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Unit 1: What is Biology?
Unit 2: Ecology
Unit 3: The Life of a Cell
Unit 4: Genetics
Unit 5: Change Through Time
Unit 6: Viruses, Bacteria, Protists, and Fungi
Unit 7: Plants
Unit 8: Invertebrates
Unit 9: Vertebrates
Unit 10: The Human Body
Unit 1: What is Biology?
Chapter 1: Biology: The Study of Life
Unit 2: Ecology
Chapter 2: Principles of Ecology
Chapter 3: Communities and Biomes
Chapter 4: Population Biology
Chapter 5: Biological Diversity and Conservation
Unit 3: The Life of a Cell
Chapter 6: The Chemistry of Life
Chapter 7: A View of the Cell
Chapter 8: Cellular Transport and the Cell Cycle
Chapter 9: Energy in a Cell
Unit 4: Genetics
Chapter 10: Mendel and Meiosis
Chapter 11: DNA and Genes
Chapter 12: Patterns of Heredity and Human Genetics
Chapter 13: Genetic Technology
Unit 5: Change Through Time
Chapter 14: The History of Life
Chapter 15: The Theory of Evolution
Chapter 16: Primate Evolution
Chapter 17: Organizing Life’s Diversity
Unit 6: Viruses, Bacteria, Protists, and Fungi
Chapter 18: Viruses and Bacteria
Chapter 19: Protists
Chapter 20: Fungi
Unit 7: Plants
Chapter 21:
Chapter 22:
Chapter 23:
Chapter 24:
What Is a Plant?
The Diversity of Plants
Plant Structure and Function
Reproduction in Plants
Unit 8: Invertebrates
Chapter 25: What Is an Animal?
Chapter 26: Sponges, Cnidarians, Flatworms, and
Roundworms
Chapter 27: Mollusks and Segmented Worms
Chapter 28: Arthropods
Chapter 29: Echinoderms and Invertebrate
Chordates
Unit 9: Vertebrates
Chapter 30: Fishes and Amphibians
Chapter 31: Reptiles and Birds
Chapter 32: Mammals
Chapter 33: Animal Behavior
Unit 10: The Human Body
Chapter 34: Protection, Support, and Locomotion
Chapter 35: The Digestive and Endocrine Systems
Chapter 36: The Nervous System
Chapter 37: Respiration, Circulation, and Excretion
Chapter 38: Reproduction and Development
Chapter 39: Immunity from Disease
Vertebrates
Fishes and Amphibians
Reptiles and Birds
Mammals
Animal Behavior
Chapter 30 Fishes and Amphibians
30.1: Fishes
30.1: Section Check
30.2: Amphibians
30.2: Section Check
Chapter 30 Summary
Chapter 30 Assessment
What You’ll Learn
You will compare and contrast the
adaptations of the different groups of
fishes and amphibians.
You will learn about the origin of
modern fishes and amphibians.
Section Objectives:
• Relate the structural adaptations of fishes
to their environments.
• Compare and contrast the characteristics
of the different groups of fishes.
• Interpret the phylogeny of fishes.
What is a fish?
• Fishes, like all vertebrates, are classified in
the phylum Chordata.
• Fishes belong to the
subphylum Vertebrata.
What is a fish?
• In addition to fishes,
subphylum
Vertebrata includes
amphibians, reptiles,
birds, and mammals.
What is a fish?
• In vertebrates, the embryo’s notochord is
replaced by a backbone in adult animals.
• All vertebrates are bilaterally symmetrical,
coelomates that have endoskeletons, closed
circulatory systems, nervous systems with
complex brains and sense organs, and
efficient respiratory systems.
Classes of fishes
Fishes
Class
Organisms
Myxini
Hagfishes
Cephalaspidomorphi
Lampreys
Chondrichthyes
Sharks, skates, rays
Osteichthyes
Lobe-finned fishes,
ray-finned fishes
Characteristics
Jawless, cartilaginous
skeleton, gills
Jawless, cartilaginous
skeleton, gills
Jaws, cartilaginous skeleton, paired
fins, gills, scales, internal fertilization
Jaws, bony skeleton, paired fins,
gills, scales, swim bladder
Fishes breathe using gills
• Fishes have gills made up of feathery gill
filaments that contain tiny blood vessels.
Gill Filaments
Fishes breathe using gills
• As a fish takes water
in through its mouth,
water passes over the
gills and then out
through slits at the
side of the fish.
Gill Filaments
Water
Artery
Capillary networks
in filament Gill
filaments
Vein
Water
Fishes breathe using gills
• Oxygen and carbon
dioxide are exchanged
through the capillaries
in the gill filaments.
Gill Filaments
Water
Artery
Capillary networks
in filament Gill
filaments
Vein
Water
Fishes have two-chambered hearts
Aorta
Gills
Heart
Capillary
network
Fishes reproduce sexually
• Although the method may vary, all fishes
reproduce sexually.
• Fertilization and development is external in
most fishes.
• Eggs and sperm can be released directly into
the water, or deposited in more protected
areas, such as on floating aquatic plants.
Fishes reproduce sexually
• Cartilaginous fishes have internal
fertilization.
• Skates deposit fertilized eggs on the
ocean floor.
• Some female sharks and rays carry
developing young inside their bodies.
Fishes reproduce sexually
• Most bony fishes have external fertilization
and development.
• This type of external
reproduction in fishes
and some other animals
is called spawning.
Salmon spawning
Fishes reproduce sexually
• In some bony fishes, such as guppies and
mollies, fertilization and development is
internal.
• Most fishes that produce millions of eggs
provide no care for their offspring after
spawning.
• Some fishes, such as the mouth-brooding
cichlids, stay with their young after they
hatch.
Most fishes have paired fins
• Fishes in the classes Chondrichthyes
and Osteichthyes have paired fins.
• Fins are fan-shaped
membranes that are
used for balance,
swimming, and
steering.
Most fishes have paired fins
• Fins are attached to and supported by the
endoskeleton and are important in locomotion.
Most fishes have paired fins
• The paired fins of fishes foreshadowed the
development of limbs for movement on land
and ultimately of wings for flying.
Pectoral
fin
Anal
Caudal fin
fin
Dorsal
fins
Pelvic
fins
Fishes have developed sensory systems
• Cartilaginous and bony fishes have an
adaptation called the lateral line system
that enables them to sense objects and
changes in their environment.
Lateral line
Gelatin-like fluid
Receptor cells
Nerve
Fishes have developed sensory systems
• The lateral line system is a line of fluidfilled canals running along the sides of a
fish that enable it to detect movement and
vibrations in the water.
Lateral line
Gelatin-like fluid
Receptor cells
Nerve
Fishes have developed sensory systems
• Fishes have eyes
that allow them to
see objects and
contrasts between
light and dark in
the water as well.
Fishes have developed sensory systems
• Some fishes that
live in areas of
the ocean where
there is no light
may have
reduced, almost
nonfunctional
eyes.
Fishes have developed sensory systems
• Some fishes also have an extremely
sensitive sense of smell and can detect
small amounts of chemicals in the water.
• Sharks can follow a trail of blood through
the water for several hundred meters.
Most fishes have scales
• Scales are thin bony plates formed from
the skin.
• Scales can be toothlike, diamond-shaped,
cone-shaped, or round. Shark scales are
similar to teeth found in other vertebrates.
Jaws evolved in fishes
Gill arches
Gill slits
Jawless, filter-feeding fish
Skull
Jaws
Gill slits
Gill arches
Beginning of jaw formation
Fish with jaws
• The advantage of jaws is that they enable
an animal to grasp and crush its prey with
great force.
Jaws evolved in fishes
Gill arches
Gill slits
Jawless, filter-feeding fish
Skull
Jaws
Gill slits
Gill arches
Beginning of jaw formation
Fish with jaws
• Jaws also allowed early fishes to prey on
a greater variety of organisms.
Jaws evolved in fishes
• Sharks have up to 20 rows of teeth that
are continually replaced.
• Their teeth point
backwards to prevent
prey from escaping
once caught.
Jaws evolved in fishes
• Sharks are among the most streamlined
of all fishes and are well adapted for
life as predators.
Most fishes have bony skeletons
• Bony fishes, a successful and widely
distributed class, differ greatly in habitat,
size, feeding behavior, and shape.
Most fishes have bony skeletons
• All bony fishes have skeletons made of
bone rather than cartilage as found in
other classes of fishes.
• Bone is the hard, mineralized, living
tissue that makes up the endoskeleton
of most vertebrates.
Bony fishes have separate vertebrae
that provide flexibility
• The evolution of a backbone composed of
separate, hard segments called vertebrae was
significant in providing the major support
structure of the vertebrate skeleton.
• Separate vertebrae provide great flexibility.
Bony fishes have separate vertebrae
that provide flexibility
An eel moves its
entire body in an
S-shaped pattern.
A mackerel flexes
the posterior end
of its body to
accentuate the tail
-fin movement.
A tuna keeps its body
rigid, moving only its
powerful tail. Fishes
that use this method
move faster than all
others.
Bony fishes
evolved swim
bladders
• A fish with a
swim bladder
can control its
depth by
regulating the
amount of gas
in the bladder.
Swim bladder
Bony fishes evolved swim bladders
• Some fishes remove gases from the swim
bladder by expelling them through a special
duct that attaches the swim bladder to the
esophagus.
• In fishes that do not have this duct their
swim bladders empty when gases diffuse
back into the blood.
A Bony
Fish
Lateral line system
Swim bladder
Kidney
Urinary bladder
Reproductive organ
Scales
Fins
Stomach
Intestine
Liver
Heart Gills
Diversity of fishes
• Fishes range in size from the tiny dwarf
goby that is less than 1 cm long, to the huge
whale shark that can reach a length of about
15 m—the length of two school buses.
Whale shark
Agnathans are jawless fishes
• Lampreys and
hagfishes belong
to the superclass
Agnatha.
Lamprey
• The skeletons of agnathans, as well as of
sharks and their relatives, are made of a
tough, flexible material called cartilage.
Agnathans are jawless fishes
• A hagfish has a toothed mouth and feeds
on dead or dying fishes.
• It can drill a hole into a fish and suck out
the blood and insides.
• Parasitic lampreys use their suckerlike
mouths to attack other fishes.
• They use their sharp teeth to scrape away
the flesh and then suck out the prey’s blood.
Sharks and rays are cartilaginous fishes
• Sharks, skates, and rays belong to the class
Chondrichthyes.
• These fishes, like agnathans,
possess skeletons composed
entirely of cartilage.
• Sharks are perhaps the
most well-known
predators of the oceans.
Sharks and rays are cartilaginous fishes
• Like sharks, most rays are predators and
feed on or near the ocean floor.
• Rays have flat bodies
and broad pectoral fins
on their sides.
Sharks and rays are cartilaginous fishes
• By slowly flapping their fins up and down,
rays can glide as they search for mollusks
and crustaceans along the ocean floor.
Subclasses of bony fishes
• Scientists recognize two subclasses of bony
fishes—the lobe-finned fishes, including
lungfishes, and the ray-finned fishes.
• The lobe-finned fishes are represented
by seven living species: six species of
lungfishes, which have both gills and
lungs, and the coelacanth.
Subclasses of bony fishes
• In the ray-finned fishes, such as catfish,
perch, salmon, and cod, fins are fanshaped membranes supported by stiff
spines called rays.
Perch
Origins of Fishes
• Scientists have identified fossils of fishes
that existed during the late Cambrian
Period, 500 million years ago.
• At this time, ostracoderms (OHS trah
koh durmz), early jawless fishes, were
the dominant vertebrates on Earth.
Origins of Fishes
Heterostracah
Anaspid
Cephalaspid
Origins of Fishes
• Bone provides a place for muscle
attachment, which improves locomotion.
• In ancestral fishes, bone that formed into
plates provided protection as well.
Origins of Fishes
• Scientists hypothesize that the jawless
ostracoderms were the common ancestors
of all fishes.
• Modern cartilaginous and bony fishes
evolved during the mid-Devonian Period.
• Lobe-finned fishes, such as coelacanths
(SEE luh kanths), are another ancient group,
appearing in the fossil record about 395
million years ago.
Question 1
Why is internal fertilization and
development more effective than
spawning? (TX Obj 2; 8C, 10A, 10B)
Answer
Because young fishes are well developed
when they are born, they have an increased
chance of survival. Only a small percentage
of external fish eggs survive.
Question 2
Why is blood flow through the body
of a fish relatively slow?
(TX Obj 2; 8C, 10A, 10B)
Blood flow is slow because most of the pumping
action of the two-chambered heart of a fish is
used to push blood through the gills.
Aorta
Gills
Heart
Capillary
network
Question 3
What evolutionary development did paired
fins foreshadow? (TX Obj 2; 8C, 10A, 10B)
Answer
Paired fins foreshadowed the development of
limbs for movement on land and ultimately
wings for flying.
Question 4
What is a fish’s lateral line system and
what is its function?
The lateral line system is a line of fluid-filled
canals running along the sides of a fish that
enable it to detect movement and vibrations in
the water.
Lateral line
Gelatin-like fluid
Receptor cells
Nerve
Question 5
What is the advantage of the development
of jaws? (TX Obj 2; 8C, 10A, 10B)
Jaws enable an animal to grasp and crush its
prey with great force. They allowed early fishes
to prey on a greater variety of organisms.
Gill arches
Gill slits
Jawless, filter-feeding fish
Skull
Gill slits
Gill arches
Beginning of jaw formation
Fish with jaws
Jaws
Section Objectives
• Relate the demands of a terrestrial
environment to the adaptations of
amphibians.
• Relate the evolution of the threechambered heart to the amphibian
lifestyle.
What is an amphibian?
• Amphibians have thin,
moist skin and most
have four legs.
• Although most adult amphibians are capable
of a terrestrial existence, nearly all of them
rely on water for reproduction.
What is an amphibian?
• Fertilization in most amphibians is external,
and water is needed as a medium for
transporting sperm.
• Amphibian eggs lack protective membranes
and shells and must be laid in water or other
moist areas.
Amphibians are ectotherms
• An ectotherm (EK tuh thurm) is an animal
that has a variable body temperature and
gets its heat from external sources.
• Because many biological processes
require particular temperature ranges in
order to function, amphibians become
dormant in regions that are too hot or
cold for part of the year.
Amphibians undergo metamorphosis
Fertilized eggs
Adult frog
Young frogs have structures
needed for life on land.
Young, legless
tadpoles live
off yolk stored
in their bodies.
Tadpoles with legs feed on plants in the water.
Amphibians undergo metamorphosis
• Young salamanders resemble adults, but, as
aquatic larvae, they have gills and usually
have a tail fin.
• Most adult salamanders
lack gills and fins.
• They breathe through
their moist skin or with
lungs.
Amphibians undergo metamorphosis
• Completely terrestrial salamander species do
not have a larval stage; the young hatch as
smaller versions of adults.
• Most salamanders
have four legs for
moving about, but a
few have only two
front legs.
Walking requires more energy
• The laborious walking of early amphibians
required a great deal of energy from food and
large amounts of oxygen for aerobic respiration.
• The evolution of the three-chambered heart
in amphibians ensured that cells received the
proper amount of oxygen.
Walking requires more energy
• In the three-chambered heart of amphibians,
one chamber receives oxygen-rich blood
from the lungs and skin, and another
chamber receives oxygen-poor blood from
the body tissues.
Walking requires more energy
• Blood from both chambers then moves to
the third chamber, which pumps oxygen-rich
blood to body tissues and oxygen-poor blood
back to the lungs and skin so it can pick up
more oxygen.
Walking requires more energy
• Because the skin of an amphibian must stay
moist to exchange gases, most amphibians
are limited to life on the water’s edge or
other moist areas.
Frogs and toads belong to the order Anura
• Frogs and toads are amphibians with no tails.
• Frogs have long hind legs and smooth,
moist skin.
Frog
Toad
Frogs and toads belong to the order Anura
• Toads have short legs and bumpy, dry skin.
• Adult frogs and toads are predators that eat
invertebrates, such as insects and worms.
Frog
Toad
Frogs and toads belong to the order Anura
• Frogs and toads also have vocal cords that are
capable of producing a wide range of sounds.
Vocal cords are sound-producing bands of
tissue in the throat.
Frogs and toads belong to the order Anura
• Most frogs and toads spend part of their
life cycle in water and part on land.
• They breathe through lungs or through
their thin skins.
• Declining numbers of frog species, or
deformities in local frogs, sometimes
indicate the presence of pollutants in
the environment.
Eyes
A Frog
Tympanic membrane
Backbone
Fat bodies
Intestine
Tongue
Vocal cords
Lungs
Heart
Calls
Liver
Legs
Salamanders belong to the order Caudata
• A salamander has a long,
slender body with a neck
and tail.
• Salamanders resemble
lizards, but have smooth,
moist skin and lack claws.
Salamanders belong to the order Caudata
• They range in size
from a few centimeters
in length up to 1.5 m.
The young hatch from
eggs, look like small
salamander adults, and
are carnivorous.
Caecilians are limbless amphibians
• Caecilians are burrowing amphibians, have
no limbs, and have a short, or no, tail.
• Caecilians are primarily tropical animals
with small eyes that often are blind.
• They eat earthworms and other invertebrates
found in the soil.
• All caecilians have internal fertilization.
Origins of Amphibians
• Most likely, amphibians arose as their
ability to breathe air through well-developed
lungs evolved.
• The success of inhabiting the land depended
on adaptations that would provide support,
protect membranes involved in respiration,
and provide efficient circulation.
Challenges of life on land
• Land life for amphibians held many dangers.
• Unlike the temperature of water, which
remains fairly constant, air temperatures
can vary greatly.
• In addition, without the support of water,
the body was clumsy and heavy.
Challenges of life on land
• Amphibians first appeared about 360
million years ago.
• Amphibians probably evolved
from an aquatic tetrapod around
the middle of the Paleozoic Era.
Challenges of life on land
• Able to breathe through their lungs,
gills, or skin, amphibians became, for a
time, the dominant vertebrates on land.
Challenges of life on land
Question 1
An animal that has a variable body temperature
and must get its heat from external sources is
called a(n) _______. (TX Obj 2; 8C, 10A, 10B)
A. ectotherm
B. placoderm
C. ostracoderm
D. amphibian
The answer is A, ectotherm.
Question 2
Why is a three-chambered heart an important
evolutionary development?
(TX Obj 2; 8C, 10A, 10B)
Answer
The three-chambered heart helps supply large
amounts of oxygen required for activities like
walking on land.
Question 3
In an adult amphibian, the _______ is the
most important organ for gas exchange.
(TX Obj 2; 8C, 10A, 10B)
A. lung
B. skin
C. gill
D. tympanic membrane
The answer is B, skin.
Question 4
Describe the difference between frogs
and toads. (TX Obj 2; 8C, 10A, 10B)
Frogs have long hind legs and smooth,
moist skin. Toads have short legs and
bumpy, dry skin.
Question 5
The most important factor for amphibians is
that their environment must be _______.
(TX Obj 2; 8C, 10A, 10B)
A. dark
B. dry
C. hot
D. moist
The answer is D, moist.
Fishes
• Fishes are vertebrates with backbones and
nerve cords that have expanded into brains.
• Fishes belong to four classes: two classes of
jawless fishes: lampreys and hagfishes, the
cartilaginous sharks and rays, and the bony
fishes. Bony fishes are made up of two groups:
the lobe-finned fishes, including lungfishes,
and the ray-finned fishes.
Fishes
• Jawless cartilaginous, and bony fishes may
have evolved from ancient ostracoderms.
Amphibians
• The class Amphibia includes three orders:
Caudata—salamanders and newts, Anura—
frogs and toads, and Apoda—legless
caecilians.
• Adult amphibians have three-chambered
hearts that provide oxygen to body tissues,
but most gas exchange takes place through
the skin.
Amphibians
• Land animals face problems of dehydration,
gas exchange in the air, and support for heavy
bodies. Amphibians possess adaptations suited
for life on land.
• Amphibians probably evolved from ancient
aquatic tetrapods.
Question 1
Which of the following features is important
in allowing a fish to maintain buoyancy?
(TX Obj 2; 8C, 10A, 10B)
A.
B.
C.
D.
lateral line system
swim bladder
fins
flexible backbone
The answer is B,
swim bladder.
Lateral line system
Swim bladder
Kidney
Urinary bladder
Reproductive organ
Fins
Stomach
Intestine
Liver
Scales
Heart Gills
Question 2
Which of the following fishes is parasitic?
(TX Obj 2; 8C, 10A, 10B, TX Obj 3; 12B, 12E)
A.
B.
C.
D.
lamprey
skate
lungfish
hagfish
The answer is A, lamprey.
Question 3
Which of the following fish was once
thought to be extinct before 1938?
(TX Obj 2; 8C, 10A, 10B)
A.
B.
C.
D.
hagfish
lungfish
coelacanth
lamprey
The answer is C. Living coelacanths were
caught off the coast of Africa in 1938.
Question 4
Which of the following male fish brood
their young in stomach pouches?
(TX Obj 2; 8C, 10A, 10B)
A.
B.
C.
D.
eels
pile
manta rays
seahorses
The answer is D, seahorses.
Question 5
Study the figure and give two physiological
reasons why the illustrated fish represent very
ancient fishes. (TX Obj 2; 8C, 10A, 10B)
The illustration shows that these fishes possess
external bony plates and lobed fins, both
physiological features of ancient fishes.
Heterostracah
Anaspid
Cephalaspid
Question 6
What were the advantages of terrestrial
living for early amphibians?
(TX Obj 2; 8C, 10A, 10B)
Answer
On land, there was a large food supply,
shelter, no predators, and more oxygen
in the air than in water.
Question 7
The closest fish relative to amphibians is most
likely the _______. (TX Obj 2; 8C, 10A, 10B)
A.
B.
C.
D.
hagfishes
lampreys
lobe-finned fishes
sharks
The answer is C, lobe-finned fishes.
Question 8
How does adaptation to life on land involve the
positioning of limbs? (TX Obj 2; 8C, 10A, 10B)
Answer
Limbs that are positioned underneath the body
allow greater speed of locomotion and help
hold the body off the ground to protect it.
Question 9
Why are some frogs known as “poisonarrow frogs”? (TX Obj 2; 8C, 10A, 10B)
The poison secreted by these frogs is used by
some native people to coat the tips of the darts
that they use in their blowguns for hunting.
Question 10
Why are caecilians often blind?
(TX Obj 2; 8C, 10A, 10B)
Answer
Blindness is an adaptation to living mostly
underground where site in not as necessary
as living above ground.
Photo Credits
• Digital Stock
• PhotoDisc
• USFWS
• Lee Emery/USFWS
• Ward's Natural Science Est.
• Lynn Stone
• Emmet Blankenship/USFWS
• John & Karen Hollingsworth/ USFWS
• Alton Biggs
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