Section 1 The Reptilian Body

Transcription

Section 1
Section 1
The Reptilian Body
Focus
Objectives
Overview
Before beginning this section
review with your students the
objectives listed in the Student
Edition. In this section, students
will learn how reptiles are welladapted to life on land. Terrestrial
adaptations include a strong
skeleton, watertight skin covered
with scales, watertight eggs, larger
lungs with greater surface area,
internal fertilization, and a partially
divided heart.
● Describe the key characteristics of reptiles.
8C
● Relate a reptile’s ectothermic
metabolism to its activity
7B 11A TAKS 3
level.
● Summarize the adaptations
that enable reptiles to live
on land.
7B TAKS 3
Key Terms
amniotic egg
oviparous
ovoviviparous
Bellringer
Ask students to design a survival
capsule for themselves. The capsule
can only be 1.5 m high by 1 m wide.
The capsule will not be opened for
three weeks. Nothing, other than
gasses, can pass through the wall of
the capsule. What should the capsule
contain? Ask students to compare
their capsule with the amniotic egg
described in this section.
www.scilinks.org
Topic: Characteristics
of Reptiles
Keyword: HX4038
Key Characteristics of Reptiles
Many people react with fear or repulsion when they see a snake
slither across a yard or field. But snakes and their reptile relatives
are important members of most ecosystems, and they kill large
numbers of insect pests and small rodents. It’s true that some reptiles—venomous snakes and crocodilians (crocodiles and alligators)
—are dangerous. Most reptiles, however, live quietly and go about
their business, preferring to avoid humans.
Members of class Reptilia live throughout the world in a wide variety of habitats, except in the coldest regions, where it is impossible
for ectotherms to survive. Reptiles share certain fundamental characteristics, features they retain from the time when reptiles replaced
amphibians as the dominant terrestrial vertebrates. Figure 1 summarizes these key features.
Reptiles have a strong, bony skeleton, and most have two pairs of
limbs, although snakes and some lizards are legless. The legs of reptiles are positioned more directly under their body than are the
limbs of amphibians. Thus, reptiles can move more easily on land
than amphibians can. Unlike amphibians, reptiles have toes with
claws, which are used for climbing and digging. Claws also enable
reptiles to get a good grip on the ground, allowing many reptiles to
run quickly for short distances.
The nervous system of a reptile is very similar to that of an
amphibian. Like their dinosaur ancestors, modern reptiles have a
brain that is small in relation to their body. For example, an alligator
about 2.5 m (8 ft) long has a brain that is about the size of a walnut.
Despite this small brain size, reptiles are capable of complex behaviors, including elaborate courtship.
TAKS 1 Bio/IPC 2C, 2D
Motivate
Activity
Favorite Reptile Have each student draw a picture of his or her
favorite reptile. Have volunteers
share their drawings with the class
and tell why they chose their particular reptile. Lead a discussion of
how reptiles are viewed in popular
culture. LS Visual Bio 3F
Figure 1 Characteristics
of living reptiles. This male
anole is extending his dewlap,
a display used during courtship and when defending
territory.
Key Features of Reptiles
• Strong, bony skeleton and toes with
claws
• Ectothermic metabolism
• Dry, scaly skin, almost
watertight
• Amniotic eggs, almost
watertight
• Respiration through well-developed
lungs
• Ventricle of heart partly divided by a
septum
• Internal fertilization
772
Chapter Resource File
pp. 772–773
Student Edition
TAKS Obj 1 Bio/IPC 2C
TAKS Obj 2 Bio 4B
TAKS Obj 2 Bio 8C
TAKS Obj 2 Bio 10A
TAKS Obj 3 Bio 7B
TEKS Bio 4B, 7B, 8C, 10A, 11A
TEKS Bio/IPC 2C
Teacher Edition
TAKS Obj 1 Bio/IPC 2C, 2D
TAKS Obj 3 Bio 7B
TEKS Bio 3F, 7B, 11A
TEKS Bio/IPC 2C, 2D
772
Chapter 34 • Reptiles and Birds
• Lesson Plan GENERAL
• Directed Reading
• Active Reading GENERAL
• Data Sheet for Data Lab GENERAL
• Data Sheet for Quick Lab GENERAL
Planner CD-ROM
• Reading Organizers
• Reading Strategies
• Basic Skills Worksheets
Reading a Thermometer
Temperature Conversions
Ectothermic Metabolism
Reptiles’ ectothermic metabolism is too slow to generate enough
heat to warm their bodies, so they must absorb heat from their surroundings. As a result, a reptile’s body temperature is largely determined by the temperature of its environment. Many reptiles regulate
their temperature behaviorally, by basking in the sun to warm up or
seeking shade to cool down. Figure 2 shows that a lizard can maintain a relatively constant body temperature throughout the day by
moving between sunlight and shade. At very low temperatures, most
reptiles become sluggish and unable to function. Intolerance of cold
generally limits their geographical range and, in temperate climates,
forces them to remain inactive through the winter.
Temperature (°C)
Resting in
shade
Activity
Basking
READING
SKILL
Returns
to den
35
Emerges
30
from
den
25
20
15
Air temperature
10
Lizard's body
temperature
5
0
4
6
5
7
8
9
10
11
Sunrise
12
1
2
3
4
Noon
5
6
7
8
Sunset
Time of day
Identifying Ectotherms
TAKS 1
Temperature (°C)
The body temperature of all animals
changes during the course of a day. How it
changes can help you identify an animal as
an ectotherm or an endotherm.
2C 11A
0100010110
011101010
0010010001001
1100100100010
0000101001001
1101010100100
0101010010010
Body Temperatures of Two Animals
Species A
Background
Species B
Identifying
Ectotherms
20
10
TAKS 1 Bio/IPC 2C; Bio 11A
12 A.M.
6 A.M.
12 P.M.
0100010110
011101010
0010010001001
1100100100010
0000101001001
1101010100100
0101010010010
6 P.M.
4. Propose a reason why the
ectotherm’s body temperature
is highest at this time.
5. Predict what the endotherm’s graph line would look
like if it were extended to
show body temperature
between 6 P.M. and midnight.
773
TT Bellringer
TT Key Features of Reptiles
TT Changes in Lizard Body
Temperature
TT Reptilian Heart Structure
Have students draw a graph that
depicts the changes in human body
temperature for a 24-hour period.
(The graph should show that the
human body remains at about 37˚C
for the entire day.) Then ask them to
compare their graphs to the one for
the lizard’s body temperature in
Figure 2. Ask: Why are the graphs
different? (The lizard depends on
external sources for heat, so its body
temperature tracks the temperature
of the environment. Humans produce
their own heat, so body temperature
is not dependent on environmental
temperature changes.) LS Visual
30
3. Identify the time
of day the animal
you identified as an ectotherm
reaches its highest body
temperature.
Transparencies
Using the Figure
TAKS 1 Bio/IPC 2C, 2D; TAKS 3 Bio 7B
Air
Time of day
2. Identify the time of day the
animal you identified as an
ectotherm reaches its lowest
body temperature.
Interactive Reading Assign
Chapter 34 of the Holt Biology
Guided Audio CD Program to help
students achieve greater success in
reading the chapter.
40
Analysis
1. Analyze the data and determine which animal species,
A or B, is most likely an ectotherm. Explain your reasoning.
GENERAL
BUILDER
Figure 2 Body
temperature in a lizard. A
lizard may regulate its body
temperature by moving repeatedly between sun and shade.
Changes in Lizard Body Temperature
40
Teach
Skills Acquired
Analyzing data,
interpreting graphs,
predicting patterns
Teacher’s Notes
Remind students that ecto- refers
to “outside,” endo- refers to
“within,” and therm refers to
“heat.” Hence, ectotherm means
“outside heat” and endotherm
means “heat within.”
Answers to Analysis
MISCONCEPTION
ALERT
Cold-blooded Emphasize that the terms
ectothermic and coldblooded are not synonyms, although they are often mistakenly
used that way. Many reptiles experience
body temperatures as high as or higher
than human body temperature. For example, the body temperature of the desert
iguana in western North America regularly
reaches 42°C (108°F), which would be fatal
for a human. TAKS 1 Bio/IPC 2D
1. Species A (yellow curve)
probably is an ectotherm. Its
temperature increases during
the day, when the air temperature increases.
2. around 12 A.M.
3. around 12 P.M.
4. It has been exposed to
sunlight-warmed air since
early in the morning.
5. It would decline steadily from
its value at 6 P.M. to its value
at 12 A.M.
773
Water Retention
Teach, continued
continued
Modeling
Watertight Skin
TAKS 1 BioIPC 2B, 2C, 2D; TAKS 3 Bio 7B
Skills Acquired
Calculating, analyzing
data, inferring
conclusions
Teacher’s Notes
Be sure to have students wipe
the pan of the scale clean
between weighings. Place an
incandescent lamp on each
table to simulate a desert
environment.
Reviewing Information
Reread the bulleted list of
key features of reptiles in
Figure 1. Then write them
down on a separate piece
of paper, leaving room to
write notes about each
characteristic. As you read,
summarize how the information relates to a particular
characteristic.
Amphibians such as frogs cannot be considered fully terrestrial
because they lose too much water through their skin. Amphibians must
stay moist to avoid dehydration, and their method of reproduction
requires a moist environment. Reptiles have evolutionary adaptations that free them from the water requirements of amphibians.
Watertight Skin
Terrestrial animals face a serious problem of water loss as water
evaporates through their skin. Modern reptiles have evolved a skin
made of light, flexible scales. These scales overlap and form a protective, almost watertight skin that minimizes water loss, as shown
in Figure 3.
Figure 3 Reptilian scales.
The scales of a reptile’s
skin form a tight seal that
retains moisture within the
reptile’s body.
Answers to Analysis
1. The mass of the skinless grape
should decrease. The mass of
the intact grape should stay
the same.
2. The skin prevents water from
evaporating from an intact
grape, so the grape’s weight
does not change. Without its
skin, a grape loses water and
becomes lighter.
3. The skinless grape represents
an amphibian’s skin. The
intact grape represents a
reptile’s skin.
4. Watertight skin, as in the
intact grape, prevents water
loss. This allows an animal to
survive in dry environments.
Most amphibians, like the
skinless grape, would dry up
if out of water or moist environment for an extended
period of time.
Modeling Watertight Skin
Scales make a reptile’s skin almost watertight. This
is one of reptiles’ adaptations to terrestrial life. You
can use grapes to model and compare water loss in
2B 2C 2D 7B
different types of skin.
Materials
TAKS 1, TAKS 3
forceps, 2 grapes, balance, Petri dish
Procedure
1. Find the mass of one grape,
and record it in a data table.
Then place the grape in an
open Petri dish.
3. Wait 15 minutes, and then
find and record the mass of
each grape again.
2. Using forceps, peel the
skin from the second grape.
Find and record the mass of
the peeled grape. Then place
it in the same Petri dish, but
do not let the two grapes
touch.
1. Calculate the difference
between the original and final
masses of each grape.
Analysis
2. Propose an explanation for
any changes in mass you
observed.
3. Determine which grape
represents an amphibian’s
skin and which represents a
reptile’s skin.
4. Describe how a watertight
skin is an adaptation to terrestrial life. Include information you have learned in this
lab in your explanation.
774
did you know?
pp. 774–775
Student Edition
TAKS Obj 1 Bio/IPC 2B, 2C, 2D
TAKS Obj 3 Bio 7B
TAKS 3 Bio 12E
TEKS Bio 7B, 12C, 12E
TEKS Bio/IPC 2B, 2C, 2D
Teacher Edition
TAKS Obj 1 Bio/IPC 2B, 2C, 2D
TAKS Obj 3 Bio 7B, 12B, 12E
TAKS Obj 5 IPC 6B
TEKS Bio 3F, 7B, 12B, 12C, 12E
TEKS Bio/IPC 2B, 2C, 2D, 3C
TEKS IPC 6B
774
Introduced Species Cause Problems In the
western United States, the tansy ragwort plant
is poisonous to cattle. The cinnabar moth,
whose larvae eat the tansy ragwort, was introduced into the region to control this plant.
However, the larvae accumulate toxins that kill
the northern alligator lizards that prey on the
larvae. Populations of these lizards may be at
risk in certain areas of the west.
TAKS 3 Bio 12B; Bio/IPC 3C; Bio 3F
IPC Benchmark Review
To prepare students for the TAKS and accompany the
discussion of thermoregulation in reptiles, have students review Convection, Conduction, and Radiation,
TAKS 5 IPC 6B on p. 1063 of the IPC Refresher in the
Texas Assessment Appendix of this book.
Watertight Eggs
For a reptile living on dry land, reproduction presents another serious water-loss problem. Without a watery environment, both sperm
and eggs will dry out. A reptile’s fertilized eggs need a moist environment in which to develop. As you will read later in this chapter,
the first problem is overcome by internal fertilization.
The nature of a reptile’s amniotic (am nee AHT ic) egg solves the
second problem. An amniotic egg contains both a water supply and
a food supply and is key to a reptile’s success as a terrestrial animal.
Because the egg’s tough shell makes it essentially watertight, it does
not dry out, even in very dry habitats. Most reptiles, all birds, and
three species of mammals reproduce by means of amniotic eggs with
shells. (Other mammals produce amniotic eggs, but the embryo
develops within the female’s uterus rather than within a shell. You
will learn about the development of these eggs in a later chapter.) The
formation of amniotic eggs with shells suggests that these three
groups of animals evolved from a common ancestor.
Trouble for Turtles in
Texas
TAKS 3 Bio 12E; Bio 12C
Teaching Strategies
• Show students a map of Texas
and trace the flow of the
Guadalupe River. Ask students to locate cities that are
near the river. Then have
students locate Canyon Lake.
• Tell students that in Cagle’s
map turtle, a turtle’s sex is
determined by the temperature during which it was incubated. When temperatures are
higher than 30.5ºC, female
turtles are produced; when it
is lower than 28ºC, male
turtles are produced.
Trouble for Turtles in Texas
TAKS 3
T
he Guadalupe River in southern Texas is home to several
threatened and endangered
species. Another may soon be
added to the list: Cagle’s map
turtle, Graptemys caglei. First
discovered in 1974, this reptile at
one time had a larger range than
it does today. It is now thought to
exist only in the Guadalupe River.
Although the turtle is not yet
considered threatened or endangered, it has been listed as a
protected species in Texas.
Cagle’s map turtles rarely leave
the water except to lay eggs. The
females eat clams and aquatic
snails. The males eat insect larvae,
which are usually found in pools
and in rocky areas with riffles.
A Changing Environment
The Guadalupe River winds
through a part of Texas that has a
rapidly growing human population
with an increasing demand for
water. Some parts of the river
attract so many recreational visi-
tors that water quality and shoreline habitat are being degraded.
Clearing of forests along the river
for building construction could
further lower the river’s water
quality and change its flow.
Numerous dams already interrupt
the flow of the river, and two additional dams have been proposed.
Dams cause riffles to disappear
and allow silt to cover rocks, making it harder for turtles to find food.
Monitoring the Situation
Researchers at West Texas A&M
University in Canyon have been
studying the ecology of Cagle’s
map turtle for more than 20 years.
The data they have collected
show how the turtle is faring in
different areas. For example, turtle populations now are greatly
reduced in Canyon Lake, a reservoir in the upper portion of the
river.
Further work by the researchers
will focus on the turtles’ water
flow requirements and habitat
characteristics. Knowing what
water flows the turtles need may
allow scientists to recommend
when and how much water
should be released from the
dams. Learning more about the
turtles’ preferred habitat, such as
the size of rocks they use most,
will help people identify sections
of the river that may have to be
preserved. Changes such as
these, the researchers believe,
are needed to keep Cagle’s map
turtle from becoming a threatened species.
www.scilinks.org
Topic: Texas Reptiles
Keyword: HXX4023
Discussion
• How do humans affect the
habitat of the Cagle’s map
turtle? (Humans disrupt turtle
habitat by drawing water from
the river, using the river for
recreation, building dams, and
developing areas along the river.)
• Even though they spend most
of their life in the water,
Cagle’s map turtles lay their
eggs on land. Why don’t their
eggs dry out? (Turtles lay
amniotic eggs. Amniotic eggs
have a food and water supply
so that they don’t dry out.)
• Male and female turtles eat
different things. What do you
think would be a benefit of
this strategy? (It might
decrease competition for food.)
775
Activity
Green Turtles Tour the Atlantic Green
turtles migrate more than 2,000 km (1,250 mi)
from the waters off Brazil to the beaches of
Ascension Island in the central Atlantic Ocean.
A female green turtle will lay her eggs on the
same beach where she hatched. Scientists do
not yet know for certain how she finds her
birthplace. Bio 12C
Comparing Eggs Using field
guides, books, and Internet
resources, have students research
the eggs of birds, reptiles, and
amphibians. Ask each student to
make life-size, full-color drawings
of several types of eggs on small
pieces of paper. When students are
finished, assemble the drawings
into three large posters for
comparison: The Eggs of
Amphibians, The Eggs of Reptiles,
and The Eggs of Birds.
LS Interpersonal
775
Respiration
Because most reptiles are far more active than amphibians, they
have greater metabolic requirements for oxygen. Their bodies meet
this demand in several ways.
Teach, continued
continued
Teaching Tip
Lungs
Surface Area Ask students which
melts faster—multiple cubes of ice
or a single block of ice of the same
weight? Lead students into a discussion of the importance of surface area in living things. Relate the
cubes of ice to alveoli in the lungs.
A reptile’s scaly skin does not permit gas exchange, so reptiles cannot use their skin as an additional respiratory surface, as many
amphibians can. However, the lungs of most reptiles have many
internal folds, as shown in Figure 4. These folds greatly increase the
respiratory surface area of a reptile’s lungs. In addition, reptiles
have strong muscles attached to their rib cage. The action of these
muscles helps to move air into and out of the lungs, increasing the
lungs’ efficiency.
LS Verbal TAKS 4 IPC 9D
SKILL
BUILDER
GENERAL
Math Skills Ask students to find
the surface area of an 8 mL cube and
the combined surface area of eight 1
mL cubes. Remind students that the
surface area of a cube is found by
l w 6 (where l length, w width, and 6 the number of sides).
Point out that an 8-mL cube has
two-centimeter sides and a 1-mL
cube has one-centimeter sides.
(Although the overall volume is the
same, the 8-mL cube has a surface area
of 24 cm2 and eight 1-mL cubes have a
combined surface area of 48 cm2.)
Figure 4 Reptilian lungs.
The lungs of reptiles contain
numerous internal folds.
Figure 5 Reptilian heart.
In most reptiles, the ventricle
of the heart is partly divided by
a septum.
Heart
Recall that the ventricle of the amphibian heart is not divided by a
septum. Oxygen-poor blood and oxygen-rich blood mix somewhat
in the amphibian’s ventricle. In most reptiles, however, the septum
extends into the ventricle, partly dividing it into right and left
halves, as shown in Figure 5. The septum enables a much better, but
still incomplete, separation of oxygen-rich and oxygen-poor blood.
As a result, oxygen is delivered to the body cells more efficiently
than in amphibians.
Unlike most reptiles, crocodilians have a heart with a completely divided ventricle that consists of two pumping chambers.
This arrangement fully separates the lung circulation from the
body circulation. Thus, the delivery of oxygen throughout the
body is further improved in these animals.
Reptilian Heart Structure
LS Logical
Group Activity
Oxygen-poor blood from the body
enters the right atrium. Oxygen-rich
blood from the lungs enters the left atrium.
Local Snakes Use a field guide to
determine what kinds of snakes
are found in your area. Have
groups research these snakes and
report to the class on the snakes’
habitat, range, reproduction,
behavior, feeding habits, and any
other relevant information.
1
To body
Right
atrium
Incomplete
septum
TAKS 1 Bio/IPC 2C, 2D; Bio 8B
776
776
SOCIAL STUDIES
CONNECTION
Snakes in Literature Throughout history,
many cultures have used snakes in literary,
cultural, and religious settings, such as The
Bible, and in stories such as the Greek myth
of Medusa. Even children’s stories like
Aladdin and The Jungle Book include snakes.
Snakes are often portrayed as evil, coldblooded animals. Have students research this
phenomenon in literature and write an essay
on whether the reputation of the snake is
deserved. TAKS 1 Bio/IPC 2D
To body
To lungs
From
lungs
Left
atrium
Right
half of
ventricle
LS Verbal Co-op Learning
pp. 776–777
Student Edition
TAKS Obj 1 Bio/IPC 2C
TAKS Obj 2 Bio 8C
TAKS Obj 2 Bio 10A
TAKS Obj 3 Bio 7B
TEKS Bio 7B, 8C, 10A, 11A
TEKS Bio/IPC 2C
Teacher Edition
TAKS Obj 2 Bio 8C, 10A
TAKS Obj 3 Bio 7B
TAKS Obj 4 IPC 9D
TEKS Bio 7B, 8B, 8C, 10A, 11A
TEKS Bio/IPC 2C, 2D
TEKS IPC 9D
An incomplete septum partly
divides the ventricle. Thus,
there is less mixing of oxygen-rich
and oxygen-poor blood than there is
in the amphibian heart.
2
From body
Left
half of
ventricle
Arteries carry oxygen-rich
blood from the left half of
the ventricle to the body and
oxygen-poor blood from the right
half of the ventricle to the lungs.
3
Reproduction
Unlike the eggs of most amphibians, reptilian eggs are fertilized
within the female, a process called internal fertilization. The male
reptile introduces his semen directly into the female’s body. The
semen contains sperm and fluid secretions. Internal fertilization
protects the gametes from drying out, even though the adult animals are fully terrestrial.
Many reptiles are oviparous (oh VIHP urh uhs), meaning the
young hatch from eggs, as shown in Figure 6. In most cases, the
eggs are not protected by the parents. Most snakes and lizards, all
turtles and tortoises, and all crocodilians are oviparous. All birds
and three species of mammals are also oviparous.
Some species of snakes and lizards are ovoviviparous , which
means the female retains the eggs within her body until shortly
before hatching, or the eggs may hatch within the female’s body.
Although the embryos receive water and oxygen from the female,
their nourishment comes from the yolk sac. The offspring of a snake,
shown in Figure 6, are born able to fend for themselves. In ovoviviparous reptiles, the eggs are less vulnerable to predators.
The term ovoviviparous
comes from three different
Latin words: ovum, meaning
“egg,” vivus, meaning
“alive,” and parere, meaning “to bring forth or bear.”
Figure 6 Reproduction.
Sea turtles hatch from eggs
buried on sandy beaches.
The eggs of some species of
snakes are incubated within
the female’s body, and the
young are born live.
Close
Reteaching
Have students pair up and list each
of the seven key features of reptiles,
which are given in Figure 1, on
individual index cards. On the back
of each card, have them write a
one-word clue to identify the characteristic on the front of the card.
Ask students to shuffle the cards
and turn them so only the clue
words are showing. Have one student choose a card at random and
read the clue word. His or her partner should respond with the key
characteristic. If the student
answers correctly, his or her partner should set the card aside.
Students should continue the game
until all of the cards are set aside.
Students should then switch roles
and repeat the process.
LS Interpersonal Co-op Learning
TAKS 2 Bio 8C
Quiz
Sea turtles
Hatchling snakes
Section 1 Review
Identify seven characteristics of reptiles.
8C
Describe how the ectothermic nature of reptiles
11A
influences their physical activity and feeding habits.
Summarize the skin and egg adaptations that
allow reptiles to live on land.
7B
Critical Thinking Forming Reasoned
Opinions Data show that an animal’s tempera-
ture changes over the course of a day. A student
asserts that this proves the animal is an ectotherm. What must the student consider before
2C 11A
making such a claim?
Describe how reptiles meet their need for more
10A
oxygen than amphibians require.
TAKS Test Prep If a lizard’s internal
temperature sensors detect a decrease in body
temperature, the lizard can maintain
11A
homeostasis by
A speeding up its metabolism.
B slowing its metabolism.
C basking in the sunshine.
D resting in the shade.
TAKS 2 Bio 8C, 10A; TAKS 3 Bio 7B
777
Answers to Section Review
1. strong, bony skeletons, and toes with claws;
ectothermic metabolism; dry scaly skin, almost
watertight; amniotic eggs; well-developed
lungs; partly or completely divided ventricle;
internal fertilization TAKS 2 Bio 8C
2. Because they are ectotherms, reptiles must
thermoregulate behaviorally. They can be
physically active and hunt for food only when
their body temperature is within a certain
critical range. Bio 11A
3. The almost watertight skin and amniotic eggs
of reptiles minimize water loss on land.
TAKS 3 Bio 7B
GENERAL
True or False:
1. As in most amphibians, fertilization in reptiles is external. (False.
Fertilization is internal, an adaptation to life on land.) TAKS 2 Bio 8C
2. The heart of most reptiles only
partially separates blood from
the lungs and blood from the
body. (True. Except in crocodilians, freshly oxygenated blood
mixes in the heart with oxygendepleted blood.)
4. The student would need to compare the
animal’s temperature changes to changes in the
environmental temperature.
TAKS 1 Bio/IPC 2C; Bio 11A
5. In contrast to amphibians, reptiles have welldeveloped lungs with alveoli, as well as strong
rib muscles. Bio 11A
6.
A. Incorrect. Ectotherms cannot
alter their metabolism to maintain homeostasis.
B. Incorrect. A slower metabolism would
not increase body temperature. C. Correct.
Ectotherms maintain body temperature by
basking. D. Incorrect. Resting in the shade
would not increase body temperature. Bio 11A
Alternative
Assessment
GENERAL
Have teams of students write brief
descriptions of what they think are
the five most important things they
have learned about reptiles. Have
teams present their descriptions to
the class, with each team member
participating in the presentation.
LS Verbal Co-op Learning
TAKS 2 Bio 8C
777
Section 2
Section 2
Today’s Reptiles
Focus
Objectives
Overview
Edition. In this section, students are
introduced to the orders of the reptiles, one of the most diverse classes
of terrestrial vertebrates. Students
will also learn the distinguishing
characteristics of all the orders.
Bellringer
Ask students to list as many
reptiles as they can. Then, have
them indicate which reptiles on
their list are closely related. After
reading the section, have students
make corrections and add any
missing groups of reptiles to their
lists. (Students should indicate that
snakes and lizards are related, turtles
and tortoises are related, and that
crocodiles and alligators are related.
Students are probably unfamiliar with
the tuataras.) TAKS 2 Bio 8C; Bio 8B
Lizards and Snakes
● Compare the four living
orders of reptiles.
8C TAKS 2
You’ve probably walked by a snake or lizard without even knowing
it was there. Most are quiet, and their coloration often conceals
them from view. Even if you visited the jungles of South America,
● Describe the timber rattle7B you might not notice an anaconda unless it moved. What’s an anasnake’s adaptations for
locating and capturing prey. TAKS 3 conda? It’s the world’s largest snake, frequently reaching 5 m (about
16 ft) in length. The largest anaconda ever found was twice that
● Compare the parental care
long. Very large anacondas have been known to prey on jaguars.
of crocodilians with that of
After such a meal, the anaconda may not eat again for up to a year.
other reptiles.
8B
Snakes and lizards belong to order Squamata. A distinguishing
characteristic of this order is a lower jaw that is only loosely conKey Terms
nected to the skull. This allows the mouth to open wide enough to
carapace
accommodate large prey and explains how an anaconda can swalplastron
low a jaguar. This ability is a contributing factor to the success of
snakes and most lizards as predators.
Lizards
Common lizards include iguanas, chameleons, geckos, anoles, and
horned lizards (often mistakenly called “horny toads”). A few species
of lizards are herbivores, but most are carnivores. Most lizards are
small, measuring less than 30 cm (1 ft) in length, but lizards that
belong to the monitor family can be quite large. The Komodo dragon
of Indonesia, shown in Figure 7, is the largest monitor lizard. It can
be up to 3 m (10 ft) in length and weigh up to 125 kg (275 lb). The
tail of some species of lizards, such as the gecko shown in Figure 7,
breaks off easily when seized by a predator, allowing the lizard to
escape. Lizards can regenerate a new tail, but it does not have any
vertebrae in it.
Motivate
Demonstration
GENERAL
Obtain a picture of a skink, and
cover its body so that only its head
shows. Ask students if the animal is
a lizard or a snake. Then reveal the
rest of the animal, pointing out
how similar some lizards are to
snakes. Ask students how to tell a
lizard from a snake. (Most lizards
have legs and external ears, a pectoral girdle, and many have movable
eyelids. Snakes lack these features.)
LS Visual TAKS 2 Bio 8C; Bio 8B
Gecko
Figure 7 Lizards. Geckos
are small reptiles, rarely
exceeding 24 cm (10 in.) in
length. The Komodo dragon is
the world’s largest lizard.
Komodo dragon
778
pp. 778–779
Student Edition
TAKS Obj 2 Bio 8C
TAKS Obj 3 Bio 7B
TAKS Obj 3 Bio 12B
TEKS Bio 7B, 8C, 12B
Teacher Edition
TAKS Obj 2 Bio 8C
TAKS Obj 3 Bio 12B
TEKS Bio 8B, 8C, 12B
TEKS Bio/IPC 3C
778
• Lesson Plans GENERAL
Transparencies
TT
TT
TT
TT
TT
Bellringer
External Structures of Snakes
Internal Structures of Snakes
Orders of Living Reptiles
Orders of Extinct Reptiles
Planner CD-ROM
• Occupational Application Worksheet:
Emergency Medical
Technician GENERAL
Snakes
Snakes probably evolved from lizards during the Cretaceous period.
The close relationship between lizards and snakes is reflected in
their many similarities. In fact, it is often difficult to distinguish the
legless species of lizards from snakes. Snakes lack movable eyelids
and external ears, as do several species of lizards. Also, both snakes
and lizards molt periodically, shedding their outer layers of skin.
Body Structure The skeleton of snakes is unique. Most snakes have
no trace of a pectoral girdle (the supporting bones for the bones of
the forelimbs), which is found even in legless lizards. The snake’s
jaw is very flexible because it has five points of movement. (Your
jaw, in contrast, has only one movement point.) One of these points
is the chin, where the halves of the lower jaw are connected by an
elastic ligament. This ligament permits the lower jaw to spread
apart when a large meal is being swallowed. The African egg-eating
snake, shown in Figure 8, can swallow eggs that are much larger
than its head in a process that can take an hour or more.
Feeding While many snakes simply seize their prey and swallow it
whole, some snakes use other methods to subdue their prey. Many
very large snakes, such as anacondas, boas, and pythons, are constrictors, as are some smaller species, such as king snakes.
Constrictors wrap their body around their prey, gradually squeezing
tighter and tighter until the prey suffocates. The snakes then swallow their prey whole, even if the prey is very large. Like all snakes,
constrictors have no teeth that are suited for cutting and chewing.
Some snakes kill their prey with venom (poison). Of the 13 families of snakes, only four are venomous: (1) cobras, kraits, and coral
snakes; (2) sea snakes; (3) adders and vipers; and (4) rattlesnakes,
water moccasins, and copperheads. In most venomous snakes,
modified salivary glands produce a venom that is injected into the
victim through grooved or hollow teeth. The African boomslang
and twig snakes produce venom but do not inject it. Instead, they
bite their prey with fangs located at the back of their mouth.
Grooved teeth direct the venom into their victim’s wound. You can
read more about the biology of snakes in Up Close: Timber Rattlesnake, on the following pages.
Real Life
Teach
Need a lizard? TAKS 3
Instead of calling an
exterminator to rid their
homes of unwanted pests,
some adventuresome
homeowners keep a Tokay
gecko. This gecko preys
voraciously on mice and
insects and is very efficient
at ridding a home of
these pests.
Finding Information
Investigate the pros and
cons of using geckos for
pest control. Who should
try this method and who
should avoid it?
Real Life
Answer TAKS 3
Bio 12B
People who have other pets that
might harass a gecko, such as a
cat or a dog, should not try to
use geckos for pest control.
Teaching Tip
Figure 8 Snake feeding.
Snakes have flexible jaws that
allow them to swallow prey
much larger than their head.
Dangerous Snakes Ask students
what venomous snake is the most
dangerous in the world. Record
their responses. (examples: king
cobra, sea snake, coral snake, and
Australian tiger snake) Ask why a
particular species is considered
more dangerous than others. Tell
them that many different venomous
snakes are touted as the “most dangerous snake alive,” or the “most
poisonous snake on Earth.” Point
out that several factors determine
how “dangerous” a snake is.
Among these factors are the toxicity of its venom, the type of venom
(hemolytic or neurotoxic), and the
amount of venom a bite victim
receives. In India, there are about
900,000 snakebites each year,
resulting in about 9,000 deaths.
Many of these bites are delivered
by the aggressive king cobra, which
is frequently encountered by India’s
large human population. LS Verbal
Bio/IPC 3C
779
MEDICINE
CONNECTION
The American Red Cross recommends
the following first-aid treatment
for snakebite:
• Wash the bite with soap and water.
• Immobilize the area and keep it lower than
the heart.
• Get medical help.
Medical professionals are nearly unanimous in
their views of what not to do for snakebite:
• No ice or any other type of cooling on the bite
• No tourniquets
• No electric shock
• No incisions in the wound Bio/IPC 3C
779
Up Close
Up Close
Timber Rattlesnake TAKS 2, TAKS 3
Timber Rattlesnake
TAKS 2 Bio 8C, 10A; TAKS 3 Bio 7B; Bio 12C
Teaching Strategies
Help students understand the
rattlesnake’s ability to sense its
prey in the dark by using a
warm object such as a heating
pad. Place the heating pad on a
table and allow it to warm the
surface. Remove the heating
pad and have students move
their hands above the tabletop
without touching the table
itself. They should be able to
feel the heat radiating from the
warmed spot. Have students
determine how close their
hands must be to detect the
heat. Inform them that a rattlesnake can locate warm prey
from a distance of 1 m (39 in.).
These snakes, however, sense
heat with their pit organs, not
through their skin.
On a sheet of paper, have students list each major heading
in the Up Close feature. After
they read each section, have
them hypothesize how that
particular feature of the timber
rattlesnake is an adaptation for
survival. Then have students
exchange papers with a partner
and read their partner’s paper,
noting how their partner may
have identified a different
survival value for some of
the features.
●
Scientific name: Crotalus horridus
●
Size: Typically 90–150 cm (36–60 in.) long; maximum 189 cm (74 in.)
●
Range: Eastern and central United States, from northern
New York to northern Florida and west, to central Texas
●
Habitat: Prefers thick brush, dense woodland, or swamp
●
Diet: Primarily small mammals
Rattle The rattle typically consists of 5 to 7 interlocking rings
made of keratin, a protein. When shaken, it produces a rattling
sound that serves as a warning. Contrary to popular belief, the
snake does not add a rattle each year. Instead, each time the
▲
External Structures
Rattle
snake sheds its skin during molting, a new ring is added
to the base of the rattle. The more rapidly the snake
grows, the more rattles it accumulates during a
given time. This is why the number of rattles
a snake has increases with the size
of the snake.
Eye
Pit organ Between each eye and nostril of the rattlesnake is an organ
Nostril
▼
that can detect infrared radiation. The snake can locate a warm-bodied
Pit organ
animal in a cool, nighttime environment by detecting the difference in
infrared radiation emitted by the animal and the cooler background. Thus,
a rattlesnake can hunt in total darkness.
780
MISCONCEPTION
ALERT
pp. 780–781
Student Edition
TAKS Obj 3 Bio 7B
TEKS Bio 7B, 8C, 10A, 12C
Teacher Edition
TAKS Obj 1 Bio/IPC 2D
TAKS Obj 3 Bio 7B
TEKS Bio/IPC 2D, 3C
780
GENERAL
Slimy Snakes Contact a local nature center,
zoo, or herpetological society to arrange for a
live, non-poisonous snake and handler to
visit the class. Have students make a list of
some of their preconceptions about snakes.
For instance, many students believe that a
snake’s skin is slimy, like that of a frog.
Another misconception is that the tongue of
a snake is poisonous, and that snakes will
attack people for no reason. Show the class a
live snake, and allow students to touch and
examine the snake. Help to dispel misconceptions by discussing possible origins for such
fears. Remain sensitive to the fact that many
people will continue to fear snakes.
TAKS 1 Bio/IPC 2D
Internal Structures
Jacobson’s organs
snake has hollow upper front teeth,
or fangs. When the rattlesnake
▼
strikes, these hinged fangs swing
forward from the roof of the mouth
and inject venom deep into the prey.
The venom contains hemotoxins,
proteins that attack the circulatory
system, destroying red blood
cells and causing internal
Jacobson’s organs Flicking its
forked tongue into the air, the rattlesnake takes in chemical samples
from the environment. These chemicals are transferred to two depressions in the roof of the mouth called
Jacobson’s organs, which detect
the odor of the chemicals. The
snake uses these organs to follow
Fang
Venom
gland
hemorrhaging. Modified salivary
glands in the upper jaw produce
the venom.
▼
Venom glands The timber rattle-
the scent trail of prey.
Tongue
Stomach
Small intestine
Trachea
Esophagus
Gallbladder
Right lung
Left lung
Pancreas
Internal anatomy
Heart
The internal organs are
elongated, matching the
snake’s body shape. The
left lung is nonfunctional.
Large
intestine
Up Close
Timber Rattlesnake
Discussion
• Explain why it would be easier for a timber rattlesnake to
kill a mouse than a lizard at
night. (The mouse is an
endotherm and the pit viper’s
heat-sensitive pits can detect
its body heat. The lizard is an
ectotherm and would not necessarily be warmer than its
surroundings.)
• What is the advantage to a
rattlesnake of announcing its
presence to other animals by
rattling? (Answers may vary
but may include that by rattling the snake keeps large
mammals, such as cattle, from
stepping on it.)
• How is an ovoviviparous
snake, such as the timber rattlesnake, different from a
viviparous snake in the way
developing embryos are sustained? (Ovoviviparous
mothers supply no nutrients
to the developing young, while
viviparous mothers do.)
Liver
Kidneys
Cloaca
▼ Testes
▼ Spine
Reproductive structures This male rattlesnake
Spine The rattlesnake’s spine is
produces sperm in his testes. Female timber rattlesnakes
made up of several hundred ver-
are ovoviviparous. A female carries her fertilized eggs in her
body while they develop. Each egg has a thin membrane
through which water and oxygen pass from the mother to
tebrae, each with its own pair of
attached ribs. It provides the framework for thousands of muscles that
the embryo. All nourishment is provided by the egg’s yolk.
After the eggs hatch in the mother’s body, the live young
are ejected and must fend for themselves.
manipulate not only the skeleton but
also the snake’s skin, causing the
overlapping scales to extend or lie flat.
781
did you know?
Triple-jointed Jaws The tiny snakes called
threadsnakes have triple-jointed jaws. When a
threadsnake burrows into the nests of ants or
other social insects, parts of its lower jaw rotate
like a pair of swinging doors. It is thought that
this action helps the snake to eat quickly and
escape injury or death from ant stings.
Venomous Snakes About 99 percent of
venomous snakebites in the United States are
from pit vipers. About 8,000 snakebites
occur in the United States each year, and
around 9 to 15 victims die. Every state
except Maine, Alaska, and Hawaii is home
to at least one poisonous snake species.
TAKS 3 Bio 7B; Bio 12C
Bio /IPC 3C
781
Other Orders of Reptiles
The remaining orders of living reptiles contain far fewer species than
the order Squamata does. There are about 250 species of turtles
(which generally live in water) and tortoises (which live on land), all
classified in the order Chelonia. The order Crocodilia is composed of
25 species of large, aquatic reptiles. The order Rhynchocephalia
(RING koh seh FAY lee uh) contains only two species of tuataras.
Teach, continued
continued
Using the Figure
GENERAL
Point out in Figure 10 that a turtle’s
shoulders lie within its rib cage.
Students should recognize that their
own shoulders are outside of their
ribs. Tell students that a turtle is
attached to its shell and cannot
crawl out of it, as cartoon turtles
often do. LS Visual TAKS 3 Bio 7B
SKILL
Turtles and Tortoises
BUILDER
Writing Skills Have students
imagine that they are the first person from their country to see a
turtle. Ask students to write a
description of a turtle, for an audience that has never seen a turtle
before. Encourage them to be both
descriptive and accurate. LS Verbal
Figure 9 Turtle and
tortoise. Like other sea
turtles, this green sea turtle
(top) spends virtually its entire
life in the sea. The Galápagos
tortoise (bottom) spends its life
on land.
TAKS 1 Bio/IPC 2D
Turtles and tortoises, shown in Figure 9, differ from other reptiles
in that their bodies are encased within a hard, bony, protective
shell. Many of them can pull their head and legs into the shell for
effective protection from predators. While most tortoises have a
dome-shaped shell, water-dwelling turtles have a streamlined, diskshaped shell that permits rapid maneuvering in water. Turtles and
tortoises lack teeth but have jaws covered by sharp plates, which
form powerful beaks. Many are herbivores but some, such as the
snapping turtle, are aggressive carnivores.
Today’s turtles and tortoises differ little from the earliest known
turtle fossils, which date to more than 200 million years ago. This
evolutionary stability may reflect the adaptive aspects of their basic
shell-covered body structure. The shell is made of fused plates of
bone covered with horny shields or tough, leathery skin. In either
case, the shell consists of two basic parts. The carapace is the dorsal (top) part of the shell, and the plastron is the ventral (bottom)
portion. The vertebrae and ribs of most species are fused to the
inside of the carapace, as shown in Figure 10. The shell provides the
support for all muscle attachments in the torso.
Teaching Tip
Endangered Crocodilians Tell
students that although crocodilians
are fierce predators, many of the 25
species of crocodilians are endangered or threatened. Overhunting
of crocodilians for their hides,
which are used to make leather
goods, is the primary cause of their
decline. TAKS 3 Bio 12B; Bio/IPC 3C
Crocodiles and Alligators
Figure 10 Turtle interior.
In this ventral view, a turtle’s
plastron has been removed to
show the relationship of the
vertebral column, ribs, pelvis,
and pectoral girdle to
the carapace.
Of all the living reptiles, the crocodilians are most
closely related to the dinosaurs. In addition to
crocodiles and alligators, shown in Figure 11, the
order Crocodilia includes the alligator-like
caimans and the long-snouted gavial. Crocodilians
are aggressive carnivores. Some are quite large.
American alligators can reach 5.5 m (18 ft) in
length, and Nile crocodiles can reach 6 m (20 ft) in
length and weigh 750 kg (1,650 lb). Crocodilians
generally capture prey by stealth, often floating
just beneath the water’s surface near the shore. When an animal
comes to the water to drink, the crocodilian explodes out of the water
and seizes its prey. The crocodilian then hauls the prey back into the
water to be drowned and eaten. The bodies of crocodilians are well
adapted for this form of hunting. Their eyes are high on the sides of
the head, and their nostrils are on top of the snout. As a result, they
can see and breathe while lying nearly submerged in the water. Crocodilians have a very strong neck and an enormous mouth studded
782
Cultural
pp. 782–783
Student Edition
TAKS Obj 2 Bio 8C
TAKS Obj 2 Bio 10A
TAKS Obj 3 Bio 7B
TAKS Obj 3 Bio 12B
TEKS Bio 7B, 8B, 8C, 10A, 11B, 12B
Teacher Edition
TAKS Obj 3 Bio 7B, 12B
TEKS Bio 7B, 8B, 8C, 10A, 11B,
12B, 12C
TEKS Bio/IPC 2D, 3C
782
Awareness
Turtle Myths The turtle appears as a central character in mythologies from around
the world. An ancient Chinese myth
describes how the turtle Kwei created the
universe. The Chinese Book of Rites names
the turtle as one of the four benevolent
spirit animals. Hindu myths from India
describe the world as being supported by
four elephants standing on a turtle’s back.
And in North America, several native cultures imagined the world as an island on the
back of a great turtle. Bio/IPC 3C
did you know?
Alligators’ Sounds Alligators are unusual
among reptiles in being able to make definite
vocalizations. The male alligator bellows
loudly during mating season. Vocal sacs on
each side of his throat inflate when he calls.
When alligators hatch from their buried eggs,
they make a sound that is almost like a bark.
The sound signals their mother that it is time
to open the nest. Hatchlings also have a distress call they use to alert their mother if they
feel threatened. TAKS 3 Bio 7B; Bio 12C
Australian crocodiles
Close
Reteaching
Write the following words or
phrases on the board: lizards and
snakes, turtles and tortoises, crocodiles and alligators, and tuataras.
Have students copy them, leaving
space for additional information.
Have students write distinguishing
traits of each group in the appropriate spaces without using their
textbooks. (lizards and snakes-lower
jaw has loose connection to skull, no
pectoral girdle in snakes, molt periodically, may lack eyelids; turtles and
tortoises-hard shell, lack teeth, jaws
have a powerful beak; crocodiles and
alligators-long snout, eyes high on
head, nostrils on top of head, large
mouth with sharp teeth; tuataraslizardlike, active at night) When the
students have finished their work,
have them share their results with a
partner, recording any characteristics they omitted but their partner
identified. LS Verbal Co-op Learning
American alligator
with sharp teeth. A valve in the back of the mouth prevents water from entering the lungs when crocodilians
feed underwater.
Unlike other living reptiles, crocodilians care for
their young after hatching. For instance, a female
American alligator builds a nest of rotting vegetation
for her eggs. After the eggs hatch, the mother may tear
open the nest to free the hatchlings. The young alligators remain under her protection for up to a year.
Figure 11 Crocodilians. In general, the
snouts of alligators are shorter and broader
than those of crocodiles.
Tuataras
The two living species of tuataras are members of the
genus Sphenodon and are native to New Zealand.
Sphenodon punctatus, the more common species, is
shown in Figure 12. Tuataras are lizardlike reptiles up
to 70 cm (2 ft) long. Unlike most reptiles, tuataras are
most active at low temperatures. They burrow or bask
in the sun during the day and feed on insects, worms,
and other small animals at night. Tuataras are sometimes called living fossils because they have survived
almost unchanged for 150 million years. Since the
arrival of humans in New Zealand about 1,000 years
ago, the tuatara’s range has diminished, and their
numbers are declining.
TAKS 2 Bio 8C; TAKS 3 Bio 7B; Bio/IPC 2D; Bio 8B
Figure 12 Tuatara. Tuataras live on
only a few small islands in New Zealand.
Quiz
Section 2 Review
Describe the characteristics shared by lizards
8C
and snakes.
Describe the function of two different organs
7B
that help snakes locate their prey.
Summarize the ways turtles and tortoises differ
from other reptiles.
8B 10A 11B
Compare the parental care shown by alligators
with that shown by most other reptiles.
8B
Critical Thinking Recognizing Relationships
How does the position of a crocodile’s nostrils and
11B
eyes relate to its method of hunting?
TAKS Test Prep The pit organ of a rattle11B
snake is sensitive to
A airborne chemicals.
B faint sounds.
C ground vibrations.
D infrared radiation.
characteristics with snakes are
the ________ (lizards) TAKS 2 Bio 8C
2. Unlike other reptiles, ________
care for their young after they
hatch. (crocodilians) TAKS 2 Bio 8C
3. The shells of turtles and tortoises
consist of a plastron on the
underside and a ________, which
fuses with the rib cage. (carapace)
TAKS 3 Bio 7B
783
1. Snakes and lizards both have scaly skin and
molt periodically. Their lower jaw is loosely
connected to the skull. TAKS 2 Bio 8C
2. Jacobson’s organs, located in the roof of the
mouth, detect microscopic airborne particles,
which the brain interprets as scent. Pit vipers
use their pit organs to detect heat. TAKS 3 Bio 7B
3. Their bodies are encased in a protective shell,
and they lack teeth. TAKS 2 Bio 10A; Bio 8B, 11B
4. Alligators and other crocodilians are the only
reptiles to care for their young. Some alligators
build nests for their young and care for them
for up to a year after they hatch. Bio 8B
GENERAL
1. The reptiles that share the most
5. The crocodile is able to keep most of its body
submerged and hidden while still being able to
breathe and look for prey. Bio 11B
6.
A. Incorrect. The Jacobson’s
organs in the roof of the mouth are sensitive to
airborne chemicals. B. Incorrect. Snakes lack
ears and do not hear faint sounds. C. Incorrect.
Snakes can feel ground vibrations through
their bodies, not the pit organs. D. Correct.
Using pit organs, warm-blooded animals can
be found even in the dark. Bio 11B
Alternative
Assessment
Assign students to work in groups
of three. Each group will research
the reptiles of an assigned continent. For each reptile, include the
following: order, appearance
(drawing), size, diet, habitat, range,
and status (common, rare, threatened, or endangered). When groups
have finished their research and
drawings, the entire collection can
be assembled on a large mural of
the continents. Ask a local elementary school to display the mural.
LS Interpersonal Co-op Learning
TAKS 2 Bio 8C
783
Section 3
Characteristics and
Diversity of Birds
Section 3
Focus
Overview
Edition. In this section, students will
summarize the key features of birds.
These include several reptile-like
characteristics, such as amniotic
eggs and scale-covered feet and legs.
Unique adaptations include feathers
for flight and insulation, a strong yet
very lightweight skeleton, a highly
efficient respiratory system and
completely divided heart. These features allow flight for nearly all birds.
Students will also examine the highly
variable beaks and feet of birds,
which allow different species to
make use of a range of diets and
habitats.
Key Characteristics of Birds
Objectives
Why do people use the expression “free as a bird”? Most likely it
● Summarize the key characteristics of birds.
8C TAKS 2 comes from a bird’s ability to fly seemingly wherever it wishes.
Through human history, the gift of flight has been celebrated in stories, poetry, and songs. But there is more to birds than flight; in
fact, some species of birds can’t fly.
The birds you see today are the modern members of class Aves.
● Summarize how a bird’s
Unlike
their reptilian relatives, birds lack teeth and have a tail that
lungs and heart are adapted
is greatly reduced in length. But they do retain some reptilian
7B 10A
for high efficiency.
TAKS 2, characteristics. For instance, birds lay amniotic eggs that are very
● Relate the structure of a TAKS 3
similar to those of reptiles, and the feet and legs of birds are
bird’s feet and beak to its
covered with scales. Other characteristics unique to birds distin7B 11B
habits and diet.
guish them from all other animals. The most obvious is the
TAKS 3
presence of feathers and the modification of the forelimbs into
Key Terms
wings. Figure 13 lists some distinguishing features of birds. To
contour feather
learn more about the anatomy and habits of one bird, see Up
preen gland
Close: Bald Eagle later in this section.
● Describe how a bird’s
feathers and bone structure
aid flight.
7B TAKS 3
down feather
Feathers
Feathers are modified reptilian scales that develop from tiny pits,
called follicles, in the skin. Just as snakes and lizards replace their
skin by molting, birds molt and replace their feathers. However, few
birds shed all of their feathers at one time.
Birds have two main types of feathers: contour feathers and
down feathers. Contour feathers cover the bird’s body and give
adult birds their shape. Specialized contour feathers, called flight
feathers, are found on a bird’s wings and tail. These feathers help
provide lift for flight. As shown in Figure 14, a contour feather has
many branches called barbs. Each barb has many projections, called
Bellringer
Ask students to list the unique adaptations of birds that allow them to
fly. TAKS 3 Bio 7B
www.scilinks.org
Topic: Characteristics
of Birds
Keyword: HX4036
Motivate
Demonstration
Bring a feather to class and ask
students what kind of animal it is
from. When students answer “a
bird,” ask them to think of any
bird that does not have feathers.
(There are none.) Ask them if they
can think of any living animals that
have feathers but are not considered birds. (no) Emphasize that
having feathers is a unique classification characteristic for the class
Aves. LS Visual TAKS 2 Bio 8C; Bio 8B
Characteristics of Birds
Figure 13 Characteristics
of birds. Like most birds, this
tern is well adapted to flight.
•
•
•
•
•
Forelimbs modified into wings
Body covered with feathers
Lightweight bones
Endothermic metabolism
Super-efficient respiratory
system
• Heart with completely
divided ventricle
784
Transparencies
pp. 784–785
Student Edition
TAKS Obj 2 Bio 8C
TAKS Obj 2 Bio 10A
TAKS Obj 3 Bio 7B
TEKS Bio 7B, 8C, 10A, 11B
Teacher Edition
TAKS Obj 2 Bio 8C
TEKS Bio 3D, 7B, 8B, 8C
TEKS Bio/IPC 2D
784
• Lesson Plan GENERAL
• Data Sheet for Math Lab
GENERAL
Planner CD-ROM
• Supplemental Reading Guide
Through a Window
TT
TT
TT
TT
TT
TT
Bellringer
Characteristics of Birds
Contour Feather Structure
Avian Skeleton
Avian Heart Structure
Avian Lung Structure
Figure 14 Contour feather
The structure of a contour feather helps create a smooth,
aerodynamic surface, aiding flight.
Teach
Vane
READING
SKILL
BUILDER
Barb
Shaft
Barbule
Paired Summarizing After
students have read silently about
birds, have pairs of students summarize what they have read without
looking at the textbook. One student
should listen without interrupting
but should be prepared to point out
any inaccuracies in the summary, and
to add any ideas that were left out.
Students may refer to the textbook
during this clarification process.
You may want to pair ELL students with native
English Language
Learners
English speakers.
Hook
barbules, that are equipped with microscopic hooks. These hooks link
the barbs to one another, giving the feather a continuous surface and
a sturdy but flexible shape. With use, the connections become
undone. When you see a bird pulling its feathers through its beak,
it is relinking these connections. This process is called preening.
Preening also serves another function. Most birds have a gland called
a preen gland which secretes oil. When a bird preens, it spreads the
oil over its feathers, cleaning and waterproofing them.
Down feathers cover the body of young birds and are found
beneath the contour feathers of adults. Their soft, fluffy structure
provides good insulation for the bird, helping the bird conserve
body heat.
Feathers are important for other reasons too. Their coloration
may be protective (as camouflage) or may be important in the selection of a mate. For example, the feathers of some birds allow them
to blend in with their surroundings. In other species, the males
develop special plumage during the breeding season.
Teaching Tip
Figure 15 Avian skeleton.
A bird’s large, keeled attachment point for flight muscles,
while its fused collarbones
(wishbone) help absorb the
stresses of flight.
Strong, Lightweight Skeleton
If you have ever picked up a bird, such as a parakeet, you may have been surprised at how light it
was compared to a mammal of a similar size. This
is because the bones of birds are thin and hollow.
Many of the bones are fused, making a bird’s skeleton more rigid than a reptile’s. The fused sections
form a sturdy frame that anchors muscles during
flight. The power for flight (or for swimming
underwater in the case of some birds, like penguins) comes from large breast muscles that can
make up 30 percent of a bird’s body weight. These
muscles stretch from the wing to the breastbone.
The breastbone is greatly enlarged and bears a
prominent keel for muscle attachment, as illustrated in Figure 15. Muscles also attach to the fused
collarbones (wishbone). No other living vertebrates
have a keeled breastbone or fused collarbones.
TAKS 2 Bio 8C; Bio 8B
TAKS 1 Bio/IPC 2D; TAKS 3 Bio 7B
Demonstration
Fused
collarbones
Keeled breastbone
785
Career
Veterinarian When most people think of a
veterinarian, they think of a “dog or cat
doctor.” Many students will know that veterinarians also treat livestock. However, most
people probably do not know that veterinarians also treat birds and reptiles. Have students
investigate the training required to become a
veterinarian, and have them find out where
vet schools are located in your region
of the country. LS Verbal Bio 3D
GENERAL
Preening Birds often sit and preen
their feathers. Students have probably observed this behavior. Have
students hypothesize about the
function of preening and the reason
that birds spend so much time doing
it. After a period of discussion,
point out that when birds preen,
they smooth out and clean their
feathers, making them more aerodynamic. Also note that birds spread
oil from a gland near the base of
their tail to waterproof the feathers
and make them more resistant to
breakage, much the way hair conditioner works. LS Logical
MISCONCEPTION
ALERT
Bird Nests Children who find bird nests
are often warned not to touch them. The
children are told, “the mother won’t return
to the nest if you touch it.” In reality, most
birds have a very poor sense of smell and
probably would not know if their nest had
been touched by a human (exceptions are
flightless birds, ducks, and vultures). To
compensate, many birds have keen vision
and hearing. LS Interpersonal TAKS 3 Bio 7B
GENERAL
Bring cooked, cleaned chicken
bones to class for students to examine. Cut a few bones in half so students can see the hollow structure.
If you have a wishbone, allow students to pull it gently to note its
flexibility. The cartilage keel on the
breast of a chicken is also interesting to examine because it provides
an attachment surface for flight
muscles. LS Visual TAKS 3 Bio 7B
785
Endothermic Metabolism
Interpreting Graphics
After studying Figure 18, use
your own words to summarize how one breath of air
circulates through a bird’s
lungs. Remember to include
both the inhalation and the
exhalation cycle.
Teach, continued
continued
Teaching Tip
Heat Source The high temperature of birds is a by-product of
their rapid metabolism. You may
wish to use the analogy of a car
engine for metabolism. If the
engine is running, heat is produced.
The faster the engine is running,
the more heat is produced.
Ectothermic reptiles are like cars
whose engines run very slowly all
the time, producing little heat. In
contrast, birds (and mammals)
keep their engines running at high
speed all of the time, producing
much heat. TAKS 3 Bio 7B
www.scilinks.org
Topic: Texas Songbirds
Keyword: HXX4021
Completely Divided Ventricle
As in crocodilians, the ventricle of birds is completely divided by a
septum, as shown in Figure 16. Oxygen-rich and oxygen-poor blood
are kept separate, meaning that oxygen is delivered to the body cells
more efficiently. The sinus venosus, which is a prominent part of
the fish heart, is not a separate chamber of the heart in birds (or
mammals). However, a small amount of tissue from it remains in
the wall of the right atrium. This tissue is the point of origin of the
heartbeat and is known as the heart’s pacemaker.
Highly Efficient Lungs
IPC Benchmark
Mini-Lesson
Biology/IPC Skills TAKS 5 IPC 4B
Investigate and describe applications
of Newton's laws.
Newton’s second law states that the
amount of force acting on an object is
equal to the object’s mass multiplied by
its acceleration. Furthermore, an
object’s momentum is the product of its
mass and velocity. This helps explain
one of the principles of flight. Bird’s
wings have a special shape called an
airfoil and airplane wings mimic this
shape. As a mass of air passes over a
wing it’s path is bent downward,
thereby changing its momentum.
Changes in the momentum of the air
result in changes on the forces acting
on the wing. The amount of lift on a
wing depends on the amount and
velocity of the air being diverted
downward. For more lift, the wing can
either divert more air—the mass—or
increase the downward velocity of the
air. Activity: Have students build paper
airplanes that have airfoil wings. Then
test them outside to see if their designs
were successful.
Birds are endotherms; that is, they generate enough heat through
metabolism to maintain a high body temperature. Birds maintain
body temperatures ranging from 40°C to 42°C (104°F to 108°F),
which is significantly higher than the body temperature of most
mammals. For comparison, your body temperature is 37°C (98°F).
These high temperatures are due to a high rate of metabolism,
which satisfies the increased energy requirements of flight.
Figure 16 Avian heart.
A bird’s heart has a
complete septum.
Birds such as the geese shown in Figure 17 use a considerable
amount of energy when they fly. Since birds often fly for long periods of time, their cellular demand for energy exceeds that of even
the most active mammals. How do birds get the energy they need?
Recall that reptiles meet their increased need for oxygen with
lungs that have a larger surface area than the lungs of amphibians.
But there is a limit to how much the efficiency of a lung can be
improved just by increasing its surface area. Another way to
Avian Heart Structure
Oxygen-poor blood from the body enters
the right atrium. The right atrium pumps
this blood to the right ventricle.
1
To body
From body
Oxygen-rich blood from the
lungs enters the left atrium,
which pumps it to the left ventricle.
3
To lungs
From
lungs
Left
atrium
Right
atrium
Left
ventricle
Complete
septum
Right
ventricle
2
The right ventricle pumps the
oxygen-poor blood to the lungs.
From body
The left ventricle pumps
the oxygen-rich blood to
the body.
4
786
Cultural
Awareness
pp. 786–787
Student Edition
TAKS Obj 2 Bio 10A
TAKS Obj 3 Bio 7B
TEKS Bio 7B,10A
Teacher Edition
TAKS Obj 3 Bio 7A, 7B
TAKS Obj 5 IPC 4B
TEKS Bio 7A, 7B, 12C
TEKS Bio/IPC 2C, 2D, 3C
TEKS IPC 4B
786
Eagle Feathers The only people in North
America who can legally own eagle feathers
are Native Americans. The eagle is so highly
valued by tribes throughout the United States
that its feathers must be earned through personal sacrifice, and then they may be used only
in special ceremonies. For instance, if a
Winnebago pow-wow dancer accidentally
drops an eagle feather during a performance,
the dance is stopped until the feather is purified
by an elder and then reclaimed by the dancer,
who is not allowed to dance again for a year.
Bio/IPC 3C
increase the efficiency of a lung is to have air
pass over its respiratory surface in one direction only, just as water flows over a fish’s gills in
one direction. This is what happens in birds.
One-way air flow is possible in birds because
they have air sacs connected to their lungs, as
shown in Figure 18. There is no gas exchange in
the air sacs. They simply act as holding tanks.
There are two important advantages to oneway air flow. First, the lungs are exposed only to
air that is almost fully oxygenated, increasing
the amount of oxygen transported to the body
cells. Second, the flow of blood in the lungs
runs in a different direction than the flow of air does. Unlike the
flow of water and blood in fish gills, the flow of air and blood in bird
lungs are not completely opposite (countercurrent). Nevertheless,
the difference in direction does increase oxygen absorption.
These three characteristics—endothermic metabolism, a completely divided ventricle, and highly efficient lungs—provide the
energy a bird needs for takeoff and sustained flight. They enable a
hummingbird to flap its wings rapidly (20–80 beats per second) as it
hovers by a flower. They also permit migrating birds to fly thousands of kilometers without stopping. One species of shorebirds
called the lesser yellowlegs flies across the open ocean from Massachusetts to Martinique in the West Indies. Incredibly, some of these
birds cover this distance of 3,220 km (about 2,000 mi) in less than
6 days. Note, however, that many birds, such as gulls and vultures,
remain aloft for long periods of time using little energy. These birds
take advantage of upward air movements that lift them.
Teaching Tip
White or Dark Meat? The dark
color of some chicken meat is partly
due to the presence of myoglobin, a
hemoglobin-related molecule that
helps provide oxygen to muscles
that must contract vigorously and
repeatedly. Ask students why a
duck has dark breast meat but a
chicken has white breast meat. (The
duck flies long distances, but the
chicken does not.) Ask what chickens usually use for locomotion and
what color that meat is. (They usually use their legs to walk, and the
legs contain dark meat.)
Figure 17 Flight. These
barnacle geese expend an
enormous amount of energy
during take off and flight.
Activity
Origin of Birds Ask students to
identify the living reptiles that are
most closely related to birds.
(crocodilians) Have them name two
characteristics that crocodilians
and birds share. (a heart with completely divided ventricle, parental
care of young, amniotic eggs, and
vocalization) Have students
research recent fossil discoveries
that have changed views on the
origin of birds. LS Verbal
Figure 18 Avian
respiration. A single breath
of air stays in a bird’s respiratory system for two cycles
of inhalation and exhalation.
Avian Lung Structure
Right lung
Inhalation
Trachea
GENERAL
inhalation, most of the
1 During
fresh air (yellow) inhaled is
pulled into the posterior air sacs.
At the same time, stale air (green)
from the previous inhalation is
pulled into the anterior air sacs.
TAKS 1 Bio/IPC 2C, 2D; TAKS 3 Bio 7A
(grade 11 only), 7B
Anterior air sacs
Posterior air sacs
During exhalation, fresh air
(yellow) from the posterior
air sacs enters the lungs. At the
same time, stale air (green) from
the previous inhalation moves
from the anterior air sacs out
of the body.
2
Exhalation
787
did you know?
Brood Parasites The brown-headed cowbird
is a brood parasite. A female brown-headed
cowbird will fly to a nest full of eggs, roll one or
two eggs out, and lay the same number as the
number she has displaced. When the owner of
the nest returns, it will incubate all the eggs,
including the cowbird’s. The cowbird eggs often
have a shorter incubation time and hatch before
the eggs of the incubating species. Therefore, the
cowbird nestlings are fed first and get a head
start in their development over the other chicks
in the nest. Cowbird nestlings may even eject
the nestlings of the incubating species, thereby
eliminating competition for food.
787
Up Close
Up Close
Bald Eagle
Bald Eagle TAKS 2 Bio 8C, 10A;
TAKS 3 Bio 7B, 12B; Bio 3F
Scientific name: Haliaeetus leucocephalus
●
Size: Wingspan is typically over 2 m (6.5 ft), and body
weight often exceeds 7 kg (15 lb)
●
Range: Nearly all of North America, from Florida to
northern Alaska
●
Habitat: Forested areas near water that have tall
trees for perching and nesting
●
Diet: Fish, small mammals, birds, carrion
External Structures
Eyes Vision is a bald
eagle’s most important
sense. The bird’s keen
eyesight allows it to see
prey at great distances.
Its visual acuity is 3–4
times higher than ours.
▲ Eye
▼ Feathers
Feathers The body of
the bald eagle is covered
with feathers everywhere
except the feet and the
beak, which are bare.
Nostril
Both sexes develop the
characteristic white head
and neck at maturity.
▼ Beak
Grasping feet The bald eagle
Beak The beak is mas-
has large feet and talons—the hind
sive, with an elongated,
talon may be 5 cm (2 in.) long. The
talons are used to snatch fish from
the water while the eagle is flying.
sharp, downward-curving
tip. Because they have no
teeth, bald eagles do not
chew their food. Instead,
they use their beak to tear
their prey into portions
that they swallow whole.
Grasping feet
When the muscles of the legs
contract, the tendons in the lower
legs are pulled, and the talons
lock together around the fish.
788
pp. 788–789
Student Edition
TEKS Bio 3F, 7B, 8C, 10A, 12B
Teacher Edition
TEKS Bio 3F, 7B, 8C, 10A, 12B
TEKS Bio/IPC 2D
788
●
▲
Teaching Strategies
• The largest bald eagle nests
in North America were
found in Vermillion, Ohio—
3.7 m (12 ft) deep, 2.6 m
(8.5 ft) in diameter, and
weighing 1,800 kg (2 tons)and in Florida—6.1 m (20 ft)
deep and 2.9 m (9.5 ft)
across. An eagle nest is called
an aerie.
• After World War II, the numbers of bald eagles in the
lower 48 states fell drastically
because of the widespread use
of the pesticide DDT. Because
DDT breaks down very
slowly, it accumulates in the
food chain and causes the
eggshells of bald eagles and
many other birds to become
thin and fragile. Affected eggs
break when a parent attempts
to incubate them. In 1972,
the use of DDT was banned
in the United States. By 1978,
fewer than 500 breeding pairs
of bald eagles remained in the
United States outside Alaska.
A slow recovery of the eagles
began, and by the summer of
1999, six states had removed
bald eagles from the endangered species list.
• Show students a picture of a
large but immature bald
eagle and ask them what
kind of bird it is. Point out
that the bald eagle does not
get its white head and tail
until its fourth or fifth year
of life.
TAKS 2, TAKS 3
Transparencies
TT
TT
TT
TT
External Structures of Birds
Internal Structures of Birds
Avian Adaptations
Major Orders of Birds
Talon
Internal Structures
Brain In the ratio of brain size to body size, birds rank
Up Close
Cerebrum
Cerebellum
second among vertebrates, behind only mammals. The
large cerebellum receives and integrates information from
the muscles, eyes, and inner ears. This makes possible the
precise control of movement and balance necessary for flight.
The optic lobe is large because it processes input from the
eagle’s most important sense organs—the eyes. The
cerebrum performs many functions, including evaluation of
sensory information, control of behavior, and learning.
Bald Eagle
Medulla oblongata
Discussion
• Identify three differences
between the internal structures of the timber rattlesnake
and the bald eagle. (The rattlesnake has one functional
lung, lacks air sacs, has neither
a crop nor a gizzard, has
venom-producing glands, and
does not have hollow bones.)
• Would the heat-sensitive pits
of the timber rattlesnake be
an effective way of sensing
prey for a bald eagle? (No, the
rattlesnake’s pits are sensitive
only to nearby heat sources,
and the bald eagle spots its
prey from great distances.)
Optic lobe
▲ Brain
Excretory system The excretory system is
efficient and lightweight. It does not store waste
liquids in a bladder. Instead, the bald eagle
(and other birds) converts its nitrogenous
wastes to uric acid, which is concenLeft lung
trated into a harmless white paste.
Left ovary
The uric acid travels to the
cloaca and is eliminated.
Kidney
Esophagus
▼
Trachea
Air sac
Crop
• Why might it be a disadvantage for an eagle to have a
urinary bladder? (Urine contains a greater amount of
water, which is heavy. The
extra weight would be a disadvantage in flight.)
• Why might teeth be a disadvantage to a bird? (Teeth are
heavy and require heavy jaws.)
Small intestine
Heart
Large intestine
Liver
Pancreas
▼ Gizzard
Digestive system Large
meals are temporarily stored in
▼ Cloaca
Cloaca The cloaca is a common
collecting chamber for the excretory,
digestive, and reproductive systems.
As fertilized eggs travel down the
female eagle’s oviduct, egg white,
membranes, and the shell are added.
The completed egg then passes
into the cloaca and out of the
female’s body.
LS Visual
the crop, the expandable
lower portion of the esophagus.
The food then passes into a
two-chamber stomach. In the
first chamber, stomach acids
begin breaking down the food.
Activity
The partially digested food is
then passed to the second
chamber, the gizzard, where
it is ground and crushed.
Undigested material is
eliminated through the cloaca.
789
GENERAL
Eagle Eyes Eagles have much
better vision than humans do. To
simulate how much better, tape a
worksheet on the wall and have
students stand about 3 m away and
try to read it. Then have them
move 1 m away and read the worksheet. Tell them that an eagle could
see the paper at 3 m as well as
humans can at 1 m.
TAKS 1 Bio/IPC 2D; TAKS 3 Bio 7B
789
Adaptations of Birds
While there is great diversity among the 28 orders of birds,
60 percent of all bird species belong to order Passeriformes.
These birds, also know as the songbirds, number approximately 5,300 species and are by far the largest group of terrestrial vertebrates. Birds are adapted for different ways of
life, and you can tell a great deal about the habits and diet of
a bird by examining its beak (bill), legs, and feet. Carnivorous
birds such as hawks have curved talons for seizing prey and
a sharp beak for tearing apart their meal. The beaks of ducks
are flat for shoveling through water or mud, and their
webbed feet enable them to swim. Finches are seed eaters,
and their short, thick beak is adapted for crushing seeds
while their curved toes enable them to cling to branches.
Other birds, such the penguins shown in Figure 19, are flightless, and their wings and feet are modified for swimming.
During the evolutionary history of birds, their beaks, legs,
and feet have been adapted to the particular environment the
birds live in, as shown in Table 1. Some birds are more highly
specialized than others, and many birds are highly flexible in
their eating habits. The song sparrow, for example, has a
strong bill that it uses in winter to crack hard seeds. In summer, the sparrow uses its bill to catch soft-bodied insects.
Teach, continued
continued
Teaching Tip
GENERAL
Reptiles and Birds Have students
make a three-column chart like the
one in the Graphic Organizer
shown at the bottom of this page.
They should use the information on
birds in Section 3 and the material
on reptiles in Sections 1 and 2.
Students should use the following
characteristics for both reptiles and
birds: type of body covering, type
of heart, mode of reproduction,
type of metabolism, and parental
care of offspring. LS Visual
TAKS 2 Bio 8C, 10A; TAKS 3 Bio 7B
Figure 19 Penguin. The
penguin’s wings are adapted
for swimming rather than flying.
Teaching Tip
Introduced Pests House sparrows and European starlings are
two common birds that may be
familiar to students. Inform students that these two species were
introduced into the United States
from Europe. Both species have
become serious pests. These exotic
species out compete native songbirds for food and nesting sites. In
fact, they are thought to be at least
partly responsible for the decline in
the numbers of bluebirds. Bio/IPC 3C
Table 1 Avian Adaptations
Type of bird
Beak adaptations
Foot adaptations
Songbirds (e.g., cardinal, robin)
Perching: Toes can cling to
branches; one toe points backward
Seed-cracking:
Short, thick,
strong beak
Insect-catching:
Long, slender
beak for probing
Hummingbirds
Probing: Thin, slightly curved beak
for inserting into flowers to sip nectar
Hovering: Legs so small the
bird cannot walk on the ground;
tiny feet
790
Graphic Organizer
Use this graphic organizer with Teaching Tip: Reptiles and Birds.
pp. 790–791
Student Edition
TAKS Obj 2 Bio 8C
TAKS Obj 3 Bio 7B
TEKS Bio 7B, 8C
Teacher Edition
TAKS Obj 3 Bio 7B
TEKS Bio/IPC 2C, 2D, 3C
790
Characteristic
Body covering
Type of heart
Reproduction
Metabolism
Parental care
Reptiles
Birds
Scaly skin
Partially or completely
divided ventricle
Oviparous or ovoviviparous
Ectothermic
Little or none
Feathers
Completely divided
ventricle
Oviparous
Endothermic
Until offspring can fly
Beak adaptations
Type of bird
Woodpeckers
Drilling: Strong, chisel-like beak
Foot adaptations
Using the Table
Grasping: Feet with two toes
pointing forward and two pointing
backward
Parrots
Cracking, tearing: Short, stout,
hooked beak used to crack seeds
and nuts and to tear vegetation
Climbing/grasping: Strong toes,
two pointing forward, two pointing
backward; adapted for perching,
climbing, and holding food
Birds of prey
Tearing: Curved, pointed beak for
pulling apart prey
Grasping: Powerful, curved talons
for seizing and gripping prey
Have students pair up. Instruct the
students to cover the two columns
on the right side of Table 1 with a
sheet of paper. Have one student
uncover the Beak adaptations column, choose one, and read the
description. The other student
should try to identify the type of
bird whose beak is described. This
process should continue until the
second student has correctly identified each bird. The students should
then switch roles and repeat the
process using the Foot adaptations
column. LS Verbal
Ducks
Sieving: Long, flattened, rounded bill
Demonstration
Show students pictures of several
different types of birds. Be sure
to include some with distinctly
different beaks and feet. A typical
assortment would be: woodpecker,
heron, pelican, grosbeak, chickadee, goose, and hummingbird.
Ask students to examine the different types of beaks and feet and to
hypothesize about each bird’s habitat and diet. LS Visual
Swimming: Three toes linked by
webs for improved swimming
Group Activity
Long-legged waders
Fishing: Long, slender, spear-shaped
beak for fishing
Wading: Long
legs; toes
spread out over
a large area to
support bird on
soft surfaces
791
Trends in Ornithology
Researchers around the country have been
monitoring bird populations each year to
determine long-term trends. One apparent
trend: of the 42 bird species that are listed as
threatened or endangered, 22 are associated
with wetlands. The trend holds true for other
animals as well. Have students research the
threatened and endangered birds in your area.
In their reports, students should discuss the
probable causes of decline, as well as plans for
species recovery. Bio/IPC 3C
REAL WORLD
CONNECTION
Birding (once called birdwatching) has been
described as the second-favorite outdoor
activity in the United States, after gardening.
Invite a local naturalist or member of a
nearby chapter of the Audubon Society to
visit your classroom and discuss tips on how
to attract and identify backyard birds. Make
a list of local birds and show slides of each
bird to your class. Slides can be purchased
from many sources, including the Cornell
University Laboratory of Ornithology.
Avian Adaptations Divide the
class into small groups, and assign
each group a particular feeding
strategy and bird habitat. Have each
group use a field guide to identify
five species of birds that share the
assigned feeding strategy and
habitat. Students should then use
drawings or written descriptions to
demonstrate the similarities in beaks,
feet, and behavior among birds with
similar lifestyles. Have each group
share its findings with the entire
class. LS Visual Co-op Learning
TAKS 1 Bio/IPC 2C, 2D;
Bio/IPC 3C; Bio 8C
791
Other Adaptations
x 2+ 6x
76
0
2
5
-7-0
Calculating
Average Bone
Density TAKS 1 Bio/IPC 2C, 2D;
TAKS 3 Bio 7B
Skills Acquired
Analyzing data,
calculating
8
0
2
493
x 2+ 6x
5
Calculating Average Bone Density
-7-0
<
493
<
18
There are many groups of birds, each of which is adapted to its particular living conditions. For example, gulls and terns have streamlined bodies that are adapted for flying over the water in search of
fish. Owls’ excellent low-light vision enables them to survive as nocturnal hunters. For a list of the orders of birds, see “Classification
in Kingdoms and Domains” in the Appendix.
Teacher’s Notes
After students read the explanatory paragraph, have them
glance at the data and predict
which animal has the higher
average bone density.
2C 2D 7B
TAKS 1, TAKS 3
Background
Density is the ratio of the mass of an object to its volume. Several teams of students
determined the density of bones from two different animals. You can use their data
to practice calculating average bone density.
DATA TABLE
Bone type
Answers to Analysis
1. Animal 1: 1.3 g/cm3;
Animal 2: 2.0 g/cm3
2. A certain amount of variation
is normal in biological systems.
3. Animal 1
Team 1
Team 2
Team 3
Team 4
Animal 1
1.6 g/cm3
1.0 g/cm3
1.2 g/cm3
1.4 g/cm3
Animal 2
2.3 g/cm3
1.8 g/cm3
1.8 g/cm3
2.1 g/cm3
1. Add the densities of one bone type. For example, if three bone samples have
densities of 3.0, 3.1, and 2.9 g/cm3, their sum would be 9.0 g/cm3.
2. Divide the sum of the densities by the number of samples.
Average density 9.0 g/cm3
sum of the densities
3.0 g/cm3
3
number of samples
Analysis
Close
1. Calculate the average bone
density for each of the two
animals in the data table.
Express your answer in grams
per cubic centimeter.
Reteaching
Have each student develop ten
questions for this section, and use
the questions in a review game.
LS Interpersonal
Quiz
2. Critical Thinking
Evaluating Methods
Why is it important to analyze
several samples and obtain
the average of your data?
MATH TAKS Obj 10, 8.14A, 8.15A, 8.16B
TAKS 1 Bio/IPC 2C, 2D
GENERAL
Section 3 Review
True or False:
1. Birds are ectotherms. (False. Birds
are endotherms.) TAKS 3 Bio 7B; Bio 8B, 12C
2. Birds have a two-way airflow during respiration. (False. Birds have a
one-way airflow.) TAKS 3 Bio 7B; Bio 8B, 12C
Identify the adaptations of birds for
Critical Thinking Evaluating Hypotheses
flight.
A student examines a bird that has delicate,
perching feet with long, slender toes. Its beak is
small but slightly long and pointed. The student
concludes that the bird is a seed-eating songbird.
3A 7B
Do you agree? Explain your reasoning.
7B
Summarize how birds obtain the energy
necessary for flight.
7B 10A
Relate the bald eagle’s methods of hunting and
7B 11B
feeding to its external body features.
TAKS Test Prep Which structure is part of the
excretory, digestive, and reproductive systems
10B
of a bird?
A kidney
C gizzard
B cloaca
D ovary
pp. 792–793
Student Edition
TAKS Obj 1 IPC 3A
TAKS Obj 2 Bio 10A, 10B
TAKS Obj 3 Bio 7B
Math TAKS Obj 10, 8.14A, 8.15A,
8.16B
TEKS Bio 3A, 7B, 10A, 10B, 11B
TEKS Bio/IPC 2C, 2D
TEKS IPC 3A
Teacher Edition
TAKS Obj 1 IPC 3A
TAKS Obj 2 Bio 8C, 10A, 10B
TAKS Obj 3 Bio 7B
TEKS Bio 3A, 7B, 8B, 8C, 10A, 10B,
11B, 12C
TEKS Bio/IPC 2C, 2D
TEKS IPC 3A
792
3. Critical Thinking Drawing
Conclusions Based on your
answer to item 1, which of the
two animals is more likely to
be a bird?
792
1. forelimbs modified as wings; feathers; streamlined shape; lightweight bones, endothermic
metabolism; highly efficient lungs; heart with
completely divided ventricle TAKS 3 Bio 7B
2. An endothermic body and a rapid metabolism
provide the energy necessary for flight.
TAKS 2 Bio 10A; TAKS 3 Bio 7B
3. The bald eagle has strong feet with sharp talons
for grabbing prey, and a massive, hooked beak
for tearing prey into pieces it can eat.
TAKS 3 Bio 7B; Bio 11B
4. The small, pointed beak indicates that it is not
a seedeater because seedeaters have thick beaks
for crushing seeds. The foot structure, however,
is consistent with the songbird anatomy.
TAKS 1 IPC 3A; TAKS 3 Bio 7B; Bio 3A
5.
A. Incorrect. The kidneys play
an important excretory role in birds, but are
not closely associated with the other systems.
B. Correct. The cloaca is an opening that
allows wastes to leave the body. In females, it
also allows sperm to enter the body and fertilized eggs to leave the body. C. Incorrect. The
gizzard is the second part of the stomach that
helps to grind food; it is not part of the excretory or reproductive systems. D. Incorrect. The
ovary is a reproductive organ; it is not part of
the digestive or excretory systems.
TAKS 2 Bio 10B (grade 11 only)
Study
CHAPTER HIGHLIGHTS
ZONE
Key Concepts
Alternative
Assessment
Key Terms
Section 1
1 The Reptilian Body
amniotic egg (775)
oviparous (777)
ovoviviparous (777)
●
Reptiles have a strong, bony skeleton.
●
Reptiles are ectothermic.
●
Reptiles have nearly watertight skin and eggs, both of which
enable them to be terrestrial animals.
●
Reptiles have paired lungs that have a greater surface area
for gas exchange than the lungs of amphibians.
●
Reptiles have a double-loop circulatory system. Most have
a ventricle that is partly divided into right and left halves,
resulting in incomplete separation of oxygen-rich and
oxygen-poor blood.
●
Reptilian fertilization is internal.
GENERAL
Have each student use the red and
blue subheadings in this chapter to
create questions based on each subheading, and then correctly answer
it. For example, “Reptiles Share
Several Key Characteristics,” could
become “What key characteristics
do reptiles share?” LS Verbal
TAKS 1 Bio/IPC 2C, 2D; TAKS 2 Bio 8C;
2 Today’s Reptiles
Section 2
●
Snakes and lizards (order Squamata) share many characteristics, such as periodic molting, but snakes have no legs.
carapace (782)
plastron (782)
●
The shells of turtles and tortoises (order Chelonia) are
made of fused plates of bone covered with horny shields or
leathery skin.
●
Unlike other reptiles, crocodilians (order Crocodilia), care
for their young after hatching. They also have a completely
divided ventricle.
●
There are only two species of tuataras (order Rhynchocephalia).
• Science Skills Worksheet GENERAL
• Critical Thinking Worksheet
• Test Prep Pretest GENERAL
• Chapter Test GENERAL
Section 3
3 Characteristics and Diversity of Birds
●
Birds are endotherms. Their high rate of metabolism helps
them meet the large energy requirements for flight.
●
A bird’s contour feathers give the bird its shape and aid
flight. Its down feathers provide insulation.
●
The bones of birds are thin and hollow, and many of them
are fused; all are adaptations for flight.
●
One-way airflow through the lungs provides the large
amounts of oxygen birds need for flight.
●
The ventricle of the bird heart is completely divided by
a septum.
contour feather (784)
preen gland (785)
down feather (785)
793
Answer to Concept Map
The following is one possible answer to Performance Zone item 15 on the following page.
birds
Reptiles
are
are
ectotherms
are
Ovoviviparous
such as
Snakes
Lizards
Tuataras
which have a
3-chambered heart
which are
Oviparous
and have
and have
Turtles
Crocodilians
which have a
endotherms
Scales
Feathers
and have a
4-chambered heart
793
Performance
ZONE
CHAPTER 34
ANSWERS
9. Snakes differ from lizards in that snakes
Using Key Terms
Using Key Terms
do not have
a. lungs.
b. kidneys.
1. All of the following reptiles belong to the
1. b Bio 8B
2. a TAKS 3 Bio 7B
3. a TAKS 3 Bio 7B
4. a TAKS 3 Bio 7B
5. a. Oviparous animals lay eggs. In
ovoviviparous animals,
embryos develop within eggs
inside the mother’s body.
These eggs hatch within the
mother, giving the appearance
of live birth.
b. Contour feathers are large and
allow the bird to fly. Down
feathers are small and fluffy;
they are found under the contour feathers and function
only to insulate.
Understanding Key Ideas
6. b TAKS 3 Bio 7B
7. b TAKS 2 Bio 10A
8. a TAKS 2 Bio 10A
9. c TAKS 3 Bio 7B
10. a TAKS 2 Bio 10A
11. d TAKS 2 Bio 8C; Bio 8B
12. d TAKS 3 Bio 7B
13. d TAKS 3 Bio 7B
14. The dams cause riffles, which
contain insects that male turtles
feed on, to disappear. Thus, turtles may not be able to find
adequate food to survive in
dammed areas. TAKS 3 Bio 7B
15. One possible answer to the concept map is found at the bottom
of the Study Zone page. Bio 3E
order Crocodilia, except
8B
a. alligators.
c. crocodiles.
b. tuataras.
d. gavials.
7B
c. a pectoral girdle.
d. a flexible jaw.
10. Jacobson’s organs are involved in the
sense of
10A
a. smell.
b. hearing.
2. The two basic parts of a turtle’s shell
are the
7B
a. carapace and plastron.
b. septum and amnion.
c. chorion and allantois.
d. keratin and cloaca.
c. sight.
d. touch.
11. Which group of living reptiles is most
closely related to birds?
8B 8C
a. snakes
c. rhynchocephalians
b. turtles
d. crocodilians
3. The eggs of reptiles and birds are
12. The feathers of most birds are well
described as
7B
a. amniotic.
b. oviparous.
c. ovoviviparous.
d. externally fertilized.
7B
4. The preen gland
a. secretes oil.
b. senses chemicals.
c. stimulates egg production.
d. causes a change in body temperature.
adapted for
7B
a. swimming and repelling water.
b. expelling heat and feeding.
c. flying and conducting heat.
d. flying and insulating.
13. The foot illustrated below is most likely of
a bird adapted for
a. wading.
b. grasping.
7B
c. perching.
d. swimming.
5. For each pair of terms, explain the
differences in their meanings.
a. oviparous, ovoviviparous
b. contour feather, down feather
Understanding Key Ideas
6. Which is not an adaptation of reptiles
for life on land?
7B
a. watertight skin
b. external fertilization
c. amniotic egg
d. kidneys
7. The heart of most reptiles has
a. no septum.
b. a partly divided ventricle.
c. a fully divided ventricle.
d. two pumping chambers.
8. In
a.
b.
c.
d.
reptiles, fertilization
10A
is internal.
is external.
always occurs in water.
does not occur.
794
Assignment Guide
Section
1
2
3
pp. 794–795
Review and Assess
TAKS Obj 1 Bio/IPC 2A, 2B, 2C, 2D
TAKS Obj 3 Bio 7B
TEKS Bio 3E, 7B, 8B, 8C, 10A, 12C
TEKS Bio/IPC 2A, 2B, 2C, 2D
794
CHAPTER REVIEW
Questions
3, 5a, 6–8, 14, 19, 22
1–3, 9–11, 14–16, 19
3, 4, 5b, 11, 12–15, 17, 18, 20, 21
10A
14.
In what ways might
the damming of the Guadalupe River
affect the ability of Cage’s map turtle to
find food?
7B
15.
Concept Mapping Construct a concept map that describes the characteristics
of both reptiles and birds. Include the following terms in your map: ectotherm,
endotherm, oviparous, ovoviviparous,
scales, feathers, three-chambered heart, and
four-chambered heart.
3E
Critical Thinking
Alternative Assessment
Critical Thinking
16. Forming Hypotheses Many viviparous
20. Applying Information Design and build a
16. Because the young are carried
inside the body, they receive some
heat as a result of the mother’s
muscular movements and basking
behavior.
snakes and lizards live in cold climates.
Why might viviparity be advantageous in
such environments?
2A 7B
bird feeder. Place the feeder where it can be
easily observed. Keep a journal of your observations to share with your class.
2A 2B 2D
17. Predicting Outcomes How might having
21. Being a Team Member and Communicating
a three-chambered heart, like that of
most reptiles, affect a hummingbird
in flight?
10A
18. Recognizing Logical Connections How
might a long period of parental care be
related to the number of offspring an
animal produces?
10A
19. Forming a Hypothesis When a piece
of a lizard’s tail breaks off, the separated
portion may wiggle about forcefully. How
might this adaptation be an advantage for
the lizard?
2C 7B
Work with two or three of your classmates
to find out what kinds of birds are common
in your area. Select at least six birds to
explore in depth and research the following:
its habitat, its food, its beak and foot adaptations, and where it winters. Present the
information you gathered in an illustrated
guide. Make copies of your guide available
2A 2B 2C 2D
for interested students.
22. Organizing Information Create a habitat in
a terrarium for a small lizard, and observe
the lizard’s behavior. Make a labeled drawing of the environment you create, and
keep a journal of your observations.
TAKS Test Prep
The chart below shows the normal ranges of
body temperature in five groups of reptiles.
Use the chart and your knowledge of science to
answer questions 1–3.
Tuataras
Turtles
Lizards
Snakes
Crocodilians
2. If a bar showing the body temperature
range of birds were added to this chart, the
bar for birds would partially overlap with
12C
the bar for
F lizards.
H crocodilians.
G tuataras.
J turtles.
10
20
30
40
50
Body temperature (°C)
1. Which groups could probably best
tolerate the temperature extremes found
in deserts?
2C
A Turtles, snakes, and crocodilians
B Turtles, lizards, and snakes
C Tuataras, turtles, and snakes
D Tuataras and crocodilians
2. F. Correct. Although birds are endotherms
with a very small temperature range, their
range overlaps with lizards, the only reptile
with temperatures above 40ºC. G. Incorrect.
Tuataras do not have body temperatures as
warm as birds, which have temperatures of
40ºC–42ºC. H. Incorrect. Crocodilians do not
have body temperatures as warm as birds.
J. Incorrect. Turtles do not have body temperatures as warm as birds. Bio 12C
Alternative Assessment
2C
the data in the chart?
A Crocodilians have a greater body
temperature range than tuataras.
B Turtles and snakes have similar body
temperature ranges.
C Lizards always have a higher body
temperature than tuataras.
D Some tuataras can have a higher body
temperature than some crocodilians.
20. Students should research both
seeds and feeder types to predict
which birds will be attracted.
TAKS 1 Bio/IPC 2A, 2B, 2D
21. Answers will vary depending on
birds chosen. Students should
acknowledge their sources and
include an illustration of each
bird. TAKS 1 Bio/IPC 2A, 2B, 2C, 2D
22. Students should research what
type of food and habitat is
appropriate for the lizard they
choose and set up their terrarium
accordingly.
Test
When a question refers to a graph, study the data
plotted on the graph to determine any trends or
anomalies before you try to answer the question.
795
3. A. Incorrect. While crocodilians have a
greater body temperature than tuataras, the
ranges of body temperatures are about the
same for both. B. Correct. According to this
data, turtles and snakes have a body temperature range of about 9ºC–38ºC. C. Incorrect.
Lizards often have a higher body temperature
than tuataras but their temperature ranges
overlap. D. Incorrect. The lowest body temperature for a crocodilian is higher than the
highest body temperature for a tuatara.
TAKS 1 Bio/IPC 2C
17. Because it mixes oxygen-rich and
oxygen-poor blood, a threechambered heart would not
distribute enough oxygen to the
hummingbird’s muscles to sustain
flight. TAKS 2 Bio 10A
18. Animals that invest a long period
of parental care typically have
fewer offspring than animals with
little or no parental care, but the
offspring that are cared for are
more likely to live to adulthood.
In both cases, only a small
number of offspring survive to
breeding age. TAKS 2 Bio 10A
19. Predators are distracted by the
wiggling tail part, which gives the
lizard time to escape.
TAKS 1 Bio/IPC 2C; TAKS 3 Bio 7B
3. Which of these statements is supported by
0
TAKS 1 Bio/IPC 2A; TAKS 3 Bio 7B
1.
A.Incorrect.
Crocodilians are not tolerant of
the low temperatures sometimes
found in deserts. B. Correct.
Turtles, lizards, and snakes are
able to tolerate both the low and
high temperatures often found in
deserts. C. Incorrect. Tuataras are
not able to tolerate the high heat
of the desert. D. Incorrect.
Tuataras are not able to tolerate
the high heat of the desert, and
crocodilians are not tolerant of the
low temperatures sometimes found
in deserts. TAKS 1 Bio/IPC 2C
795

Section 1 The Reptilian Body

Transcription

Similar documents

To setup your new webpage: Navigate to LDISD new website: Click

Reptile Brumation - Amador Valley Veterinary Center

presentation - Ag Innovation Showcase

stain-proof

EPK

PN backbencher speaks out on Gonzi`s `preferential` treatment for

Capital as a transformation tool Design as a change tool

Brochure