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528

VertebrateAnimalsFish, amphibians, reptiles,

birds, and mammals are allvertebrate animals.

SECTION 1Chordate AnimalsMain Idea Vertebrateshave an internal system ofbones including a backbone.

SECTION 2Amphibians and ReptilesMain Idea Amphibians andreptiles are both egg-laying,exothermic vertebrates.

SECTION 3BirdsMain Idea Birds are theonly animals with feathers.

SECTION 4MammalsMain Idea Mammals’ bodysystems are adapted to theirenvironment.

Traits We Share With AnimalsAn eagle flies through the sky, a salmon swims through a stream,a snake slithers along the ground, and a grizzly bear walks along a river’s edge. Each of these animals appears different, but theseanimals, as well as humans, share a common trait—an internalskeleton.

What other traits do these animals and humans share? Science Journal

Tom & Pat Leeson

529

Animals with a BackboneAn internal skeleton is common to many ani-mals. Skeletons are made of bones or carti-lage. They give your body its overall shapeand work with your muscles to help moveyour body. WARNING: Do not eat or drinkanything in the lab.

1. Use pasta wheels, soft-candy circles, and longpipe cleaners to make amodel of a backbone.

2. On a pipe cleaner, stringin an alternating patternthe pasta wheels and thesoft-candy circles until thestring is about 10 cm long.

3. Fold over each end of thepipe cleaner so the pastaand candy do not slide off.

4. Think Critically Slowlybend the model. Does itmove easily? How far canyou bend it? What do youthink makes up your back-bone? Write your observa-tions and answers in your Science Journal.

Vertebrates Make the followingFoldable to help you organizeyour thoughts about vertebrateanimals before you begin reading.

Collect three sheetsof paper and layerthem about 1.25 cmapart vertically. Keepthe edges level.

Fold up the bottomedges of the paper toform 6 equal tabs.

Fold the papers andcrease well to holdthe tabs in place.Staple along thefold. Label the flapsVertebrates, Fish, Amphibians,Reptiles, Birds, and Mammals, asshown.

Sequence Before you read the chapter, writewhat you know about each group under thetabs. As you read the chapter, add to or changethe information you wrote under the tabs.

STEP 3

STEP 2

STEP 1

Vertebrates

FishAmphibians

ReptilesBirds

Mammals

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Start-Up Activities

Tom & Pat Leeson, (inset)Amanita Pictures

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530 A CHAPTER 18 Vertebrate Animals

Apply It! Identify one para-graph that is difficult to understand. Discuss itwith a partner to improve your understanding.

Learn It! An important strategy to help you improve yourreading is monitoring, or finding your reading strengths and weaknesses.As you read, monitor yourself to make sure the text makes sense. Discoverdifferent monitoring techniques you can use at different times, dependingon the type of test and situation.

Practice It! The paragraph below appears in Section 2.Read the passage and answer the questions that follow. Discuss youranswers with other students to see how they monitor their reading.

• What questions do you still have after reading?• Do you understand all of the words in the passage?• Did you have to stop reading often? Is the reading level appropriate

for you?

Adult amphibians use lungs instead of gills toexchange oxygen and carbon dioxide. This is animportant adaptation for survival on land.However, because amphibians have three-cham-bered hearts, the blood carrying oxygen mixeswith the blood carrying carbon dioxide. Thismixing makes less oxygen available to the amphib-ian. Adult amphibians also exchange oxygen andcarbon dioxide through their skin, which increasestheir oxygen supply. Amphibians can live on land,but they must stay moist so this exchange canoccur.

—from page 536

530 B

Monitor your reading by

slowing down or speeding

up depending on your

understanding of the text.

Use this to focus on the main ideas as you read the chapter.

Before you read the chapter, respond to the statements

below on your worksheet or on a numbered sheet of paper.

• Write an A if you agree with the statement.

• Write a D if you disagree with the statement.

After you read the chapter, look back to this page to see if you’ve

changed your mind about any of the statements.

• If any of your answers changed, explain why.

• Change any false statements into true statements.

• Use your revised statements as a study guide.

Before You Read Statement After You ReadA or D A or D

1 Fish have an organ that keeps them from sink-ing or floating to the surface in water.

2 Amphibians spend their lives in water.

3 Amphibians undergo metamorphosis.

4 Reptiles and amphibians lay the same type ofeggs.

5 All birds can fly.

6 While flying, birds use their tails to steer.

7 There are two types of bird feathers.

8 All mammals have the same type of teeth.

9 Every mammal has either hair or fur.

10 All mammals give birth to live young.

Print out a worksheetof this page at red.msscience.com


530 CHAPTER 18 Vertebrate Animals

What is a chordate? Suppose you asked your classmates to list their pets. Dogs,

cats, birds, snakes, and fish probably would appear on the list.Animals that are familiar to most people are animals with a back-bone. These animals belong to a larger group of animals calledchordates (KOR dayts). Three characteristics of all chordates area notochord, a nerve cord, and pharyngeal pouches at sometime during their development. The notochord, shown inFigure 1, is a flexible rod that extends along the length of thedeveloping organism. Pharyngeal pouches are slitlike openingsbetween the body cavity and the outside of the body. They arepresent only during the early stages of the organism’s develop-ment. In most chordates, one end of the nerve cord developsinto the organism’s brain.

Vertebrates Scientists classify the 42,500 species of chordatesinto smaller groups, as shown in Figure 2. The animals withineach group share similar characteristics, which may indicate thatthey have a common ancestor. Vertebrates, which includehumans, are the largest group of chordates.

Vertebrates have an internal system of bones called anendoskeleton. Endo- means “within.” The vertebrae, skull, andother bones of the endoskeleton support and protect inter-nal organs. For example, vertebrae surround and protect thenerve cord. Many muscles attach to the skeleton and makemovement possible.

■ Identify the major characteristicsof chordates.

■ List the major characteristicscommon to all vertebrates.

■ Explain the difference betweenectotherms and endotherms.

■ Name the characteristics of thethree classes of fish.

You and other vertebrate animalshave an internal skeleton thatsupports and protects yourinternal organs.

Review Vocabularyinvertebrate: an animal withouta backbone

New Vocabulary

• chordate • endotherm

• ectotherm • cartilage

Chordate Animals

Notochord

Gill slitsNerve cord

Movementof water

Figure 1 Lancelets are filterfeeders that grow to 7 cm in lengthand live in the ocean. Its pharyn-geal pouches develop into gill slits.

SECTION 1 Chordate Animals 531

Body Temperature Most vertebrate body temperatureschange as the surrounding temperature changes. These animalsare ectotherms (EK tuh thurmz), or cold-blooded animals. Fishare examples of ectotherms.

Humans and many other vertebrates are endotherms(EN duh thurmz), or warm-blooded animals. Their body tem-perature doesn’t change with the surrounding temperature.Your body temperature is usually about 37°C, but it can vary byabout 1°C, depending on the time of day. Changes of more thana degree or two usually indicate an infection or overexposure toextreme environmental temperatures.

Are humans endotherms or ectotherms?

FishThe largest group of vertebrates—fish—lives in water. Fish

are ectotherms that can be found in warm desert pools and thesubfreezing Arctic Ocean. Some species are adapted to swim inshallow freshwater streams and others in salty ocean depths.

Fish have fleshy filaments called gills, shown in Figure 3,where carbon dioxide and oxygen are exchanged. Water, con-taining oxygen, flows over the gills. When blood is pumped intothe gills, the oxygen in the water moves into the blood. At thesame time, carbon dioxide moves out of the blood in the gillsand into the water.

Most fish have pairs of fanlike fins. The top and the bottomfins stabilize the fish. Those on the sides steer and move the fish.The tail fin propels the fish through the water.

Most fish have scales. Scales are thin structures made of a bonymaterial that overlap like shingles on a house to cover the skin.

Animal Kingdom

Chordates

Tunicates Lancelets Vertebrates

Jawlessfish

Cartilaginousfish

Bony fish Amphibians Reptiles Birds Mammals

Invertebrates

Gills

Gillfilament

Figure 3 Gas exchange occurs inthe gill filaments.

Figure 2 This diagram illustrateshow vertebrates are classified.Infer what characteristics may havebeen used to classify vertebrates.


Types of Fish Scientists classify fish into three groups—bony, jawless, and

cartilaginous (kar tuh LA juh nuhs)—which are illustrated inFigure 4 on the opposite page. Bony fish have skeletons made ofbone, while jawless fish and cartilaginous fish have endoskele-tons made of cartilage. Cartilage (KAR tuh lihj) is a tough, flex-ible tissue that is similar to bone but is not as hard or brittle.Your external ears and the tip of your nose are made of cartilage.

Bony Fish About 95 percent of all fish have skeletons madeof bone. Goldfish, trout, bass, and marlins are examples ofbony fish. The body structure of a typical bony fish is shown inFigure 5. As a bony fish swims, water easily flows over its bodybecause its scales are covered with slimy mucus.

If you’ve ever watched fish in a tank, you know that they riseand sink to different levels in the water. An important adapta-tion in most bony fish is the swim bladder. This air sac helpscontrol the depth at which the fish swims. The swim bladderinflates and deflates as gases—mostly oxygen in deep-water fishand nitrogen in shallow-water fish—move between the swimbladder and the blood. As the swim bladder fills with gas, thefish rises in the water. When the gas leaves the bladder, it deflatesand the fish sinks lower in the water.

Most bony fish use external fertilization (fur tuh luh ZAY shun)to reproduce. External fertilization means that the eggs are fertilizedoutside the female’s body. Females release large numbers of eggsinto the water. Then, a male swims over the eggs, releases the sperminto the water, and many eggs are fertilized.

Changing Mass Submarinespump water into and out ofspecial chambers, whichcauses the submarine tosink or rise. In a similar way,gases move into and out ofa fish’s swim bladder. Thisallows the fish to sink or risein the water. How do fishwithout swim bladdersmove up and down in thewater? Write your answer in your Science Journal.

Swimbladder

Bonyvertebra

Scales

Intestine

Stomach

Mouth

Nostril

Liver

Brain

Heart

Gills

Figure 5 The many types ofbony fish range in size from a few millimeters to many meters in length. Infer why all bony fish might have the same basic body plan.

NGS TITLEVISUALIZING FISH DIVERSITY

SECTION 1 Chordate Animals 533

Figure 4

F ish are the most numerous and varied of all vertebrates,with more than 20,000 living species. These species canbe organized into three groups—jawless, cartilaginous,

and bony. Jawless fish are the most primitive and form thesmallest group. Cartilaginous fish include more than 600species, nearly all of them predators. Bony fish are the mostnumerous and diverse group. This page features photos of fish from each group.

JAWLESS FISH Only about70 species make up thejawless group of fish.Jawless fish are oftenparasitic. The hagfish,right, often crawls into fishtrapped in nets and eatsthem from the inside out.

Sturgeon

Whale Shark

Hammerhead shark

Hagfish

Ratfish

CARTILAGINOUS FISH The cartilage that givesthese fish their shape is a lightweight materialthat is softer than bone. The hammerhead sharkbelow has been known to use the carti-lage in its hammer-shaped head to pindown stingrays,one of its favoritemeals, before itdevours them.

ElectricRay

BONY FISH The bodiesof bony fish vary. Thefins of the coelacanthbelow have jointedbones, like the legs of many land animals.Amphibians may haveevolved from ancestorsof coelacanths.

Coelacanth

Angelfish

Wolf Eel

(t)Gerard Lacz/Animals Animals, (l)Stuart Westmoreland/Stone, (cl)D. Fleetham/OSF/Animals Animals, (cr)Joyce & Frank Burek/Animals Animals, (r)Mickey Gibson/Animals Animals, (bcl)D. Fox/OSF/Animals Animals,(bcr)Tom McHugh/Photo Researchers, (bl)Amos Nachoum/CORBIS, (br)Brandon D. Cole/CORBIS


Self Check1. List the three groups of fish. What are some of the dif-

ferences that separate these groups?

2. Compare and contrast ectothermic and endothermicanimals.

3. Form a Hypothesis Sharks don’t have swim bladders andmust move constantly or they sink. Hypothesize about theamount of food that a shark must eat compared to theamount eaten by a bony fish of the same size.

4. Think Critically In one lake, millions of fish eggs arelaid and fertilized annually. Why doesn’t the lakebecome overcrowded with fish?

SummaryChordate

• All chordates have a notochord, a nerve cord,and pharyngeal pouches at some time duringtheir development.

• A vertebrate is a chordate with an internalsystem of bones called an endoskeleton.

• Most vertebrates are ectotherms (cold-blooded animals), but humans and manyother vertebrates are endotherms (warm-blooded animals).

Fish

• Fish are ectotherms that live in the water andbelong to the largest group of vertebrates.

Types of Fish

• About 95 percent of all fish have bony skeletons.

• Lampreys, sharks, skates, and rays are fishwith a skeleton made of cartilage.

5. Make and Use Graphs Make a circle graph of thenumber of fish species currently classified: jawlessfish—70; cartilaginous fish—820; and bony fish—23,500.

Jawless and Cartilaginous Fish Only a few species of fishare classified as jawless fish, like the one in Figure 6. Jawless fishhave scaleless, long, tubelike bodies; an endoskeleton made ofcartilage; and a round, muscular mouth without a jaw. But themouth contains sharp, toothlike structures. One type of jawlessfish, the lamprey, attaches itself to a larger host fish using itsstrong mouth and toothlike structures. Its tongue has sharpridges that scrape through the host fish’s skin. The lampreyobtains nutrients by feeding on the host fish’s blood.

Sharks, skates, and rays are cartilaginous fish. They haveskeletons made of cartilage just like the jawless fish. However,cartilaginous fish have rough, sandpaperlike scales and movablejaws. Many sharks have sharp teeth made from modified scales.Most cartilaginous fish are predators.

Figure 6 Lampreys are special-ized predators. In places such asthe Great Lakes, lampreys havecaused a decrease in some fishpopulations.

The inside of a lamprey’smouth contains structuresthat are used to attach tolarger fish.

red.msscience.com/self_check_quiz(l)Science VU/Visuals Unlimited, (r)Runk/Schoenberger from Grant Heilman


AmphibiansA spy might lead a double life, but what about an animal?

Amphibians (am FIH bee unz) are animals that spend part oftheir lives in water and part on land. In fact, the term amphibiancomes from the Greek word amphibios, which means “doublelife.” Frogs, toads, newts, and salamanders, such as the red-spottedsalamander pictured in Figure 7, are examples of amphibians.

Amphibian Adaptations Living on land is different fromliving in water. Think about some of the things an amphibianmust deal with in its environment. Temperature changes morequickly and more often in air than in water. More oxygen isavailable in air than in water. However, air doesn’t support bodyweight as well as water does. Amphibians are adapted for sur-vival in these different environments.

Amphibians are ectotherms. They adjust to changes in thetemperature of their environment. In northern climates wherethe winters are cold, amphibians bury themselves in mud orleaves and remain inactive until the warmer temperatures ofspring and summer arrive. This period of cold-weather inactiv-ity is called hibernation. Amphibians that live in hot, dry envi-ronments move to cooler, more humid conditions undergroundand become inactive until the temperature cools down. Thisperiod of inactivity during hot, dry summer months is calledestivation (es tuh VAY shun).

Amphibians andReptiles

■ Describe how amphibians haveadapted to live in water andon land.

■ Explain what happens duringfrog metamorphosis.

■ Identify the adaptations thatallow reptiles to live on land.

Amphibians are sensitive to envi-ronmental changes, which mayhelp identify problems that couldaffect humans.

Review Vocabularymetamorphosis: change of bodyform that can be complete (egg,larva, pupa, adult) or incomplete(egg, nymph, adult)

New Vocabulary

• hibernation

• estivation

• amniotic egg

Figure 7 Amphibians havemany adaptations that allow forlife both on land and in the water.This red-spotted salamanderspends most of its life on land.Explain why they must return tothe water.

535S.R. Maglione/Photo Researchers


Amphibian Characteristics Amphibians are vertebrateswith a strong endoskeleton made of bones. The skeleton helpssupport their body while on land. Adult frogs and toads havestrong hind legs that are used for swimming and jumping.

Adult amphibians use lungs instead of gills to exchange oxy-gen and carbon dioxide. This is an important adaptation forsurvival on land. However, because amphibians have three-chambered hearts, the blood carrying oxygen mixes with theblood carrying carbon dioxide. This mixing makes less oxygenavailable to the amphibian. Adult amphibians also exchangeoxygen and carbon dioxide through their skin, which increasestheir oxygen supply. Amphibians can live on land, but they muststay moist so this exchange can occur.

Amphibian hearing and vision also are adapted to life onland. The tympanum (TIHM puh nuhm), or eardrum, vibratesin response to sound waves and is used for hearing. Large eyesassist some amphibians in capturing their prey.

What amphibian senses are adapted for life on land?

Land environments offer a great variety of insects as food foradult amphibians. A long, sticky tongue extends quickly to cap-ture an insect and bring it into the waiting mouth.

Figure 8 Most young amphib-ians, like these tadpoles, looknothing like their parents whenthey hatch. The larvae go throughmetamorphosis in the water andeventually develop into adult frogs that live on land.

Tadpoles hatch from eggs that arelaid in or near water.

Tadpoles use their gills for gasexchange.

Topic: AmphibiansVisit for Weblinks to information about theenvironment and amphibians.

Activity List as many possiblecauses of amphibian declines as you can find. Explain why it is important to humans to deter-mine what could be causing thesedeclines.

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SECTION 2 Amphibians and Reptiles 537

Amphibian Metamorphosis Young animals such as kittensand calves are almost miniature versions of their parents, butyoung amphibians do not look like their parents. A series ofbody changes called metamorphosis (me tuh MOR fuh sus)occurs during the life cycle of an amphibian. Most amphibiansgo through a metamorphosis, as illustrated in Figure 8. Eggs arelaid most often in water and hatch into larvae. Most adultamphibians live mainly on land.

The young larval forms of amphibians are dependent onwater. They have no legs and breathe through gills. Over time,they develop body structures needed for life on land, includinglegs and lungs. The rate at which metamorphosis occursdepends on the species, the water temperature, and the amountof available food. If food is scarce and the water temperature iscool, then metamorphosis will take longer.

Like fish, most amphibians have external fertilization andrequire water for reproduction. Although most amphibiansreproduce in ponds and lakes, some take advantage of othersources of water. For example, some species of rain forest treefrogs lay their eggs in rainwater that collects in leaves. Even moreunusual is the Surinam toad shown in Figure 9. The fertilizedeggs are placed on the mother’s back. Her skin swells and coversthe eggs to keep them moist. After metamorphosis occurs, fullyformed toads emerge from under her skin.

Figure 9 Surinam toads livealong the Amazon River. A femalecarries 60 to 100 fertilized eggs onher back. Complete metamorphosistakes 12 to 20 weeks.Explain how this would be anadvantage for young Surinamtoads.

Legs begin to develop. Soon, the tailwill disappear.

An adult frog uses lungs and skin for gas exchange.

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ReptilesReptiles come in many shapes, sizes, and colors. Snakes, lizards,

turtles, and crocodiles are reptiles. Reptiles are ectothermic verte-brates with dry, scaly skin. Because reptiles do not depend on waterfor reproduction, most are able to live their entire lives on land.They also have several other adaptations for life on land.

Types of Reptiles As shown in Figure 10, reptilian body plansvary. Turtles are covered with a hard shell, into which they with-draw for protection. Turtles eat insects, worms, fish, and plants.

Alligators and crocodiles are predators that live in and nearwater. These large reptiles live in warmer climates such as thosefound in the southern United States.

Lizards and snakes make up the largest group of reptiles.They have a highly developed sense of smell. An organ in theroof of the mouth senses molecules collected by the tongue. Theconstant in-and-out motion of the tongue allows a snake orlizard to smell its surroundings. Lizards have movable eyelidsand external ears, and most lizards have legs with clawed toes.Snakes don’t have eyelids, ears, or legs. Instead of hearingsounds, they feel vibrations in the ground.

Figure 10 Reptiles havedifferent body plans.

Sea turtles, like this loggerheadturtle, are threatened around theworld because of pollution, loss ofnesting habitat, drowning in nets,and lighted beaches.

Colorado desert fringe-toedlizards are camouflaged, whichhelps them avoid their preda-tors. These lizards mostly eatinsects, but some includeplants in their diet.

Crocodiles and American alligators like thisone build their nests on land near a body ofwater. They protect their eggs while theywait for them to hatch.

Herpetologist Most peopleare familiar with herpetolo-gists, who are responsiblefor naming and classifyingreptiles and amphibians.They often work in muse-ums or universities. Theirwork usually involves fieldtrips and gathering infor-mation for publication.What methods do taxono-mists use to determinerelationships betweenorganisms? Write youranswer in your ScienceJournal.

The rubber boa is one ofonly two species of boas inNorth America. Rubberboas have flexible jawsthat enable them to eatprey that is larger thantheir head.

(tl)Robert J. Erwin/Photo Researchers, (tr)Wendell D. Metzen/Bruce Coleman, Inc., (bl)Photo Researchers, (br)Dan Suzio/Photo Researchers

SECTION 2 Amphibians and Reptiles 539

Self Check1. Infer how a thick, dry, waterproof skin helps a reptile to

live on land.

2. Sequence the steps of a frog’s two-stage metamorphosis.

3. Infer why internal fertilization is efficient.

4. Explain how amphibians use adaptations to deal withcold winter months and hot, dry summer months.

5. Think Critically Some nonpoisonous snakes’ patternsare similar to those of poisonous snakes. How is thiscoloring an advantage for a nonpoisonous snake?

SummaryAmphibians

• Amphibians are animals that spend part oftheir lives in water and part on land.

• Although they have a strong endoskeleton tosupport their body while on land, amphibiansdepend on water for external fertilization.

• Amphibians go through a series of bodilychanges called metamorphosis.

Reptiles

• Reptiles are ectothermic vertebrates with dry,scaly skin.

• Lizards and snakes make up the largest groupof reptiles.

• Two adaptations enable reptiles to reproducesuccessfully on land: internal fertilization andlaying shell-covered, amniotic eggs.

6. Compare and contrast the exchange of oxygen andcarbon dioxide in adult amphibians and reptiles.

7. Communicate Write an explanation about why amphibians must live in wet or moist environments.

Reptile Adaptations A thick, dry, waterproof skin is anadaptation that reptiles have for life on land. The skin is coveredwith scales that reduce water loss and help prevent injury.

What are two functions of a reptile’s skin?

All reptiles have lungs for exchanging oxygen and carbondioxide. Even sea snakes and sea turtles, which can stay sub-merged for long periods of time, must eventually come to thesurface to breathe. Reptiles also have a neck that allows them toscan the horizon.

Two adaptations enable reptiles to reproduce successfully onland—internal fertilization and laying shell-covered, amniotic(am nee AH tihk) eggs. During internal fertilization, sperm aredeposited directly into the female’s body. Water isn’t necessaryfor reptilian reproduction.

The embryo develops within the moist protective environ-ment of the amniotic egg, as shown in Figure 11. The yolk sup-plies food for the developing embryo, and the leathery shellprotects the embryo and yolk. When eggs hatch, young reptilesare fully developed. In some snake species, the female does notlay eggs. Instead, the eggs are kept within her body, where theyincubate and hatch. The young snakes leave her body soon afterthey hatch.

Figure 11 Young reptileshatch from amniotic eggs.Describe the advantages of this.

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Frogs and other amphibians use external fertil-ization to reproduce. Female frogs lay hundredsof jellylike eggs in water. Male frogs then fertil-ize these eggs. Once larvae hatch, the processof metamorphosis begins.

Real-World QuestionWhat changes occur as a tadpole goes throughmetamorphosis?

Goals■ Observe how body structures change as a

tadpole develops into an adult frog.

■ Determine how long metamorphosis takes.

Materials4-L aquarium or jar aquatic plantsfrog egg mass washed gravellake or pond water lettucestereoscopic microscope (previously watch glass boiled)small fishnet large rock

Safety Precautions

WARNING: Handle the eggs with care.

Procedure1. Copy the data table in your Science Journal.

2. As a class, use the aquarium, pond water,gravel, rock, and plants to prepare a waterhabitat for the frog eggs.

3. Place the egg mass in theaquarium’s water. Usethe fishnet to separate afew eggs from themass and place themon the watch glass.Observe the eggs usingthe microscope. Recordall observations in yourdata table. Return theeggs to the aquarium.

4. Observe the eggs twice a weekuntil hatching begins. Then observe the tad-poles twice weekly. Identify the mouth, eyes,gill cover, gills, nostrils, back fin, and legs.

5. In your Science Journal, write a descriptionof how tadpoles eat cooled, boiled lettuce.

Conclude and Apply1. Explain why the jellylike coating around

the eggs is important.

2. Compare the eyes of young tadpoles withthe eyes of older tadpoles.

3. Calculate how long it takes for eggs tohatch, legs to develop, and to become a frog.

Frmg Metamorphosis

Draw the changes you observe as the egghatches and the tadpole goes throughmetamorphosis. For more help, refer to the Science Skill Handbook.

Frog Metamorphosis

Date Observations

540 CHAPTER 18 Vertebrate AnimalsStephen Dalton/Photo Researchers

Do not write in this book.

SECTION 3 Birds 541

Characteristics of Birds Ostriches have strong legs for running, and pelicans have

specialized bills for scooping fish. Penguins can’t fly but areexcellent swimmers, and house wrens and hummingbirds areable to perch on branches. These birds are different, but they,and all birds, have common characteristics. Birds are endother-mic vertebrates that have two wings, two legs, and a bill or beak.Birders, or bird-watchers, can tell where a bird lives and what iteats by looking at the type of wings, feet, and beak or bill it has.Birds are covered mostly with feathers—a feature unique tobirds. They lay hard-shelled eggs and sit on these eggs to keepthem warm until they hatch. Besides fish, birds are the mostnumerous vertebrates on Earth. Figure 12 illustrates some of themore than 8,600 species of birds and their adaptations.

Birds

Figure 12 Emus can’tfly but they have stronglegs and feet that areadapted for running.

Birds of prey, like this osprey, havesharp, strong talons that enablethem to grab their prey.An albatross glides in the air.

Horned puffins can fly and their sleek bodiesand small, pointed wings also enable themto “fly” underwater.

■ Identify the characteristicsof birds.

■ Describe the adaptations birdshave for flight.

■ Explain the function of feathers.

Humans modeled airplanes afterthe flight of birds.

Review Vocabularyappendage: structure such as aclaw, leg, or antenna that growsfrom the body

New Vocabulary

• contour feather

• down feather

(l)Photo Researchers, (cl)Jane McAlonen/Visuals Unlimited, (cr)Erwin C. Nielson/Visuals Unlimited, (r)Fritz Polking/Visuals Unlimited


Adaptations for Flight The bodies of most birds are designed for flight. They are

streamlined and have light yet strong skeletons. The inside of abird’s bone is almost hollow. Internal crisscrossing structuresstrengthen the bones without making them as heavy as mammalbones are. Because flying requires a rigid body, a bird’s tail ver-tebrae are joined together to provide the needed rigidity,strength, and stability. Birds use their tail to help them steerthrough the air. While a bird can still fly without a tail, theirflight is usually shorter and not as smooth.

What advantage do birds’ bones give them for flight?

Flight requires a lot of energy and oxygen. Birds eat insects,nectar, fish, meats, or other high-energy foods. They also havea large, efficient heart and a specialized respiratory system. Abird’s lungs connect to air sacs that provide a constant supplyof oxygen to the blood and make the bird more lightweight.

Slow-motion video shows that birds beat their wings up anddown as well as forward and back. A combination of wingshape, surface area, air speed, and angle of the wing to the mov-ing air, along with wing movements, provide an upward pushthat is needed for the flight of a bald eagle, as shown in Figure 13.Inventors of the first flying machines, such as gliders, used thebody plan of birds as a model for flight. As wind passes aboveand below the wing, it creates lift. Lift is what allows birds, aswell as planes, to stay in flight.

Figure 13 Wings provide an upward force called lift inboth birds and airplanes.

Bald eagles are able to soar for long periods of timebecause their wings have a large surface area to provide lift.

The glider gets lift from its wings the same way a baldeagle gets lift.

Topic: Wing DesignsVisit for Weblinks to information about wingdesigns of different aircraft.

Activity Draw as many wingdesigns as you can find and explainhow they are different.

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(l)Jeff Lepore/Photo Researchers, (r)Arthur R. Hill/Visuals Unlimited


SECTION 3 Birds 543

Figure 14 Microscopic barbs,located along contour feathers,keep the feathers smooth by hold-ing the individual parts of thefeather together.

Color-enhanced SEMMagnification: 844�

Modeling FeatherFunctionProcedure1. Wrap polyester fiber or

cotton around the bulb ofan alcohol thermometer.Place it into a plastic bag.Record the temperature inyour Science Journal.

2. Place a second alcoholthermometer into a plastic bag and record the temperature.

3. Simultaneously submergethe thermometers into acontainer of cold water,keeping the top of each bagabove the water’s surface.

4. After 2 min, record thetemperature of each thermometer.

Analysis1. Which thermometer had

the greater change in temperature?

2. Infer the type of featherthat the fiber or cottonmodels.

Figure 15Some species ofbirds, like chickensand these pheas-ants, are covered withfeathers when they hatch. Explain how this might be an advantage.

Functions of Feathers Birds are the only animals with feathers. They have two main

types of feathers—contour feathers and down feathers. Strong,lightweight contour feathers give adult birds their stream-lined shape and coloring. A close look at the contour feather inFigure 14 shows the parallel strands, called barbs, that branchoff the main shaft. Outer contour feathers help a bird movethrough the air or water. It is these long feathers on the wingsand tail that help the bird steer and keep it from spinning out ofcontrol. Feather colors and patterns can help identify species.They also are useful in attracting mates and protecting birdsfrom predators because they can be a form of camouflage.

Have you ever noticed that the hair on your arm stands upon a cold day? This response is one way your body works to trapand keep warm air close to your skin. Birds have down feathersthat trap and keep warm air next to their bodies. These fluffyfeathers, as shown in Figure 15, provide an insulating layerunder the contour feathers of adult birds and cover the bodiesof some young birds.

What are two ways feathers protect birds?

(tl)Tom & Pat Leeson/Photo Researchers, (tr)Andrew Syred/Science Photo Library/Photo Researchers, (b)Marcia Griffen/Animals Animals, (inset)Crown Studios


Self Check1. List several reasons why birds preen their feathers.

2. Describe how a bird’s skeletal system, respiratory sys-tem, and circulatory system all work together to enableit to fly.

3. Think Critically Explain why birds can reproduce inAntarctica when temperatures are below 0°C.

SummaryCharacteristics of Birds

• Birds are endothermic vertebrates, have twowings, two legs, and a bill or beak, and arecovered mostly with feathers.

Adaptations for Flight

• Birds are streamlined and have light, yetstrong, skeletons.

• The inside of a bird’s bone is almost hollow.

• Wings provide an upward force called lift.

Functions of Feathers

• Birds have contour feathers that help themmove through the air or water.

• Down feathers trap and keep warm air next to birds’ bodies.

4. Use an Electronic Spreadsheet During every 10 sec-onds of flight, a crow beats its wings 20 times, a robin23 times, a chickadee 270 times, and a hummingbird700 times. Use a spreadsheet to find out how manytimes the wings of each bird beat during a 5-minute flight.

Care of Feathers Clothes keep you warm only if they are dryand in good condition. In a similar way, well-maintained feath-ers keep birds dry, warm, and able to fly. Birds preen to clean andreorganize their feathers. During preening, many birds alsospread oil over their bodies and feathers. This oil comes from agland found on the bird’s back at the base of its tail. The oilhelps keep the skin soft, and feathers and scales from becomingbrittle. The oil does not waterproof the feathers as once thought.It is the arrangement of a feather’s microscopic structures thatrepels water more than the oil does. Cormorants, like the one inFigure 16, have wettable outer feathers that must be air-driedafter diving for food.

Figure 16 Cormorants’ feathersget wet when they go underwaterto catch fish. When they return totheir roost, they have to hold theirwings out to dry.

red.msscience.com/self_check_quizVisuals Unlimited


SECTION 4 Mammals 545

Mammal Characteristics How many different kinds of mammals can you name?

Moles, dogs, bats, dolphins, horses, and people are all mam-mals. They live in water and in many different climates onland. They burrow through the ground and fly through the air.

Mammals are endothermic vertebrates. They have mam-mary glands in their skin. In females, mammary glands pro-duce milk that nourishes the young. A mammal’s skin usuallyis covered with hair that insulates its body from cold and heat. Italso protects the animal from wind and water. Some mammals,such as bears, are covered with thick fur. Others, like humans,have only patches of thick hair while the rest of their body issparsely covered with hair. Still others, like the dolphins shownin Figure 17, have little hair. Wool, spines, quills, and certainhorns are modified hair. What function do you think quills andspines serve?

Mammary Glands Mammals put a great deal of time andenergy into the care of their young, even before birth. Whenfemale mammals are pregnant, the mammary glands increase insize. After birth, milk is produced and released from theseglands. For the first weeks or months of a young mammal’s life,the milk provides all of the nutrition the young mammal needs.

Mammals

■ Identify the characteristics com-mon to all mammals.

■ Explain how mammals areadapted to the differentenvironments on Earth.

■ Distinguish among monotremes,marsupials, and placentals.

All mammals have similar bodystructures.

Review Vocabularysymmetry: refers to the arrange-ment of the individual parts of anobject that can be divided intomatching halves

New Vocabulary

• herbivore • monotremes

• carnivore • marsupial

• omnivore • placental

Figure 17 The type of hair mammals have varies from speciesto species.Explain the advantages and disad-vantages of having hair.

Porcupines have fur next to theirskin but sharp quills on the outside.Quills are modified hairs.

Dolphins do not have much hair ontheir bodies. A layer of fat under theskin acts as insulation.

(l)Gerard Fuehrer/Visuals Unlimited, (r)Francois Gohier/Photo Researchers

Different Teeth Mammals have teeth that are specialized for the type of food they eat. Plant-eating animals are calledherbivores. Animals that eat meat are called carnivores, andanimals that eat plants and animals are called omnivores. Asshown in Figure 18, you usually can tell from the kind of teetha mammal has whether it eats plants, other animals, or both.The four types of teeth are incisors, canines, premolars, andmolars.

How are herbivores, carnivores, and omnivoresdifferent?

Body Systems Mammals live active lives. They run, swim,climb, hop, and fly. Their body systems must interact and beable to support all of these activities.

Mammals have well-developed lungs made of millions ofmicroscopic sacs called alveoli, which enable the exchange ofcarbon dioxide and oxygen during breathing. They also have acomplex nervous system and are able to learn and remembermore than many other animals. The brain of a mammal is usu-ally larger than the brain of other animals of the same size.

All mammals have internal fertilization. After an egg is fer-tilized, the developing mammal is called an embryo. Most mam-mal embryos develop inside a female organ called the uterus.Mammals can be divided into three groups based on how theirembryos develop. The three groups of mammals are mono-tremes, marsupials, and placentals.

Figure 18 Mountain lions arecarnivores. They have sharp caninesthat are used to rip and tear flesh.

Inferring How BlubberInsulatesProcedure1. Fill a self-sealing plastic

bag about one-third fullwith solid vegetable shortening.

2. Turn another self-sealingplastic bag inside out. Placeit inside the first bag so youare able to zip one bag tothe other. This is a blubbermitten.

3. Put your hand in theblubber mitten. Place yourmittened hand in ice waterfor 5 s. Remove the blubbermitten when finished.

4. Put your other bare hand inthe same bowl of ice waterfor 5 s.

Analysis1. Which hand seemed colder? 2. Infer the advantage a layer

of blubber would give in thecold.

Herbivores, like this beaver, haveincisors that cut vegetation and large,flat molars that grind it.

Humans are omnivores. They have incisors that cutvegetables, premolars that aresharp enough to chew meat,and molars that grind food.



Mammal Types The duck-billed platypus, shown in

Figure 19, along with two species of echid-nas (ih KID nuhs)—spiny anteaters—belong to the smallest group of mammalscalled the monotremes. They are differentfrom other mammals because monotremeslay eggs with tough, leathery shells instead ofhaving live births. The female incubates theeggs for about ten days. Monotremes alsodiffer from other mammals because theirmammary glands lack nipples. Instead, themilk seeps through the skin onto their fur.The young monotremes then nurse by licking the milk from the fursurrounding the mammary glands. Duck-billed platypuses andspiny anteaters are found in New Guinea and Australia.

Figure 19 Duck-billed platypusesand spiny anteaters are the onlyspecies of mammals that lay eggs.

Working with Percentages

1. On a typical day during those four months, how much time do elephant seals stay at thesurface from 11:00 P.M. until 6:00 A.M.?

2. On a typical day during those four months, how much time do elephant seals spendunderwater from 9:00 A.M. until 6:00 P.M.?

HOW MUCH TIME? It is estimated that during the four months elephant seals spend at sea,90 percent of their time is spent underwater. On a typical day, how much of the timebetween the hours of 10:00 A.M. and 3:00 P.M. does the elephant seal stay at the surface?

SolutionThis is what you know:

This is what you need toknow:

This is the procedure youneed to use:

Check your answer:

● Total time: From 10:00 A.M. to 3:00 P.M. is 5 h.1 h � 60 min, so 5 � 60 � 300 min

● % of time on surface � 100% � 90% � 10% � 0.10

How much time is spent on the surface?

● Use this equation:surface time � (total time)(% of time on surface)

● Substitute the known values:surface time � (300 min)(0.10) � 30 min

Divide your answer by the total time. Is the answer equalto 10 percent?

For more practice, visit red.msscience.com/math_practice

Dave Watts/Tom Stack & Associates



Marsupials Most marsupials carry their young in a pouch.Their embryos develop for only a few weeks within the uterus.When the young are born, they are without hair, blind, andnot fully formed. Using their sense of smell, the young crawltoward a nipple and attach themselves to it. Here they feedand complete their development. Most marsupials—such askangaroos, koalas, Tasmanian devils, and wallabies—live inAustralia, Tasmania, and New Guinea. The opossum, shownin Figure 20, is the only marsupial that lives in North America.

Why do most marsupials have a pouch?

Placentals The largest number of mammals belongs to agroup called placentals. Placentals are named for the placenta,which is a saclike organ that develops from tissues of the embryoand uterus. In the placenta, food, oxygen, and wastes areexchanged between the mother’s blood and the embryo’s blood,but their bloods do not mix. An umbilical cord, as seen in Figure 21, connects the embryo to the placenta. Food and oxy-

gen are absorbed from the mother’sblood for the developing young. Bloodvessels in the umbilical cord carry foodand oxygen to the developing young,then take away wastes. In the placenta,the mother’s blood absorbs wastesfrom the developing young. This timeof development, from fertilization tobirth, is called the gestation period.Mice and rats have a gestation periodof about 21 days. Human gestationlasts about 280 days. The gestationperiod for elephants is about 616 days,or almost two years.

Figure 20 Marsupials,such as opposums, are bornbefore they are completelydeveloped. Newborn marsu-pials make the journey to anipple that is usually in themother’s pouch where theywill finish developing.

Figure 21 Placental embryosrely on the umbilical cord to bringnutrients and to remove wastes.Your navel is where your umbilicalcord was connected to you.

(tl)S.R. Maglione/Photo Researchers, (tr)SuperStock, (b)Carolina Biological Supply/PhotoTake, NYC


Self Check1. Infer why the brain of a mammal usually is larger

than the brain of other animals of the same size.

2. Explain why animals are in trouble today.

3. List examples of how the teeth of mammals are specialized.

4. Research Information The monotremes are the small-est group of mammals. Using the library and onlineresources, explain where monotremes likely originatedfrom and what continents monotreme fossils have beenfound on.

5. Think Critically Compare and contrast the develop-ment of embryos in placentals and marsupials.

SummaryMammal Characteristics

• Mammals have mammary glands that pro-duce milk for their young.

• Mammals have teeth that are specialized forthe type of food they eat.

• The body systems of mammals are designedto support activities such as running, swim-ming, climbing, hopping, and flying.

Mammal Types

• The smallest group of mammals, calledmonotremes, lay eggs with leathery shells.

• Marsupials are born before they are com-pletely developed, and most marsupials carrytheir young in a pouch.

• The placentals are the largest group of mammals.

Mammals Today

• More than 4,000 species of mammals exist on Earth today.

6. Solve One-Step Equations The tallest mammal is thegiraffe at 5.6 m. Calculate your height in meters anddetermine how many of you it would take to be as tall as a giraffe.

Mammals Today More than 4,000 species of mammals exist on

Earth today. Mammals can be found on every conti-nent, from cold arctic regions to hot deserts. Eachkind of mammal has certain adaptations that enableit to live successfully within its environment.

Mammals, like all other groups of animals, havean important role in maintaining a balance in theenvironment. Large carnivores, such as wolves, helpcontrol populations of herbivores, such as deer andelk, thus preventing overgrazing. Bats and othersmall mammals such as honey possums help polli-nate flowers. Other mammals unknowingly pick up plant seedsin their fur and distribute them. However, mammals and otheranimals are in trouble today because their habitats are beingdestroyed. They are left without enough food, shelter, and spaceto survive as millions of acres of wildlife habitat are damaged bypollution or developed for human needs. The grizzly bear, pic-tured in Figure 22, lives in North America and Europe and is anendangered species—a species in danger of becoming extinct—in most of its range because of habitat destruction.

Figure 22 Grizzly bears, some-times called brown bears, used torange all over the western half ofthe United States. Now, because ofhuman settlement, habitat loss,and overhunting, grizzly bears arefound only in Alaska, Montana,Wyoming, Idaho, and Washington.

red.msscience.com/self_check_quizTed Kerasote/Photo Researchers


Model and InventModel and Invent

HcMES FOR ENDANGEREDANIMALS

550 CHAPTER 18

Goals■ Research the natural

habitat and basic needsof one endangered ver-tebrate species.

■ Research and modelan appropriate zoo,animal park, or aquar-ium environment forthis animal. Workingcooperatively with yourclassmates, design anentire zoo or animalpark.

Possible Materialsposter boardmarkers or colored pencilsmaterials with which to

make a scale model

Real-World QuestionZoos, animal parks, and aquariumsare safe places for endangered ani-mals. Years ago, captive animals werekept in small cages or behind glasswindows. The animals were on dis-play like artwork in a museum. Now,some captive animals are kept inexhibit areas that closely resembletheir natural habitats. These areasprovide suitable environments for theanimals so that they can reproduce,raise young, and have healthier andlonger lives. What types of environ-ments are best suited for raising ani-mals in captivity? How canendangered animals be rescued?

(t)Mark Newman/Photo Researchers, (b)Alan Carey

Make a Model1. Choose an endangered animal to research. Find

out where this animal is found in nature. Whatdoes it eat? Who are its natural predators? Does itexhibit unique territorial, courtship, or other typesof social behavior? How is this animal adapted to itsnatural environment?

2. Why is this animal considered to be endangered?

3. Design a model of your proposed habitat in whichthis animal can live successfully.

4. Research how a zoo, animal park, or aquarium pro-vides a habitat for this animal. This information canbe obtained by contacting a zoo, animal park, or aquarium.

5. Present your design plan to your class in the form of a poster, slide show, orvideo. Compare your proposed habitat with that of the animal’s natural environ-ment. Make sure you include a picture of your animal in its natural environment.

Test the Model1. Using all of the information you have gathered, create a model exhibit area for

your animal.

2. List other plants and animals that might be present in the exhibit area.

Analyze Your Data1. Decide whether all of the endangered animals studied in this activity could

exist in the same zoo or wildlife preserve.

2. Predict which animals could be grouped together in exhibit areas.

Conclude and Apply1. Determine how much land your zoo or

wildlife preservation needs. Which animalsrequire the largest habitat?

2. Using the information provided by all your class-mates, design a zoo or wildlife preserve for themajority of endangered animals you’ve studied.

3. Analyze which type of problems might exist inyour design.

LAB 551

Give an oral presentation on endangeredanimals and wildlife conservation toanother class of students using your model.Use materials from zoos to supplement yourpresentation.

Mella Panzella/Animals Animals

What killed the dinosaurs? Here is one theory.

T iny bits of dust from comets andasteroids constantly sprinkle down onEarth. This cosmic dust led scientists

Luis and Walter Alvarez to a hypothesisabout one of science’s most intriguing mysteries: What caused the extinction of dinosaurs?

It began some 65 million years ago whenmass extinction wiped out 60 percent of allspecies alive on Earth, including the dinosaurs.Walter Alvarez and his father Luis Alvarezwere working together on a geology expeditionin Italy analyzing a layer of sedimentary rock.Using dating techniques, they were able todetermine that this layer was deposited atroughly the same time that the dinosaursbecame extinct. The younger Alvarez hypothe-sized that the rock might hold some clue to themass extinction.

The Alvarezes proposed that the sedi-mentary rock be analyzed for the presenceof the element iridium. Iridium is a denseand rare metal found in very low concen-trations in Earth’s core. The scientistsexpected to find a small amount of iridium.To their surprise, the sedimentary rock contained unusually high levels of iridium.

High concentrations of iridium are be-lieved to be common in comets and asteroids.

If a huge asteroid collided with Earth, itsimpact would send tons of dust, debris, andiridium high into the atmosphere. The dustwould block the Sun, causing global tempera-tures to decrease, plants to die, and animals tostarve, resulting in a mass extinction. When thedust settled, iridium would fall to the ground asevidence of the catastrophe.

The Alvarez hypothesis, published in1980, is still debated. However, it has sincebeen supported by other research, includingthe discovery of a huge, ancient crater inMexico. Scientists theorize that this craterwas formed by the impact of an asteroid asbig as Mount Everest.

Did asteroids kill the dinosaurs? An artist drew this picture to show howEarth might have looked.

SOMETIMESGREAT

DISCOVERIESHAPPEN BY ACCIDENT!

Write Imagine that an asteroid has collided with Earth. You are one of the few human survivors. Write a five-day journal describing the events that take place.

For more information, visitred.msscience.com/oops

Mark Garlick/Science Photo Library/Photo Researchers


Chordate Animals

1. All chordates, at some time in their development, have a notochord and gill slits.

2. Endothermic animals maintain an internalbody temperature. Ectothermic animalshave body temperatures that change withthe temperature of their surroundings.

3. The three classes of fish are jawless,cartilaginous, and bony. All fish areectotherms.

Amphibians and Reptiles

1. Amphibians are ectothermic vertebratesthat spend part of their lives in water andpart on land. Most amphibians go througha metamorphosis, which includes water-living larva and land-living adult stages.

2. Reptiles are ectothermic land animals thathave dry, scaly skin.

3. Most reptiles lay eggs with a leathery shell.

Birds

1. Birds are endotherms with feathers, andthey lay eggs enclosed in hard shells.

2. Wings, feathers, and a light, strong skeletonare adaptations that allow birds to fly.

Mammals

1. Mammals are endotherms that have mammary glands. All mammals have some hair.

2. Mammals have specialized teeth thatmostly determine what foods they eat.

3. There are three groups of mammals.Monotremes lay eggs. Most marsupials have pouches in which embryos develop.Placentals have a placenta, and the embryosdevelop within the female’s uterus.

4. Mammals have a variety of adaptations that allow them to live in different types of environments.

CHAPTER STUDY GUIDE 553

Vertebrate Characteristics

Characteristic Fish Amphibians Reptiles

Body temperature ectotherm

Body covering

Respiratory organs

Method of movement legs

Fertilization internal

Kind of egg lacks shell

Copy and complete the following table comparing the characteristics of fish, amphibians, and reptiles.

red.msscience.com/interactive_tutor(t)John Cancalosi/DRK Photo, (c)Alvin E. Staffan/Photo Researchers

Do not write in this book.


Using complete sentences, explain how thevocabulary words in each pair listed below are alike and how they are different.

1. contour feather—down feather

2. ectotherm—endotherm

3. chordate—cartilage

4. estivation—hibernation

5. carnivore—herbivore

6. marsupial—monotreme

7. amniotic egg—monotreme

8. down feather—endotherm

9. omnivore—carnivore

10. placental—marsupial

Choose the word or phrase that best answers thequestion.

11. Which of the following animals have fins,scales, and gills?A) amphibians C) reptilesB) crocodiles D) fish

12. Which of these is an example of acartilaginous fish?A) trout C) sharkB) bass D) goldfish

13. Which of the following fish has a swimbladder?A) shark C) troutB) lamprey D) skate

14. Which of the following is an adaptationthat helps a bird fly?A) lightweight bonesB) webbed feetC) hard-shelled eggsD) large beaks

15. Which of the following animals has skinwithout scales? A) dolphin C) lizardB) snake D) fish

16. Lungs and moist skin are characteristics ofwhich of the following vertebrates?A) amphibians C) reptilesB) fish D) lizards

17. Which of these are mammals that layeggs?A) carnivores C) monotremesB) marsupials D) placentals

18. Which of the following animals eat onlyplant materials?A) carnivores C) omnivoresB) herbivores D) endotherms

Use the illustration below to answer question 19.

19. What is the primary function of thefeather in the illustration above?A) flight C) attracting matesB) insulation D) repelling water

554 CHAPTER REVIEW

amniotic egg p. 539carnivore p. 546cartilage p. 532chordate p. 530contour feather p. 543down feather p. 543ectotherm p. 531endotherm p. 531

estivation p. 535herbivore p. 546hibernation p. 535marsupial p. 548monotreme p. 547omnivore p. 546placental p. 548

red.msscience.com/vocabulary_puzzlemakerBuddy Mays/CORBIS


20. Discuss why there are fewer species ofamphibians on Earth than any other type of vertebrate.

21. List the important adaptation that allows a reptile to live and reproduce on landwhile an amphibian must return to waterto reproduce and complete its life cycle.

22. Draw a Conclusion You observe a mammal in afield catching and eating a rabbit. Whatkind of teeth does this animal probablyhave? Explain how it uses its teeth.

23. Explain how the development of the amni-otic egg led to the early success of reptileson land.

24. Compare and contrast the teeth of herbivores,carnivores, and omnivores. How is eachtype of tooth tooth adapted to the ani-mal’s diet?

25. Draw a Conclusion How can a bird like thearctic tern stand on ice and not lose toomuch body heat?

26. Concept Map Copy and complete this concept map that describes groups ofmammals.

27. Identify and Manipulate Variables and ControlsDesign an experiment to find out theeffect of water temperature on frog eggdevelopment.

28. Debate Reptiles are often portrayed as dan-gerous and evil in fairy tales, folktales, andother fictional stories. Nonfiction informa-tion about reptiles presents another view.What is your opinion? Use the library oronline resources to find evidence to sup-port your position. Debate this issue with aclassmate who has an opposing opinion.

CHAPTER REVIEW 555

Use the following table to answer questions 29 and 30.

29. Population Changes Make a line graph from thedata in the table above.

30. Fish Population Density Calculate the averagenumber of bull trout per 100-m2 section ofstream for all years combined. Which years hada larger population than the average?

31. Egg Development A salamander egg in water at 15–16°C will hatch after 60–70 days. A sala-mander egg in water at 17°C will hatch after69–92 days. What are the minimum and maxi-mum differences in hatching times?

Bull Trout Population

Year Number per

100-m2 Section

1996 4

1997 7

1998 5

1999 3

2000 4

have have

example example

Shelled eggs

Mammals

Placentals

groups are

are divided into three groupsbased on

have

example

red.msscience.com/chapter_review


Record your answers on the answer sheetprovided by your teacher or on a sheet of paper.

1. Which of the following is NOT anectotherm?A. amphibian C. reptileB. mammal D. fish

2. Three of the following are made of carti-lage. Which is made of bone?A. goldfishB. earsC. tip of your noseD. jawless fish

3. Which of the following is NOT a group offish?A. cartilaginous C. bonyB. jawless D. angelfish

Use the photo below to answer questions 4 and 5.

4. The fish in the illustration is an example ofA. jawless fish C. bony fishB. ratfish D. cartilaginous fish

5. Which of the following is NOT one of itstraits?A. scaleless, long, tubelike bodyB. rough, sandpaperlike scalesC. round, muscular mouth without a jawD. sharp, toothlike structures

6. Which of the following spend part of theirlife on land and part in the water?A. reptiles C. amphibiansB. fish D. mammals

Use the photo below to answer questions 7 and 8.

7. This animal becomes inactive in coldweather using which of the following?A. hibernation C. hydrationB. estivation D. hyperthermia

8. This animal has three of the following char-acteristics. Which one doesn’t it possess?A. three-chambered heartB. vibrating tympanumC. exchange of oxygen and carbon dioxide

through skinD. lays shell-covered, amniotic eggs

9. Which of the following is a monotreme?A. kangaroo C. wallabyB. koala D. platypus

556 STANDARDIZED TEST PRACTICE

Listen and Read Listen carefully to the instructions from theteacher and read the directions and each question carefully.

STANDARDIZED TEST PRACTICE 557

Record your answers on the answer sheetprovided by your teacher or on a sheet of paper.

Use the illustration below to answer questions 10 and 11.

10. This animal has a particular method ofswimming to different levels. Explain howthey do this.

11. How do most of these animals reproduce?

12. How are jawless fish different from bonyfish?

13. How do amphibians survive hot summers?

14. Animals need to get oxygen and dispose ofcarbon dioxide. How do adult amphibiansget enough oxygen and get rid of carbondioxide?

15. Birds use a special method to keep theirfeathers in good shape. What is thisprocess called and how do they do it?

16. What characteristics do all mammals havein common?

17. Mammals also can be classified by whatthey eat. What are these three differentclassifications?

18. Name two ways that monotremes are different from other animals.

Record your answers on a sheet of paper.

19. Animals possess a great variety of bodyplans that help them reproduce. Compareand contrast the way fish and mammalsreproduce.

20. Animals may have to compete with oneanother for survival. Explain how someanimals compete for the same food andhow predators can help in this process.

Use the illustration below to answer questions 21 and 22.

21. Walter Alvarez and his father, Luis Alvarez,came up with a theory as to howdinosaurs became extinct. This illustrationis an artist’s rendering of this theory.Explain it.

22. They did not set out to determine howdinosaurs became extinct. How did thetheory depicted in the illustration comeabout?

23. Animals have various outer coverings forprotection and various functions.Compare and contrast the various outercoverings of birds and mammals.

DEBRIS

Tampico

Tropic of Cancer

Mexico City

Mexico

Guatemala

Belize

YucatanPeninsula

Gulf of Mexico

IMPACT SITE

Swimbladder

Bonyvertebra

ScalesIntestine

Stomach

Mouth

Nostril

Liver

Brain

HeartGills

red.msscience.com/standardized_test


vertebrate - mryoungblut.weebly.com · the vertebrae, skull, and other bones of the endoskeleton...

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