Section 1
The Fish Body
Section 1
Focus
Key Characteristics
of Modern Fishes
Objectives
Overview
Before beginning this section
review with your students the
objectives listed in the Student
Edition. This section introduces
students to the characteristics of
fishes and their special adaptations
to life in water.
Bellringer
K-W-L Have students make short
individual lists of all the things
they already Know about fish.
Then have students list things they
Want to know about fish. Have
students save their lists for later
use in the Reteaching at the end of
Section 1.
● Describe the characteristics
of modern fishes.
8C
● Summarize how fish
obtain oxygen.
10A TAKS 2
● Summarize how blood
circulates through
a fish.
10A TAKS 2
● Contrast how marine and
freshwater fishes balance
their salt and water
content.
11A
● Describe two methods of
10A
reproduction in fishes.
TAKS 2
Key Terms
gill filament
gill slit
countercurrent flow
nephron
3. Vertebral column (backbone). All fishes have an internal skeleton made of either cartilage or bone, with a vertebral column
surrounding the spinal cord. The brain is fully encased within a
protective covering called the skull or cranium.
GENERAL
Write the following words on the
board: starfish, sea horse, sea cow,
lamprey, eel, and stingray. Ask students to identify which organisms
they think are fish. Ask students to
write down whether it is a fish or
not and why. (The starfish is not a
fish—it is an echinoderm; and the sea
cow, or manatee, is also not a fish—
it is a mammal. The sea horse,
lamprey, eel, and stingray are all
fish. This demonstrates that fishes
are a very diverse group of organisms
that all share important characteristics the students will learn about in
Section 1.) LS Verbal
TAKS 2 Bio 8C; Bio 8B
1. Gills. Fishes normally obtain oxygen from the oxygen gas dissolved in the water around them. They do this by pumping a
great deal of water through their mouths and over their gills.
2. Single-loop blood circulation. Blood is pumped from the heart
to the capillaries in the gills. From the gills, blood passes to the
rest of the body and then returns to the heart. (Lungfishes,
which have a double-loop circulation, are an exception.)
Motivate
Discussion
What makes a goldfish instantly recognizable as a fish? You might
name characteristics such as its fins, gills, scales, and typical fish
shape as traits that contribute to the goldfish’s “fishiness.” But
some fishes don’t look quite so fishy. This is because the term fish
refers to any member of one of three general categories of vertebrates: Agnatha (jawless fishes), Chondrichthyes (cartilaginous
fishes), and Osteichthyes (bony fishes). The great diversity of fishes
found today reflects various adaptations that enable fishes to live in
the oceans and fresh waters around the world. Fishes vary in size
from whale sharks longer than a moving van to gobies no larger
than your fingernail. Despite the variation seen among fishes,
shown in Figure 1, all share certain key characteristics.
Figure 1 Fish diversity.
While these three fish appear
quite different externally, they
share a number of characteristics.
To learn about one common fish, read Up Close: Yellow Perch
later in this chapter.
Stingray
Sea horse
Trout
746
Chapter Resource File
pp. 746–747
Student Edition
TAKS Obj 2 Bio 8C
TAKS Obj 2 Bio 10A
TEKS Bio 8C, 10A, 11A
Teacher Edition
TAKS Obj 2 Bio 8C
TAKS Obj 4 IPC 9D
TEKS Bio 3E, 8B, 8C, 12C
TEKS IPC 9D
746
• Lesson Plan GENERAL
• Directed Reading
• Active Reading GENERAL
• Data Sheet for Data Lab
GENERAL
Transparencies
TT Bellringer
TT Respiration in Fishes
TT Fish Heart Structure
Chapter 33 • Fishes and Amphibians
Planner CD-ROM
• Reading Organizers
• Reading Strategies
• Problem Solving Worksheet
Solution Concentration GENERAL
Gills
One challenge faced by all animals is the need to get enough
oxygen for cellular respiration. Sponges, cnidarians, many flatworms
and roundworms, and some annelids obtain oxygen by diffusion
through the body surface. Other marine invertebrates, such as mollusks, arthropods, and echinoderms have gills, which are specialized
respiratory organs. Fishes also respire with gills.
If you look closely at the face of a swimming fish, you will notice
that as it swims, the fish continuously opens and closes its mouth, as
if it were trying to eat the water. What looks like eating is actually
breathing. The major respiratory organ of a fish is the gill, shown in
Figure 2. Gills are made up of rows of gill filaments —fingerlike
projections through which gases enter and leave the blood. The gill
filaments hang like curtains between a fish’s mouth and cheeks. At
the rear of the cheek cavity is an opening called a gill slit . When a
fish “swallows,” water is forced over the gills and out through the
gill slits.
This swallowing procedure is the core of a great change in gill
design shown by fishes—countercurrent flow, also shown in Figure 2.
In countercurrent flow , water passes over the gills in one direction
as blood flows in the opposite direction through capillaries in the
gills. Countercurrent flow ensures that oxygen diffuses into the blood
over the entire length of the capillaries in the gills. Due to this
arrangement, the gills of bony fishes are extremely efficient respiratory organs. Fish gills can extract up to 85 percent of the oxygen in
the water passing over them.
Teach
Using the Figure
Have students locate the portion of
Figure 2 that shows countercurrent
flow. Point out that water flows
over the fish’s gill from front to
back. At the same time, the blood
in the capillaries in the gills flows
from back to front. Explain that
this arrangement permits gas
exchange to occur all along the
capillaries in the gills. If the water
and blood flowed in the same
direction, the oxygen content of
the two equilibrate at about 50
percent saturation, far lower than
in countercurrent flow. LS Visual
Bio 3E
Figure 2 Fish gill
structure. Countercurrent
flow increases the gill’s
efficiency.
Respiration in Fishes
Oxygen-rich water enters the
fish’s mouth and passes over the
gills as it exits through the gill slits.
1
Gill
filaments
Each gill is composed of rows of gill filaments, which have thin membranes through
which oxygen and carbon dioxide can diffuse.
2
Blood flow
in capillaries
(back to front)
Water flow
across filaments
(front to back)
Water passes over the filaments from
front to back. Blood circulates through
the filaments from back to front. When blood
enters the filaments, its oxygen content is
low (blue). When it exits the filaments, its
oxygen content is high (red).
3
Gill slit
Gill
filaments
Water flow
747
IPC Benchmark Fact
Several factors affect the amount of oxygen gas
dissolved in the water around fish, including
temperature and pressure. Remind students that
as temperature increases, a solvent holds less
dissolved gas. In addition, as pressure increases,
a solvent holds more dissolved gas. Ask student
where a higher concentration of dissolved oxygen
gas is likely to be found, near the surface or deeper
in the water? (Higher concentrations of dissolved
oxygen will be found in deep water because the
temperature decreases and pressure increases as
one moves into deeper water.)
TAKS 4 IPC 9D (grade 11 only)
GENERAL
INCLUSION
Strategies
• Learning Disability
• English as a Second
Language
Have students research the fish known as
the sea horse. Students should give an oral
report to the class that includes the characteristics of this fish, descriptions or pictures
of different species of sea horses, and a
description of the life cycle of the sea horse.
In the course of their research, students may
encounter other fishes that do not necessarily
look like a “typical” fish. Encourage students
to report on these fish as well. Bio 12C
Teaching Tip
Understanding Countercurrent
Flow Have students make a chart,
dividing their paper into two
columns: same direction flow and
opposite direction flow. Each column should be further subdivided
into O2 in water and O2 in fish.
Have students record 80% O2
saturation in water and 20% O2
saturation in fish gill capillaries for
both flow directions. Assume that
10% of the O2 can be exchanged by
diffusion for each subsequent chart
row (representing a certain length of
gill capillary). Under same direction
flow, the next row would be 70%
in the water and 30% in the fish.
What is the maximum O2 content
that can be achieved in this fish if it
had a same direction flow? (50%;
both fluids continue their respective
increase and decrease by 10% intervals until there is no further
concentration difference at 50%.)
To complete the other part of the
chart, students need to realize that
the O2 content of water remains at
80% since new water is continually
passing over the gills. The second
row under opposite direction flow
would be 80% and 30%. What is
the maximum O2 content that can
be achieved if the fish had an opposite direction flow? (80%; O2 content
in the fish increases by 10% intervals
until there is no further difference in
O2 content at 80%.) LS Logical
Chapter 33 • Fishes and Amphibians
747
Circulation of Blood
Teach, continued
continued
Demonstration
To demonstrate the simple tubular
“heart” of ancestral chordates, use
an aquarium siphon (available at
pet stores) that has a bulb attached
to it. Insert a small piece of rubber
or glass tubing into the siphon to
keep the valve open. Place the end
of the siphon in a jar of colored
water and fill the rest of the tube
with water. Place the other end of
the siphon in another jar containing an equal volume of clear water.
Squeeze the bulb, representing the
primitive “heart,” to show how
blood is inefficiently moved in both
directions. Water will flow out in
both directions, and when the bulb
is released, water will be sucked in
from both ends. The level of each
jar will go down very slightly when
the bulb is squeezed and rise an
equal amount when it is released.
You can also demonstrate the value
of valves by showing the efficiency
of the pump when the valve is
operating properly. With the valve
enabled, water will move from one
jar to the other. LS Visual
The term sinus venosus is
Latin, as are many anatomical terms. The Latin word
sinus means “bend,” and
the Latin word venosus
refers to veins. The sinus
venosus is a bent collecting
chamber that conducts
blood into the heart.
Chordates that were ancestral to the vertebrates had a simple tubular
“heart.” This structure was little more than a specialized zone of
one artery that had more muscle tissue than the other arteries had.
When a tubular heart contracts, blood is pushed in both directions,
and circulation is not very efficient.
For an organism with gills, such as a fish, a simple tubular heart
is not an adequate pump. The tiny capillaries in a fish’s gills create
resistance to the flow of blood, so a stronger pump is needed to
overcome this resistance. In fishes, the tubular heart of early chordates has been replaced with a simple chamber-pump heart, shown
in Figure 3. The chamber-pump heart can be thought of as a tube
with four chambers in a row.
1. Sinus venosus (SIE nuhs vuh NOH suhs). This collection chamber acts to reduce the resistance of blood flow into the heart.
2. Atrium. Blood from the sinus venosus fills this large chamber,
which has thin, muscular walls.
3. Ventricle. The third chamber is a thick-walled pump with
enough muscle tissue to contract strongly, forcing blood to flow
through the gills and eventually to the rest of the body.
4. Conus arteriosus (KOH nuhs ahr TIHR ee oh suhs). This chamber is a second pump that smoothes the pulsations and adds still
more force.
Figure 3 Fish chamberpump heart. These four
steps show how blood flows
through the heart of a fish.
The fish heart represents one of the great evolutionary changes
found in vertebrates—a heart that pumps fully oxygenated blood
through a single circulatory loop to the body’s tissues.
Fish Heart Structure
Oxygen-poor blood from the
body enters the sinus venosus.
From there it moves into the atrium.
1
2
Atrium
Sinus
venosus
TAKS 2 Bio 10A; Bio 3E
The atrium delivers
blood to the ventricle.
Conus
arteriosus
Ventricle
The conus arteriosus
smooths the pulsations
of the bloodstream.
4
3
Contractions of the ventricle
pump the blood toward the gills.
748
CHEMISTRY
CONNECTION
pp. 748–749
Student Edition
TAKS Obj 2 Bio 8C
TAKS Obj 2 Bio 10A
TAKS Obj 2 Bio 10B (grade 11)
TAKS Obj 3 Bio 7B
TEKS Bio 4B, 7B, 8C, 10A, 10B
TEKS Bio/IPC 2C
Teacher Edition
TAKS Obj 2 Bio 4B, 10A
TAKS Obj 4 IPC 9D
TEKS Bio 3D, 3E, 4B, 10A, 11A, 12C
TEKS IPC 9D
748
Invite a chemistry teacher to your class to
discuss the amazing chemical properties of
water. Topics could include cohesion, surface
tension, heat of vaporization, heat of fusion,
polar covalent and ionic bonds, and the
relationship between the temperature and
density of water. IPC 9D (grade 11 only)
Chapter 33 • Fishes and Amphibians
Career
Aquaculturist Aquaculture, or fish farming,
is one of the fastest-growing sectors of agriculture. Both freshwater and saltwater species can
be raised commercially. Operating a fish farm
requires a knowledge of how to keep the fish’s
environment clean, proper feeding techniques,
and how to control fish infections, such as
those caused by bacteria and parasites. Bio 3D
Kidneys
Vertebrates have a body that is about two-thirds water, and most
will die if the amount of water in their body falls much lower than
this. Therefore, minimizing dehydration (water loss) has been a key
evolutionary challenge facing all vertebrates. Even some fishes
must cope with the problem of water loss. If this seems strange to
you, remember that osmosis causes a net movement of water
through membranes toward regions of higher ion concentration.
The ion (salt) concentration of sea water is three times that of the
tissues of a marine bony fish. As a result, these fishes lose water to
the environment through osmosis. To make up for the water they
lose, marine bony fishes drink sea water and actively pump excess
ions out of their body. Freshwater fishes have the opposite problem.
Because their bodies contain more ions than the surrounding
water, they tend to take in water through osmosis. The additional
water dilutes their body salts, so freshwater fishes regain salts by
actively taking them in from their environment.
Although the gills play a major role in maintaining a fish’s salt and
water balance, another key element is a pair of kidneys. Kidneys are
organs made up of thousands of nephrons. Nephrons are tubelike
units that regulate the body’s salt and water balance and remove
metabolic wastes from the blood. Excess water and bodily wastes
leave the kidneys in the form of a fluid called urine. The properties
of a fish’s urine depend upon the environment in which the fish
lives. Marine fishes excrete small amounts of urine while freshwater
fishes excrete large amounts of dilute urine.
Analyzing Ion Excretion in Fish
Demonstration
www.scilinks.org
Topic: Kidneys
Keyword: HX4110
The day before this lesson, fill two
beakers with distilled water. Add
one tablespoon of salt to one
beaker and mix well. Cut two
equal lengths of potato. Put one
potato piece in each beaker, and let
it sit overnight. The next day, tell
students that each potato piece represents a freshwater fish. Tell them
one fish has been placed in fresh
water, and one has been placed in
the ocean. Remove the potato
pieces, and let students observe
each. Ask students which “fish”
was in the ocean. (the limp one)
Ask them how they arrived at their
conclusions. (In the ocean, the water
concentration was greater in the
potato than in the beaker, so water
diffused out of it; the opposite is true
for the freshwater potato.) Ask students why fishes have difficulty
living in water environments other
than their own. (They would need
some mechanism to regulate their
water and salt concentrations.)
4B 11A
Background
A few species of fish, such as adult
salmon, are able to move between saltwater and freshwater environments. The
graph at right shows the excreted ion concentration of a fish as it travels from one
body of water to another. Examine the
graph, and answer the analysis questions.
Analysis
1. Determine if the fish is losing or gaining ions
by excretion as it travels.
LS Visual Bio 3E; Bio 12C
Ion Excretion in Fish
Analyzing Ion
Excretion in Fish
Excreted ion
concentration
0100010110
011101010
0010010001001
1100100100010
0000101001001
1101010100100
0101010010010
2. Critical Thinking Inferring Conclusions
Is the fish traveling from fresh to salt water or
from salt to fresh water?
TAKS 2 Bio 4B; Bio 11A
0100010110
011101010
0010010001001
1100100100010
0000101001001
1101010100100
0101010010010
Distance traveled
3. Summarize the reasoning you used to answer
item 2.
749
IPC Benchmark Review
Skills Acquired
Analyzing, inferring
Teacher’s Notes
After finishing the three analysis
questions, have students speculate on what mechanisms allow
fish to move successfully
between fresh water and salt
water. (They should come up
with ideas about osmosis through
the kidneys and gills.)
Answers to Analysis
MATH
CONNECTION
To prepare students for the TAKS and accompany
the discussion of ion solubility, have students review
Solubility and Factors That Affect Solubility, TAKS 4
IPC 9D on pp. 1054–1055 of the IPC Refresher in the
Texas Assessment Appendix of this book.
GENERAL
Salmon return to spawn in the stream where
they were hatched. During spawning, females
lay from 2,000 to 10,000 eggs. The young
salmon hatch and make their way downstream to the sea; most perish during this
journey. A Canadian study reported that
fewer than 1 percent, or approximately 20 to
100 hatchlings, of the young from each
female survive to spawn. (2,000 ⫻ 0.01 ⫽ 20,
and 10,000 ⫻ 0.01 ⫽ 100) LS Logical
1. losing ions by excretion
2. from fresh water to salt water
3. The graph shows that the farther the fish travels, the greater
it’s excreted ion concentration.
A fish’s tissues have a lower
concentration of ions than is
found in salt water, and they
lose water through osmosis.
One would expect the fish to
excrete more ions as the water
becomes saltier.
Chapter 33 • Fishes and Amphibians
749
Reproduction
Real Life
Close
Reteaching
K-W-L Tell students to return to
their lists of things they want to
know about fish, which they created
for the Bellringer. Have them place
check marks next to the questions
that they are now able to answer.
Students should finish by making a
list of what they have Learned.
Ask students:
• Which questions are still
unanswered?
• What new questions do
you have?
Quiz
How many eggs do
female fish lay during
spawning season?
The number
of eggs
laid during
spawning
varies from
species to
species.
Some fishes, such as
sea horses, lay between a
dozen and several hundred eggs. These eggs are
well protected, and most
develop into young sea
horses.
Finding Information
Find out how many eggs
are laid by cod.
The sexes are separate in most fishes, and generally fertilization
takes place externally. In a process called spawning, male and female
gametes are released near one another in the water, as shown in
Figure 4. A yolk sac within each egg contains nutrients the developing embryo will need for growth. The yolk sac remains attached to
the hatchling fish but is quickly used up. Then, the growing fish must
seek its own food. More likely than not, it will become food for some
larger animal. Many species of fishes release large numbers of eggs
that are fertilized in a single spawning season. This practice helps
ensure that some individuals will survive to maturity.
The eggs of sharks, skates, and rays are fertilized inside the
female’s body. During mating, the male uses two organs called
claspers to insert sperm into the female. In most species, the eggs
develop inside the female and the young are born live. A few species
of sharks lay eggs.
GENERAL
1. What is the major respiratory
organ of fishes? (gill)
2. What organ eliminates waste
and helps maintain water and
salt balance in fishes? (kidney)
TAKS 2 Bio 10A
Alternative
Assessment
GENERAL
Have students make two columns on
a sheet of paper. Have them label
one column External characteristics
and the other column Internal characteristics. Have them review the
chapter and list the major internal
and external characteristics of fishes.
TAKS 2 Bio 8C
Figure 4 Fish spawning.
These salmon spawn in shallow
river waters. Thousands of
eggs are released in a single
mating, but only a small
percentage of hatchlings live
until adulthood.
Section 1 Review
Discuss the key characteristics found in
Critical Thinking Forming a Hypothesis
all fishes.
A student removes Fish A from a saltwater
aquarium and Fish B from a freshwater aquarium.
By mistake, the student returns each fish to the
wrong aquarium. The next day, both fish are dead.
11A
Form a hypothesis that explains why.
8C
Describe how countercurrent flow aids a fish
10A
in obtaining oxygen.
Summarize why the fish heart and circulatory
system are considered important evolutionary
7B 10A
changes.
Contrast reproduction in sharks with that of most
10A 11A
other fishes.
TAKS Test Prep Which chamber of a fish’s
heart generates most of the force that pumps blood
through the body?
10A
A atrium
C sinus venosus
B ventricle
D conus arteriosus
750
Answers to Section Review
pp. 750–751
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, 8C, 10A, 11A, 12B
Teacher Edition
TAKS Obj 2 Bio 8C, 10A
TAKS Obj 3 Bio 7B
TEKS Bio 7B, 8B, 8C, 10A, 11A
750
5. Fish A was unable to prevent the inflow of
1. Gills allow fish to extract oxygen from the water.
water by osmosis when placed in fresh water.
Single-loop blood circulation allows blood to
Fish B was unable to prevent the outward flow
be pumped through the gills and back to the
of water by osmosis when placed in salt water.
heart. A bony vertebral column surrounds and
In each case, the resulting imbalance in the
protects the spinal cord. TAKS 2 Bio 8C
fish’s salt concentration caused the fish’s death. Bio 11A
2. Countercurrent flow ensures that oxygen dif6.
A. Incorrect. The atrium is large
fuses into the blood over the entire length of
but its muscular walls are thin. B. Correct. The
the gill capillaries. TAKS 2 Bio 10A
ventricle is capable of pumping blood with strong
3. The fish heart pumps blood through a singlecontractions. C. Incorrect. The sinus
loop circulatory pathway. The blood goes to the
2 Bio 10A;
venosus is a collection chamber for oxygen-poor
gills and then to the body tissues. TAKS
TAKS 3 Bio 7B
blood from the body. D. Incorrect. The conus
4. Fertilization in sharks is internal; most other
arteriosus smooths the blood flow and provides
fishes have external fertilization. TAKS 2 Bio 10A; Bio 11A
only slightly more force. TAKS 2 Bio 10A
Chapter 33 • Fishes and Amphibians
Today’s Fishes
Section 2
Section 2
Focus
Jawless Fishes
Objectives
Perhaps the most unusual fishes found today are the surviving jawless
fishes, the lampreys and hagfishes. These primitive creatures have
changed little over the past 330 million years. Little is known about
hagfishes, which is not surprising when you consider where they
live—on the ocean floor at depths as great as 1,700 m (about 1 mi).
Lampreys are better understood and are found in both salt and fresh
water. Interestingly, all species of lampreys must return to fresh water
to reproduce, suggesting that their ancestors lived in fresh water.
Lampreys and hagfishes have scaleless, eel-like bodies with
multiple gill slits and unpaired fins. Their skeletons are made of
cartilage, a strong fibrous connective tissue, and both kinds of
fishes retain their notochord into adulthood. Hagfishes, such as the
one shown in Figure 5, are scavengers of dead and dying animals on
the ocean bottom. Because of this behavior, they are sometimes
called the “vultures of the sea.” When threatened, a hagfish can produce huge quantities of slime from its roughly 200 slime glands.
Recently, biologists have discovered that hagfishes are far more
numerous than once thought and play a vital role in the ecology of
the oceans.
Most lampreys, such as the one shown in Figure 5, are parasitic
on other living fishes. A lamprey has a suction-cup-like structure
around its mouth that it uses to attach itself to its host. After
attachment, the lamprey gouges out a wound with its rough tongue,
feeding on blood and bits of flesh from the wound.
Overview
● Distinguish between the
three general categories of
modern fishes.
8C TAKS 2
● Describe the major
external and internal
characteristics of the
10A
yellow perch.
● Summarize features of
bony fishes.
8C TAKS 2
Bellringer
Key Terms
Have students draw a quick picture
of the strangest fish they have ever
seen (and name it if possible). Tell
students to list characteristics that
it has in common with all fishes.
Then ask them to list characteristics that they think are unique to
this fish. TAKS 2 Bio 8C; Bio 8B
lateral line
operculum
swim bladder
teleost
Motivate
Discussion
Figure 5 Hagfish and lamprey
These two modern jawless fishes have changed little
over the past 330 million years.
Hagfish
Before beginning this section
review with your students the
objectives listed in the Student
Edition. This section introduces
students to the three groups of
fishes that exist today, and explains
how they differ from each other.
Lamprey
751
Provide students with pictures of
the following fishes: lamprey, eel,
hagfish, hammerhead shark, dogfish shark, stingray, salmon, trout,
and bass. Display the pictures at
the front of the room, and explain
that they are classified into three
distinct groups. Have students try
to determine which fish belong in
the same groups and why. List the
characteristics students mention as
similar or dissimilar for each fish.
(Students may note jaws or lack of
jaws, paired or unpaired fins, scales
or no scales, gill slits or no gill slits,
etc.) Discuss how structural characteristics are often important in
classifying organisms, and how the
fishes are good examples of this.
LS Visual TAKS 2 Bio 8C; Bio 8B
Chapter Resource File
• Lesson Plan GENERAL
• Directed Reading
• Active Reading GENERAL
• Data Sheet for Quick Lab
GENERAL
Planner CD-ROM
• Reading Organizers
• Reading Strategies
• Basic Skills Worksheet Mass
and Density
Transparencies
TT
TT
TT
TT
Bellringer
Lateral Line in Bony Fish
External Structures of Fish
Internal Structures of Fish
Chapter 33 • Fishes and Amphibians
751
Cartilaginous Fishes
Teach
www.scilinks.org
Topic: Sharks
Keyword: HX4163
Teaching Tip
Natural Selection of Body
Shape To look for similarities in
body shape, have students diagram
the profile of several living and
nonliving things that move quickly
through water. Examples you
might provide include a shark, a
tuna, a bottlenose dolphin, a seal,
a submarine, and a torpedo. All
have the basic shape shown below.
Ask students why this shape occurs
in things that need to move rapidly
through water. (Direct students to
think about water resistance and the
need to direct movement through
water using fins.) LS Visual
www.scilinks.org
Topic: Sharks in Texas
Waters
Keyword: HXX4011
TAKS 2 Bio 8C; TAKS 3 Bio 7B
Using the Figure
GENERAL
In Figure 6 point out how the
shark’s teeth are arranged in rows
on its jaw, with the newer teeth
behind the old ones. Explain that a
shark’s teeth and scales are very
similar in structure and that the
teeth probably evolved from scales.
Both have an inner pulp cavity that
is covered by a layer of dentine and
then by enamel. The shark’s teeth
are not embedded in its jaw as
human teeth are. Rather, they sit
on top of the jaw and therefore
break off easily. LS Visual
Figure 6 Shark scales and
teeth. The shark’s skin feels
like sandpaper because it is
covered with toothlike scales.
The teeth, which are modified
scales, are similar in structure
but are much larger.
Sharks, skates, and rays are cartilaginous (KAHRT’l AJ uh nuhs)
fishes. Their skeletons are made of cartilage strengthened by the
mineral calcium carbonate (the material oyster shells are made of).
Calcium carbonate is deposited in the outer layers of cartilage and
forms a thin layer that reinforces the cartilage. The result is a very
light but strong skeleton.
The shark’s light, streamlined body allows it to move quickly
through the water in search of prey. Its skin contains cone-shaped
placoid scales, which give the skin a rough texture. As you can see
in Figure 6, the shark’s scales and teeth are quite similar in structure. This is because the teeth are actually modified scales. The
teeth are arranged in 6 to 10 rows along the shark’s jaw. The teeth
in front are pointed and sharp and are used for biting and cutting.
Behind the front teeth, rows of immature teeth are growing. When
a front tooth breaks or is worn down, a replacement tooth moves
forward. One shark may use more than 20,000 teeth during its lifetime. This system of tooth replacement guarantees that the teeth
being used are always new and sharp.
Two smaller groups of cartilaginous fishes, the skates and rays,
have flattened bodies that are well adapted to life on the sea floor.
Rays are usually less than 1 m (3.3 ft) long, while skates are typically
smaller. However, the giant manta ray may be up to 7 m (23 ft) wide.
Most species of skates and rays have flattened teeth that are used to
crush their prey, mainly small fishes and invertebrates.
Magnification: 5ⴛ
Scales
TAKS 2 Bio 8A, 10A
Teeth
Magnification: 1ⴛ
752
MISCONCEPTION
ALERT
pp. 752–753
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, 8C, 10A, 12B
Teacher Edition
TAKS Obj 2 Bio 8A, 8C, 10A
TAKS Obj 3 Bio 7B
TAKS Obj 5 IPC 5A, 5B
TEKS Bio 7B, 8A, 8C, 10A, 11B, 11C
TEKS IPC 5A, 5B
752
Fear of Sharks Shark attacks are often
highly publicized. This has created a fear of
shark attacks that is often greater than the
actual probability of an attack. Bees, wasps,
and snakes are responsible for far more
fatalities each year. In the United States, the
annual risk of death from being struck by
lightning is 30 times greater than that from
a shark attack. An attack by a shark is also
less common than such beach-related
injuries as spinal damage, dehydration,
jellyfish and stingray stings, and sunburn.
Chapter 33 • Fishes and Amphibians
Bony Fishes
Jawless and cartilaginous fishes are not as diverse as bony fishes,
which are the most numerous of all the fishes. In addition to a
strong, internal skeleton made completely of bone, bony fishes have
a series of unique structural adaptations that contribute greatly to
their success.
1. Lateral line system. Bony fishes have a fully developed lateral
line system. The lateral line , shown in Figure 7, is a sensory
system that extends along each side of a bony fish’s body.
As moving water presses against the fish’s sides, nerve impulses
from ciliated sensory cells within the lateral line permit the
fish to perceive its position and rate of movement. For example,
a trout moving upstream to spawn uses its lateral line system to
obtain the sensory information it needs to orient its head
upstream.
Organizing Information
Use the information on this
page and the next four
pages to draw a concept
map that summarizes the
characteristics of bony fishes.
On your concept map,
include information from
Up Close: Yellow Perch.
Lateral line
canal
Nerve
753
IPC Benchmark Fact
A fish’s lateral line senses other objects in the
water by detecting reflected water movements from
nearby objects. These water movements or waves
are an example of a mechanical wave—a wave that
requires a medium. The energy of the vibration that
sets a wave into motion moves through the medium
as the wave passes through. Vibrating particles pass
energy down the line to neighboring particles. Ask
students to identify the medium that perpetuates
the waves from an object to the lateral line of
a fish. TAKS 5 IPC 5A, 5B
Train Your Fish Fish have the
ability to detect pressure changes,
such as sound waves, through their
lateral line system, so it is possible
to train a fish to come to the surface in response to a sound. Tell
students who have fish to tap the
side of their aquarium very gently
and in the same manner each time
they feed the fish. After a couple of
weeks, the fish will come to the top
to feed whenever the aquarium is
tapped in this manner. Bio 11B
Activity
Sensory
cells
Opening to
exterior
Learners
Teaching Tip
Figure 7 Lateral line.
The lateral line contains sensory
cells that help a fish perceive its
position in the water.
Lateral line
GENERAL
Obtain a transparent tropical fish
called a glass catfish, commonly
available in pet stores. This fish
gives a real-life view of the internal
organs of a bony fish. Have students view the glass catfish and see
what internal organs they can identify. Have them study the drawings
of the internal structure of the
yellow perch for help in identifying
the organs.
English Language
LS Visual
The lateral line system also enables a fish to detect a motionless
object by the movement of water deflected by that object. The way
that a fish detects an object with its lateral line and the way that you
hear music with your inner ear are quite similar. Both processes
share the same basic mechanism—sensory cells with cilia detect
vibrations and send this information to the brain.
Lateral Line in Bony Fishes
Demonstration
did you know?
Salmon return to their hatching stream.
Pacific salmon find their way to the stream
where they hatched primarily by the sense of
smell. Vegetation and minerals in the water
give each stream a unique “flavor.” Young
salmon imprint on this flavor and can remember it 4 or 5 years later when they return to
spawn. All Pacific salmon die shortly after
spawning. Interestingly, when young salmon
(smote stage) migrate to the sea, they go
downstream backward. TAKS 2 Bio 8C
GENERAL
Fish and Diet It is a good idea to
include some fish in one’s diet.
Have students go to local grocery
stores and record the different types
of fish offered. Remind students to
look for canned and frozen fish as
well as fresh fish. Some students
may want to survey local restaurants to determine what kind of
fish they offer. Have students
research these fish to determine
where they were caught or raised;
their habitats; their nutrient, vitamin, and mineral contents; and any
other interesting characteristics of
the fish, such as characteristic
behaviors. LS Kinesthetic Bio 11C
Chapter 33 • Fishes and Amphibians
753
Up Close
Up Close
Yellow Perch
Yellow Perch TAKS 2, TAKS 3
TAKS 2 Bio 10A;
TAKS 3 Bio 7B
Teacher’s Notes
Have students relate the
perch’s external structures to
its lifestyle and habitat. Have
students pay special attention
to the specialized senses and
swimming adaptations of this
successful fish. Then ask students to classify each labeled
internal structure of the perch
according to the following
body systems: nervous system,
circulatory system, reproductive system, digestive system,
respiratory system, excretory
(urinary) system, muscular system, and skeletal system.
Discussion
1. How does the yellow perch
control roll, pitch, and yaw
when it swims? (The dorsal
fins prevent roll, the caudal
fin controls pitch, and the
anal fin controls yaw.)
●
Scientific name: Perca flavescens
●
Size: About 0.3 m (1 ft) long and up to 2.3 kg (5 lb)
●
Range: Found in lakes and rivers from the Great Lakes to
the Atlantic coast and as far south as South Carolina
●
Habitat: Lives concealed among vegetation or submerged
tree roots
●
Diet: Feeds on insect larvae, crustaceans, and other fishes
External Structures
Lateral line The lateral line is a sense organ
Opercula Movements of the opercula draw water into
the perch’s mouth. The water then moves over the gills,
where oxygen and carbon dioxide are exchanged. Then
that detects vibrations in water that are caused by
currents or pressure waves. The perch uses this
sensory information to direct its movement as it
swims and to detect objects in its environment,
including predators and prey.
the water is forced out through the gill slits.
▲ Operculum
Anterior
dorsal fin
▲ Lateral line
Eye
Nostril
Posterior
dorsal fin
Caudal fin
Pectoral fin
Pitch
Fins
Anal fin
Anus
▼ Pelvic fin
Fins The caudal fin thrusts
from side to side to propel the
▼ Scales
Roll
Yaw
2. How would a perch find
food if it were kept in the
dark? (It could smell the food
and sense the food’s movement with its lateral line.)
Scales Perch scales are thin, bony disks that grow from
cavities in the skin. Scales grow throughout the life of the
fish. Because a scale grows more rapidly when food is plentiful (in spring and summer) than when food is scarce (in
winter), a scale forms growth rings. Counting the growth
rings can give a good estimate of a perch’s age.
754
pp. 754–755
Student Edition
TAKS Obj 2 Bio 8C
TAKS Obj 2 Bio 10A
TAKS Obj 3 Bio 7B
TEKS Bio 7B, 8C, 10A
Teacher Edition
TAKS Obj 2 Bio 8C, 10A
TAKS Obj 3 Bio 7B
TEKS Bio 7B, 8C, 10A, 11A
754
Chapter 33 • Fishes and Amphibians
fish forward. The dorsal fins
prevent the perch from rolling
over as it swims, and the anal
fin keeps the fish from veering
sideways. Paired pectoral and
pelvic fins assist the fish in
going up or down through the
water, in turning sharply, and
in stopping quickly.
Internal Structures
Up Close
Reproductive organs Yellow perch produce
Brain The optic lobe receives information from
gametes during their breeding season in the spring.
The female lays strings of eggs that are fertilized
externally. In warm water, the young hatch within
the eyes, and the olfactory bulbs receive information
from chemical-sensing cells. The cerebrum processes
this and other information. The cerebellum coordinates
Yellow Perch
days and grow quickly. In cold water, the development of the eggs may take much longer.
muscle activity, and the medulla oblongata controls
the function of many internal organs.
opercula needed for a perch
to respire? (Movements of
the opercula draw water in
through the open mouth and
force the water over the gills,
where oxygen is removed
from the water.)
4. What would happen to a
yellow perch that was missing each body system?
(nervous system—it could not
move or sense its environment; circulatory system—its
cells could not get oxygen
and nutrients or get rid of
wastes; reproductive system—
it could not produce offspring; respiratory system—it
could not obtain oxygen or
eliminate carbon dioxide;
digestive system—it could not
break down food; excretory
(urinary) system—it could not
get rid of nitrogen wastes;
muscular system—it could
not move; skeletal system—its
body would collapse)
Female
Spinal cord
Optic lobe
Cerebellum
Cerebrum
Female
Kidney
Ovary
Oviduct
Medulla
oblongata
Olfactory bulb
Male
▲ Brain
Testis
Male
Vas deferens
Bladder
Tongue
Spinal cord
Kidney
▲ Reproductive organs
Liver
Vertebra
Swim bladder
Jaws
Muscle
Gills
Heart
3. Why are the mouth and
5. What would happen if the
Anus
▼ Intestine
Gallbladder
▼ Stomach
▼ Esophagus
Digestive system The digestive system reflects a basic arrangement
of structures found in all vertebrates. Food enters the mouth and passes
from the esophagus to the stomach. The liver secretes bile, and the pancreas secretes enzymes into a short intestine. The bile and enzymes help
break down the food. Absorption of digested food occurs through the
inner lining of the intestine. Undigested material exits through the anus.
755
did you know?
Swim bladders can be damaged. Swim
bladders on some fish have been known to
leak or rupture, releasing the gas into the body
cavity. In some instances, the fish floats to the
top of the water, causing it to be easy prey for
hungry predators. Only by frenzied swimming
can the fish manage to stay under water, and it
will soon tire and return to float on the top.
Ask students to imagine trying to dive under
water while holding a large balloon.
swim bladder of a perch was
suddenly unable to absorb
more gas or get rid of gas?
(The perch would be unable to
achieve neutral buoyancy at
different levels in the water. It
would have to use more
energy to move up or down
in the water.)
6. Why is the number of sperm
cells produced by the perch
so much greater than the
number of egg cells?
(Because of external fertilization, most sperm cells will not
reach the egg cells. A great
number is needed to ensure
that each egg is fertilized.)
LS Intrapersonal TAKS 2 Bio 8C; Bio 11A
Chapter 33 • Fishes and Amphibians
755
Operculum
closed
Water
Teach, continued
continued
Modeling the
Action of a Swim
Bladder
Operculum
open
TAKS 1 Bio/IPC 2A, 2C; Bio 3E
Skills Acquired
Observing, analyzing,
applying knowledge
Teacher’s Notes
Have all students drop their
raisins into the soft drink at the
same time.
Answers to Analysis
1. The raisins sank to the bottom.
As bubbles collected on them
they rose to the top, then they
sank again.
2. The bubbles clung to the
raisins and imparted buoyancy,
causing the raisins to rise.
When the raisins reached the
top, the bubbles burst, and the
raisins sank again.
3. The bubbles formed on the
outside of the raisin. A swim
bladder is internal. Also, the
amount of gas in the swim
bladder can be increased or
decreased, unlike the bubbles
on the raisins.
Water
Figure 8 Operculum.
When a fish’s mouth opens,
water enters and the opercula
close over the gills. When the
mouth closes, the opercula
open and water moves across
the gills and out of the fish.
2. Gill cover. Most bony fishes have a hard plate, an operculum ,
that covers the gills on each side of the head. Movements of certain muscles and of the opercula, shown in Figure 8, permit a
bony fish to draw water over the gills, which enables the fish to
take in oxygen. By using this mechanism, most bony fishes can
move water over their gills while remaining stationary in the
water. A bony fish doesn’t have to swim forward with its mouth
open to move water over its gills. This ability to respire without
swimming enables a bony fish to conserve energy that can be
spent chasing after prey and escaping from predators.
3. Swim bladder. The density of the fish body is slightly greater
than that of sea water. How then do bony fishes keep from sinking?
Bony fishes contain a special gas sac called a swim bladder . By
adjusting the gas content of the swim bladder, bony fishes can
regulate their buoyancy. As the swim bladder fills, the fish rises,
and as it empties, the fish sinks. The swim bladder of early bony
fishes was connected to their throat, and they gulped air to fill it.
The swim bladder of modern bony fishes, shown on the previous
page, does not have a direct passage to the mouth. Instead, gas is
exchanged between the bloodstream and the swim bladder. This
permits the fish to maintain or change its depth in the water.
There are two groups of bony fishes, the ray-finned fishes and the
lobe-finned fishes. The yellow perch described in Up Close: Yellow
Perch on the previous two pages is a common type of ray-finned fish.
Modeling the Action of a
Swim Bladder 2A 2C 3E TAKS 1
Most fish use a swim bladder to regulate their
depth in water. As gas enters the swim bladder, the
fish rises in the water. As gas is expelled, the fish
sinks to a lower depth.
Materials
100 mL beaker or small glass; cold, clear, carbonated
soft drink; 2 very dry raisins
Procedure
1. Fill a 100 mL beaker with a
cold, carbonated soft drink.
2. Drop two raisins into the
beaker, and observe what
happens over the next
5 minutes.
Analysis
2. Forming Hypotheses
Develop a hypothesis to
explain your observations.
3. Critical Thinking
Analyzing Results How
does the lifting of the raisins
differ from the use of a swim
bladder to control buoyancy?
4. Critical Thinking Forming Reasoned Opinions
Think about the energy you
would have to expend to
keep yourself in one position
under water. What advantage
might a swim bladder provide
to a fish?
1. Describe what happened
after you dropped the raisins
into the soft drink.
756
pp. 756–757
Student Edition
TAKS Obj 1 Bio/IPC 2A, 2C
TAKS Obj 2 Bio 10A
TAKS Obj 2 Bio 10B (grade 11)
TAKS Obj 3 Bio 12B
TEKS Bio 3E, 10A, 10B, 12B
TEKS Bio/IPC 2A, 2C
Teacher Edition
TAKS Obj 1 Bio/IPC 2A, 2C
TAKS Obj 2 Bio 8C, 10A, 10B
TAKS Obj 3 Bio 7B, 12B
TAKS Obj 4 IPC 7A
TEKS Bio 3E, 7B, 8C, 10A, 10B,
11A, 11B, 12B
TEKS Bio/IPC 2A, 2C
TEKS IPC 7A
756
(continued)
4. It would take a great deal of energy to stay in
one position under water with two lungs
full of air. A swim bladder offers a fish
tremendous savings of energy because the
fish controls the amount of gas in the swim
bladder. This makes more energy available
for daily activities, such as catching prey or
escaping predators.
Chapter 33 • Fishes and Amphibians
IPC Benchmark Fact
Remind students that buoyancy increases as the density of an object decreases. Ask them what happens
to a fish’s average density and therefore its buoyancy
when the swim bladder increases or decreases in
size. Also, ask students whether a fish’s swim bladder
should increase of decrease in size if a fish wants to
swim in deeper water. TAKS 4 IPC 7A (grade 11 only)
Ray-Finned Bony Fishes
Figure 9 Pacific bluefin tuna
Ray-finned bony fishes, such as the ones shown in Figure 9,
comprise the vast majority of living fishes. Their fins are supported
by bony structures called rays. Teleosts (TEL ee ahsts), such as the
yellow perch you saw in Up Close, are the most advanced of the rayfinned bony fishes. Teleosts have highly mobile fins, very thin
scales, and completely symmetrical tails. About 95 percent of all living fish species are teleosts.
At sexual maturity, Pacific
bluefin tuna can weigh about
136 kg (300 lb), although
some grow larger.
Close
Reteaching
Have students work in small
groups to make a table that compares each type of fish they have
studied in this section. Across the
top of their table they should write
Jawless Fish, Cartilaginous Fish,
and Bony Fish. The titles of the
rows down the side of the table will
vary from group to group. Have
groups fill in the table with information they have learned. Each
group can then present its table to
the class. Have individual students
copy his or her group’s table and
place it in his or her portfolio.
Lobe-Finned Bony Fishes
Only seven species of lobe-finned fishes survive today. One species is
the coelacanth (SEE luh kanth), shown in Figure 10, and the other six
species are all lungfishes. The lobe-finned fishes have paired fins that
are structurally very different from the fins of ray-finned fishes. In
many lobe-finned fishes, each fin consists of a long, fleshy, muscular
lobe that is supported by a central core of bones. These bones are connected by joints, like the joints between the bones in your hand. Bony
rays are found only at the tips of each lobed fin. Muscles within each
lobe can move the bony rays independently of each other.
Scientists have debated whether the direct ancestor of amphibians
was a coelacanth or a lungfish. However, recent evidence has led biologists to believe that it was neither. The ancestor of the amphibians
most likely was a third type of lobe-finned fish that is now extinct.
Quiz
GENERAL
1. How are the skeletons of sharks,
Figure 10 Coelacanth.
Coelacanths were thought to
have been extinct for millions
of years, until one was caught
off the coast of Africa in 1938.
Coelacanths can reach up to
nearly 3 m (9.8 ft) in length.
Section 2 Review
Compare the three categories of modern fishes.
8C
Summarize the role of the operculum in fish
respiration.
10A
Summarize how the swim bladder can be
viewed as an energy-saving mechanism.
10A
Describe the digestive process in a yellow
perch.
8C 10A
Relate a yellow perch’s lateral line system to
the human ear.
8C 10A
Critical Thinking Evaluating Conclusions
An unidentified species of fish has rough skin,
several rows of teeth, and no opercula. Based on
these characteristics, a student infers that the
fish has a swim bladder. Explain why you agree
8C 10A 10B
or disagree with this conclusion.
TAKS Test Prep
The mouth of a lamprey is
specialized for
7B 12B
straining plankton.
chewing seaweed.
scavenging dead animals.
parasitizing other fish.
A
B
C
D
757
Answers to Section Review
1. Agnathans: jawless, scaleless, have unpaired fins.
Cartilaginous fishes: cartilaginous skeletons,
streamlined bodies, placoid scales. Bony fishes:
bony skeletons, opercula, swim bladders, welldeveloped lateral line system. TAKS 2 Bio 8C
2. The operculum pumps water through the mouth
and over the gills for oxygen extraction.
TAKS 2 Bio 10A
3. A fish can maintain a particular depth in the
water by adjusting the amount of gas in the
bladder rather than by using muscular force.
TAKS 2 Bio 10A
4. Food enters the mouth and moves to the stomach. Substances in the intestine help break
down food. Nutrients are absorbed in the
intestine and undigested food exits the body
through the anus. TAKS 2 Bio 8C, 10A
5. Both have sensory cells that sense vibrations and
send nerve impulses to the brain. TAKS 2 Bio 8C, 10A
6. Disagree; these are characteristics of cartilaginous fishes, which have no swim bladder.
skates, and rays similar to those
of jawless fishes? (Both groups
of fishes have skeletons made of
cartilage.)
2. What are teleosts and how common are they? (Teleosts are
ray-finned bony fishes with highly
mobile fins, thin scales, and symmetrical tails. They represent 95%
of all living fish species.)
TAKS 2 Bio 8C
Alternative
Assessment
GENERAL
After reviewing the section, have
each student choose a favorite fish.
Have them give a short oral report,
explaining to the class how the
particular characteristics of their
chosen fish enable it to survive and
give it an advantage over other
types of fish. Have each student
write the name and category of
their fish on the board prior to
their presentation and provide a
picture or illustration of the fish
for class viewing. Bio 11B, 12B
TAKS 2 Bio 8C, 10A, 10B (grade 11 only)
7.
A. Incorrect. Whales have comblike teeth for straining plankton. B. Incorrect. See
answer D. C. Incorrect. Hagfishes have mouths
adapted to eating dead animals. D. Correct. The
lamprey’s mouth is like a suction-cup to attach
itself to its host. TAKS 3 Bio 7B; Bio 12B
Chapter 33 • Fishes and Amphibians
757
Section 3
Section 3
Amphibians
Focus
Key Characteristics
of Modern Amphibians
Objectives
Overview
Before beginning this section
review with your students the
objectives listed in the Student
Edition. This section introduces
students to how amphibians differ
from fish and discusses the adaptations amphibians have for life in
and out of water.
● Summarize the
characteristics of modern
The next time you see a frog, consider that it is a surviving member
amphibians.
7B 8C TAKS 3
of an ancient amphibian group, the first vertebrates to walk on
● Compare the three orders of
living amphibians.
8B 8C
land. The croaking and peeping of frogs, such as the one shown in
Figure 11, make it difficult not to notice them, but their smaller, quiTAKS 2
eter relatives live nearby, hidden in damp habitats. Class Amphibia
● Describe the major external
contains three orders of living amphibians: order Anura (frogs and
and internal characteristics
10A
of the leopard frog.
toads), order Urodela (salamanders and newts), and order Apoda
TAKS 2 (caecilians). Most amphibians share five key characteristics.
Key Terms
Bellringer
Tell students to think about how
big the largest frog species gets.
Then ask them to list some things
that a frog that size would eat. (The
largest frog species is Gigantorana
goliath of West Africa. It can be more
than 30 cm (1 ft) long and can weigh
over 3.3 kg (7.5 lb). It eats other animals as large as rats and ducks.
1. Legs. The evolution of legs was an important adaptation for living on land. Frogs, toads, salamanders, and newts have four legs.
Caecilians lost their legs during the evolutionary course of
adapting to a burrowing existence.
lung
pulmonary vein
septum
2. Lungs. Although larval amphibians have gills, most adult
amphibians breathe with a pair of lungs. Lungless salamanders
are an exception.
3. Double-loop circulation. Two large veins called pulmonary
veins return oxygen-rich blood from the lungs to the heart. The
blood is then pumped to the tissues at a much higher pressure
than in the fish heart.
4. Partially divided heart. The atrium of the amphibian heart is
divided into left and right sides, but the ventricle is not. A mixture of oxygen-rich and oxygen-poor blood is delivered to the
amphibian’s body tissues.
Motivate
Activity
GENERAL
Explain that a caecilian is a legless,
wormlike animal. Ask students to
close their books, and write the
words Apoda, Anura, and Urodela
at the top of three columns on the
board. Tell students that these
order names come from the Greek
language. To the side write a—
“without,” oura—“tail,” pous—
“foot,” and delos—“visible.” Ask
students to place the following
amphibians into the proper
columns by thinking of each animal’s characteristics and what the
three column headings mean: toad,
salamander, bullfrog, caecilian,
newt, and tree frog. (Apoda—
caecilian; Anura—toad, bullfrog, and
tree frog; Urodela—salamander and
newt) LS Verbal TAKS 2 Bio 8C; Bio 8B
pp. 758–759
Student Edition
TAKS Obj 2 Bio 8C
TAKS Obj 2 Bio 10A
TAKS Obj 3 Bio 7B
TEKS Bio 7B, 8B, 8C, 10A
Teacher Edition
TAKS Obj 2 Bio 8C
TAKS Obj 2 Bio 10A
TEKS Bio 3E, 8B, 8C, 10A, 12C
758
Figure 11 Spring peeper.
In some areas, the call of the
spring peeper is one of the first
signs of spring.
5. Cutaneous respiration. Most amphibians supplement their
oxygen intake by respiring directly through their moist skin.
Cutaneous respiration (“skin breathing”) limits the maximum
body size of amphibians because it is efficient only when there
is a high ratio of skin surface area to body volume.
Lungs
Although air contains about 20 times as much oxygen as sea water
does, gills cannot function as respiratory organs when out of
water. Thus, one of the major challenges that faced the first land
vertebrates was that of obtaining oxygen from air. The evolutionary
solution to this challenge was the lung.
A lung is an internal, baglike respiratory organ that allows oxygen and carbon dioxide to be exchanged between the air and the
bloodstream. The amount of oxygen a lung can absorb depends on
its internal surface area. The greater the surface area, the greater
the amount of oxygen that can be absorbed. In amphibians, the
758
Transparencies
Chapter Resource File
• Lesson Plan GENERAL
• Directed Reading
• Active Reading GENERAL
Planner CD-ROM
• Reading Organizers
• Reading Strategies
• Supplemental Reading Guide
Through a Window
Chapter 33 • Fishes and Amphibians
TT
TT
TT
TT
TT
TT
Bellringer
Fish and Amphibian Circulation
Amphibian Heart Structure
Life Cycle of a Frog
External Structure of a Frog
Internal Structure of a Frog
lungs are hardly more than sacs with folds on their inner
membrane that increase their surface area, as shown in
Figure 12. With each breath, fresh oxygen-rich air is drawn
into the lungs. There it mixes with a small volume of air
that has already given up most of its oxygen. Because of
this mixing, the respiratory efficiency of lungs is much less
than that of gills. Because there is much more oxygen in
air than there is in water, however, lungs do not
have to be as efficient as gills. Many amphibians also obtain oxygen through their thin,
moist skin.
Teach
SKILL
Double-Loop Circulation
As amphibians evolved and became active on
land, their circulatory system changed, resulting in a second circulatory loop. This change
allowed more oxygen to be delivered to their
muscles. Figure 13 compares the single-loop circulation of most
fishes with the double-loop circulation of amphibians (also found
in lungfishes). Notice that amphibians have a pair of blood vessels
not found in fishes, the pulmonary veins. The pulmonary veins
carry oxygen-rich blood from the amphibian’s lungs to its heart.
The heart pumps the oxygen-rich blood to the rest of the body.
The advantage of this arrangement is that oxygen-rich blood can be
pumped to the amphibian’s tissues at a much higher pressure than
it can in fishes. (Recall that in fish, blood is pumped through the
gills before reaching the body organs. As a result, much of the force
of the heartbeat is lost.)
Figure 12 Amphibian
lungs. The lungs of an
amphibian are sacs with a
folded internal membrane that
provides a large surface for
gas exchange.
Reading Organizer Have students create a Venn diagram
similar to the one shown in the
Graphic Organizer at the bottom
of this page. As students read
Section 3, have them list, in the
appropriate regions of the diagram,
the characteristics that are
exclusive to fish, exclusive to
amphibians, and common to both
groups. After the diagram is complete, have each student use the
information in the diagram to
write a paragraph that either supports or rejects the placement of
fish and amphibians into two
separate groups. LS Logical
Teaching Tip
Gas Exchange Tell students that
although most amphibians have
lungs, some species of salamanders
exchange oxygen and carbon dioxide through gills, even as adults.
Ask students where they would
expect to find these amphibians
and why. (in an aquatic environment; because gills collapse in air)
Tell students that many species of
salamanders have neither lungs nor
gills and respire entirely through
their skin. LS Verbal
Circulation in fishes involves a single loop. Amphibians have a second loop that
goes from the heart to the lungs and back to the heart.
Lung capillaries
Pulmonary vein
Heart
GENERAL
Bio 8B; Bio 3E
Figure 13 Circulatory loops
Gill capillaries
BUILDER
Heart
TAKS 2 Bio 8C; Bio 12C
Oxygen-rich
blood
Body organ
capillaries
Using the Figure
Oxygen-poor
blood
Amphibian
Fish
759
Graphic Organizer
Use this graphic organizer with the Skill Builder on this page.
Fish
characteristics
exclusive characteristics
common
characteristics
Amphibian
characteristics
exclusive characteristics
Use Figure 13 to compare the circulatory pathways of fish and
amphibians. Ask: Which system is
a single loop and which is a double
loop? (The fish system is a single
loop, and the amphibian system is a
double loop.) What is the function
of the second loop in the amphibian system? (The second loop creates
a circulatory pathway to and from
the lungs.) What advantage does
the double-loop system provide?
(The amphibian’s heart pumps
oxygen-rich blood to the amphibian’s
tissues at much higher pressures than
can happen in the fish’s single-loop
system.) LS Visual TAKS 2 Bio 10A
Chapter 33 • Fishes and Amphibians
759
Circulation of Blood
Teach, continued
continued
Teaching Tip
GENERAL
www.scilinks.org
Topic: Circulation in
Amphibians
Keyword: HX4043
Comparing Heart Anatomy
Have students compare the heart of
the amphibian in Figure 14 with that
of the fish in Figure 3. Ask them to
list the similarities and differences
between the two. Then have each
student compare his or her list with
that of a partner.
English Language
Learners
LS Visual
Demonstration
GENERAL
To illustrate that oxygen-rich and
oxygen-poor blood tends to stay
separate in the amphibian’s ventricle, show how two liquids with
different densities tend to separate.
Fill a graduated cylinder about half
full with corn syrup. Ask students
what they think will happen if you
add colored water to the cylinder.
(The clear corn syrup will remain at
the bottom.) Then fill the rest of the
cylinder with colored water. In a
second cylinder, reverse the order
in which you add the liquids. Ask
students to predict what will happen when you add the corn syrup
to the colored water. (The syrup
will sink to the bottom.) LS Visual
Using the Figure
Amphibian Heart Structure
blood
1 Oxygen-poor
from the body enters
the right atrium.
TAKS 2 Bio 8C, 10A
Sinus
venosus
Student Edition
TAKS Obj 2 Bio 8C
TAKS Obj 2 Bio 10A
TAKS Obj 3 Bio 7B
TEKS Bio 7B, 8C, 10A
Teacher Edition
TAKS Obj 2 Bio 8C, 10A
TAKS Obj 4 IPC 9D
TEKS Bio 8C, 10A, 11B, 12C, 12D
TEKS IPC 9D
To lungs
From
body
The pulmonary veins
carry oxygen-rich
blood from the lungs to the
left atrium.
2
From
lungs
Pulmonary
vein
Conus
arteriosis
Left
atrium
Right
atrium
A mixture of oxygenrich and oxygen-poor
blood enters the ventricle.
3
Ventricle
ventricle pumps
4 The
blood to the lungs
and the body tissues.
From body
760
MISCONCEPTION
ALERT
pp. 760–761
To body
Pulmonary
vein
GENERAL
Have students closely examine
Figure 14. Tell them that the
heart shown in the frog is drawn in
dorsal view, with the blue sinus
venosus on top. Explain that the
heart shown in the enlargement is
drawn in ventral view. The sinus
venosus is not visible in the
enlargement, but the three blue
veins that carry blood to the sinus
venosus are visible. LS Visual
760
Figure 14 Amphibian
heart. These four steps show
how blood flows through the
heart of an amphibian.
Not only did the path of circulation in amphibians change, but
several important changes occurred in the heart. As you read about
these changes, use Figure 14 to trace the flow of blood through the
amphibian heart.
The sinus venosus continues to deliver oxygen-poor blood from
the body to the right side of the heart, as shown in step 1. (You can
see the sinus venosus on the left side of Figure 14.) In addition,
oxygen-rich blood from the lungs enters the left side of the heart
directly, as shown in step 2.
A dividing wall known as the septum separates the amphibian
atrium into right and left halves. You cannot see the septum in
Figure 14 as it is beneath the conus arteriosus. The septum prevents
the complete mixing of oxygen-rich and oxygen-poor blood as each
enters the heart. As shown in step 3, both types of blood empty into
a single ventricle, where some mixing of oxygen-rich and oxygenpoor blood occurs. However, due to the anatomy of the ventricle,
the two streams of blood remain somewhat separate, as shown in
step 4. Oxygen-rich blood tends to stay on the side that directs
blood toward the body. Oxygen-poor blood tends to stay on the side
that directs blood toward the lungs.
A number of amphibians have a spiral valve that divides the
conus arteriosus. The spiral valve also helps to keep the two streams
of blood separate as they leave the heart. Even so, some oxygenpoor blood is delivered to the body’s tissues. Recall, however, that
amphibians also obtain oxygen through their skin. This additional
oxygen partly offsets the limitations of their circulatory system.
Do toads cause warts? Some students
may have the false idea that they can get
warts from toads. Explain that this is not
true. Warts are caused by viruses that are
not carried on toads. The rough, “warty”
appearance of the toad’s skin is an adaptation for living successfully in dry habitats
and is not due to skin problems.
Chapter 33 • Fishes and Amphibians
IPC Benchmark Fact
Fish gills and amphibian lungs have large surface
areas for gas exchange which increases the amount
of oxygen absorbed. Other factors, such as stirring or
shaking and usually heating, also increase the rate
at which a solute dissolves in a solvent. However,
remind students that even though the rate at which a
solute dissolves varies, a solute’s solubility is constant at a given temperature.
TAKS 4 IPC 9D (grade 11 only)
Frogs and Toads
The order Anura is made up of frogs and toads that live in environments ranging from deserts to rain forests, valleys to mountains, and ponds to puddles. Adult anurans are carnivorous, eating
a wide variety of small prey. Some species have a sticky tongue that
they extend rapidly to catch their prey. The frog body, particularly
its skeleton, is adapted for jumping, and its long muscular legs
provide the power. To learn about the leopard frog, see Up Close:
Leopard Frog on the next two pages. Toads, such as the one shown
in Figure 15, are very similar to frogs but have squat bodies and
shorter legs. Their skin is not smooth like that of a frog but is
covered with bumps.
Reproduction in Frogs
Like most living amphibians, frogs depend on the presence of water
to complete their life cycle. The female releases her eggs into the
water and a male’s sperm fertilize them externally. After a few days,
the fertilized eggs hatch into swimming, fishlike larval forms called
tadpoles. Tadpoles breathe with gills and feed mostly on algae. After
a period of growth, the body of the tadpole changes into that of an
adult frog. The rate at which tadpoles develop depends on the
species and the availability of food. This process of dramatic physical
change, called metamorphosis, is shown in Figure 16.
Teaching Tip
Figure 15 Toad. Toads like
this common Asian toad have
dry, bumpy skin and relatively
short legs.
Figure 16 Frog life cycle
The transition of a larval frog (tadpole) to an adult involves a complex series of
external and internal body changes.
Young
frog
Adult
Tadpole Metamorphosis
Purchase some “hind limb budstage” tadpoles from a biological
supply company. Keep the
tadpoles in a small, aerated
aquarium, and have students
make written or drawn observations every few days. Students will
note that the tail gets shorter, the
body gets squarer, and the hind
limb buds develop into hind legs.
Some tadpoles also may begin to
develop front legs, but the mortality rate at this stage is high. Point
out that while these dramatic
external changes are taking place,
important internal changes are
occurring as well. In most species,
the tadpole’s digestive system
changes to accommodate the
switch from an herbivorous to a
carnivorous diet. The respiratory
system changes from gills to lungand-skin respiration in the adult
frog. If neither plant nor animal
food is available to the metamorphosing tadpole at the precise
time, it can starve. Likewise, if the
tadpole does not have a place to
rest its head above water, it can
drown as its respiratory system
changes.
English Language
LS Visual
Learners
Bio 11B, 12D
Using the Figure
Front legs
appear
Hind legs
appear
Hatchling
tadpole
Fertilized
eggs
761
INCLUSION
Strategies
• Developmental Delay
• Attention Deficit
Disorder
• Learning Disability
Have students create a poster showing the
differences between frogs and toads. The
poster should compare and contrast the characteristics of these amphibians, describing the
individual characteristics of the frog and the
toad, as well as the similarities or differences
of how and where these two amphibians live.
The poster should have drawings or pictures
of different frogs and toads.
did you know?
Some frogs have developed amazing ways
to prevent their eggs from drying out.
The female Surinam toad (actually a frog) of
South America carries her eggs in pockets of
skin on her back. As many as 60 young pass
through the tadpole stage while imbedded in
her back and then emerge as small frogs.
Another species of frog in Australia swallows
the eggs and keeps them in the stomach until
the young emerge out of the adult’s mouth.
GENERAL
Have students examine Figure 16.
Have them note the external
changes that are taking place in the
frog. Then ask students to hypothesize about what internal changes
are also occurring. Have them
think about the different lifestyles
of a frog and a tadpole. (digestive
system—herbivore to carnivore; respiratory system—gills to lungs)
LS Visual Bio 8C
Bio 11B, 12C
Chapter 33 • Fishes and Amphibians
761
Up Close
Up Close
Leopard Frog TAKS 2, TAKS 3
Leopard Frog
TAKS 2 Bio 8C, 10A; TAKS 3 Bio 12B
Discussion
Guide discussion by posing the
following questions:
1. How do you think the leopard frog got its name? (its
spotted appearance)
2. How is the ear of the frog
similar to the lateral line of
the yellow perch? (Both
structures contain ciliated sensory cells.)
3. Why do frogs produce so
many eggs and sperm?
(Their eggs and larvae are
eaten by many predators.)
4. How do leopard frogs
breathe? (with lungs and
through their skin)
Scientific name: Rana pipiens
●
Size: Body length (legs excluded) of 5–9 cm (2–3.5 in.)
●
Range: From northern Canada to southern New Mexico and
from eastern California to the Atlantic coast
●
Habitat: Lives in the short grass of meadows and around
ponds
●
Diet: Feeds on crickets, mosquitoes, and other small animals
External Structures
Tympanic membrane
When sound causes the tympanic membrane (eardrum) to
vibrate, a tiny bone transmits
the vibrations to the inner ear.
▼
Teacher’s Notes
• Have pairs of students make
two columns on a sheet of
paper. Ask them to label one
Water and the other Land.
As students read about the
leopard frog, have them put
the characteristics of the frog
into one or both of the
columns, depending on the
nature of each characteristic.
For example, Tympanic
membrane would go in both
columns, while Webbed toes
would go under Water. Lead
a discussion in which conflicting results are analyzed.
• Have students compare the
organ systems of the frog with
those of the yellow perch.
Have them describe the similarities and differences.
●
Tympanic membrane
There, ciliated sensory cells
(similar to those found in the
lateral line of a fish) detect the
vibrations and help the frog
maintain balance. Leopard
frogs hear well in both water
and air.
▼ Skin
▼ Eye
Skin Mucous glands embedded within the skin supply a
lubricant that keeps the skin
moist, a necessity for respiration. Unlike those of many
frogs and toads, the leopard
frog’s skin glands do not
secrete poisonous or foultasting substances. Instead,
the leopard frog must rely on
its protective coloration and
speed to evade predators.
Student Edition
TAKS Obj 2 Bio 8C
TAKS Obj 2 Bio 10A
TAKS Obj 3 Bio 12B
TEKS Bio 8C, 10A, 12B
Teacher Edition
TAKS Obj 2 Bio 8C
TAKS Obj 2 Bio 10A
TAKS Obj 3 Bio 12B
TEKS Bio 8C, 10A, 12B, 12C
762
Eye Because its eyes bulge out from its
head, the leopard frog can stay almost
fully submerged while literally “keeping
an eye out” for predators above the
water. Its eyes work equally well in or out
of water. Eyelids that blink protect the
eyes from dust. In addition, a transparent
membrane covers each eyeball, keeping
it moist and protecting it when the frog
is underwater.
Jumping leg
Webbed toe
762
did you know?
pp. 762–763
Foreleg
A frog’s ears are external. Most frogs and
toads have a tympanic membrane on the surface of both sides of their head. The tympanic
membranes of a human are called eardrums,
and each is protected inside the ear canal.
TAKS 2 Bio 10A
Chapter 33 • Fishes and Amphibians
Internal Structures
Brain The frog’s brain differs from the
fish’s brain in that its components are
more complex. For example, the larger,
more complex cerebrum of a frog is able
Tongue and jaw The tongue flicks out with
great speed, curls around the prey, and returns
to the mouth. Two large teeth that project from
Brain
▼
Cerebrum
▼
to process a wider assortment of sensory information than the cerebrum of
a fish can.
the roof of the mouth impale struggling prey.
In addition the upper jaw is lined with small,
sharp teeth that prevent the prey from escaping. Food is not chewed but swallowed whole.
Optic lobe
Cerebellum
Tongue
Teeth
Esophagus
Olfactory lobe
Sacral
vertabra
Medulla oblongata
Urostyle
▼
Skeleton The skeletal system of
the leopard frog (and all other modern frogs) has only nine vertebrae
Kidney
Pelvic girdle
and no ribs. The rest of the vertebrae are fused into a single bone
(urostyle). When a frog is sitting, the
urostyle points upward, which gives
the frog its characteristic humped
back. When a frog jumps the long
hind legs extend, which produces
a powerful thrust forward.
Lung
Intestine
Urinary
bladder
Stomach
Heart
Liver
▼ Reproductive organs
Male
Female
Mature
ovary
Oviduct
Testis
▼ Cloaca
Kidney
Ureter
Cloaca
Cloaca Undigested material passes
into the cloaca, a chamber that opens
to the outside of the body. Urine from
the kidneys travels to the bladder and
then passes into the cloaca, as do
gametes from the reproductive organs.
All of these materials exit the body
through the cloacal opening.
Reproductive organs Prior to breeding, the reproductive organs of male and
female leopard frogs produce enormous
numbers of gametes. The female releases
a large cluster of eggs into the water.
The male then discharges his sperm
over them, fertilizing them externally.
Up Close
Leopard Frog
5. Why is a fish more agile
in the water than a frog?
(A more-developed cerebellum in the fish enables it to
have better muscle coordination. Also, a fish’s streamlined
body and fins are modifications for movement through
water.)
6. Why will a fish suffocate
if it is taken out of water?
(Its gills will collapse, dry
out, and no longer absorb
oxygen.)
7. How does a frog change its
depth in water? (It swims
using its webbed feet.)
8. Why is it vital for male
frogs to call to females?
(Frogs are camouflaged and
may not find each other by
sight alone. Each species of
frog has its own mating call,
which prevents females from
mating with the wrong
species of male.)
9. What is the advantage of a
frog of having its eyes on
the top of its head? (In
water, the frog can keep most
of its body hidden from predators while still being able to
watch for them or for prey.)
10. How can a frog stay underwater for so long with such
small lungs? (It can also
absorb oxygen through its
skin.)
763
Chapter 33 • Fishes and Amphibians
763
Salamanders and Caecilians
Salamanders have elongated bodies, long tails, and smooth, moist
skin. There are about 369 species of salamanders, all belonging to
the order Urodela. They typically range from 10 cm to 0.3 m (4 in.
to 1 ft) in length. However, giant Asiatic salamanders of the genus
Andrias grow as long as 1.5 m (5 ft) and weigh up to 41 kg (90 lb).
Because salamanders need to keep their skin moist, most are unable
to remain away from water for long periods, although some salamander species manage to live in dry areas by remaining inactive
during the day.
Salamanders lay their eggs in water or in moist places,
as shown in Figure 17. Fertilization is usually external. A
few species of salamanders practice a type of internal
fertilization in which the female picks up a sperm packet
that has been deposited by the male and places it in her
cloaca. Unlike frog and toad larvae, salamander larvae
do not undergo a dramatic metamorphosis. The young
that hatch from salamander eggs are carnivorous and
resemble small versions of the adults, except that the
young usually have gills. A few species of salamanders,
such as the North American mudpuppy and the Texas
spring salamander, never lose their larval characteristics.
They retain their external gills as adults.
Close
Reteaching
Have students make a list of characteristics that distinguish amphibians
from fish. (Answers might include
that amphibians have legs and lungs,
can live on land, exchange gases
through their skin, and have a doubleloop circulatory system.)
Quiz
Figure 17 Salamander.
This four-toed salamander has
deposited its eggs in a damp,
mossy environment.
GENERAL
1. What is the main respiratory
organ of most adult amphibians?
(lungs)
2. What are two important ways
that most amphibians depend on
the presence of water? (for
reproduction and for cutaneous
respiration)
3. How are toads different from
frogs? (Toads have squat bodies
with shorter legs and their skin is
dry and bumpy to prevent water
loss in drier environments; frogs
are have moist skin and longer
bodies and legs.)
TAKS 2 Bio 8C, 10A; Bio 8B
Alternative
Assessment
Caecilians (order Apoda) are a highly specialized group
of tropical, burrowing amphibians with small, bony
scales embedded in their skin. They feed on small invertebrates found in soil. These legless, wormlike animals,
shown in Figure 18, grow to about 0.3 m (1 ft) long,
although some species can be up to 1.2 m (4 ft) long.
During breeding, the male deposits sperm directly into the female.
Depending on the species, the female may bear live young or lay
eggs that develop externally. Caecilians are rarely seen, and scientists do not know a lot about their behavior.
Figure 18 Caecilian. Like
most caecilians, this one from
Colombia, South America,
burrows beneath the soil and
is rarely seen.
GENERAL
Have students work in groups to
prepare a poster showing the frog’s
life cycle. The poster should
include drawings of each of the
four stages of a frog’s life. Next to
each drawing, students should add
a paragraph that explains what is
illustrated by the drawing and
what they have learned about it.
For example, next to the drawing
of frog eggs, the paragraph could
explain how frog eggs are fertilized
and where they are laid.
pp. 764–765
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, 12B
Teacher Edition
TAKS Obj 1 Bio/IPC 2B
TAKS Obj 2 Bio 8C, 10A
TAKS Obj 3 Bio 7B, 12B
TEKS Bio 7B, 8B, 8C, 10A, 12B
TEKS Bio/IPC 2B
764
Caecilians
Section 3 Review
Summarize how amphibians take in oxygen.
10A
Contrast the single-loop circulation of fish with
the double-loop circulation of amphibians.
7B 10A
Explain why it is difficult to “sneak up” on
a frog.
Compare the external characteristics of each
order of amphibians.
10A
TAKS Test Prep
In a frog’s heart, the blood
that enters the left atrium
10A
A comes from the lungs. C then goes to the lungs.
B comes from the body. D then goes to the body.
8B 8C
Compare reproduction and development in
frogs and salamanders.
Relate the tongue of the leopard frog to its
7B 12B
feeding habits.
8B 10A
764
Answers to Section Review
1. through gills, lungs, or skin TAKS 2 Bio 10A
2. In single-loop circulation, blood is pumped
through gills and then travels through the body.
In double-loop circulation, blood is pumped to
the lungs and then travels back to the heart,
which pumps it to the rest of the body.
TAKS 2 Bio 10A; TAKS 3 Bio 7B
3. Apoda—small bony scales embedded in the
skin, legless; Urodela—elongated bodies with
tails; Anura—elongated hind legs and no tail
TAKS 2 Bio 10A; Bio 8B
4. Except for a few species of salamanders, both
have external fertilization. Tadpoles undergo a
radical metamorphosis to become frogs; larval
Chapter 33 • Fishes and Amphibians
salamanders resemble adults with gills.
TAKS 2 Bio 10A; Bio 8B
5. The tongue can be flicked out at great speed to
capture prey. TAKS 3 Bio 7B, 12B
6. Bulging eyes give a wide field of vision. Large
tympanic membranes readily detect sounds.
TAKS 2 Bio 10A
7.
A. Correct. The left atrium
receives oxygen-rich blood from the lungs.
B. Incorrect. Oxygen-poor blood from the
body is received in the right atrium.
C. Incorrect. From the left atrium, blood goes
to the ventricle. D. Incorrect. Blood goes to the
ventricle from the left atrium. TAKS 2 Bio 10A
Study
CHAPTER HIGHLIGHTS
ZONE
Key Concepts
Alternative
Assessment
Key Terms
Have students make a timeline of
the evolution of vertebrates from
the first jawless fishes through
amphibians. Next to each of the
organisms listed on the timeline,
students should describe the new
characteristics that arose in the
organism through natural selection.
Section 1
1 The Fish Body
●
All fishes have gills and a backbone, and they circulate
oxygen-rich blood from their gills directly to body tissues.
●
Countercurrent flow maximizes the amount of oxygen that
can be extracted from water.
●
The four-chambered fish heart collects oxygen-poor blood
from the body and pumps it through the gills where it
receives oxygen. Oxygen-rich blood then circulates to the
rest of the body.
●
A fish relies on its gills and a pair of kidneys to regulate its
salt and water balance.
●
Most fishes fertilize their eggs externally as males and
females release their gametes near one another in the water.
2 Today’s Fishes
gill filament (747)
gill slit (747)
countercurrent flow (747)
nephron (749)
TAKS 1 Bio/IPC 2B
Chapter Resource File
• Science Skills Worksheet GENERAL
• Critical Thinking Worksheet
• Test Prep Pretest GENERAL
• Chapter Test GENERAL
Section 2
●
Hagfishes and lampreys are the only surviving jawless
fishes.
●
Sharks have light, highly streamlined bodies well suited
for rapid swimming, which makes them swift and
efficient predators.
●
Bony fishes are the most diverse and abundant group
of fishes.
●
Bony fishes have an internal skeleton made completely of
bone, a swim bladder, a lateral line sensory system, and a
set of gill covers called opercula.
lateral line (753)
operculum (756)
swim bladder (756)
teleost (757)
Section 3
3 Amphibians
●
Most amphibians have legs, breathe with lungs and through
their skin, and have two circulatory loops.
●
Most amphibians supplement their oxygen intake through
cutaneous respiration—respiration through their moist skin.
●
An amphibian lung is basically an air sac with a large
surface area for gas exchange.
●
The amphibian heart pumps oxygen-poor blood to the lungs
and receives oxygen-rich blood from the lungs. The oxygenrich blood is then pumped to the body.
●
Salamanders are semiaquatic predators with tails, and
caecilians are legless amphibians specialized for burrowing.
lung (758)
pulmonary vein (759)
septum (760)
765
Answer to Concept Map
The following is one possible answer to
Performance Zone item 15.
Fishes
can be
cartilaginous
jawless
bony
have skeleton of
cartilage
have an
operculum
most are
teleosts
have
gills
with
countercurrent flow
Chapter 33 • Fishes and Amphibians
765
Performance
ZONE
CHAPTER 33
ANSWERS
Using Key Terms
1. d TAKS 2 Bio 8C
2. d TAKS 2 Bio 10A
3. c TAKS 2 Bio 10A
4. d TAKS 2 Bio 8C
5. a. A gill filament is the part of a
gill in which capillaries for gas
exchange are found. A lung is
the entire organ used by many
terrestrial animals for gas
exchange.
b. The swim bladder is an airfilled sac in bony fish that
helps the fish maintain buoyancy in water. The lateral line
is a structure in fish that contains groups of sensory cells
that detect pressure and vibrations in the water.
c. Pulmonary veins return blood
to the heart from the lungs.
The septum is a dividing wall
in the heart.
Understanding Key Ideas
6. d
7. b
8. d
9. a
10. d
11. b
12. a
13. a
TAKS 2
TAKS 3
TAKS 2
TAKS 2
TAKS 2
TAKS 2
TAKS 2
Bio 5B
Bio 8C
Bio 7B
Bio 10A
Bio 10A
Bio 10A
Bio 8C
Bio 8C
CHAPTER REVIEW
9. A shark’s skeleton is
10A
a. composed of cartilage.
b. composed of bone.
c. very dense.
d. quite rigid.
Using Key Terms
1. Hagfish and lampreys are
a. bony fishes.
b. scavengers.
c. scaled, finless fishes.
d. primitive fishes.
8C
2. In bony fishes, the organ that senses pres-
sure changes in water is the
10A
a. gill.
c. operculum.
b. septum.
d. lateral line.
c. swim bladder.
d. conus arteriosus.
12. Which of the following characteristics
c. lampreys.
d. caecelians.
of leopard frogs is not an adaptation for
8C
avoiding predators?
a. fast, flicking tongue
b. skeleton adapted for jumping
c. cloaca
d. position of the eyes
5. For each pair of terms, explain the
difference in their meanings.
a. gill filament, lung
b. swim bladder, lateral line
c. pulmonary veins, septum
Understanding Key Ideas
6. Which of the following is not a key charac-
teristic of fishes?
8C
a. vertebral column
b. gills
c. single-loop circulation
d. tympanic membrane
13. How do tadpoles differ from frogs?
5B
a. Tadpoles have gills; frogs do not.
b. Tadpoles are carnivorous; frogs are
herbivorous.
c. Frogs show body symmetry; tadpoles
do not.
d. Frogs live in water; tadpoles live in
damp vegetation.
7. Which of the following shark characteristics
is not an adaptation for predation?
a. streamlined body
b. internal fertilization of eggs
c. sharp, replaceable teeth
d. lightweight skeleton
10A
8C
tic of amphibians?
a. lungs
b. heart with two ventricles
c. cutaneous respiration
d. double-loop circulation
10A
4. The group of amphibians that is legless
8C
is the
a. toads.
b. skates.
amphibians respire
their skin.
their skin and gills.
their lungs.
their skin and lungs.
11. Which of the following is not a characteris-
3. The organ in bony fishes that regulates
buoyancy is the
a. atrium.
b. lateral line.
10. Most adult
a. through
b. through
c. through
d. through
14. Compare amphibian metamorphosis
with insect metamorphosis. (Hint: See
8B
Chapter 30, Section 3.)
7B
8. Yellow perch and sharks share all of the
following characteristics except
10A
a. gills.
b. an internal skeleton.
c. a single-loop circulatory system.
d. a swim bladder.
15.
Concept Mapping Construct a
concept map describing the characteristics
of jawless, cartilaginous, and bony fishes.
Try to include the following terms in your
concept map: gills, countercurrent flow,
cartilage, operculum, and teleosts.
3E
766
pp. 766–767
Review and Assess
TAKS Obj 1 Bio/IPC 2A, 2B, 2C, 2D
TAKS Obj 2 Bio 8C, 10A
TAKS Obj 3 Bio 7B
TEKS Bio 3D, 3E, 5B, 7B, 8B, 8C,
10A, 11A, 12C
TEKS Bio/IPC 2A, 2B, 2C, 2D
766
14. Metamorphosis in amphibians takes place in
gradual stages—from egg to tadpole to frog.
In many insects, after the egg and larval
stages, a pupa is formed. After a period of
time, the adult form emerges. The adult looks
quite different from the larva. Bio 8B
15. One possible answer to the concept map is
found at the bottom of the Study Zone page.
Bio 3E
Chapter 33 • Fishes and Amphibians
Assignment Guide
Section
1
2
3
Questions
5, 6, 15, 16, 18, 21
1, 2, 3, 5, 7, 8, 9, 15, 17, 18, 22
4, 5, 10, 11, 12, 13, 14, 15, 18, 19, 20
Critical Thinking
Alternative Assessment
Critical Thinking
16. Inferring Relationships Explain how marine
20. Finding and Communicating Information
16. Marine fish lose water to their
environment through osmosis, so
they drink a lot of sea water.
Because sea water contains a high
concentration of salts, marine
fish must actively pump excess
salt out of their body. Freshwater
fish actively take in salts from
their environment. Bio 11A
17. Yes, one could determine the age
of the carp by counting the number of growth rings on one of its
scales. TAKS 1 Bio/IPC 2C
18. Osmotic balance refers to the
concentration of salts in the body
fluids. The operculum is the
cover over the gills. Cutaneous
respiration is the process of taking in oxygen through the skin.
and freshwater fishes differ in the way they
maintain their salt and water balance.
11A
17. Recognizing Verifiable Facts A newspaper
article reports that some carp in a local
pond are approximately 50 years old. A representative from the State Department of
Fish and Wildlife states that the claim can
be verified. How can this claim be verified?
2C
18. Distinguishing Relevant Information
A student is writing a paper on the
evolution of the heart. Which of the
following terms do not pertain to her
topic? Explain. Sinus venosus, pulmonary
veins, septum, osmotic balance, atrium,
operculum, conus arteriosus, and
cutaneous respiration.
10A
19. Justifying Conclusions Would you expect
the digestive system of a tadpole to function like that of an adult frog? Explain.
10A
Use the media center or Internet resources
to learn more about amphibians that live in
your area. Create an illustrated reference
table that includes their scientific and
common names and information about
size, habitat, diet, and population
size. Make the table available as a
classroom reference. Prepare an oral or
2A 2B 2C 2D
video presentation.
21. Forming a Model Construct a model
that shows how water passes over the gills
of a bony fish. Then explain in writing why
countercurrent flow increases respiratory
10A
efficiency.
22. Career Connection Ichthyologist Research
the field of ichthyology (the study of
fishes), and write a report that includes a
job description, training required, kinds of
employers, growth prospects, and
3D
starting salaries.
TAKS 2 Bio 10A
19. No, most tadpoles are herbivores
whereas adult frogs are carnivores.
TAKS Test Prep
The diagrams below show two vertebrate
circulatory systems. Arrows indicate the direction
of blood flow. Use the diagrams and your
knowledge of science to answer questions 1–3.
X
2. In which environment would you be most
likely to find an animal that has circulatory
12C
system B?
F deep ocean
H moist habitat on land
G coral reef
J freshwater lake
3. Which statement applies to circulatory
10A
system A?
A Blood returns to the heart from the gills
before being pumped to the rest of the
body.
B The body organs receive fully oxygenated
blood.
C A mixture of oxygen-rich and oxygen-poor
blood is pumped to the gills.
D Blood is pumped to the body organs at
a higher pressure than in circulatory
system B.
A
B
1. Where are the capillaries labeled X located?
10A
A in the gills
C in the lungs
B in the brain
D in other body organs
1. A. Correct. The diagram shows a single-loop
circulatory system which is a characteristic of
fishes, and the blood from the heart in the diagram is oxygen-poor (blue) and becomes
oxygen-rich (red) after the X. Gills are the organs
of gas exchange in fishes. B. Incorrect. Blood is
becoming oxygenated at the X, but the brain
would deoxygenate the blood. C. Incorrect.
Lungs are not present in the single-loop system
of fishes. D. Incorrect. Other body parts would
deoxygenate the blood. TAKS 2 Bio 10A
2. F. Incorrect. See answer H. Amphibians do not
live in the deep ocean. G. Incorrect. See answer
H. Amphibians do not live in coral reefs.
Test
If a question or an answer choice contains an
unfamiliar term, try to break the word into parts
to determine its meaning.
767
H. Correct. B is a double-loop circulatory system characteristic of amphibians, which can be
found in moist land habitats. J. Incorrect.
Although amphibians may be found near the
edges of freshwater lakes, they are infrequently
in the aquatic habitat of lakes. Bio 12C
3. A. Incorrect. Blood flows from the gills to the
body to the heart. B. Correct. Blood flows from
the gills to the body, providing fully oxygenated
blood directly from the gills. C. Incorrect. In
fishes, only oxygen-poor blood is pumped to the
gills. D. Incorrect. Blood is pumped to body
organs at a lower pressure in single-loop
circulatory systems than in double-loop
circulatory systems. TAKS 2 Bio 10A
TAKS 2 Bio 10A
Alternative Assessment
20. Tables will vary. The table should
list frogs and toads separately
from salamanders and newts.
Presentations will vary. They
should explain all features of the
reference table.
TAKS 1 Bio/IPC 2A, 2B, 2C, 2D
21. Models should resemble the
drawings in Figure 2. Countercurrent flow ensures that oxygen
diffuses into the blood over the
entire length of the capillaries in
the gills. TAKS 2 Bio 10A
22. Ichthyologists study aspects of
fish anatomy, physiology, and
ecology. They are employed by
federal and state wildlife agencies
in park systems, by fish hatcheries, and by zoos and wildlife
parks. Ichthyologists may also be
hired to conduct environmental
impact studies when commercial
development plans might affect
fish habitats. Training requirements vary according to position,
but most positions require at
least a master’s degree. Growth
prospects are fair. Starting salary
will vary by region. Bio 3D
Chapter 33 • Fishes and Amphibians
767