedule of tests,
procedures, medications, and dosages; and the length
of the study.
Randomized trial — A study in which participants
are randomly (i.e., by chance) assigned to one of two
or more treatment arms of a clinical trial.
Single-blind study — A study in which one party,
either the investigator or participant, is unaware of
what medication the participant is taking; also called
single-masked study.
You can find more definitions at ClinicalTrials.gov.
INFORMATION ON THIS PAGE WAS ADAPTED FROM “GLOSSARY OF CLINICAL TRIALS TERMS” AVAILABLE AT CLINICALTRIALS.GOV.
159
UNDERSTANDING CLINICAL TRIALS: EXAMPLE STUDY
BENEFICIAL BACTERIA TO PREVENT MALNUTRITION
AND DIARRHEA IN PAKISTANI INFANTS
Sponsored by
National Center for Complementary
and Alternative Medicine (NCCAM)
Information provided by
National Center for Complementary
and Alternative Medicine (NCCAM)
PURPOSE
This study will determine whether lactobacillus GG
(LGG), a beneficial bacterium, when given in yogurt, will reduce growth faltering in babies living in a
poor area of Pakistan who are being weaned from
breastfeeding.
Study Hypothesis: Use of the probiotic bacteria
LGG at the time of weaning will lessen the impact
of faltering growth in babies living in the slums of
Pakistan.
Study Type: Interventional
Study Design: Prevention, Randomized, Open Label,
Placebo Control, Parallel Assignment, Efficacy Study
Official Title: Feasibility Study of Probiotics for
Growth Faltering in Pakistan
Primary Outcome Measures:
• Growth, as measured by weight for age and height
Secondary Outcome Measures:
• Number of episodes of diarrhea
• Duration of episodes of diarrhea
Expected Total Enrollment: 100
Study Start: March 2006
Expected Completion: January 2008
Detailed Description: Faltering growth due to
malnutrition and recurrent diarrhea is a serious
public health concern in developing nations,
particularly among infants who are being weaned
from breastfeeding. Evidence suggests that the use of
160
the probiotic bacterium LGG reduces
the risk of diarrhea, shortens episodes
of diarrhea, and enhances the immune
system. Babies who are being weaned
from breastfeeding will be given
LGG-containing yogurt in this study
to determine whether LGG will reduce
faltering growth caused by diarrhea and
malnutrition.
Infant participants will be enrolled at or within 5
weeks of birth and followed throughout the weaning
period. During the weaning period, participants will
be randomly assigned to either receive LGG-containing yogurt or placebo yogurt everyday for 3 months.
All participants will have height and weight measurements taken at study entry and at Month 3 (study
completion). The number of diarrhea episodes experienced by participants during the study will be assessed
at study completion to determine participants’ health.
ELIGIBILITY
Ages Eligible for Study: Up to 5 Weeks
Genders Eligible for Study: Both
Inclusion Criteria:
• Born and reside in Bilal Colony, Karachi Pakistan
during the study
• Parent or guardian willing to provide informed
consent
• Parent or guardian willing to permit home visits
• Predominantly breastfed at study start
Exclusion Criteria:
• Malnutrition at time of weaning
• Medical condition that would affect response to
LGG
Condition
Intervention
Malnutrition, diarrhea
Drug: food supplement:
Lactobacillus GG
UNDERSTANDING CLINICAL TRIALS: EXAMPLE STUDY
QUESTIONS ABOUT “BENEFICIAL BACTERIA TO PREVENT MALNUTRITION
AND DIARRHEA IN PAKISTANI INFANTS”
You can find answers to these questions in the researchers’ description of this clinical trial. 1. What are the inclusion criteria for this study?
2. What are the exclusion criteria for this study?
3. Would you qualify for this study?
4. Where will this trial take place?
5. What is the problem the researchers are trying to solve?
6. What is the researchers’ hypothesis?
7. What do the researchers plan to do in order to test their hypothesis?
8. How will the researchers know if their approach is successful? List three measurements the
researchers are going to use to evaluate the effectiveness of their approach.
9. The study design includes a “placebo control.” What is a placebo? What is the particular
placebo that will be used in this trial? Who will receive the placebo?
10. The study is “interventional.” What does it mean if you “intervene” in something? How
are the researchers “intervening” in the lives of the study participants?
There may be different opinions about the following questions. So you will need to use a combination of
information from the researchers’ description of their planned clinical trial and your own understanding to respond to these questions.
11. While they may never read the actual study, many members of the general public may benefit from this clinical trial. In your view, which of the following groups could potentially benefit from what the researchers find out? Briefly explain your thinking.
• Health-care workers.
• New mothers and fathers in Pakistan.
• New mothers and fathers in the United States.
• Researchers who are interested in the connections between health and bacteria.
• Dairy farmers.
• Companies that manufacture yogurt.
• Marketing and advertising companies.
12. In your view, is this a good idea for a clinical trial? Why or why not?
161

The Power Within - Morehead Planetarium and Science Center

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