Table of Contents – pages iii

Unit 1: What is Biology?Unit 2: EcologyUnit 3: The Life of a CellUnit 4: GeneticsUnit 5: Change Through TimeUnit 6: Viruses, Bacteria, Protists, and FungiUnit 7: PlantsUnit 8: InvertebratesUnit 9: VertebratesUnit 10: The Human Body

Unit 1: What is Biology?

Chapter 1: Biology: The Study of LifeUnit 2: Ecology Chapter 2: Principles of Ecology Chapter 3: Communities and Biomes Chapter 4: Population Biology Chapter 5: Biological Diversity and ConservationUnit 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: What Is a Plant?

Chapter 22: The Diversity of Plants

Chapter 23: Plant Structure and Function

Chapter 24: 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.

• Relate the structural adaptations of fishes to their environments.

Section Objectives:

• Compare and contrast the characteristics of the different groups of fishes.

• Interpret the phylogeny of fishes.

• Fishes, like all vertebrates, are classified in the phylum Chordata.

• Fishes belong to the subphylum Vertebrata.

What is a fish?What is a fish?


• In addition to fishes, subphylum Vertebrata includes amphibians, reptiles, birds, and mammals.

• 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 fishesClasses of fishes

Fishes

Class Organisms Characteristics

Myxini

Cephalaspidomorphi

Chondrichthyes

Osteichthyes

Hagfishes

Lampreys

Sharks, skates, rays

Lobe-finned fishes, ray-finned fishes

Jawless, cartilaginous skeleton, gillsJawless, cartilaginous skeleton, gillsJaws, cartilaginous skeleton, pairedfins, gills, scales, internal fertilizationJaws, bony skeleton, paired fins,gills, scales, swim bladder

• Fishes have gills made up of feathery gill filaments that contain tiny blood vessels.

Fishes breathe using gillsFishes breathe using gills

Gill Filaments

• 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

Capillary networksin filament Gill

filaments

Water

Water

Artery

Vein


• Oxygen and carbon dioxide are exchanged through the capillaries in the gill filaments.

Gill Filaments

Gillfilaments

Water

Water

Artery

Vein

Capillary networksin filament

Fishes have two-chambered heartsFishes have two-chambered hearts

Heart

Gills

Aorta

Capillary network

• Although the method may vary, all fishes reproduce sexually.

Fishes reproduce sexuallyFishes 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.

• Cartilaginous fishes have internal fertilization.


• Skates deposit fertilized eggs on the ocean floor.

• Some female sharks and rays carry developing young inside their bodies.

• Most bony fishes have external fertilization and development.


• This type of external reproduction in fishes and some other animals is called spawning.

Salmon spawning

• 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.

• Fishes in the classes Chondrichthyes and Osteichthyes have paired fins.

Most fishes have paired finsMost fishes have paired fins

• Fins are fan-shaped membranes that are used for balance, swimming, and steering.


• Fins are attached to and supported by the endoskeleton and are important in locomotion.

• The paired fins of fishes foreshadowed the development of limbs for movement on land and ultimately of wings for flying.


Caudal fin

Anal fin

Pelvicfins

Pectoralfin

Dorsal fins

• Cartilaginous and bony fishes have an adaptation called the lateral line system that enables them to sense objects and changes in their environment.

Fishes have developed sensory systemsFishes have developed sensory systems

Lateral line

Gelatin-like fluidReceptor cellsNerve

Fishes have developed sensory systemsFishes have developed sensory systems• 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

Receptor cellsGelatin-like fluid

Nerve

• Fishes have eyes that allow them to see objects and contrasts between light and dark in the water as well.



• Some fishes that live in areas of the ocean where there is no light may have reduced, almost nonfunctional eyes.

• 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.

• Scales are thin bony plates formed from the skin.

Most fishes have scalesMost fishes have scales

• Scales can be toothlike, diamond-shaped, cone-shaped, or round. Shark scales are similar to teeth found in other vertebrates.

• The advantage of jaws is that they enable an animal to grasp and crush its prey with great force.

Jaws evolved in fishesJaws evolved in fishes

Jawless, filter-feeding fish

Beginning of jaw formation Fish with jaws

Gill arches

Gill slits

Gill slits

Gill arches

Skull Jaws


• Jaws also allowed early fishes to prey on a greater variety of organisms.



Gill arches

Gill slits

Gill slits

Gill arches

Skull Jaws

• Sharks have up to 20 rows of teeth that are continually replaced.


• Their teeth point backwards to prevent prey from escaping once caught.


• Sharks are among the most streamlined of all fishes and are well adapted for life as predators.

• Bony fishes, a successful and widely distributed class, differ greatly in habitat, size, feeding behavior, and shape.

Most fishes have bony skeletonsMost fishes have bony skeletons

Most fishes have bony skeletonsMost 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.

• The evolution of a backbone composed of separate, hard segments called vertebrae was significant in providing the major support structure of the vertebrate skeleton.

Bony fishes have separate vertebrae that provide flexibilityBony fishes have separate vertebrae that provide flexibility

• Separate vertebrae provide great flexibility.

Bony fishes have separate vertebrae that provide flexibilityBony 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 toaccentuate 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.

Swim bladder

Bony fishes evolved swim bladders

Bony fishes evolved swim bladders

• A fish with a swim bladder can control its depth by regulating the amount of gas in the bladder.

• Some fishes remove gases from the swim bladder by expelling them through a special duct that attaches the swim bladder to the esophagus.

Bony fishes evolved swim bladdersBony fishes evolved swim bladders

• In fishes that do not have this duct their swim bladders empty when gases diffuse back into the blood.

A Bony FishA Bony Fish Lateral line system

Swim bladder

Scales

Gills

Fins

KidneyUrinary bladder

Reproductive organ

StomachIntestine

LiverHeart

• 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.

Diversity of fishesDiversity of fishes

Whale shark

• Lampreys and hagfishes belong to the superclass Agnatha.

Agnathans are jawless fishesAgnathans are jawless fishes

• The skeletons of agnathans, as well as of sharks and their relatives, are made of a tough, flexible material called cartilage.

Lamprey

• A hagfish has a toothed mouth and feeds on dead or dying fishes.

Agnathans are jawless fishesAgnathans are jawless 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, skates, and rays belong to the class Chondrichthyes.

Sharks and rays are cartilaginous fishesSharks and rays are cartilaginous fishes

• These fishes, like agnathans, possess skeletons composed entirely of cartilage.

• Sharks are perhaps the most well-known predators of the oceans.

• Like sharks, most rays are predators and feed on or near the ocean floor.

Sharks and rays are cartilaginous fishesSharks and rays are cartilaginous fishes

• Rays have flat bodies and broad pectoral fins on their sides.

Sharks and rays are cartilaginous fishesSharks 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.

• Scientists recognize two subclasses of bony fishes—the lobe-finned fishes, including lungfishes, and the ray-finned fishes.

Subclasses of bony fishesSubclasses of bony 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 fishesSubclasses of bony fishes• In the ray-finned fishes, such as catfish,

perch, salmon, and cod, fins are fan-shaped membranes supported by stiff spines called rays.

Perch

Origins of FishesOrigins 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.


Anaspid

Cephalaspid

Heterostracah


• Bone provides a place for muscle attachment, which improves locomotion.

• In ancestral fishes, bone that formed into plates provided protection as well.

Origins of FishesOrigins 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 1Why is internal fertilization and development more effective than spawning? (TX Obj 2; 8C, 10A, 10B)

AnswerBecause 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.

Heart

Aorta

Capillary networkGills

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 fluidReceptor cellsNerve

Question 5

What is the advantage of the development of jaws? (TX Obj 2; 8C, 10A, 10B)



Gill arches

Gill slits

Gill slits

Gill arches

Skull Jaws

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.

Section Objectives

• Relate the evolution of the three-chambered heart to the amphibian lifestyle.

• Relate the demands of a terrestrial environment to the adaptations of amphibians.

• Amphibians have thin, moist skin and most have four legs.

What is an amphibian?What is an amphibian?

• Although most adult amphibians are capable of a terrestrial existence, nearly all of them

rely on water for reproduction.

• Fertilization in most amphibians is external, and water is needed as a medium for transporting sperm.

What is an amphibian?What is an amphibian?

• Amphibian eggs lack protective membranes and shells and must be laid in water or other moist areas.

• An ectotherm (EK tuh thurm) is an animal that has a variable body temperature and gets its heat from external sources.

Amphibians are ectothermsAmphibians are ectotherms

• 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 metamorphosisAmphibians undergo metamorphosis

Fertilized eggs

Young, leglesstadpoles liveoff yolk storedin their bodies.

Tadpoles with legs feed on plants in the water.

Young frogs have structuresneeded for life on land.

Adult frog

• 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.

• 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.

• The laborious walking of early amphibians required a great deal of energy from food and large amounts of oxygen for aerobic respiration.

Walking requires more energyWalking requires more energy

• The evolution of the three-chambered heart in amphibians ensured that cells received the proper amount of oxygen.

• 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.


• 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.


• 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 are amphibians with no tails.

Frogs and toads belong to the order AnuraFrogs and toads belong to the order Anura

• Frogs have long hind legs and smooth, moist skin.

FrogToad

• Toads have short legs and bumpy, dry skin.

• Adult frogs and toads are predators that eat invertebrates, such as insects and worms.

FrogToad


• 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.


• 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.


A FrogA Frog Eyes

Tympanic membrane

Tongue

Lungs

Calls

Legs

Vocal cords

Heart

Liver

IntestineFat bodies

Backbone

Salamanders belong to the order CaudataSalamanders 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 CaudataSalamanders 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 amphibiansCaecilians 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 AmphibiansOrigins 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 landChallenges 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 landChallenges 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 landChallenges 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 landChallenges of life on land

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)

Question 1

D. amphibian C. ostracoderm B. placoderm A. ectotherm

The answer is A, ectotherm.

Why is a three-chambered heart an important evolutionary development? (TX Obj 2; 8C, 10A, 10B)

Question 2

Answer

The three-chambered heart helps supply large amounts of oxygen required for activities like walking on land.

In an adult amphibian, the _______ is the most important organ for gas exchange.(TX Obj 2; 8C, 10A, 10B)

Question 3

D. tympanic membrane

C. gill

B. skin

A. lung

The answer is B, skin.

Describe the difference between frogs and toads. (TX Obj 2; 8C, 10A, 10B)

Question 4

Frogs have long hind legs and smooth, moist skin. Toads have short legs and bumpy, dry skin.

The most important factor for amphibians is that their environment must be _______.(TX Obj 2; 8C, 10A, 10B)

Question 5

D. moist

C. hot

B. dry

A. dark

The answer is D, moist.

• Fishes are vertebrates with backbones and nerve cords that have expanded into brains.

Fishes

• 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.

• Jawless cartilaginous, and bony fishes may have evolved from ancient ostracoderms.

Fishes

• The class Amphibia includes three orders: Caudata—salamanders and newts, Anura—frogs and toads, and Apoda—legless caecilians.

Amphibians

• Adult amphibians have three-chambered hearts that provide oxygen to body tissues, but most gas exchange takes place through the skin.

• 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

• Amphibians probably evolved from ancient aquatic tetrapods.

Question 1Which of the following features is important in allowing a fish to maintain buoyancy?(TX Obj 2; 8C, 10A, 10B)

D. flexible backbone C. fins

B. swim bladder

A. lateral line system

The answer is B, swim bladder.

Lateral line system

Swim bladder

Scales

Gills

Fins

KidneyUrinary bladder

Reproductive organ

StomachIntestine

LiverHeart

Question 2

Which of the following fishes is parasitic?(TX Obj 2; 8C, 10A, 10B, TX Obj 3; 12B, 12E)

D. hagfish

C. lungfish

B. skate

A. lamprey

The answer is A, lamprey.

Question 3Which of the following fish was once thought to be extinct before 1938?(TX Obj 2; 8C, 10A, 10B)

D. lampreyC. coelacanth

B. lungfish

A. hagfish

The answer is C. Living coelacanths were caught off the coast of Africa in 1938.

Question 4Which of the following male fish brood their young in stomach pouches?(TX Obj 2; 8C, 10A, 10B)

D. seahorses

C. manta rays

B. pile

A. eels

The answer is D, seahorses.

Question 5Study 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.

Anaspid

Heterostracah

Cephalaspid

Question 6What were the advantages of terrestrial living for early amphibians? (TX Obj 2; 8C, 10A, 10B)

AnswerOn land, there was a large food supply, shelter, no predators, and more oxygen in the air than in water.

Question 7The closest fish relative to amphibians is most likely the _______. (TX Obj 2; 8C, 10A, 10B)

D. sharksC. lobe-finned fishes

B. lampreys A. hagfishes

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 “poison-arrow 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 10Why are caecilians often blind?(TX Obj 2; 8C, 10A, 10B)

AnswerBlindness is an adaptation to living mostly underground where site in not as necessary as living above ground.

Photo CreditsPhoto 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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Table of Contents – pages iii