Chapter 18 – Classification Chapter Mystery – Grin and Bear It

BHS Biology – Chapter 18 – Classification
BIG IDEA: EVOLUTION
Essential Question: What is the goal of biologists who classify living things?
1
Chapter 18 – Classification
Chapter Mystery – Grin and Bear It
If you compared polar bears and brown bears, you would probably never
doubt that there are different species. Polar bears grow much larger than brown
bears, and their paws have adapted to swimming long distances and to walking on
snow and ice. Their white fur camouflages them, but the coats on brown bears are,
well, brown – and their paws aren’t adapted to water.
Clearly polar bears and brown bears are very different physically. But do
physical characteristics tell the whole story? Remember the definition of species:
“a group of similar organisms that can breed and produce fertile offspring.” Well,
polar bears and brown bears can mate and produce fertile offspring. They must be
members of the same species, then.
But are they? As you read this chapter, look for clues as to whether polar
bears are a separate species. Then, solve the mystery.
18.1
Finding Order in Diversity
Guiding Question: Why do scientists classify living things? 1. Finding order in the chaos that is the diversity of life has long been a goal
2. Assigning Scientific Names
a. Old way had flaws
• Names were looonnnngggggg descriptions
• More than one species = same common name (e.g. “buzzard”)
• More than one name = same species (based on language, culture)
b. Bionomical Nomenclature
• Each species has a standardized two-part name
• First part is the genus (kind of like our last name)
• Second part is the species (kind of like our first name) and is
unique to the organism
• Canis lupis (genus Canis a.k.a. dog, species lupus a.k.a. wolf)
BHS Biology – Chapter 18 – Classification
BIG IDEA: EVOLUTION
Essential Question: What is the goal of biologists who classify living things?
2
• In writing, always italicize scientific name with species always
lowercase…subsequent references can shorten genus to first
letter (e.g. C. lupis)
3. Linnaean Classification System
a. Connects species into categories (“taxa”) by visible characteristics*
b. There are seven categories
• Kingdom (Animal, plant, fungi, bacteria, protist, or
archaebacteria are the only choices)
• Phylum
• Class
• Order
• Family
• Genus (first part of scientific name)
• Species (second part of scientific name)
c. Changes in recent time
• Species determined by nature; who can interbreed
• Genus through Kingdom determined by scientists
• *We now group based on common ancestry
18.2
Modern Evolutionary Classification
Guiding Question: How do evolutionary relationships affect the way
scientists classify organisms?
1. Evolutionary Classification
a. All members of a single classification should descend from a common
ancestor = clade
2. Cladogram
a. A chart showing descent and what traits changed over time
BHS Biology – Chapter 18 – Classification
BIG IDEA: EVOLUTION
Essential Question: What is the goal of biologists who classify living things?
3
b. Reading/creating cladograms
• bottom is the oldest common ancestor which all the others got
their traits from
• along the line between branches are points w/derived characters
• species that went extinct stop short of the top most row
c. Information from DNA is allowing us to redo some of the old
cladograms into more accurate ones
18.3
Building the Tree of Life
Guiding Question: What are the major groups within which all organisms
are currently classified?
1. Changing Ideas about kingdoms
a. Originally two kingdoms
• Plant
• Animal
b. 1800's we invent microscopes we find micro-organisms
• all went into Protista (for now)
c. We figure out yeast, mold, and fungi are really weird
• Fungi
d. We figure out bacteria are quite unique (e.g. no nucleus)
• Monera
e. We explore remote parts of the world and find really strange bacteria
• Bacteria split into Eubacteria and Archaebacteria
f. After determining Eubacteria, Archaebacteria, and others (eukaryotes)
are even more different than originally thought…
• 3 Domains to go above kingdoms
⇒ Bacteria (kingdom Eubacteria)
BHS Biology – Chapter 18 – Classification
BIG IDEA: EVOLUTION
Essential Question: What is the goal of biologists who classify living things?
4
⇒ Archaea (kingdom Archaebacteria)
⇒ Eukarya (eukaryotes -- everything else)
2. Tree of Life (Foundations = p.440-441 or p.526-527)
a. Bacteria are the oldest - blue
• Single celled no nucleus
b. Archaebacteria specialized from them - purple
• Single celled no nucleus, live in extreme environments
c. Fungi - brown
• Heterotrophs (they eat) but have cell walls
d. Plants - green
• Autotrophs (they make food)
e. Animals - red
• Heterotrophs, no cell walls
f. Protists - yellow
• Most single celled, some multicellular; most heterotrophs, some
autotrophs
• This is basically the miscellaneous category
• They are the only ones not their own clade, hence them being all
over the tree of life