815

Unit Projects

Unit ProjectsUnit ProjectsUnit Projects

Unit 9Unit 9Advance PlanningChapter 30■ Order Xenopus eggs, preserved

adult frogs, Ringer’s solution,and tadpoles for the BioLaband MiniLab 30-2.

■ Purchase plastic or clay modelsof the three orders of amphib-ians for Meeting IndividualNeeds.

Chapter 31■ none

Chapter 32■ Order prepared slides of longi-

tudinal sections of humancanine teeth for MiniLab 32-1.

■ Order owl pellets from a bio-logical supply house forMiniLab 32-2.

■ Borrow a collection of mam-mal skulls from a local collegeor museum for the Focus OnPlacental Mammals.

Chapter 33■ none

ModelingKinesthetic Have students makeanother map of the area showing

how the area could be improved forwildlife living there. The map can bethree-dimensional if materials are avail-able. L2

P

LS

DemonstrationKinesthetic If student groupsfound animal tracks in their study

area, have them make plaster of Parismolds of the tracks. Students can preparemolds and bring them into class. Havefield guides available so students cancompare their molds to tracks in thesebooks. Make sure students can identify

the tracks and name the animal thatmade their tracks.

Final ReportAsk students to present their findings tothe owners of the property. L3

P

LS

P

ELL

LS

L1

P

LS

VertebratesVertebratesBears, salmon, gulls—and humans—belong to the group of animals known as vertebrates, animals with backbones.Their ability to survive the rigors ofchanging environments, such as theAlaskan tundra, and engage in complexbehaviors, such as migration, are just a few of the characteristics that dis-tinguish vertebrates from other members of the animal kingdom.

814

3030

3131

3232

3333

UNIT CONTENTSUNIT CONTENTS

Fishes and Amphibians

Reptiles and Birds

Mammals

Animal Behavior

UNIT PROJECTUNIT PROJECT

Use the Glencoe Science Web Site for more project

activities that are connected to this unit.www.glencoe.com/sec/science

Unit 9Unit 9

VertebratesBIODIGESTBIODIGEST

Unit ProjectsUnit ProjectsUnit Projects

Unit Projects

Unit 9Unit 9

814

Vertebrates

Unit OverviewStudents learn about the diversityof animals with backbones inUnit 9. In Chapter 30, studentsbegin to appreciate the evolu-tionary movement of animalsfrom water to land environmentsas they explore the structure,adaptations, ecology, and phy-logeny of fishes and amphibians.The movement of animals toland is completed with the rep-tiles, studied in Chapter 31. Inthis chapter, students also exam-ine adaptations that enable birdsto fly.

Included in Chapter 31 isFocus On Dinosaurs, a detailedexamination of these remarkable,extinct animals.

In Chapter 32, students dis-cover why mammals are able tooccupy nearly all environmentson Earth. The unit concludes inChapter 33 with an explorationof animal behavior.

Introducing the UnitHave examples of live vertebratesfrom different classes availablefor observation. Examples mayinclude: mouse, frog, lizard, andgoldfish. Ask students to work in groups to make a table com-paring how the animals are alike and how they are different.Vertebrate skeletons may be pur-chased from biological supplyhouses. Ask students to compareand contrast the skeletons.

Animal Census/HabitatAnalysisHave students do one of the projects forthis unit as described on the GlencoeScience Web Site. As an alternative, theycan do one of the projects described onthese two pages.

DisplayVisual-Spatial Have student groupsdo a census of animals on the

school grounds or areas near the school.They should look for animals and theirsigns. Ask students to make a map of thearea to scale, indicating where theyfound animals or their signs.

P

COOP LEARN

LS

P

ELL

LS

L2

P

LS

Using the LibraryIntrapersonal Ask students to findout the habitat requirements of the

animals found in their study area. L2

P

LS

Refer to pages 4T-5T of the Teacher Guide for an explanation of the National Science Education Standards correlations. Teacher Classroom Resources

Assessment Resources Additional Resources

Products Available FromGlencoeTo order the following products,call Glencoe at 1-800-334-7344:CD-ROMNGS PictureShow: Structure ofVertebrates 1Curriculum KitGeoKit: Fish, Reptiles, andAmphibiansTransparency SetNGS PicturePack: Structure ofVertebrates 1

Products Available FromNational Geographic SocietyTo order the following products,

call National Geographic Societyat 1-800-368-2728:VideoReptiles and Amphibians

Index to NationalGeographic MagazineThe following articles may beused for research relating to thischapter:“Coelacanths, The Fish ThatTime Forgot,” by Hans Fricke,June 1988.“The Preposterous Puffer,” byNoel D. Vietmeyer, August 1984.

Teacher’s Corner

816B

Fishes and AmphibiansFishes and Amphibians

TransparenciesReproducible MastersSection

Fishes

Amphibians

Section 30.1

Section 30.2

Teacher Classroom Resources

Reinforcement and Study Guide, pp. 133-134Concept Mapping, p. 30BioLab and MiniLab Worksheets, pp. 133-134Laboratory Manual, pp. 211-212Tech Prep Applications, pp. 37-38Content Mastery, pp. 149-150, 152

Reinforcement and Study Guide, pp. 135-136Concept Mapping, p. 30Critical Thinking/Problem Solving, p. 30BioLab and MiniLab Worksheets, pp. 135-138Laboratory Manual, pp. 213-218Content Mastery, pp. 149, 151-152Inside Story Poster

P

ELL

LS

L1

P

LS

L2

P

LS

L2

P

LS

L3

P

LS

P

ELL

LS

L3

P

LS

L2

P

LS

L1

P

LS

L2

P

LS

L2

P

LS

L2

P

LS

P

ELL

LS

L3

P

LS

L2

P

LS

Section Focus Transparency 73Basic Concepts Transparency 52Basic Concepts Transparency 53

Section Focus Transparency 74Basic Concepts Transparency 53Reteaching Skills Transparency 44

P

ELL

LS

L1

P

LS

P

ELL

LS

L2

P

LS

P

ELL

LS

L1

P

LS

P

ELL

LS

L2

P

LS

P

ELL

LS

L2

P

LS

P

ELL

LS

L1

P

LS

Assessment Resources Additional ResourcesSpanish ResourcesEnglish/Spanish AudiocassettesCooperative Learning in the Science ClassroomLesson Plans/Block Scheduling

COOP LEARN

LS

P

ELL

LS

P

ELL

LS

Chapter Assessment, pp. 175-180MindJogger VideoquizzesPerformance Assessment in the Biology ClassroomAlternate Assessment in the Science ClassroomComputer Test BankBDOL Interactive CD-ROM, Chapter 30 quiz

Chapter 30 OrganizerChapter 30 Organizer

Activities/FeaturesObjectivesSection

FishesNational Science EducationStandards UCP.1-5; A.1, A.2;C.3, C.5, C.6; F.4, F.5; G.3(11/2 sessions, 1/2 block)

AmphibiansNational Science EducationStandards UCP.1-5; A.1, A.2; C.3, C.5, C.6; E.1, E.2;F.4-6; G.1-3 (2 sessions, 1block)

1. Relate the structural adaptations offishes to their environments.

2. Compare and contrast the adaptationsof the different groups of fishes.

3. Relate the demands of a terrestrial environment to the adaptations ofamphibians.

4. Relate the evolution of the three-cham-bered heart to the amphibian lifestyle.

MiniLab 30-1: Measuring Breathing Rate inFishes, p. 818Problem-Solving Lab 30-1, p. 820Inside Story: A Bony Fish, p. 825

Inside Story: A Frog, p. 828MiniLab 30-2: Looking at Frog and TadpoleAdaptations, p. 830Investigate BioLab: Development of FrogEggs, p. 834Chemistry Connection: Killer Frogs, p. 836

Section 30.2

Section 30.1

MATERIALS LIST

BioLabp. 834 Ringer’s solution for frogs, cul-ture dishes (4), light bulbs, thermom-eter, stereomicroscope, fertilized frogeggs (Xenopus laevis), flashlight

MiniLabsp. 818 beaker, thermometer, goldfish,ice cube (2), pencil, paperp. 830 preserved adult frog, preservedtadpole, pencil, paper

Alternative Labp. 822 aquarium, black gravel, whitegravel, tropical fishes (zebra, catfish,gourami), timer or stopwatch, blackconstruction paper, masking tape

Quick Demosp. 821 stereomicroscope, microscopeslides, coverslips, fish scalesp. 822 2-L soda bottle, goldfish, water,plastic ketchup packetp. 829 live frog, clear plastic containerp. 831 tape recording of frog calls

Need Materials? Contact Carolina Biological Supply Company at 1-800-334-5551or at http://www.carolina.com

816A

Key to Teaching StrategiesKey to Teaching Strategies

Level 1 activities should be appropriatefor students with learning difficulties.Level 2 activities should be within theability range of all students.Level 3 activities are designed for above-average students.ELL activities should be within the abilityrange of English Language Learners.

Cooperative Learning activitiesare designed for small group work.These strategies represent student prod-ucts that can be placed into a best-workportfolio.These strategies are useful in a blockscheduling format.

L1

P

LS

L2

P

LS

L3

P

LS

P

ELL

LS

P

COOP LEARN

LS

PP

LS

P

LS

The following multimedia resources are available from Glencoe.

Biology: The Dynamics of LifeCD-ROM

BioQuest: Biodiversity ParkExploration: The Five KingdomsVideo: Salmon MigrationVideo: SchoolingExploration: AmphibiansVideo: Feeding FrogVideo: Frog Behavior

Videodisc ProgramFish SchoolingFrog BehaviorFeeding Frog

P

LS

P

ELL

LS

Section

What Is a Fish?Fishes, like all vertebrates, are clas-

sified in the phylum Chordata. Thisphylum includes three subphyla:Urochordata, the tunicates; Cephalo-chordata, the lancelets; and Verte-brata, the vertebrates. Fishes belongto the subphylum Vertebrata. Inaddition to fishes, subphylumVertebrata includes amphibians, rep-tiles, birds, and mammals. Recallfrom the previous chapter that allchordates have four traits in com-mon—a notochord, gill slits, muscleblocks, and a dorsal hollow nervecord. In vertebrates, the notochordof the embryo becomes a backbone

in adult animals. All vertebrates arebilaterally symmetrical, coelomateanimals that have endoskeletons,closed circulatory systems, nervoussystems with complex brains andsense organs, and efficient respira-tory systems.

Three classes of fishesFishes comprise three classes of

the subphylum Vertebrata: ClassAgnatha (AG nuh thuh), with jawlessfishes, lampreys and hagfishes; ClassChondrichthyes (kahn DRIHK theez),with cartilaginous fishes, sharks andrays; and Class Osteichthyes (ahs teeIHK theez), with bony fishes. Anexample of each class is shown in

30.1 FISHES 817

Have you ever visited an aquarium to seethe amazing diversity

of fishes? As you pass tankafter tank, you can see fishesof all shapes, sizes, and colors.What’s interesting is thateven though fishes share acommon environment, theyhave evolved a variety of different adaptations.Although fishes may showconsiderable variety instructure and behavior,they all share commoncharacteristics.

SECTION PREVIEW

ObjectivesRelate the structuraladaptations of fishes totheir environments.Compare and contrastthe adaptations of thedifferent groups offishes.Interpret the phylog-eny of fishes.

Vocabularyspawningfinlateral line systemscaleswim bladdercartilage

30.1 Fishes

Saltwater aquarium(above) and a bluetang (inset)

817

Section 30.1

BIOLOGY: The Dynamics of Life SECTION FOCUS TRANSPARENCIES

Use with Chapter 30,Section 30.1

Which of the animals in this picture are called fish, but reallyaren’t fish? Which are not called fish, but really are fish?

How does the body plan of a fish differ from that of theother animals pictured?

11

22

Transparency Fishes in the Sea73 SECTION FOCUS

Cop

yrig

ht ©

Gle

ncoe

/McG

raw

-Hill

, a d

ivis

ion

of T

he M

cGra

w-H

ill C

ompa

nies

, Inc

.

PrepareKey ConceptsStudents learn about the charac-teristics all fishes have in commonwhile developing an understand-ing of the characteristics that dis-tinguish the three classes offishes: jawless fishes, cartilaginousfishes, and bony fishes.

Planning■ Purchase small goldfishes for

MiniLab 30-1.■ Purchase mounts of three

kinds of fish scales, fishinglures, a model of a fish, and a 2 L plastic soda bottle for theDemos.

■ Purchase tropical fishes suchas zebra fish, catfish, andgourami for the AlternativeLab.

1 FocusBellringer Before presenting the lesson,display Section Focus Trans-parency 73 on the overhead pro-jector and have students answerthe accompanying questions.

P

ELL

LS

L1

P

LSAssessment PlannerAssessment Planner

Portfolio AssessmentBioLab, TWE, pp. 834-835Portfolio, TWE, pp. 824, 829Assessment, TWE, 820, 830

Performance AssessmentMiniLab, SE, pp. 818, 830BioLab, SE, pp. 834-835Alternative Lab, TWE, pp. 822-823Assessment, TWE, p. 832

Knowledge AssessmentSection Assessment, SE, pp. 826, 833Chapter Assessment, SE, pp. 837-839Assessment, TWE, pp. 824, 826

Skill AssessmentAssessment, TWE, pp. 818, 833

ChapterChapter

816 FISHES AND AMPHIBIANS

Fishes and Amphibians

What You’ll Learn■ You will compare and

contrast the adaptations of the different groups offishes and amphibians.

■ You will relate the move to land to the evolution offishes and amphibians.

Why It’s ImportantFishes are the most diverse andsuccessful vertebrate group.Amphibians are adapted to live both in water and on land.The development of a bonyendoskeleton in fishes andlungs in amphibians weremajor steps in animal evolu-tion—steps that eventually ledto human evolution.

Observing a FishObserve a fish swimming in abowl. Drop fish food into thewater and observe how the fishfinds and eats the food. Whatstructure for obtaining foodcan be found in fishes but notin invertebrates?

To find outmore about

fishes and amphibians, visit theGlencoe Science Web Site.www.glencoe.com/sec/science

30

GETTING STARTEDGETTING STARTED

Leopard frog eggshatch into wigglingtadpoles. A fewmonths later, theybecome four-legged, jumping,croaking animals.

816

Theme DevelopmentEvolution is a major theme ofthis chapter. Emphasis is placedon how animals evolved adapta-tions to life on land. The themeof unity within diversity isapparent through the discussionof how varied the features of ani-mals within a classification groupcan be even though all membersof the group share many charac-teristics.

Chapter 30Chapter 30

MultipleLearningStyles

Look for the following logos for strategies that emphasize different learning modalities.

Kinesthetic Meeting IndividualNeeds, p. 827; Tech Prep, p. 832Visual-Spatial Tech Prep, p. 819;Quick Demo, p. 821; Meeting

Individual Needs, p. 821; Portfolio, pp. 824, 829; Biology Journal, p. 829

Linguistic Project, pp. 820, 831; Enrichment, p. 823;

Biology Journal, pp. 824, 832;

Meeting Individual Needs, p. 825;Check for Understanding, p. 825

Auditory-Musical QuickDemo, p. 831Naturalist Quick Demo, p. 829

GETTING STARTED DEMOGETTING STARTED DEMO

Logical-MathematicalRemove the hooks from a

variety of fish-shaped lures allmade of the same material. Havestudents work in small groupsand drop each lure into a 1000mL graduated cylinder filledwith water. Ask them to measurethe amount of time it takes foreach of the lures to touch thebottom of the cylinder. Ask stu-dents to correlate their results tothe shape of the lures. Ask themwhat other variables might beimportant in their observations.

P

LSP

ELL

LS

L2

P

LS

If time does not permit teach-ing the entire chapter, use theBioDigest at the end of theunit as an overview.

Resource ManagerResource Manager

Section Focus Transparency 73and Master

P

ELL

LS

L1

P

LS

gravel on stream bottoms. Althoughmost fishes produce large numbers ofeggs at one time, agnathans calledhagfishes produce small numbers oflarge eggs. Some cartilaginous fisheshave internal fertilization. For exam-ple, some female sharks and rays pro-duce as few as 20 eggs and keep theminside their bodies until they havehatched and developed to about 40cm in length. These young, whenreleased, behave like miniatureadults, and many survive.

Most bony fishes have external fer-tilization. Reproduction in fishes andsome other animals is called spawn-ing. During spawning, some femalebony fishes, such as cod, produce asmany as 9 million eggs, of which onlya small percentage survive. In somebony fishes, such as guppies, mollies,and swordtails, fertilization is inter-nal and young fishes develop withinthe mother’s body. These species areknown as live-bearers because theiroffspring are born fully developed.Most fishes that produce millions of

eggs provide no care for their off-spring after spawning; in thesespecies, only a few of the young sur-vive to adulthood. But some, such asthe mouth-brooding cichlids, staywith their young after hatching.When their young are threatened bypredators, the parent fish scoop theminto their mouths for protection.

30.1 FISHES 819

Figure 30.1The three classes of fishesinclude jawless fishes, cartilagi-nous fishes, and bony fishes.

Circulation in a Fish

Aorta

Heart

Gills Bodycells

AV

Figure 30.2In a fish’s heart,deoxygenated bloodflows from the firstchamber to the sec-ond chamber, thenon to the gills whereit picks up oxygen.Blood in a fish flowsin a one-way circuitthroughout the body.

Jawless fishes called lampreyshave long, tubular bodies with-out paired fins, and no scales.

AA

Cartilaginous fishes calledskates have a flattened bodyshape with large paired finsthat enable them to “fly”over the ocean bottom asthey search for food.

CC

Most fishes youare familiar withare bony fishes,such as thisswordfish.

BB

819

Visual LearningFigure 30.1 Have students lookat the fishes shown in Figure30.1. Ask them to list the adapta-tions that these fishes have totheir habitat. fins, streamlined body,gills for obtaining oxygen dissolvedin water

Chalkboard ExampleDraw the two-chambered heartof a fish on the chalkboard.Beside this drawing, sketch thefour-chambered heart of a mam-mal. Briefly trace the path ofblood through each heart andexplain that the four-chamberedheart is more efficient for an ani-mal that must move quickly andmaintain a constant body temper-ature.

L1

P

LS

Figure 30.1. More than 20 000species of fishes exist. In fact, thereare more fish species than all otherkinds of vertebrates added together.

Fishes inhabit nearly every type ofaquatic environment on Earth. Theyare adapted to living in shallow, warmwater and deeper cold and sunlesswater. They are found in freshwaterand salt water, and some fishes evensurvive in heavily polluted water.

Fishes breathe using gillsAgnathans, like all fishes, have gills

made up of feathery gill filaments thatcontain tiny blood vessels. Gills arean important adaptation for fishes andother vertebrates that live in water.As a fish takes water in through itsmouth, water passes over the gillsand then out through slits at the sideof the fish. Oxygen and carbon diox-ide are exchanged through the capil-laries in the gill filaments. You canfind out more about respiration infishes in the MiniLab on this page.

Fishes have two-chambered hearts

All fishes have two-chamberedhearts, as shown in Figure 30.2. Onechamber receives deoxygenated bloodfrom the body tissues, and the secondchamber pumps blood directly to thecapillaries of the gills, where oxygenis picked up and carbon dioxidereleased. Oxygenated blood is carriedfrom the gills to body tissues. Bloodflow through the body of a fish is rel-atively slow because most of theheart’s pumping action is used topush blood through the gills.

Fishes reproduce sexuallyAll fishes have separate sexes.

Fertilization is external in mostfishes, with eggs and sperm depositedin protected areas, such as on floatingaquatic plants or in shallow nests of

Measuring Breathing Rate in Fishes Fishes are able toextract oxygen from water as it flows over their gills. Theirrate of breathing is related to the availability of oxygen inthe water. More oxygenresults in a slower breath-ing rate. The breathingrate of a fish can be esti-mated by counting thenumber of times perminute its gill covers opento allow water to flowacross its gills.

Procedure! Make a hypothesis about how the breathing rate of a

fish may be influenced by a change in temperature of the water in which it is swimming. Record your hypothesis.

@ Fill a beaker with non-chlorinated water. Let the beakersit until the water reaches room temperature (about20°C). Measure the temperature with a thermometer and record it in a data table.

# Add a small goldfish. CAUTION: Handle animals with care.Wait 5 minutes for the fish to acclimatize to the watertemperature.

$ Count the number of times the goldfish’s gill covers openin one minute. This is a measure of the rate at which thefish is breathing. Record your result in a data table.

% Repeat step 4 four more times. Find an average for yourtrials and record these data in your table.

^ Remove the goldfish from the beaker. Add one ice cube made from non-chlorinated water to the beaker.

& When the ice cube has melted, record the water’s temperature.

* Repeat steps 3-5. Remove goldfish from the beaker, and add another ice cube to the beaker. Repeat step 7.

( Repeat steps 3-5. CAUTION: Wash your hands after working with animals.

Analysis1. How does water temperature influence the rate at which

breathing occurs in a goldfish?2. Do your data support your hypothesis? Explain.3. Was the breathing rate faster or slower in colder water

compared with warmer water?4. How might the amount of oxygen in cold water compare

with that in warm water? Explain your answer.5. Sequence the events associated with a fish obtaining

oxygen. Start with a molecule of oxygen in water and besure to include the capillaries located in the fish’s gills.

MiniLab 30-1MiniLab 30-1 Experimenting

Gill cover

818 FISHES AND AMPHIBIANS

818

2 Teach

Purpose Students will experimentallydetermine that fish breathing rateslows as water temperature de-creases and oxygen content of thewater increases.

Process Skillsexperiment, hypothesize, se-quence, acquire information, collect data, draw a conclusion,interpret data, measure in SI

Teaching Strategies■ Inexpensive goldfish are avail-able locally from most pet oraquarium shops.■ 500 mL beakers are ideal insize, but smaller beakers may beused.■ Review the location of the gillcovering (operculum) with stu-dents.■ Caution students about not“shaking down” thermometers.■ Water temperature may beadjusted by adding ice cubes orcold water to the beakers.

Expected ResultsBreathing rate will decrease aswater temperature decreases.

Analysis1. The breathing rate, as well as

all body functions, decreasesas the water temperaturedecreases.

2. Student answers will vary.Many students will havehypothesized that a decreasein water temperature results inan increase in breathing rate.

3. slower in cold water4. Generally, there is more dis-

solved oxygen in cold wateras compared with warmwater.

5. An oxygen molecule in waterpasses over the gills, diffusesinto gill capillaries, passesinto the blood stream, and ispumped to body cells byheart.

P

LS

MiniLab 30-1MiniLab 30-1

Fish Farming Visual-Spatial Have agroup of students visit a

nearby fish farm or fish hatch-ery and make a videotapereport to the class.P

LS P

ELL

LS

L2

P

LS

Cultural DiversitySamuel Milton NabritAfrican-American zoologist Samuel M.Nabrit conducted many experiments on tailregeneration in fishes. Nabrit earned a Ph.D.in Zoology in 1932 and became a researcherat Woods Hole Marine Biology Laboratory.Papers describing his work may be found inthe Journal of Experimental Zoology,

Anatomical Record, and Biological Bulletin.Nabrit is perhaps best known for his worktoward promoting African Americans in sci-ence. He helped to organize the NationalInstitute of Science in 1943, an organizationdesigned to explore the teaching andresearch problems of African-American scientists.

Skill Have students prepare a linegraph of their data. Have them identify theindependent and dependent variables andselect and label the axes accordingly. Use thePerformance Task Assessment List forGraph from Data in PASC, p. 39. L2

P

LS

AssessmentAssessment

VIDEODISCThe Secret of LifeFish Gills

Fish Gills—Gas Exchange

!7;J8G"

!7;JBH"

Resource ManagerResource ManagerBioLab and MiniLab Worksheets,

pp. 133-134Concept Mapping, p. 30Laboratory Manual, pp. 211-212 L2

P

LS

P

ELL

LS

L3

P

LS

L2

P

LS

Gill arches

Gill arches

Gill slitsSkull JawsJawless, filter-feeding fish

Beginning of jaw formation Fish with jaws

blood through the water for severalkilometers. This ability helps themlocate their prey.

Most fishes have scalesCartilaginous and bony fishes have

skin covered by intermittent or over-lapping rows of scales. Scales are thinbony plates formed from the skin.Scales, shown in Figure 30.4, can betoothlike, diamond-shaped, cone-shaped, or round. Shark scales aresimilar to teeth found in other verte-brates. The age of some species offishes can be estimated by countingannual growth rings in their scales.

Jaws evolved in fishesPerhaps one of the most important

events in vertebrate evolution was theevolution of jaws in ancestral fishes.The advantage of a jaw is that itenables an animal to grasp and crushits prey with great force. Sharks areable to eat large chunks of food.This, among other factors, explainswhy some early fishes were able toreach such great size. Figure 30.5shows the evolution of jaws in fishes.

When you think of a shark, do youimagine gaping jaws and rows ofrazor-sharp teeth? Sharks have six to20 rows of teeth that are continuallyreplaced. The teeth point backwards,preventing prey from escaping once

caught. Sharks are among the moststreamlined of all fishes and are welladapted for life as predators.

Most fishes have bony skeletonsThe majority of the world’s fishes

belong to the class Osteichthyes, thebony fishes. Bony fishes, a successfuland widely distributed class, differgreatly in habitat, size, feedingbehavior, and shape, as Figure 30.6shows. All bony fishes have skeletonsmade of bone rather than the carti-laginous skeletons found in other

30.1 FISHES 821

Figure 30.4Fishes can be classified by the typeof scales present. Diamond-shapedscales are common to bony fishes,such as gars (a). Bony fishes suchas chinook salmon have eithercone-shaped or round scales (b).Tooth-shaped scales are character-istic of the sharks (c).

Figure 30.5You can see how jawsevolved from the car-tilaginous gill archesof early jawless fishesin this series of illus-trations. Teethevolved from skin.

OriginWORDWORD

scaleFrom the OldEnglish word sceala,meaning “shell” or“husk.” A scale is athin, bony plate onthe skin of a fish.

a

b

c

821

Visual LearningFigure 30.4 Direct students’attention to the different types ofscales. Ask students how theycould determine that a scale camefrom a shark by observing theshape of the scale. The scales of ashark have a toothlike shape. Noother fish scales have this shape.

Why are fish species numbers declining? There are threemajor threats to the survival of freshwater fishes. These are:agricultural runoff; dams and water diversion; and competi-tion from introduced non-native species. All of these threatsexist in the southern United States.

AnalysisThe two maps that appear here (A and B) illustrate the

problem described in the introduction.

Thinking Critically1. Sequence the general areas of the United States that have

the highest to lowest number of fish species and percent-age of species at risk.

2. Do the two patterns tend to agree? Explain why.3. Compare the approximate number of species at risk to the

total number of fish species present in: California, Texas,Hawaii, North Carolina, Florida, Illinois, and North Dakota.

4. Explain why or how the following may be a problem tofish survival: agricultural runoff; dams and water diver-sion; introduction of non-native fish species.

5. Explain how the three problems associated with decliningfish populations might be caused by humans.

Problem-Solving Lab 30-1Problem-Solving Lab 30-1 Cause and Effect

In the Problem-Solving Lab on thispage, find out some other reasonswhy the numbers of some species offreshwater fishes are declining.

Most fishes have paired finsFishes in the classes Chondrich-

thyes and Osteichthyes have pairedfins. Fins are fan-shaped membranesthat are used for balance, swimming,and steering. Fins are attached to andsupported by the endoskeleton andare important in locomotion. Thepaired fins of fishes, illustrated inFigure 30.3, foreshadowed thedevelopment of limbs for movementon land and ultimately of wings forflying.

Fishes have developed sensory systems

All fishes have highly developedsensory systems. Cartilaginous andbony fishes have an adaptation calledthe lateral line system that enablesthem to sense their environment.The lateral line system is a line offluid-filled canals running along thesides of a fish that enable it to detectmovement and vibrations in thewater.

Some fishes also have an extremelysensitive sense of smell and candetect small amounts of chemicals inthe water. Sharks can follow a trail of

820 FISHES AND AMPHIBIANS

Figure 30.3The paired fins of a fish include the pec-toral fins and the pelvic fins. Fins foundon the dorsal and ventral surfaces caninclude the dorsal fins and anal fin.

AA

BB

Total number of species

< 100100 – 199200 +

Percent ofspecies at risk

< 1010 – 29.930 +

Dorsal fin

Caudalfin Pelvic

fins

Pectoralfins

820

Purpose Students correlate the impact ofhuman activities on the decliningnumbers of fish species in theU.S.

Process Skillsacquire information, analyzeinformation, think critically, drawa conclusion, interpret data,interpret scientific illustrations

Teaching Strategies■ Make sure that students areable to locate the various statesreferred to in the activity.■ Remind students of terminol-ogy that can be used to describegeneral areas of the country, suchas southwest, midwest, etc.

Thinking Critically

1. southeast, midwest, north-east, south-central, far west;southwest, northwest, south-east, midwest, northeast

2. no; one compares total specieswhile the other comparesspecies at risk

3. California: between 30 and60; Texas: between 10 and 60;Hawaii: 30 or more; N.Carolina: between 20 to 60;Florida: between 10 and 60;Illinois: fewer than 10 to 60;N. Dakota: fewer than 10.

4. Fertilizers, pesticides, andherbicides wash into water-ways and affect the fish.Dams and water diversionsdecrease the water availablefor reproduction and feedingand prevent fish from reach-ing breeding sites. Non-native fish species competefor food and breeding siteswith native fish species andmay prey upon native fishes.

5. Humans apply agriculturalchemicals that run off intowaterways. Humans build thedams and divert water forirrigation and drinking.Humans also introduce non-native species, sometimes forsport fishing.

P

LS

Problem-Solving Lab 30-1Problem-Solving Lab 30-1

P R O J E C TThe Aquarium

Linguistic Ask students toprepare a written plan that

identifies all materials needed to set upand maintain an aquarium, along with anexplanation of why each material isneeded. Allow students to set up andmaintain their aquariums according totheir plans.

P

LS

L2

P

LS

Quick DemoQuick Demo

Visual-Spatial Have stu-dents make and examine

mounts of scale types using astereomicroscope. Briefly dis-cuss how the age of a fish canbe determined by counting therings on its scales. Ask studentsto draw the scales they observeand include a summary in theirportfolios that identifies thetypes of scales observed andthe ages of the fishes fromwhich the scales came.

P

LS

PP

LS

L2

P

LS

MMEETING EETING IINDIVIDUAL NDIVIDUAL NNEEDS EEDS MEETING INDIVIDUAL NEEDS

Learning DisabledVisual-Spatial Use visualization strate-gies for students who have learning

disabilities. Prepare a set of large cards withvisual depictions of concepts in the chapter.Ask them to look carefully at a card forabout 10 seconds. Then have them closetheir eyes and imagine placing the card on abulletin board. Have students do this for 10

concept cards. When they have finished plac-ing these 10 cards on their imaginary bul-letin boards, have them close their eyes andfocus on their boards for about 10 seconds.The next day, you can put a list of conceptson the chalkboard and ask students to recalltheir imaginary bulletin boards and explainwhat they remember.

P

LSP

ELL

LS

L1

P

LS

Portfolio Have students examinetheir own state and describe the species offish at risk versus total existing number ofspecies. Have them write a paragraphexplaining what steps might be taken to slowthe decline of fish species in their area. Usethe Performance Task Assessment List forWriting in Science in PASC, p. 87. L2

P

LS

AssessmentAssessment

CD-ROMBiology: The Dynamicsof Life, Bioquest:

Biodiversity Park, Disc 3, 4Exploration: The Five KingdomsDisc 3Video: Salmon MigrationDisc 4Video: SchoolingDisc 4

bladder. The gas works like the gas ina blimp that adjusts the height of theblimp above the ground.

Fishes that live in oxygen-poorwater or in ponds or rivers that dryup in the hot season often have otherways to get oxygen. The Africanlungfish, for example, has a structurethat allows it to obtain oxygen bygulping air. This structure is a modi-fied swim bladder. The modifiedswim bladder is connected to thefish’s mouth by a tube.

Diversity of FishesFishes range in size from the tiny

dwarf goby that is less than 1 cmlong, to the huge whale shark thatcan reach a length of 15 m—thelength of two school buses.

Agnathans are jawless fishesLampreys and hagfishes belong to

the class Agnatha. Though they donot have jaws, they are voraciousfeeders. Hagfishes, Figure 30.8, havea slitlike, toothed mouth and feed ondead or dying fish by drilling a holeand sucking the blood and insidesfrom the animal. Parasitic lampreysattack other fishes and attach them-

selves by their suckerlike mouths.They use their sharp teeth to scrapeaway the flesh and then suck out theprey’s blood. The skeletons ofagnathans, as well as of sharks andtheir relatives, are made of a tough,flexible material called cartilage.

Sharks and rays are cartilaginous fishes

Sharks, skates, and rays, likeagnathans, possess skeletons com-posed entirely of cartilage. Sharks,skates, and rays belong to the classChondrichthyes, illustrated in Figure30.9. Because living sharks, skates,and rays are classified in the samegenera as species that swam the seasmore than 100 000 years ago, theyare considered living fossils. Sharksare perhaps the most well-known

30.1 FISHES 823

Figure 30.8When touched, ahagfish’s skin givesoff a tremendousamount of mucus,thus allowing thefish to slither awaywithout becoming ameal.

Figure 30.9Cartilaginous fishes includesharks, skates, and rays.

The hammerhead shark is a large sharkfound in warm ocean water. It has eyes atthe ends of its flattened, extended skull.

AA

Most rays are ocean bottomdwellers, but the Atlantic mantaray prefers to glide along justunder the water’s surface.

BB

MisconceptionStudents often think of sharks asbeing blood-craving predators ofpeople. Explain that of the 370species of sharks, only 25 havebeen known to attack humans.When sharks attack people, thisoccurs largely because the shark’slateral line system detects move-ment in the water. Such move-ment usually signals to a sharkthat food in the form of a fish isnearby.

EnrichmentLinguistic Ask students toprepare a report on endan-

gered sharks. Make sure they findout how peoples’ fear of sharkshas contributed to the decline inshark populations. L2

P

LS

aquarium that contains black gravelwith black construction paper.

6. Develop a hypothesis about where thefish will spend its time, in the light orthe dark. Then, observe the fish fortwo minutes and time in which part ofthe tank the fish spends its time.Record your data.

7. Compare your data with that of yourclassmates.

Expected ResultsCatfish prefer the dark, but others preferthe light.Analysis

1. Which fishes preferred dark gravel andthe dark half of the tank? catfish

2. Do your data for each habitat type sup-port your hypotheses? Explain. Somestudents will find that their data sup-ported their hypotheses.

Performance Give students a fishthey have not seen and ask them todetermine the fish’s preferred habitat.Ask them to explain how this preferencemay have adaptive value. Use thePerformance Task Assessment List forMaking Observations and Inferences inPASC, p. 17. L2

P

LS

AssessmentAssessment

823

el

classes of fishes. Bone is the hard,mineralized, living tissue that makesup the endoskeleton of most verte-brates. The appearance of bone wasimportant for the evolution of fishesand vertebrates in general because itallowed fishes to adapt to a variety ofaquatic environments, and finallyeven to land.

Bony fishes have separate vertebrae that provide flexibility

The evolution of a backbone com-posed of separate, hard segmentscalled vertebrae was significant in pro-viding the major support structure ofthe vertebrate skeleton. Separate ver-tebrae provide great flexibility. This isespecially important for fish locomo-tion, which involves continuous flex-ing of the backbone. You can see howmodern bony fishes propel themselvesin water in Figure 30.7. Some fishesare effective predators, in part becauseof the fast speeds they can attain as aresult of having a flexible skeleton.

Bony fishes evolved swim bladders

Another key to the evolutionarysuccess of bony fishes was the evolu-tion of the swim bladder. A swimbladder is a thin-walled, internal sacfound just below the backbone inbony fishes; it can be filled withmostly oxygen or nitrogen gases thatdiffuse out of a fish’s blood. Fish witha swim bladder control their depth byregulating the amount of gas in the

822 FISHES AND AMPHIBIANS

Figure 30.6Bony fishes vary in appearance,behavior, and way of life.

Figure 30.7Most bony fishes swim in one of three possible ways.

An eel moves itsentire body in anS-shaped pattern.

AA

A mackerel flexes the posterior end of its body to accen-tuate the tail-fin movement.

BB

A tuna keeps its body rigid, movingonly its powerful tail.Fishes that use thismethod move fasterthan all others.

CC

Predatory bony fishes, such asthis pike, have sleek bodieswith powerful muscles and tailfins for fast swimming.

CC

Sea horses move slowlythrough the underwaterforests of seaweed wherethey live. They are unusual in that the males brood theiryoung in stomach pouches.

BB

Eels are long andsnakelike and canwriggle through mudand crevices in searchof food.

AA

Alternative LabFish Behavior

Purpose Students will gain an understanding ofhow fish behavior is adaptive. Have stu-dents treat live animals with care. Makesure they wash their hands before andafter handling live animals.

P

LS

Materials aquarium setup, black and white gravel,tropical fishes (zebra, catfish, gourami),timer or stopwatch, black constructionpaper, masking tapeProcedureGive students the following directions.

1. Prepare a data table with columns indi-cating time spent over white gravel,over black gravel, at the top, bottom,and middle of the tank, and in light

and dark areas.2. Place a fish into an aquarium that has

white gravel on one side and blackgravel on the other.

3. Develop a hypothesis about in whichpart of the tank the fish will spendmost of its time.

4. For two minutes, time how long thefish spends over each color of gravel.Record your data.

5. Cover the sides of the half of the822

Quick DemoQuick Demo

Ask students to predict what will happen to a small plasticpackage of ketchup when youdrop it into a 2 L plastic sodabottle full of water. Ask themwhat will happen to the condi-ment package if you thensqueeze the bottle. After youdemonstrate this, ask studentswhat will happen to a goldfishyou place in a similar bottle ofdechlorinated water. Ask themto predict what will happen tothe goldfish when you squeezethe bottle. Ask students torelate the results to similaritiesand differences between thestructures of fish and ketchuppackages.

P

LS

VIDEODISCThe Secret of LifeChordate Body Plan

!7;FLE"

VIDEODISCBiology: TheDynamics of Life

Fish Schooling (Ch. 2)Disc 2, Side 118 sec.!7@Ä"

INSIDESSTORTORYY

INSIDE

11

22

33

55

30.1 FISHES 825

A Bony Fish

The bony fishes, class Osteichthyes, includesome of the world’s most familiar fishes, such

as the bluegill, trout, minnow, bass, swordfish, andtuna. Though diverse in general appearance and behav-ior, bony fishes share some common adaptations withother fish classes.

Critical Thinking Compare the ideal shapes for fishesthat swim in rocky crevices and those that swim inopen water.

Lateral line system When fishes swim past obsta-cles, pressure changes occur in the water. Fishes candetect these changes with their lateral line systems,which enable them to swim in the dark and in complexcoral reefs.

Swim bladder The mass of a fish’s tissue isgreater than that of water; therefore, withouta swim bladder, a fish would not be able tofloat. Gas pressure in the swim bladder altersthe specific gravity of the whole body,enabling the fish to float at any depth.

Gills Gills are thin, blood vessel-richtissues where gases are exchanged.

Scales Scales are covered with slipperymucus, allowing a fish to move throughwater with minimalfriction. Fins The structure and

arrangement of fins arerelated to a particulartype of locomotion.Tropical fishes that liveamong coral reefs tendto have small fins capa-ble of maneuvering inthis complex, three-dimensional environ-ment, whereas a tunahas large, broad fins formoving quicklythrough open water.

Rainbow trout,Salmo gairdneri

KidneyUrinary bladder

Reproductive organ

StomachIntestine

LiverHeart

44

825

IINSIDENSIDESSTORTORYY

INSIDE

Purpose Students study features of bonyfishes and examine the adaptiveadvantages of these features.

Teaching Strategies■ On the chalkboard, make atable that compares the featuresof bony fishes with those of jaw-less and cartilaginous fishes.

Visual Learning■ Ask students to study the fea-

tures shown. Have them iden-tify the external featuresdiscussed on a live goldfish.

■ Purchase a fish from a fishmarket that has not beencleaned. Carefully cut openthe fish to show students theswim bladder. The swim blad-der is very fragile, so be carefulas you cut into the fish with arazor blade or scalpel.

Critical ThinkingFishes that swim in crevices maybe laterally flattened, whereas fishthat swim in the open may bewider but streamlined.

3 AssessCheck for Understanding

Linguistic Ask students tosummarize in writing the

characteristics of jawless fishes,cartilaginous fishes, and bonyfishes.

ReteachHave students work in groups tomake a table that compares thecharacteristics of the three fishclasses. Make sure they includefeatures such as unique bodystructures, scale types, methodsof getting food, and skeletal fea-tures. Have other groups con-struct a table that compares thethree subclasses of bony fishes.Review the tables as a class.

L2

P

LS

P

LS

predators of the oceans. Like sharks,most rays are predators and feed onor near the ocean floor. Rays haveflat bodies and broad pectoral fins ontheir sides. By slowly flapping theirfins up and down, rays can glide,searching for mollusks and crus-taceans, along the ocean floor. Somespecies of rays have sharp spines withpoison glands for defense on theirlong tails. Other species have organsthat generate electricity to kill bothprey and predators.

Three subclasses of bony fishesScientists recognize three sub-

classes of bony fishes—the lung-fishes, the lobe-finned fishes, and theray-finned fishes. Figure 30.10shows examples of each subclass.Lungfishes have both gills and lungs.The lobe-finned fishes are repre-sented by only one living species. Inthe ray-finned fishes, fins are fan-

shaped membranes supported by stiffspines called rays. Ray-finnedfishes—such as catfish, perch,salmon, and cod—are more familiarto humans because most of the fisheswe consume belong to this subclass.You can see the parts of a ray-finnedfish in the Inside Story.

Origins of FishesScientists have identified fossils of

fishes that existed during the earlyOrdovician period, 500 million yearsago. For 50 million years, ostraco-derms (oh STRAHK oh durmz), earlyjawless fishes, were the only verte-brates on Earth. Although mostostracoderms became extinct at theend of the Devonian period, 400 mil-lion years ago, present-day agnathansappear to be their direct descendants.

Weighed down by heavy, bonyexternal armor, ostracoderms, shown

824 FISHES AND AMPHIBIANS

Figure 30.10Lungfishes, lobe-finned fishes,and ray-finned fishes are thesubclasses of the bony fishes.

Lungfishes representan ancient subclassthat arose nearly 400million years ago.Lungfishes such asthis African lungfishhave both gills andlungs.

AA

Lobe-finned fishes, such asthis coelacanth, appeared inthe fossil record about 395million years ago. Longthought to be extinct, livingexamples of coelacanthswere caught off the coast ofAfrica beginning in 1938.

BB

You can easily see therays that support thepectoral fins of thisflying fish, an exampleof a ray-finned fish.

CC

824

Knowledge Provide stu-dents with sheets of three differ-ent colors of paper. Ask them tooutline what they have learnedabout each class of fishes on onesheet of colored paper. Have stu-dents write their names on theirpapers and place their outlines onthe bulletin board. As they con-tinue to learn about fishes, havethem include new information ontheir papers. L1

P

LS

AssessmentAssessment

BIOLOGY JOURNAL BIOLOGY JOURNAL

The Geologic History of FishesLinguistic Ask students to look upfishes in geologic history. Ask them to

choose a fish that interests them and towrite about a day in the life of their fossilfish. They should describe other aquaticorganisms in the environment at the timeand incorporate science facts into their cre-ative writing.

P

LS

L3

P

LS

PortfolioPortfolio

Exploring Traits of Bony FishesVisual-Spatial Have students eachcut out a picture of a bony fish from

a magazine. Ask them to use the InsideStory as a model to label and identify thefunctions of the structures of the fishes intheir pictures. They can paste the pictureon a piece of paper and include it in theirportfolios.

P

LSP

ELL

LS

L1

P

LS

MEETING INDIVIDUAL NEEDS MEETING INDIVIDUAL NEEDS

English Language LearnersLinguistic To help students whospeak English as a second language,

have them work with native Englishspeakers and practice their English byexplaining the terms and concepts in thissection to their partners.

P

LSP

ELL

LS

L2

P

LS

VIDEODISCGTV: PlanetaryManager

Animal, Side 2

!7S7$A"

!7S7.B"

Resource ManagerResource Manager

Tech Prep Applications, pp. 37-38 L2

P

LS

Resource ManagerResource ManagerBasic Concepts Transparency 52 and

Master

P

ELL

LS

L2

P

LS

in Figure 30.11, were fearsome-looking animals that swam sluggishlyover the murky seafloor. Although allostracoderms had cartilaginous skele-tons, they also had shields of bonecovering their heads and necks. Thedevelopment of bone in these ani-mals was an important evolutionarystep because bone provides a placefor muscle attachment, whichimproves locomotion. In ancestralfishes, bone that formed into platesprovided protection as well.

Lobe-finned fishes, the coelacanths(SEE luh kanthz), are another ancient

group, appearing in the fossil recordabout 395 million years ago. They arecharacterized by lobelike, fleshy fins,and live at great depths where they aredifficult to find. The limblike skeletalstructure of fleshy fins is thought to bean ancestral condition of all tetrapods(animals with four limbs). The earli-est tetrapods discovered also had gillsand therefore were still aquatic.

Scientists hypothesize that the jaw-less ostracoderms were the commonancestors of all fishes. Modern carti-laginous and bony fishes evolved dur-ing the mid-Devonian period.

Section AssessmentSection Assessment

Understanding Main Ideas1. List three characteristics of fishes.2. Compare how jawless fishes and cartilaginous

fishes feed.3. Why was the evolution of a swim bladder

important to fishes?4. How does a flexible skeleton aid swimming in

fishes?

Thinking Critically5. Why was the development of jaws an important

step in the evolution of fishes?

6. Making and Using Tables Construct a table tocompare the characteristics of the jawless, carti-laginous, and bony fishes. For more help, refer toOrganizing Information in the Skill Handbook.

SKILL REVIEWSKILL REVIEW

Figure 30.11Ostracoderms, theearliest vertebratefossils found, werecharacterized bybony, external platescovering the bodyand a jawless mouth.Lacking jaws, ostra-coderms obtainedfood by sucking upbottom sedimentsand sorting out thenutrients.

Anaspid

Cephalaspid

Heterostracan

826 FISHES AND AMPHIBIANS

826

ExtensionHave interested studentsinterview a fly-fishing

expert to find out about the sportof fly-fishing. Encourage studentsto videotape the interview or takephotographs of the techniquesused in the sport. Have studentsreport their findings to the classand include a demonstration offly tying.

Knowledge Ask studentsto list adaptations fishes mighthave for each of the followingniches: live on a muddy pond bot-tom; feed on other fishes; feed onclams and other mollusks; live increvices in a coral reef; live indeep water where there is nolight.

4 CloseDiscussionAsk students to speculate aboutwhy there are more fishes thanany other type of vertebrate.Responses may state that all lifebegan in the water and this environ-ment has undergone fewer changesthan have terrestrial habitats, thusreducing the risk of extinctionbecause of the inability to adapt tonew conditions. Have students pre-dict how the extinction of fisheswould affect world food supplies.Because people in many parts of theworld rely on fishes as a major foodsource, starvation would occur inthese areas.

L2

P

LS

AssessmentAssessment

L2

P

LS

Section AssessmentSection AssessmentSection Assessment1. They have scales, gills, and fins.2. Lampreys are parasites. Hagfishes are

scavengers. Cartilaginous fishes arepredators.

3. It enables fishes to control their depth by regulating the amount of gas in thebladder.

4. Continuous flexing of the backboneenables fishes to propel themselves with

muscles attached to the backbone.5. Jaws enable fishes to grasp and crush

prey with great force and to eat largechunks of food.

6. Make sure that students compare in theirtables structural features such as skeleton,lateral line, scales, and swim bladder, aswell as behavioral features such as waysof getting food and ways of swimming.

Resource ManagerResource Manager

Reinforcement and StudyGuide, pp. 133-134

Content Mastery, p. 150 L1

P

LS

L2

P

LS

Section

What Is an Amphibian?The striking transition from a

completely aquatic larva to an air-breathing, semiterrestrial adult givesthe class Amphibia (am FIHB ee uh)its name, which means “double life.”The class Amphibia includes threeorders: Caudata (kaw DAHT uh), withsalamanders and newts; Anura (uhNUHR uh), with frogs and toads; andApoda (uh POH duh), with leglesscaecilians, as shown in Figure 30.12.Amphibians have thin, moist skin andfour legs. They have no claws ontheir toes. Although most adultamphibians are capable of a terrestrialexistence, nearly all of them rely onwater for reproduction. Fertilizationin most amphibians is external, andwater is needed as a medium fortransporting sperm. Amphibian eggs

lack protective membranes and shellsand must be laid in water to staymoist. How do frogs capture theirfood? Find out by reading the InsideStory on the next page.

Amphibians are ectothermsAmphibians are more common in

regions that have warm temperaturesall year because they are ectotherms.

If an alien visitor to our planetwere to watch our television programs and read our children’s

literature, it might return home with wondrous stories of how frogs on Earth can talk and change by the touch of a kiss into princes. Frogsand toads don’t talk, but they dochange—from fishlike tadpolesto four-legged animals withbulging eyes, long tongues,loud songs, and remark-able jumping ability.

SECTION PREVIEW

ObjectivesRelate the demands of a terrestrial environ-ment to the adaptationsof amphibians.Relate the evolution of the three-chamberedheart to the amphibianlifestyle.

Vocabularyectothermvocal cords

30.2 Amphibians

Figure 30.12Caecilians, orderApoda, are long,limbless amphibians.They look like wormsbut have eyes thatare covered by skin.

Pickerel frog (above)and tadpoles (inset)

827

Section 30.2

PrepareKey ConceptsStudents will relate the demandsof a terrestrial environment tothe adaptations of amphibians.They will also study the diversityof amphibians.

Planning■ Purchase a recording of frog

calls and live frogs that havenot been collected from thewild for the Quick Demos.

■ Gather culture dishes, ther-mometers, and binocular mi-croscopes for the BioLab.

1 FocusBellringer Before presenting the lesson,display Section Focus Trans-parency 74 on the overhead pro-jector and have students answerthe accompanying questions.

P

ELL

LS

L1

P

LS

BIOLOGY: The Dynamics of Life SECTION FOCUS TRANSPARENCIES

Use with Chapter 30,Section 30.2

How do you think these animals get food and oxygen?

Do you think these animals could live away from waterfor a few days? Explain your reasoning.

11

22

SECTION FOCUS

Cop

yrig

ht ©

Gle

ncoe

/McG

raw

-Hill

, a d

ivis

ion

of T

he M

cGra

w-H

ill C

ompa

nies

, Inc

.

Transparency Living inAir and Water74

MEETING INDIVIDUAL NEEDS MEETING INDIVIDUAL NEEDS

Visually ImpairedKinesthetic Provide visuallyimpaired students with plastic or

clay models of animals from the threeorders of amphibians. Have students com-pare and contrast the features of eachand describe their adaptations to moisthabitats.

P

LS

L1

P

LS

CD-ROMBiology: The Dynamics of LifeExploration: Amphibians

Disc 4

Resource ManagerResource Manager

Section Focus Transparency 74and Master

P

ELL

LS

L1

P

LS

827

Adult frog

Young frog with stucturesneeded for life on land.

Tadpoles with legs feedon plants in the water.

Fertilized eggs

Young leglesstadpoles liveoff yolk storedin their bodies

An ectotherm (EK tuh thurm) is ananimal in which the body tempera-ture changes with the temperature ofits surroundings. Because many bio-logical processes require particulartemperature ranges in order to func-tion, amphibians become dormant inregions that are too hot or cold forpart of the year. During such times,many amphibians burrow into themud and stay there until suitableconditions return.

Amphibians undergo metamorphosis

Unlike fishes, most amphibians gothrough the process of metamorpho-sis. Fertilized eggs hatch into tadpoles,the aquatic stage of most amphibians.You can compare tadpoles with adultfrogs in the MiniLab on the nextpage. Tadpoles possess fins, gills, anda two-chambered heart as seen infishes. As tadpoles grow into adult

frogs and toads, they develop legs,lungs, and a three-chambered heart.Figure 30.13 shows this life cycle.You can observe the development offrog eggs in the Investigate BioLab atthe end of this chapter.

Young salamanders resemble adults,but they have gills and usually have atail fin. Most adult salamanders lackgills and fins. Instead, they breathethrough their moist skin or with lungs.Up to one-fourth of all salamandershave no lungs and breathe onlythrough their skin. Most salamandershave four legs for moving about, buta few have only two front legs.

Walking requires more energyThe laborious walking of early

amphibians required a great deal ofenergy from food and large amountsof oxygen for aerobic respiration.The evolution of the three-cham-bered heart in amphibians ensured

30.2 AMPHIBIANS 829

Figure 30.13The amphibian life cycle includesan aquatic tadpole stage and aterrestrial adult stage.

829

Liver

Intestine

Fat bodies

Backbone

Heart

Vocalcords

828 FISHES AND AMPHIBIANS

A Frog

Many species of frogs look similar. As adults, theyhave short, bulbous bodies with no tails. This

adaptation allows them to jump more easily.

Critical Thinking How does a three-chambered heartbenefit a frog?

Green frog, Rana clamitans

INSIDESSTORTORYY

INSIDE

Tympanic membrane Vibrationsfrom water or air are picked up bythe tympanic membrane and trans-mitted to the inner ear and then tothe brain. The tympanic membranealso amplifies the sounds frogs make.

22

Eyes Some frogs’ eyes protrude from thetops of their heads—an adaptation thatenables them to stay submerged in the waterwith only their eyes above the surface.

11

Tongue A frog’stongue is long, sticky,and fastened to thefront of the mouth.These adaptationsallow frogs to snaretheir prey, such asflies, with amazingaccuracy.

33

Lungs Lungs enableadult amphibians tobreathe air.

44

Calls Male frogsuse sound to attractfemales. Femaleshave distinct calls toindicate whether ornot they are willingto mate.

55

Legs The hind legs of afrog are muscular. If youhave ever tried to catch afrog, you can appreciate thepower in these leg muscles.

66

828

IINSIDENSIDESSTORTORYY

INSIDE

2 TeachPurpose Students learn about the impor-tant features of frogs.

Teaching Strategies■ Have a live frog available aswell as wall charts showing theinternal and external anatomy ofa frog. As each feature is dis-cussed in the Inside Story, pointout the corresponding feature onthe live frog and wall charts.■ Divide students into teams.Provide each team with birthdayblowers that have a small piece ofVelcro attached to the tip of theblowers. Attach the complemen-tary piece of Velcro to a smallpiece of ribbon. Have one stu-dent on each team move the rib-bon “fly” while another studentuses the blower “tongue” to tryto catch the “fly.” Ask studentshow this model illustrates how afrog obtains food. Ask them topoint out how the model is notlike a real frog’s tongue.

Visual Learning■ Provide each student with

an acetate transparency andmarkers. Have them lay thetransparency on the frog dia-gram shown and trace the out-line of the frog on the acetate.Encourage students to labeleach of the structures shown inthe diagram. L1

P

LS

P

COOP LEARN

LS

P

ELL

LS

L1

P

LS

P

LS

Quick DemoQuick Demo

Naturalist Divide theclass into groups. Give

each group a live frog inside a large, clear container. Askstudents to describe any behav-iors they observe in the frog.Students are likely to describethe frog jumping, movingabout, or breathing. Elicit fromstudents how these activitiesmay be suited to life on land.Make sure the frogs you usehave not been collected fromthe wild.

P

LS

L1

P

LS

BIOLOGY JOURNAL BIOLOGY JOURNAL

Mapping Amphibian HabitatsVisual-Spatial Give students a blankworld map and ask them to use an

atlas of world wildlife to find out wherevarious amphibians live. Have them colorcode their maps for various types ofamphibians and place their maps in theirjournals.

P

LSP

ELL

LS

L2

P

LS

PortfolioPortfolio

Frog Life CycleVisual-Spatial Have students makea flowchart that traces the stages in

the frog life cycle. Ask students todescribe the features of each stage of thelife cycle and how each feature benefitsthe organism at that stage.P

LS

PP

LS

L2

P

LS

The BioLab at theend of the chaptercan be used at thispoint in the lesson.

INVESTIGATEINVESTIGATE

CD-ROMBiology: The Dynamics of LifeVideo: Feeding Frog

Video: Frog BehaviorDisc 4

VIDEODISCThe Secret of LifeFish/Amphibian—

Air Exchange

Fish/Amphibian Heart

!7;JLI"

!7;H.D"

Visual LearningFigure 30.13 Ask students howhaving two different stages in alife cycle could have survivalvalue for a species. Responses maysuggest that the two stages help thespecies survive during adverse orchanging climate conditions on landor in water.

■ Ask students to use the trans-parencies they made to preparea presentation about frogs foran elementary school scienceclass. Have students outline thefeatures to be covered in theirpresentations.

Critical ThinkingThe frog’s three-chamberedheart can pump more oxygenatedblood and thereby make moreenergy available to it.

L2

P

LS

Resource ManagerResource ManagerReteaching Skills Transparency 44 and

Master Critical Thinking/Problem Solving, p.30

Concept Mapping, p. 30Laboratory Manual, pp. 213-218 L2

P

LS

P

ELL

LS

L3

P

LS

L3

P

LS

P

ELL

LS

L1

P

LS

have short legs and bumpy, dry skin.Like fishes, frogs and toads have jawsand teeth. All adult frogs and toadseat insects. Many species of frogs andtoads secrete chemicals through theirskin as a defense against predators.Some frogs and toads produce toxinsthat can kill predators, such as dogs,quickly. You can find out more aboutpoisonous frogs in the ChemistryConnection at the end of this chapter.

Frogs and toads also have vocalcords that are capable of producing awide range of sounds. Vocal cordsare sound-producing bands of tissuein the throat. As air moves over thevocal cords, they vibrate and causemolecules in the air to vibrate. Inmany male frogs, air passes over thevocal cords, then passes into a pair ofvocal sacs lying underneath thethroat, illustrated in Figure 30.14.

Frogs and toads, like all amphib-ians, spend part of their life cycle inwater and part on land. They breathethrough lungs or through their thinskins. As a result, frogs and toadsoften are among the first organismsto be exposed to pollutants in the air,on land, or in the water. Decliningnumbers of frog species, or deformi-ties in local frogs, sometimes indicatethat the environment is no longerhealthy.

Salamanders belong to the order Caudata

Unlike a frog or toad, a salaman-der has a long, slender body with aneck and tail. Salamanders resemblelizards, but have smooth, moist skinand lack claws. Some salamanders aretotally aquatic, and others live indamp places on land. They range insize from a few centimeters in lengthup to 1.5 m. Newts are salamandersthat live entirely in water. The youngthat hatch from salamander eggs looklike small adults and are carnivorous.

Caecilians are limbless amphibians

Caecilians are amphibians thathave no limbs, with a short, or no,tail. Caecilians are primarily tropicalanimals with small eyes that are oftenblind. They eat earthworms andother invertebrates found in the soil.

Origins of AmphibiansImagine a time 350 million years

ago when the inland, freshwater seaswere filled with carnivorous fishes.One type of tetrapod had evolvedthat retained gills for breathing and afinned tail for swimming. In later fos-sils, the four limbs are found furtherbelow the body to lift it off theground. Any animal that could moveover land from the mud of a dryingstream to another water source mightsurvive. Most likely, amphibiansarose as their ability to breathe airthrough well-developed lungsevolved. The success of inhabitingthe land depended on adaptationsthat would provide support, protectmembranes involved in respiration,and provide efficient circulation.

30.2 AMPHIBIANS 831

Figure 30.14Most male frogs havethroat pouches that,along with the tym-panic membrane,increase the volumeof their calls.

831

Using an AnalogyA frog senses sound and othervibrations by means of tympanicmembranes, circular structureslocated just behind the eyes ofthe frog. The tympanic mem-brane vibrates much like the skinof a drum to alert the frog tosounds. Ask students to hypothe-size why the sense of hearing isimportant to a frog. The sense ofhearing is important to a frog forhearing the calls of mates and toavoid predators.

Looking at Frog and Tadpole AdaptationsAn adult frog and its larval stage are adapted to dif-ferent habitats. How are the structures of a frog and a tadpole adapted to their environments?

Procedure! Copy the data table.@ Examine a living or preserved adult frog and larval

(tadpole) stage. CAUTION: Wear disposable latex glovesand use a forceps when handling preserved specimens.

# Observe the first seven traits listed. Complete your datatable for these observations.

$ Use references to fill in the information for the last threetraits listed.

Analysis1. Explain how hind leg musculature aids in adult frog survival. 2. Correlate the type of respiratory organ in an adult and a

tadpole with their differing habitats. 3. Correlate the type of appendages (arm, leg, tail) in an

adult and a tadpole with their differing habitats.4. Correlate mouth size in an adult and a tadpole with their

differing diet.5. Explain how eyes may aid in the survival of both stages.6. Explain why the tympanic membrane may not be essential

to the survival of a tadpole.7. Predict how skin color and texture aids in adult frog

survival. CAUTION: Wash your hands after working withlive or preserved animals.

MiniLab 30-2MiniLab 30-2 Comparing and Contrastingthat cells received the proper amountof oxygen. This heart was an impor-tant evolutionary transition from thesimple circulatory system of fishes.

In the three-chambered heartof amphibians, one chamberreceives oxygen-rich bloodfrom the lungs and skin, andanother chamber receives oxygen-poor blood from thebody tissues. Blood from bothchambers then moves to thethird chamber, which pumps

oxygen-rich blood to body tissuesand oxygen-poor blood back to thelungs and skin so it can pick up moreoxygen. This results in some mixingof oxygen-rich and oxygen-poorblood in the amphibian heart and inblood vessels leading away from theheart. Thus, in amphibians, the skinis much more important than thelungs as an organ for gas exchange.

Because the skin of an amphibianmust stay moist to exchange gases,most amphibians are limited to lifeon the water’s edge. However, somenewts and salamanders remain totallyaquatic. Amphibians such as toadshave thicker skin, and although theylive primarily on land, they still mustreturn to water to reproduce.

Diversity of AmphibiansBecause amphibians still complete

part of their life cycle in water, theyare limited to the edges of ponds,lakes, streams, and rivers or to areasthat remain damp during part of theyear. Although they are not easilyseen, amphibian species are numer-ous worldwide.

Frogs and toads belong to the order Anura

Frogs and toads are amphibianswith no tails. Frogs have long hindlegs and smooth, moist skin. Toads

830 FISHES AND AMPHIBIANS

Trait or information AdultTadpole

Limbs present?

Eyes present?

Tympanic membrane present?

Tail present?

Mouth present?

Nature of skin (color and texture)

General size

Respiratory organ type

Diet

Habitat

Data Table

Rana temporaria

830

Purpose Students will compare and con-trast the appearance and traits ofan adult frog and a tadpole.

Process Skillscompare and contrast, acquireinformation, recognize cause andeffect, think critically

Teaching Strategies■ Preserved materials are avail-able from biological supplyhouses. Retain preserved speci-mens for the following year.■ Place preserved materials onpaper toweling or on trays.■ Binocular microscopes may beused to observe the skin.■ Provide references for theinformation regarding diet; larvaefeed on algae, adults feed oninsects, small fishes, and worms.

Expected ResultsTadpoles have a tail, gills, notympanic membrane, and nolimbs at early stages. Adults havelungs. All other traits are shared.Coloration of stages may varywith species being observed.Tadpoles feed on algae, adults oninsects, worms, and small fishes.Tadpoles are confined to aquatichabitats; adults live both on landand in water.

Analysis1. allows frog to escape preda-

tors, aids in swimming2. Diffusion of oxygen occurs

between lungs and air, andbetween gills and water.

3. A tadpole has a tail for swim-ming in water. An adult froghas legs for jumping awayfrom predators and catchingprey.

4. A tadpole has a small mouthfor eating algae. An adultfrog has a large mouth foreating insects, worms, andfishes.

5. seeing food and predators6. An adult can hear mating

calls to enable reproduction.Tadpoles do not reproduce.

7. protective coloration frompredators, thin skin aids ingas exchange

P

LS

MiniLab 30-2MiniLab 30-2 Quick DemoQuick Demo

Auditory-Musical Play arecording of frog calls.

Use the recording to initiate aclass discussion about how frogscall using vocal cords and airsacs. Ask students to speculateabout why frogs call. Responsesmay indicate to identify a terri-tory, to attract mates, or to sig-nal distress.

P

LS

P R O J E C TAmphibians in Decline

Linguistic Ask students to report onthe results of recent studies of the

worldwide decline of amphibians.P

LS

L3

P

LS

Portfolio Have students locate refer-ences that describe time needed for meta-morphosis to occur. Ask them to prepare aposter that compares length of metamorpho-sis for different frog species. Use thePerformance Task Assessment List forPoster in PASC, p. 73. L2

P

LS

AssessmentAssessment

VIDEODISCBiology: The Dynamics of LifeFrog Behavior (Ch. 3)

Disc 2, Side 132 sec.!7JÅ"

Feeding Frog (Ch. 4)Disc 2, Side 113 sec.!7TÇ"

VIDEODISCGTV: PlanetaryManager

Animal Side 2

!7RS~I"

Resource ManagerResource ManagerBioLab and MiniLab Worksheets,

pp. 135-136 L2

P

LS

Recall that early vertebratesevolved from mud-sucking, swim-ming fishes to aquatic tetrapods.Scientists have found fossil evidencethat supports the hypothesis thatlimbs first evolved in aquatic animals.Some of these aquatic vertebratesevolved into air-gulping animals that

crawled from one pond to another,and finally to fully developedamphibians that lived mainly on land.Although the fossil record for fishesand amphibians is incomplete, mostscientists agree that the relationshipsshown in Figure 30.17 represent thebest fit for the available evidence.

30.2 AMPHIBIANS 833

PRESENTCENOZOICPALEOZOICPRECAMBRIAN MESOZOIC

Frogs and Toads3700 species

Salamanders400 species

Lungfishes6 species

Placoderms

Lobe-finnedfishes

1 species Ray-Finned Fishes18 000 species

Sharksand Rays850 species

Ostracoderms

Earlytetrapod

Reptiles

Lampreys

63 species

Hagfishes

Osteichthyes

Agnatha

Amphibians

Chondrichthyes

Section AssessmentSection Assessment

Understanding Main Ideas1. Describe the events that may have led early ani-

mals to move to land.2. List three characteristics of amphibians.3. Name two ways that amphibians depend on

water.4. How does metamorphosis through two different

forms benefit amphibians?

Thinking Critically5. How does a three-chambered heart enable

amphibians to obtain the energy needed formovement on land?

6. Sequencing Trace the evolutionary develop-ment of amphibians from lungfishes. For morehelp, refer to Organizing Information in the SkillHandbook.

SKILL REVIEWSKILL REVIEW

Figure 30.17The radiation of classes of fishesand orders of amphibians on theGeologic Time Scale shows theirrelationships.

ANIMALS

ReteachPrepare six sets of flash cardswith the vocabulary terms andnames of the anatomical struc-tures discussed in this section onone side and the meaning of theterm or function of the structureon the other side. Have studentswork in groups to use the cardsto review the terms and conceptsin this section.

ExtensionAsk students to prepare a cartoonthat includes a frog. The cartoonshould be humorous and accu-rately portray some aspect of thefrog’s environment, life history,or evolution. Have studentsexamine some Far Side cartoonsby Gary Larson as examples.

Skill Have students write adescription for a perfectly adaptedtoad that lives in a dry regionwith puddles that form after rainand with many hawks that preyon toads. Students’ descriptionsshould include how the toadwould protect itself, reproduce,prevent water loss from its body,and obtain food.

4 CloseAudiovisualShow slides or a videotape ofamphibians from around theworld.

L2

P

LS

AssessmentAssessmentP

ELL

LS

L3

P

LS

P

COOP LEARN

LS

L1

P

LS

Challenges of life on landLife on land held many advantages

for early amphibians. There was alarge food supply, shelter, and nopredators. In addition, there wasmuch more oxygen in air than inwater. However, land life also heldmany dangers. Unlike the tempera-ture of water, which remains fairlyconstant, air temperatures vary a great

deal. In addition, without the supportof water, the body was clumsy andheavy. Some of the efforts to moveon land by early amphibians probablywere like movements of modern-daysalamanders. The legs of salamandersare set at right angles to the body.You can see in Figure 30.15 why thebellies of these animals may havedragged on the ground.

Amphibians first appeared about360 million years ago. Amphibiansprobably evolved from an aquatictetrapod, as shown in Figure 30.16,around the middle of the PaleozoicEra. At that time, the climate onEarth is known to have become warmand wet, ideally suited for an adaptiveradiation of amphibians. Able tobreathe through their lungs, gills, orskin, amphibians became, for a time,the dominant vertebrates on land.

832 FISHES AND AMPHIBIANS

Figure 30.16Transitional fossils with four limbsfrom the Devonian period showthat they had amphibian charac-teristics, but they also retainedsome fishlike features.

Figure 30.15Adaptation to life onland involves thepositioning of limbs.The evolution oftetrapods led to thediversification of landvertebrates.

Reptiles such asthis crocodile havelegs on the sidesof their bodies,like amphibians,but the limbs havejoints that enablethem to bend andhold the body upoff the ground.

BB

Like reptiles, mammal bodies are raisedabove the ground, but the limbs arepositioned underneath the body. Thisposition allows greater speed of locomo-tion, making mammals such as this chee-tah the fastest-moving land animals.

CC

The salamander, anamphibian, has legsthat extend at rightangles to its body.

AA

832

Performance Ask a groupof students to design a reviewgame for concepts in this section.Tell them to base their game on aTV quiz show and to preparecards or other materials needed sothat the class or groups in theclass can play the game. L2

P

LS

AssessmentAssessment

Frog Greeting CardsKinesthetic Have a groupof students design a chil-

dren’s greeting card featuringfrogs. The card should includeinformation about frogs orother amphibians. Studentsshould use their creativity todevelop this card. Remind stu-dents that cards can pop up,make sound, and have shapesother than a rectangle.

P

LSP

ELL

LS

L2

P

LS

BIOLOGY JOURNAL BIOLOGY JOURNAL

Researching Local AmphibiansLinguistic Provide students withsources about local amphibians. Ask

them to draw sketches and write a para-graph about several local amphibians. Askthem to place this information in theirjournals.

P

LS

L2

P

LS

3 AssessCheck for UnderstandingHave students develop a tablewith the following headings:Trait, Anura, and Caudata.Beneath the Trait heading, havestudents list: Symmetry, Habitat,Food getting, Reproduction,Locomotion, Respiration, Pro-tection, Examples. Have themreview this section to completetheir tables. L2

P

LS

Section AssessmentSection AssessmentSection Assessment1. Shallow inland seas were affected by

periodic droughts. Early tetrapodswith gills and limbs were able tomove briefly across land to anotherwater source for survival.

2. three-chambered hearts, eggs with-out shells laid in water, smooth, moistskin

3. external fertilization, growth anddevelopment of eggs, developmentof larval stage

4. Tadpoles and adult frogs use differentfood sources and, therefore, do notcompete with one another for food.

5. Cells obtain oxygen quickly in a three-chambered heart. The heart is a more

efficient pump, enabling oxygen toreach cells quickly, thereby enablingthe animal to move quickly.

6. Amphibians first appeared about 350million years ago, probably evolvingfrom the lungfishes. Over time, thelungfishes evolved legs and feetsuited to a land environment.

833

Resource ManagerResource ManagerBasic Concepts Transparency 53 and

Master Reinforcement and Study Guide,

pp. 135-136Content Mastery, pp. 149, 151-152

L1

P

LS

L2

P

LS

P

ELL

LS

L2

P

LS

32-cell stage at 3 hours, the lategastrula stage at 9 hours, and avisible head area between 18 and20 hours. Hatching will occur atabout 50 hours (about two days).

4. Set up the appropriate numbers of light bulbs of different wattagesover the water to keep the temperatures at 20°, 25°, and30°C.

5. Place a dish of eggs in the refrig-erator. Measure the temperatureof your refrigerator. Keep a flash-light on in the refrigerator at alltimes so that you have only onevariable, the temperature.

6. Make a hypothesis about howtemperature will affect develop-ment of the eggs.

7. Set up a time schedule for obser-vations and making sketchesbased on what stage you areobserving. Make observationsuntil the eggs hatch. Record yourobservations in a journal.

8. Observe your eggs under themicroscope according to the sched-ule you have made. Draw sketchesof your eggs in the data table.

30.2 AMPHIBIANS 835

30° C

25° C

20° C

refrigerator

Day 2Day 1Temperature Day 3

Data Table

Going FurtherGoing Further

Make a Hypothesis Make a hypothesisabout what other environmental factorswould affect the development of frog eggs.Explain your reasoning.

To find out more aboutmetamorphosis, visit the

Glencoe Science Web Site.www.glencoe.com/sec/science

1. Interpreting ObservationsWhich eggs develop the fastest?The slowest? Explain.

2. Interpreting Observations Didyour data support your hypothesis?Explain.

3. Drawing Conclusions Whatadvantage is it for frogs to haveeggs that develop at differentrates that correspond to differenttemperatures?

4. Thinking Critically What wouldhappen if frog eggs developed

when the weather was still cold inthe spring?

ANALYZE AND CONCLUDEANALYZE AND CONCLUDE

INVESTIGATEINVESTIGATE

1. Egg development and celldivision occur more quicklyat warmer temperatures. Celldivision is slower at lowertemperatures.

2. Check students’ data to seehow they supported theirhypotheses.

3. The tadpoles will hatch whentemperature is most con-ducive for survival. Perhapsmore food is available atwarmer temperatures.

4. The tadpoles might not sur-vive or adequate food maynot be available when thewater is cold.

Error AnalysisLight bulbs and their distancesfrom the dishes should not bedisturbed during the experiment.Ask students why this is impor-tant. Ask students why it isimportant for them to wash theirhands both before and after mak-ing observations.

Portfolio Ask students tosummarize in their portfolioswhat they have learned in this lab.Use the Performance TaskAssessment List for Lab Reportin PASC, p. 47. L2

P

LS

AssessmentAssessment

ANALYZE AND CONCLUDEANALYZE AND CONCLUDE

835

Data and ObservationsEggs develop more quickly at warmer tem-peratures and more slowly at cooler temper-atures.

Going FurtherGoing Further

Students’ hypotheses may in-clude that UV light or chemicalpollution of water may destroydeveloping egg cells; or lack ofoxygen in water due to decom-position of organic matter mayaffect egg development.

834 FISHES AND AMPHIBIANS

Development of Frog Eggs

Most frogs breed in water. The male releases sperm over the female’seggs as she lays them. Some frogs lay up to a thousand eggs. A jel-

lylike casing protects the eggs as they grow into embryos. When the em-bryos hatch, they develop into aquatic larvae commonly called tadpoles.Tadpoles feed by scooping algae from the water or by scraping algae fromwater plants with small, toothlike projections in their mouths.

During metamorphosis, tadpoles lose their tails and develop legs.Many internal changes take place as well. Gills are reabsorbed by thebody, and lungs form. Development and metamorphosis to the adult frogtake from three weeks up to several years, depending upon the species.

INVESTIGATEINVESTIGATE

ProblemHow does temperature affect the

development of frog eggs?

ObjectivesIn this BioLab, you will:■ Compare develop-

ment of frog eggs atvarying tempera-tures.

■ Distinguish amongvarious stages ofdevelopment.

MaterialsRinger’s solution4 culture disheslight bulbs with source of electricitythermometerbinocular microscopefrog eggs, Xenopus laevisflashlight

Safety PrecautionsAlways wear goggles in the lab.

Wash hands before and after eachobservation.

Skill HandbookUse the Skill Handbook if you need

additional help with this lab.

PREPARATIONPREPARATION

1. Obtain four culture dishes ofRinger’s solution and fertilizedfrog eggs.

2. Make a data table similar to theone shown for sketching of stagesof development of the eggs.

3. Observe your eggs and determinetheir stage of development. Atroom temperature, you shouldsee the two-cell stage about 1.5hours after fertilization, theeight-cell stage at 2.25 hours, the

PROCEDUREPROCEDURE

INVESTIGATEINVESTIGATE

Time Allotment First day—one class period.Every day for 2 weeks—10 min-utes.

Process Skillsobserve and infer, compare andcontrast, form a hypothesis,interpret data, recognize causeand effect

Safety Precautions■ Encourage students to treat

living organisms in a humanemanner at all times.

■ Students should wash theirhands after each observation.

■ Caution students to avoid skinand eye contact with Ringer’ssolution.

■ Make sure students’ hands andwork area are dry when usingelectrical materials.

■ Use sterile Ringer’s solution tohelp prevent contamination bybacteria and fungi. Ask stu-dents to avoid touching thesolution to prevent contamina-tion.

Alternative Materials■ Make sure to use frog eggs

that have a short developmenttime. It is best not to collecteggs from the wild as amphib-ians are declining worldwide.Order eggs from a biologicalsupply house.

PREPARATIONPREPARATION

P

LS

834

PROCEDUREPROCEDURE

Teaching Strategies■ Review frog development before studentscarry out the lab.■ Have students work in cooperativegroups to reduce the materials needed. Eachperson in the group should have a specificjob during the data collection period.■ Explain that the white part of the egg isthe yolk and the black part is the developing

tadpole. The yolk is used for food by thedeveloping tadpole. The jellylike substancesurrounds and protects the egg.■ Students should be able to observe move-ment of the tadpole just before it hatches.

Resource ManagerResource ManagerBioLab and MiniLab Worksheets,

pp. 137-138 L2

P

LS

Chapter 30 AssessmentChapter 30 Assessment

SUMMARYSUMMARY

Section 30.1

Section 30.2

Main Ideas■ Fishes are vertebrates with backbones and nerve

cords that have expanded into brains.■ Fishes belong to three groups: the jawless lam-

preys and hagfishes, the cartilaginous sharks andrays, and the bony fishes. Bony fishes are madeup of three groups: the lobe-finned fishes, thelung-fishes, and the ray-finned fishes.

■ Jawless, cartilaginous, and bony fishes may haveevolved from ancient ostracoderms.

Vocabularycartilage (p. 823)fin (p. 820)lateral line system

(p. 820)scale (p. 821)spawning (p. 819)swim bladder (p. 822)

Fishes

Main Ideas■ Adult amphibians have three-chambered hearts

that provide oxygen to body tissues, but mostgas exchange takes place through the skin.

■ Land animals face problems of dehydration, gasexchange in the air, and support for heavy bod-ies. Amphibians possess adaptations well-suitedfor life on land.

■ Amphibians probably evolved from ancientaquatic tetrapods.

Vocabularyectotherm (p. 829)vocal cords (p. 831)Amphibians

CHAPTER 30 ASSESSMENT 837

1. An animal with gill slits, a dorsal hollownerve cord, and a backbone is a(n) ________.a. invertebrateb. invertebrate chordatec. vertebrated. echinoderm

2. In addition to fishes, the subphylum Verte-brata includes ________.a. amphibians, reptiles, birds, and mammalsb. echinoderms, reptiles, birds, and mammalsc. tunicates, lancelets, reptiles, and birdsd. tunicates, reptiles, birds, and mammals

3. Scientists hypothesize that the commonancestors to all fishes are the ________.a. amphibians c. ostracodermsb. echinoderms d. lancelets

UNDERSTANDING MAIN IDEASUNDERSTANDING MAIN IDEAS 4. How do jawless fishes obtain food?a. by injecting prey with poison from their

hooklike fangsb. by using their round mouths like vacuum

cleaners to suck up organic matterc. by drilling a hole and sucking out blood

and insides of a prey animald. by using their sharp teeth to grab and

swallow smaller fishes5. Which of the following is NOT a character-

istic of most fishes?a. have scalesb. have a two-chambered heartc. breathe using gillsd. exchange gases through thin, moist skin

6. ________ use fins like the stabilizers of boats.a. Frogs c. Sea starsb. Fishes d. Lancelets

837

Main IdeasSummary statements can be usedby students to review the majorconcepts of the chapter.

Using the VocabularyTo reinforce chapter vocabulary, usethe Content Mastery Booklet andthe activities in the Interactive Tutorfor Biology: The Dynamics of Life onthe Glencoe Science Web Site.www.glencoe.com/sec/science

1. c2. a3. c4. c5. d6. b

UNDERSTANDING MAIN IDEASUNDERSTANDING MAIN IDEAS

Chapter 30 AssessmentChapter 30 Assessment

All ChapterAssessment

questions and answers have beenvalidated for accuracy and suitabil-ity by The Princeton Review.

Resource ManagerResource Manager

Chapter Assessment, pp. 175-180MindJogger VideoquizzesComputer Test BankBDOL Interactive CD-ROM, Chapter 30

quiz

The most colorful frogs in the world are found inSouth and Central America. These poisonous

frogs, including 130 species of the Dendrobatidaefamily, range in size from 1 to 5 cm. Although

all frogs have glands that produce secretions, thesefrogs secrete toxic chemicals through their skin. Apredator will usually drop the foul-tasting frogwhen it feels the numbing or burning effects of

the poison in its mouth. The frogs advertise theirpoisonous personalities by bright coloration; theymay be red or blue, solid colored, marked withstripes or spots, or have a mottled appearance.

The poison secreted by these frogs is used by nativepeoples to coat the tips of the darts they use in

their blow guns for hunting. Thus, these frogs areknown as poison-arrow frogs.

The secretions of the poison-arrow frogs ofthe frog family Dendrobatidae are alkaloid

toxins. An alkaloid toxin is a compound thatincludes a ring consisting of five carbon atomsand one nitrogen atom. The toxins secreted bypoisonous frogs act on an ion channel betweennerve and muscle cells. Normally, the channel isopen to allow movement of sodium, potassium,and calcium ions. The toxins can block the flowof potassium and stop or prolong nerve impulsetransmission and muscle contraction. One groupof alkaloids affects the transport of calcium ions,which are responsible for muscle contraction.Current research indicates that these alkaloidsmay have clinical applications for muscle diseasesand as pain killers.

Frog poison eases pain Recent research showsthat a drug derived from the extract from thepoison-arrow frog, Epipedobates tricolor, works as apowerful pain killer. The drug ABT-594 mayhave the same benefits as morphine, but not theside effects. Morphine is the primary drug usedto treat the severe and unrelenting pain caused by

cancer and serious injuries. Side effects of mor-phine include suppressed breathing and addic-tion. The “frog drug” does not interfere withbreathing and does not appear to be addictive ininitial testing. Another benefit of ABT-594 isthat as it blocks pain, it does not block other sen-sations, such as touch or mild heat. One day painyou experience might be eased by a frog!

836 FISHES AND AMPHIBIANS

ConnectionChemistryChemistry

Connection Killer Frogs

Research on newly discovered organisms such aspoisonous frogs may result in drugs to treat spe-cific disorders in human patients. Find out whathuman diseases are caused by problems in thetransmission of nerve impulses and write an essayidentifying the disorders that might be treated bytoxins from poisonous frogs.

To find out more about poiso-nous frogs, visit the Glencoe

Science Web Site.www.glencoe.com/sec/science

CONNECTION TO BIOLOGYCONNECTION TO BIOLOGY

Cl

O

N

N

H

Poison-arrow frog, Epipedobates tricolor

836

Purpose Students will study the nature ofpoisonous frogs and how theirsecretions affect cell chemistry ofthe prey.

Teaching Strategies■ Review details of ion channelsin cell membranes.■ Have students diagram the twodifferent actions frog toxins mayhave on cells.■ Poisons from all species ofpoison arrow frogs are extremelytoxic. Barely 2 micrograms ofthese toxins can kill an adulthuman. Each frog can produce200 micrograms of poison. Askstudents to speculate about whythese frogs are brightly colored.The color advertises their deadly con-dition to potential predators.■ Have students research speciesof poison arrow frogs to find outwhich species are the mostdeadly.■ Ask students whether scientistsshould lobby for tropical rain for-est protection in view of themedical potential of some ofthese species.

Connection to BiologyResponses will vary dependingupon the human diseases re-searched.

P

LS

ConnectionChemistryChemistry

Connection

Internet Address Book

Note Internet addresses that you find useful in the spacebelow for quick reference.

VIDEODISCSTV: Rain ForestPoison-Arrow Frog

Side 1

!7Vi~3"VIDEOTAPEMindJogger Videoquizzes

Chapter 30: Fishes and AmphibiansHave students work in groups as they playthe videoquiz game to review key chapterconcepts.

Chapter 30 AssessmentChapter 30 Assessment

CHAPTER 30 ASSESSMENT 839

24. A male sea horse incubates fertilized eggs in abrood pouch. A codfish lays its eggs in theopen sea. Which of these two types of fisheswould need to lay more eggs? Why?

25. Using a Graph The following graph showsthe number of leopard frogs in a wetland on afarm. One year, there was a prolongeddrought in the farmer’s area. What year didthe drought occur? Explain.

26. Concept Mapping Complete the conceptmap by using the following vocabulary terms:lateral line system, scales, swim bladder.

THINKING CRITICALLYTHINKING CRITICALLY

ASSESSING KNOWLEDGE & SKILLSASSESSING KNOWLEDGE & SKILLS

Amphibian populations are declining inmany parts of the world. To reintroducenative amphibians into your state, assumeyou have a grant to breed frogs on a farm.To find out what temperature you need foroptimum hatching of frog eggs, you testeggs at four different temperatures.

Interpreting Data Answer the followingquestions based on the graph.1. How many eggs hatched at 25°C?

a. 150 c. 110b. 70 d. 15

2. At which temperature did the fewesteggs hatch?a. 15°C c. 25°Cb. 20°C d. 30°C

3. Based on the results of your experiment,what temperature will you use for opti-mum hatching of eggs?a. 15°C c. 25°Cb. 20°C d. 30°C

4. Designing an Experiment You are trying to find out the optimum pH forhatching frog eggs. Design a controlledexperiment that would give you quantitative data.

Num

ber o

f fro

gs h

atch

ing

15°C 20°CTemperature

25°C 30°C

180

150

120

90

60

30

Number of Frogs Hatching at VariousTemperatures in 5 Days

Num

ber o

f fro

gs

1995 1996

Year

1997 1998

Number of Frogs in a Wetland

Fishes

are vertebrates that

two-chamberedheart

1. 2.

3.

have a

sense vibrations

with a

have a

protect skin with

For additional review, use the assessmentoptions for this chapter found on the Biology: TheDynamics of Life Interactive CD-ROM and on theGlencoe Science Web Site.www.glencoe.com/sec/science

CD-ROM

839

24. Cod are a type of fish that laygreater numbers of eggs. Theeggs are unprotected in theocean and most hatchlings diebefore reaching adult size.

25. Probably in 1997 because therewas a decrease in the size of thefrog population that year.

26. 1. Lateral line system; 2. Scales;3. Swim bladder

THINKING CRITICALLYTHINKING CRITICALLY

Chapter 30 AssessmentChapter 30 Assessment

1. a2. a3. c4. Grow frog eggs in sepa-

rate solutions with variouspH levels. Count howmany eggs hatch in eachsolution after a specificnumber of days.

Chapter 30 AssessmentChapter 30 Assessment

7. The lateral line system enables a ________ todetect movement and vibrations in the water.a. frog c. toadb. salamander d. fish

8. The class Amphibia is well-named becauseamphibians ________.a. spend part of their lives on land and

part in waterb. lay shelled eggs on land but develop

in waterc. spend part of their lives in the air and

part on landd. use swim bladders for breathing in water

but use lungs on land9. Reptiles have legs on the sides of their

bodies, but the limbs are flexed. Salamandershave legs that ________.a. extend straight out from the body

and do not bendb. extend at right angles from the sides

of the body c. are missing some of the key bones

of reptilesd. evolved from shark’s fins

10. The evolution of a three-chambered heart inamphibians ensured that cells receive theproper amount of ________.a. oxygen c. bloodb. carbon dioxide d. heat

11. The skeletons of lampreys, hagfishes, sharks,and their relatives are made of ________.

12. In all fishes, gas exchange takes place in the________.

13. The ________-chambered heart pictured to the right belongs to a(n) ________.

14. A fish that has a niche similar to a leech isa(n) ________.

15. Fishes control their depth in the water byaltering the amount of ________ in their________.

16. The ________ enables a fish to navigate inthe dark.

17. Fossil evidence shows that early tetrapodshad ________ like fishes and ________ likeamphibians.

18. Both hagfishes and sharks have ________skeletons.

19. Fishes and amphibians are ________because their body temperature reflects thetemperature of their surroundings.

20. The ________ in the diagram below has legsthat show an earlier evolutionary origin thanthe other animals pictured.

21. What accounts for the different body shapesof fishes?

22. What are the advantages and disadvantagesof internal fertilization?

23. Describe the importance of the evolution of bone in fishes to the evolution of verte-brates.

APPLYING MAIN IDEASAPPLYING MAIN IDEAS

838 CHAPTER 30 ASSESSMENT

TEST–TAKING TIPTEST–TAKING TIP

Skip Around, if You Can Just because the questions are in order doesn’tmean that you have to answer them that way. Youmay want to skip over hard questions and comeback to them later, after you’ve answered all theeasier questions that will guarantee you morepoints toward your score.

a.

c.

b.

838

7. d8. a9. b

10. a11. cartilage12. gills13. two; fish14. lamprey15. gases; swim bladder16. lateral line system17. gills; limbs18. cartilaginous19. ectotherms20. salamander

21. They occupy different niches.22. Advantages: egg and sperm are

assured of coming together;male and female do not have toproduce as many gametes.Disadvantages: male andfemale must find each otherand be ready for reproductionat the same time.

23. Bone provides the support landvertebrates need for locomo-tion on land.

APPLYING MAIN IDEASAPPLYING MAIN IDEAS

Chapter 30 AssessmentChapter 30 Assessment