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What You’ll Learn■ You will distinguish between
innate and learned behavior.■ You will identify the adaptive
value of specific types ofbehavior.
Why It’s ImportantAnimals have patterns of behav-ior that help them survive andreproduce. Some of thesebehavior patterns are inheritedand some are learned. You willrecognize that humans, likeother animals, have both typesof behavior, and that thesebehavior patterns enable you tosurvive as well.
Animal BehaviorAnimal Behavior
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In a honeybee hive, a singlequeen lays all the eggs. Workerbees build combs, store pollenand nectar, feed the queen, andkeep the hive ventilated andclean. The sole purpose of thedrones is to mate with thequeen. In this highly organizedsystem, some behaviors areinnate, while others are learned.
Understandingthe Photo
ca.bdol.glencoe.com
Gerry Ellis/Minden Pictures
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33.1SECTION PREVIEWObjectivesDistinguish among thetypes of innate behavior.Demonstrate, by exam-ple, the adaptive value ofinnate behavior.
Review Vocabularypopulation: group of
organisms of onespecies that interbreedand live in the sameplace at the same time(p. 38)
New Vocabulary behaviorinnate behaviorreflexfight-or-flight responseinstinctcourtship behaviorterritoryaggressive behaviordominance hierarchycircadian rhythmmigrationhibernationestivation
What is behavior?A peacock displaying his colorful tail, a whale spending the winter months
in the ocean off the coast of southern California, and a lizard seeking shadefrom the hot desert sun are all examples of animal behavior. Behavior isanything an animal does in response to a stimulus. A stimulus is an environ-mental change that directly influences the activity of an organism. The pres-ence of a peahen stimulates a peacock to open its tail feathers and strut.Environmental cues, such as a change in day length, might be the stimulusthat causes the whale to leave its summertime arctic habitat. Heat stimulatesthe lizard to seek shade. Figure 33.1 shows two examples of stimuli thataffect animal behavior.
Do you exhibit innate behavior?Finding Main Ideas Construct an outline about innate behavior. Use the red and blue titles in this section as a guideline. As you read the paragraphs that follow the titles, add important information and vocabulary words to your outline. An example follows.I. Inherited Behavior
A. Natural selection favors certain behaviors1. Individuals with behavior
that makes them more successful at surviving and reproducing tend to produce more offspringthan individuals without the behavior.
2. Inherited behavior of animals is called innate behavior.3. Innate behaviors include fixed action patterns, automatic
responses, and instincts.Use your outline to help you answer questions in the Section Assessmenton page 867. For more help, refer to Outline in the Skill Handbook.
Innate Behavior
Figure 33.1Animals respond to stimuliby exhibiting a variety ofbehaviors.
859
Squirrels collect andstore acorns and nuts in response to shorterday length and coldertemperatures.
A
Cedar waxwings and their nestlings
Spots that resemble the eyes ofowls cause predatory birds to stoptheir pursuit of this insect.
B
(t)Ralph Reinhold/Animals Animals, (bl)Tom & Pat Leeson/DRK Photo, (br)Holt Studios International/Photo Researchers
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Animals carry on many activities—such as getting food, avoiding preda-tors, caring for young, finding shelter,and attracting mates—that enablethem to survive and reproduce. Thesebehavior patterns, therefore, haveadaptive value. For example, a parentgull that is not incubating eggs or car-ing for chicks joins a noisy flock ofgulls to dive for fishes. If the parentcannot catch a lot of fishes, not onlywill it die, but its chicks will not surviveeither. Therefore, this feeding behav-ior has adaptive value for the gull.
Inherited BehaviorInheritance plays an important role
in the ways animals behave. You don’texpect a hummingbird to tunnelunderground or a mouse to fly. Yet,why does a mouse run away when acat appears? Why does a humming-bird fly south for the winter? Thesebehavior patterns are genetically pro-grammed. An animal’s genetic make-up determines how that animal reactsto certain stimuli.
Natural selection favors certain behaviors
Often, a behavior exhibited by ananimal species is the result of naturalselection. The variability of behavioramong individuals affects their abilityto survive and reproduce. Individualswith behavior that makes them moresuccessful at surviving and reproduc-ing tend to produce more offspringthan individuals without the behavior.These offspring will inherit thegenetic basis for the successful behav-ior. You can observe the behavior ofisopods in the MiniLab on this page.
Explain how animalactivities that enable them to surviveand reproduce are a result of natural selection.
Tape
Blackpaper
Lightsource
Top of dish
Moistpapertoweling
Data Table
Number of Isopods PresentObservationin Minutes Light Side Dark Side
5
10
15
20
25
ExperimentTesting an Isopod’s Response to Light Isopods, such as pillbugs and sow bugs, are common arthropods on sidewalks orpatios. They are actually land crustaceans and respire throughgill-like organs that must be kept moist at all times.
Procedure! Copy the data table.@ Prepare a plastic dish using the diagram as a guide.
Moisten the paper toweling.
# Place six isopods in the center of the dish and quickly addthe cover. Place the dish near a lamp or next to a class-room window with light. Have the light strike the dish asshown in the diagram. CAUTION: Treat isopods gently.
$ Wait five minutes and observe the dish. Count and recordin your data table the number of isopods on the dark orlight side. This is your “five minute observation.”
% Repeat step 4 three more times, waiting five minutesbefore each observation.
Analysis 1. Analyze Do isopods tend to move toward light or dark
areas? Support your answer with specific numbers fromyour data.
2. Infer Is the behavior of isopods toward light or darkness innate or learned? Explain your answer.
3. Think Critically What might be the adaptive advantagefor the observed isopod behavior? Explain how natural selection may have influenced this isopod behavior.
4. Make and Use Graphs Prepare a bar graph that depictsyour data.
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Inherited behavior of animals iscalled innate (ih NAYT) behavior. Atoad captures prey by flipping out itssticky tongue. To capture prey, a toadmust first be able to detect and followits movement. Toads have “insectdetector” cells in the retinas of theireyes. As an insect moves across a toad’sline of sight, the “insect detector” cellssignal the brain of the prey’s changingposition, thus initiating an innateresponse; the toad’s tongue flips out.Figure 33.2 shows a toad that cap-tured its prey using an innate behaviorknown as a fixed-action pattern. Afixed-action pattern is an unchange-able behavior pattern that, once initi-ated, continues until completed.
Genes form the basis of innate behavior
Through experiments, scientistshave found that an animal’s hormonalbalance and its nervous system—espe-cially the sense organs responsible forsight, touch, sound, or odor identifica-tion—affect how sensitive the individ-ual is to certain stimuli. In fire antcolonies, a single gene influences theacceptance or rejection of the antqueen, thereby controlling the colo-ny’s social structure. Innate behaviorincludes fixed-action patterns, auto-matic responses, and instincts. You canobserve the response of animals to cer-tain stimuli in the BioLab at the end ofthis chapter.
Automatic Responses What happens if something quickly
passes in front of your eyes or if some-thing is thrown at your face? Your firstreaction is to blink and jerk back yourhead. Even if a protective clear shield isplaced in front of you, you can’t stopyourself from behaving this way whenthe object is thrown. This reaction is anexample of the simplest form of innate
behavior, called a reflex. A reflex (REE
fleks) is a simple, automatic response toa stimulus that involves no consciouscontrol. Figure 33.3 shows an exampleof a reflex.
The adaptive value of anotherautomatic response is obvious. Thinkabout a time when you were suddenlyscared. Immediately, your heartbegan to beat faster. Your skin gotcold and clammy, your respirationincreased, and maybe you trembled.You were having a fight-or-flightresponse. A fight-or-flight responsemobilizes the body for greater activ-ity. Your body is being prepared toeither fight or run from the danger. Afight-or-flight response is automaticand controlled by hormones and thenervous system.
33.1 INNATE BEHAVIOR 861(t)David M. Dennis, (b)KS Studio
Figure 33.2A toad can starve eventhough it is surroundedby dead insects becauseit cannot recognize non-moving animals as prey.
Figure 33.3Reflexes have survivalvalue for animals.When you accidentallytouch a hot stove, youjerk your hand awayfrom the hot surface.The movement savesyour body from seriousinjury.
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instinct from the Latin wordinstinctus, meaning“impulse”; Aninstinct is a complexpattern of innatebehavior.
Instinctive Behavior Compare the fixed-action pattern
of a toad capturing prey with a fight-or-flight response. Both are quick,automatic responses to stimuli. Butsome behaviors take a longer timebecause they involve more complexactions. An instinct (IHN stingt) is acomplex pattern of innate behavior.Instinctive behavior begins when theanimal recognizes a stimulus and con-tinues until all parts of the behaviorhave been performed.
As shown in Figure 33.4, greylaggeese instinctively retrieve eggs thathave rolled from the nest. They willgo through the motions of eggretrieval even if the eggs roll or aretaken away until they are comfort-ably back on their nest. If they seethe egg has not been retrieved theybegin the process again.
Courtship behavior ensuresreproduction
Much of an animal’s courtshipbehavior is instinctive. Courtshipbehavior is the behavior that malesand females of a species carry outbefore mating. Like other instinctivebehaviors, courtship has evolvedthrough natural selection. Imaginewhat would happen to the survival ofa species if members were unable torecognize other members of thatsame species. Individuals often can
recognize one another by the behav-ior patterns each performs. Incourtship, behavior ensures thatmembers of the same species findeach other and mate. Obviously, suchbehavior has an adaptive value for thespecies. Different species of fireflies,for example, can be seen at dusk flash-ing distinct light patterns. However,female fireflies of one species respondonly to those males exhibiting thespecies-correct flashing pattern.
Some courtship behaviors help pre-vent females from killing males beforethey have had the opportunity tomate. For example, in some spiders,the male is smaller than the femaleand risks the chance of being eaten ifhe approaches her. Before mating, themale in some species presents thefemale with an object, such as aninsect wrapped in a silk web. Whilethe female is unwrapping and eatingthe insect, the male is able to matewith her without being attacked. Aftermating, however, the male may beeaten by the female anyway.
In some species, such objects play animportant role in allowing the femaleto exercise a choice as to which male tochoose for a mating partner. Thehanging fly, shown in Figure 33.5, issuch a species.
Explain the resultsof natural selection in the courtshipbehavior of fireflies.
862 ANIMAL BEHAVIOR
Figure 33.4The female greylaggoose instinctivelyretrieves an egg thatshe sees has rolled outof the nest. She doesthis by arching her neckaround the stray eggand moving it like ahockey player advanc-ing a puck. The femalegoose will retrievemany objects outsidethe nest, includingbaseballs and tin cans.Explain Why is thisbehavior considereda fixed-action pattern?
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Territoriality reducescompetition
You may have seen a chipmunkchase another chipmunk away fromseeds on the ground under a birdfeeder. The chipmunk was defendingits territory. A territory is a physicalspace an animal defends against othermembers of its species. It may containthe animal’s breeding area, feedingarea, and potential mates, or all three.
Animals that have territories willdefend their space by driving awayother individuals of the same species.For example, a male sea lion patrolsthe area of beach where his harem offemale sea lions rests. He does notbother a neighboring male that has aharem of his own because both havemarked their territories, and eachrespects the common boundaries. Butif an unattached, young male tries toenter the sea lion’s territory, theowner of the territory will attack anddrive the intruder away from hisharem.
Although it may not appear so, set-ting up territories actually reducesconflicts, controls population growth,and provides for efficient use of envi-ronmental resources. When animalsspace themselves out, they don’t com-pete for the same resources within alimited space. This behavior improvesthe chances of survival of the young,and, therefore, survival of the species.If the male has selected an appropri-ate site and the young survive, theymay inherit his ability to select anappropriate territory. Therefore, ter-ritorial behavior has survival value,not only for individuals, but also forthe species. The male sticklebackshown in Figure 33.6 is another ani-mal that exhibits territoriality, espe-cially during breeding season.
Recall that pheromones are chemi-cals that communicate informationamong individuals of the same
species. Many animals producepheromones to mark territorialboundaries. For example, wolf urinecontains pheromones that warn otherwolves to stay away. The male prong-horn antelope uses a pheromonesecreted from facial glands. Oneadvantage of using pheromones isthat they work both day and night,and whether or not the animal thatmade the mark is present.
33.1 INNATE BEHAVIOR 863(t)J. Alcock/Visuals Unlimited, (b)O.S.F./Animals Animals
Figure 33.5Female hanging fliesinstinctively favor themale that supplies the largest object—inthis case, a moth. Theamount of sperm thefemale will accept fromthe male is determinedby the size of the object.
Figure 33.6The male three-spined stickleback displays a red belly to otherbreeding males near his territory. The male instinctively respondsto other red-bellied males by attacking and driving them away.
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John Winnie, Jr./DRK Photo
864 ANIMAL BEHAVIOR
Figure 33.7In many species, such asbighorn sheep, individu-als fight in relativelyharmless ways amongthemselves.
Aggressive behavior threatens other animals
Animals occasionally engage inaggression. Aggressive behavior isused to intimidate another animal ofthe same species. Animals fight orthreaten one another in order todefend their young, their territory, ora resource such as food. Aggressivebehaviors, such as bird calling, teethbaring, or growling, deliver the mes-sage to keep away.
When a male bighorn sheep isthreatened by another male movinginto his territory, for example, he doesnot kill the invader. Animals of thesame species rarely fight to the death.The fights are usually symbolic, asshown in Figure 33.7. Male bighornsheep do not usually even injure oneanother. Why does aggressive behaviorrarely result in serious injury? Oneanswer is that the defeated individualshows signs of submission to the victor.These signs inhibit further aggressionby the victor. Continued fightingmight result in serious injury for thevictor; thus, its best interests are servedby stopping the fight.
Submission leads to dominance hierarchies
Do you have an older or youngersibling? Who wins when you argue?In animals, usually the oldest orstrongest wins the argument. Butwhat happens when several individu-als are involved in the argument?Sometimes, aggressive behavioramong several individuals results ina grouping in which there are different levels of dominant andsubmissive animals. A dominancehierarchy (DAH muh nunts • HI rarkee) is a form of social rankingwithin a group in which some indi-viduals are more subordinate thanothers. Usually, one animal is thetop-ranking, dominant individual.This animal might lead others tofood, water, and shelter. A dominantmale often sires most or all of theoffspring. There might be severallevels in the hierarchy, with individ-uals in each level subordinate to theone above. The ability to form adominance hierarchy is innate, butthe position each animal assumesmay be learned.
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The term pecking order comes from adominance hierarchy that is formed bychickens. The top-ranking chicken canpeck any other chicken. The chickenlowest in the hierarchy is pecked at byall the other chickens in the group.
Behavior resulting from internaland external cues
Some instinctive behavior is exhib-ited in animals in response to internal,biological rhythms. Behavior based ona 24-hour day/night cycle is one exam-ple. Many animals, humans included,sleep at night and are awake during theday. Other animals, such as owls,reverse this pattern and are awake atnight. A 24-hour, light-regulated,sleep/wake cycle of behavior is called acircadian (sur KAY dee uhn) rhythm.Circadian rhythms keep you alert dur-ing the day and help you relax at night.They may even wake you if you forgetto set your alarm clock or on days that
you could sleep in. Circadian rhythmsare controlled by genes, yet are alsoinfluenced by factors such as jet lagand shift work.
Rhythms also can occur on a yearlyor seasonal cycle. Migration, for ex-ample, occurs on a seasonal cycle.Migration is the instinctive, season-al movement of animals, shown in Figure 33.8. In North America, abouttwo-thirds of bird species fly south inthe fall to areas such as South America,where food is available during the win-ter. The birds fly north in the spring toareas where they breed during thesummer. Whales migrate seasonally, aswell. Change in day length is thoughtto stimulate the onset of migration inthe same way that it controls the flow-ering of plants. You can find out howmigrating turtles are tracked in theBiotechnology at the end of this chapter.
Infer why some animals migrate.
33.1 INNATE BEHAVIOR 865(l)Kim Heacox Photography/DRK Photo, (c)Tim Davis/PhotoResearchers, (r)Phyllis Greenberg/Animals Animals
Figure 33.8A variety of animals respond to the urge to migrate.
Canadian and Alaskan caribou migratefrom their winter homes in the taigaforests to the tundra for the summer.
A
Both thefreshwater eeland all species ofsalmon migrateto their spawninggrounds.
B
Adult monarch butterfliesfly southward where theyroost. In the spring, theiryoung fly back north.
C
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Migration calls for remarkablestrength and endurance. The arctictern migrates between the arctic circle and the Antarctic, a one-wayflight of almost 18 000 km.
Animals navigate in a variety ofways. Some use the positions of thesun and stars to navigate. They mayuse geographic clues, such as moun-tain ranges. Some bird species seemto be guided by Earth’s magneticfield. You might think of this as beingguided by an internal compass.
Animals that migrate might beresponding to colder temperaturesand shorter days, as well as to hor-mones. Young animals may learnwhen and where to migrate by follow-ing their parents. You can easily seewhy animals migrate from a coldplace to a warmer place, yet most ani-mals do not migrate. How many ani-mals cope with winter is anotherexample of instinctive behavior.
You know that many animals storefood in burrows and nests. But otheranimals survive the winter by undergo-ing physiological changes that reducetheir need for energy. Some mammals,such as bats and chipmunks, and a few
other types of animals go into a deepsleep during parts of the cold wintermonths. This period of inactivity iscalled hibernation. Hibernation (hibur NAY shun) is a state in which thebody temperature drops substantially,oxygen consumption decreases, andbreathing rates decline to a few breathsper minute. Hibernation conservesenergy. Animals that hibernate typi-cally eat vast amounts of food to buildup body fat before entering hiberna-tion. This fat fuels the animal’s bodywhile it is in this state. The golden-mantled ground squirrel shown inFigure 33.9 is an example of an animalthat hibernates. You can find out moreabout hibernation in the Problem-Solving Lab on the next page.
What happens to animals that liveyear-round in hot environments?Some of these animals respond in away that is similar to hibernation.Estivation (es tuh VAY shun) is astate of reduced metabolism thatoccurs in animals living in condi-tions of intense heat. Desert animalsappear to estivate sometimes inresponse to lack of food or periodsof drought.
866 ANIMAL BEHAVIOR
Figure 33.9The golden-mantledground squirrel has anormal body tempera-ture of around 37°C.When the day lengthshortens in the fall, the ground squirrel’stemperature drops to5°C, and it goes intohibernation.
Stephen J. Krasemann/DRK Photo
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Australian long-necked turtles,shown in Figure 33.10, will estivateeven when they are kept in a labora-tory with constant food and water.Clearly, estivation is an innatebehavior that depends on both inter-nal and external cues.
33.1 INNATE BEHAVIOR 867Belinda Wright/DRK Photo
Understanding Main Ideas1. How is a reflex different from an instinct?2. Explain by example two types of innate behavior.3. Explain behaviors that reduce competition.
Thinking Critically4. How is innate behavior an advantage to a species
in which the young normally hatch after themother has left?
5. Experiment Earthworms live in deep, long, andnarrow burrows in moist soil. They leave their bur-rows at night and when it rains, because it is eas-ier for them to move on a wet surface. Design anexperiment to determine what stimulus causes anearthworm to return to its burrow. For more help,refer to Experiment in the Skill Handbook.
SKILL REVIEWSKILL REVIEW
Figure 33.10Australian long-necked turtles are amongthe reptiles and amphibians that respond tohot and dry summer conditions by estivating.
ca.bdol.glencoe.com/self_check_quiz
Design an ExperimentIs hibernation an innate or learned behavior? Circadianrhythms occur on an almost 24-hour cycle in certain organisms.The word circadian comes from Latin: circa (“about”) and dies(“day”).
Solve the ProblemGround squirrels were placed in a room free from all outsidestimuli. The room contained food and water, was kept at a tem-perature of 22°C, and a light remained on for 12 hours each day.Body mass was measured and recorded weekly. The graph showsthe results of the experiment. The dark bands correspond totimes when the squirrels were in hibernation.
Thinking Critically1. Sequence Describe the squirrels’ cyclic pattern of activity.2. Lab Techniques Why did scientists keep temperature,
food and water, and light constant?3. Use Variables, Constants, and Controls Why is it appro-
priate experimental procedure to repeat the experimentusing different temperatures?
4. Experiment Suggest an experiment that supports theconclusion that this pattern of hibernation is genetic.
Bo
dy
mas
s (g
ram
s)
Days
Body Mass of Golden-Mantled Ground Squirrels
350
300
250
200
0 100 200 300 400 500 600 700
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Learned Behavior33.2
What is learnedbehavior?
Learning, or learned behavior, takesplace when behavior changes throughpractice or experience. The more com-plex an animal’s brain, the more elabo-rate the patterns of its learned behavior.As you can see in Figure 33.11, innatebehaviors are more common in inverte-brates, and learned behaviors are morecommon in vertebrates. In humans,many behaviors are learned.
Learning has survival value for all ani-mals in changing environments becauseit permits behavior to change in responseto varied conditions. Learning allows an animal to adapt to change, an abilitythat is especially important for animals with long life spans. The longer that ananimal lives, the greater the chance thatits environment will change.
Instinct
Reflex
Learning
Reasoning
Human
s
Prim
ates
Mammals
BirdsInsects
Worms
Protists
Fishes, r
eptiles,
amphibians
Invertebrates Vertebrates
Type
s of
beh
avio
r
Comparison of Animal Behaviors
SECTION PREVIEWObjectivesDistinguish among typesof learned behavior.Demonstrate, by example,types of learned behavior.
Review Vocabularypheromones: chemical
signals given off by ani-mals that signal animalsto engage in specificbehaviors (p. 745)
New Vocabularyhabituationimprintingtrial-and-error learningmotivationclassical conditioninginsightcommunicationlanguage
868 ANIMAL BEHAVIOR
Learned Behavior Make the following Foldable to help you understand the vocabulary terms in this chapter.
Build Vocabulary As you read Section 33.2, list the vocabulary words about learned behavior on the tabs. As you learn the definitions, write them under the appropriate tab.
Fold a vertical sheet of notebook paper from side to side.
Cut along every third line of only the top layer to form tabs.
Label each tab.
STEP 1
STEP 3
STEP 2
Figure 33.11By examining thegraph, you can see that humansdemonstrate themost learnedbehavior. Insects,fishes, amphibians,and reptiles demon-strate the mostinnate behavior.
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Kinds of LearnedBehavior
Just as there are several types ofinnate behavior, there are several typesof learned behavior. Some learnedbehavior is simple and some is com-plex. Which group of animals do youthink carries out the most complextype of learned behavior?
Habituation: A simple form of learning
Horses normally shy away from anobject that suddenly appears from thetrees or bushes, yet after a while theydisregard noisy cars that speed by thepasture honking their horns. Thislack of response is called habituation.Habituation (huh bit choo AY shun)illustrated in Figure 33.12, occurswhen an animal is repeatedly given astimulus that is not associated withany punishment or reward. An animalhas become habituated to a stimuluswhen it finally ceases to respond tothe stimulus.
Imprinting: A permanent attachment
Have you ever seen young duck-lings following their mother? Thisbehavior is the result of imprinting.Imprinting is a form of learning inwhich an animal, at a specific criticaltime of its life, forms a social attach-ment to another object. Many kindsof birds and mammals do not innatelyknow how to recognize members oftheir own species. Instead, they learnto make this distinction early in life.Imprinting takes place only during aspecific period of time in the animal’slife and is usually irreversible. Forexample, birds that leave the nestimmediately after hatching, such asgeese, imprint on their mother. They
learn to recognizeand follow her withina day of hatching.
In birds such as ducks,imprinting takes place during the firstday or two after hatching. A ducklingrapidly learns to recognize and followthe first conspicuous moving object itsees. Normally, that object is theduckling’s mother. Learning to recog-nize their mother and follow herensures that food and protection willalways be nearby.
Learning by trial and errorDo you remember when you first
learned how to ride a bicycle? Youprobably tried many times beforebeing able to successfully completethe task. Nest building, like riding a bicycle, may be a learning expe-rience. The first time a jackdaw builds a nest, it uses grass, bits ofglass, stones, empty cans, old light-bulbs, and anything else it can find.
33.2 LEARNED BEHAVIOR 869(t)Bruce Mathews/ImageQuest, (inset)Eastcott/Momatiuk/Animals Animals
Figure 33.12Habituation is a loss ofsensitivity to certainstimuli. Young horsesoften are afraid of cars and noisy streets.Gradually, they becomehabituated to the cityand ignore normalsights and sounds.
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With experience, the bird finds thatgrasses and twigs make a better nestthan do lightbulbs. The jackdaw hasused trial-and-error learning inwhich an animal receives a rewardfor making a particular response.When an animal tries one solutionand then another in the course ofobtaining a reward, in this case asuitable nest, it is learning by trialand error. Find out for yourself howtrial and error learning works in theMiniLab on this page.
Learning happens more quickly ifthere is a reason to learn or be suc-cessful. Motivation is an internalneed that causes an animal to act, andit is necessary for learning to takeplace. In most animals, motivationoften involves satisfying a physicalneed, such as hunger or thirst. If ananimal isn’t motivated, it won’t learn.Animals that aren’t hungry won’trespond to a food reward. Mice livingin a barn, shown in Figure 33.13, dis-cover that they can eat all the grainthey like if they first chew through thecontainer in which the grain is stored.
Michael Durham/ENP Images
870 ANIMAL BEHAVIOR
Figure 33.13Mice soon learn where grain is stored in abarn and are motivated by hunger to chewthrough the storage containers.
ExperimentSolving a Puzzle You are given a bunch of keys and asked toopen a door. How do you go about finding the right key?Several attempts are needed, and then finally, the door opens.The next time you are asked to perform the same task, canyou go directly to the correct key? Chances are, you can. Youhave learned how to solve this problem.
Procedure! Copy the data table
below.@ Obtain a paper puzzle
from your teacher.# Time how long it takes
you to assemble thepuzzle pieces into aperfect square.
$ Record the time it tookand call this Trial 1.
% Disassemble the squareand mix the pieces.
^ Repeat step 3 for four more trials.
Analysis 1. Interpret data Explain how the time needed to complete
the puzzle changed from Trial 1 to Trial 5.2. Infer Was the final completion of the puzzle an example
of innate or learned behavior? Explain your answer.3. Analyze When solving the puzzle, what role might
imprinting, trial and error, conditioning, and insight haveplayed in improving your trial times?
Data Table
Trial Time Needed to Complete Square Puzzle
1
2
3
4
5
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Classical conditioning: Learning by association
Suppose that when you first got anew kitten, it would meow as soon asit smelled the aroma of cat food in thecan you were opening. After a fewweeks, the sound of the can openeralone attracted your kitten, causing itto meow. Your kitten had becomeconditioned to respond to a stimulusother than the smell of food. Classicalconditioning is learning by associa-tion. A well-known example of anearly experiment in classical condi-tioning is illustrated in Figure 33.14.
Insight: The most complex type of learning
In a classic study of animal behav-ior, a chimpanzee was given twobamboo poles, neither of which waslong enough to reach some fruitplaced outside its cage. By connect-ing the two tapering short pieces to
make one longer pole, the chimpan-zee learned to solve the problem ofhow to reach the fruit. This type oflearning is called insight. Insight islearning in which an animal usesprevious experience to respond to anew situation.
Much of human learning is basedon insight. When you were a baby,you learned a great deal by trial anderror. As you grew older, you reliedmore on insight. Solving math prob-lems is a daily instance of usinginsight. Probably your first experi-ence with mathematics was when youlearned to count. Based on your con-cept of numbers, you then learned toadd, subtract, multiply, and divide.Years later, you continue to solveproblems in mathematics based onyour past experiences. When youencounter a problem you have neverexperienced before, you solve theproblem through insight.
33.2 LEARNED BEHAVIOR 871
Pavlov noted that dogssalivate when they smell food.Responding to the smell offood is a reflex, an exampleof innate behavior.
A By ringing a bell each timehe presented food to a dog,Pavlov established anassociation between thefood and the ringing bell.
B Eventually, the dog salivated at thesound of the bell alone. The doghad been conditioned to respondto a stimulus that it did notnormally associate with food.
C
Figure 33.14In the early 1900s, Ivan Pavlov, a Russian biologist, first demonstrated classical conditioning in dogs.
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The Role ofCommunication
When you think about interactionsamong animals as a result of theirbehavior, you realize that some sort of communication has taken place.Communication is an exchange ofinformation that results in a change ofbehavior. Black-headed gulls visuallycommunicate their availability formating with instinctive courtshipbehavior. The pat on the head from adog’s owner after the dog retrieves astick signals a job well done.
Define the term communication.
Most animals communicateAnimals have several channels of
communication open to them. Theysignal each other by sounds, sights,touches, or smells. Sounds vibrate inall directions and can be heard a longway from their sources. Sounds such assongs, roars, and calls communicate alot of information quickly. For exam-ple, the song of a male cricket tells hissex, his location, his social status, and,because communication by sound isusually species specific, his species.
Signals that involve odors may bebroadcast widely and carry a generalmessage. Ants, shown in Figure 33.15,leave odor trails that are followed byother members of their nest. Theseodors are species specific. As youknow, pheromones, such as those ofmoths, may be used to attract mates.Because only small amounts of pher-omones are needed, other animals,especially predators, may be unable todetect the odor.
Jacana/Photo Researchers
872
Figure 33.15Ants follow chemicaltrails left by other ants to find food resources.
Interpret DataDo birds learn how to sing? Do birds learn how to sing, oris this innate behavior? Most experimental evidence points tothe fact that singing may be a combination of the two typesof behavior, but in certain species, learning is critical in orderto sing the species song correctly.
Solve the ProblemBird sound spectrograms allow scientists to record and visuallystudy the song patterns of birds. Using this tool, they recordedspectrograms for white-crowned sparrows. The top spectrogram isthat of a wild white-crowned sparrow. The bottom spectrogram is that of a white-crowned sparrow hatched and raised in total isolation from all other birds. Segments of the song have beenidentified with the letters A–C.
Thinking Critically1. Compare and Contrast In general, how do the two
spectrograms compare?2. Read Graphs Which segment of the sparrow’s song may
be innate? Learned? Explain your answers.3. Interpet Graphs Does it appear that the majority of the
sparrow’s song is learned or innate? Explain your answer.4. Predict In a different experiment, a recording of a
white-crowned sparrow song was repeatedly played for a young bird raised in isolation. If a bird’s song is mainlylearned, predict the outcome of the experiment.
AA BB CC
AA BB CC
Wildsparrow
Sparrowraised inisolation
Birds‘ Songs
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Using both innate and learned behavior
Some communication is a combina-tion of both innate and learned behav-ior. In some species of songbirds, suchas the one shown in Figure 33.16,males automatically sing when theyreach sexual maturity. Their songs arespecific to their species, and singing isinnate behavior. Yet members of thesame species that live in differentregions learn different variations of thesong. They learn to sing with aregional dialect. In other species, birdsraised in isolation never learn to singtheir species song. Find out more aboutthe songs birds sing in the Problem-Solving Lab on the previous page.
Some animals use languageLanguage, the use of symbols to
represent ideas, is present primarily inanimals with complex nervous sys-tems, memory, and insight. Humans,with the help of spoken and writtenlanguage, can benefit from what otherpeople and cultures have learned anddon’t have to experience everythingfor themselves. People can use theaccumulated knowledge in the booksshown in Figure 33.17 to build newknowledge.
Understanding Main Ideas1. How is imprinting different from other types of
learned behavior?
2. Compare and contrast trial-and-error learning andinsight. Give an example of each.
3. Explain by example the difference between trial-and-error learning and classical conditioning.
4. What is the difference between communicationand language?
5. How does an animal become habituated to a stimulus?
Thinking Critically6. How does learning have survival value in a chang-
ing environment? Explain your answer by using anexample from your daily life.
7. Observe and Infer Two dog trainers teach dogsto do tricks. One trainer gives her dog a foodtreat whenever the dog correctly performs thetrick. The other trainer does not use treats. Whichtrainer will be more successful at dog training?Why? For more help, refer to Observe and Inferin the Skill Handbook.
SKILL REVIEWSKILL REVIEW
33.2 LEARNED BEHAVIOR 873(t)Steve & Dave Maslowski/Photo Researchers, (b)Aaron Haupt
Figure 33.16The Indigo bunting sings a high-pitched series of notes thatdescend the scale, then ascend again at the end of the song.
Figure 33.17English and other lan-guages are made up ofwords that have specificmeanings. An amazingnumber of meaningscan be communicatedusing words of anyhuman language.
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Before You BeginLand snails are membersof the mollusk class Gas-tropoda. Land snails liveon or near the ground,feed on decaying organicmatter, and breathe withgills or, in some cases, witha simple lung. Land snailssense their environmentwith a pair of antennaeand eyes. Snails are excel-lent organisms for behav-ioral studies because theyshow a variety of consis-tent responses to certainstimuli.
Behavior of a Snail
ProblemHow can you test the behavior of snails to touch stimuli?
Objectives In this BioLab, you will: ■ Test the response of snails to touch. ■ Measure the time needed for habituation to occur after
repeated touch stimuli.
Materialssnails spring waterdropper small dishscissors dissecting microscopeprobe constructed from tape,
rubber band, and pencil
Safety PrecautionsCAUTION: Always wear goggles in the lab. Wash your handswith soap and water both before and after handling anyanimals. Use caution when working with live animals. Becareful not to harm the snails.
Skill HandbookIf you need help with this lab, refer to the Skill Handbook.
1. Copy the data table.2. Prepare a stimulator probe by taping a small piece of
a cut rubber band to the tip of a pencil.3. Cover the bottom of a small dish with spring water.
4. Obtain a snail from yourteacher and place it in the dish.
5. Use a dissecting micro-scope to examine and locate its head. Its head has two antennae that it can extend and retract.
6. Place the dish on your desk.
PROCEDUREPROCEDURE
PREPARATIONPREPARATION
A land snail
Alvin E. Staffan
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33.2 LEARNED BEHAVIOR 875
7. Lightly touch the snail’s anteriorend using the end of the probe.Note if it responds (yes or no), andrecord any movement. Conduct atotal of five trials.
8. Repeat step 7, touching the snail’sposterior end.
9. Repeat step 7, touching the middle of the snail’s body.
10. Test the snail’s ability to becomehabituated.a. Continue to touch the snail’s
anterior end with the probe every 10 seconds until habitua-tion occurs. Continue testing fora reasonable length of time if habituation does not occur.
b. Count and record the number of stimulations needed for habituation.
11. Return your snail to the area designated byyour teacher. Clean all equipment and return everything to its properplace for reuse. Wash your hands thoroughly with soap and water.
CLEANUP AND DISPOSAL
Trial Anterior
1
2
3
4
5
Posterior
Response to TouchBody Area
Data Table
Middle
Rate ofStimulation
Number of StimulationsNeeded to Reach Habituation
Habituation Studies
ANALYZE AND CONCLUDEANALYZE AND CONCLUDE
1. Hypothesize Are the responses to touch shown by snails learned orinnate? Explain your answer.
2. Observe Describe the direction that a snail moves when its anterior andposterior ends are stimulated. Does one end appear to be more sensitivethan the other? Is the middle sensitive to touch? Is the speed of responseslow or rapid?
3. Explain How is the behavior of responding to touch an adaptation for survival?
4. Experiment Why did you perform severaltrials for each experiment involving stimula-tion of the anterior, posterior, and middle ofthe snail?
5. Define Operationally Define the termhabituation.
6. Suppose you hypothesizedthat snails are quickly habituated to touch. Isthis hypothesis supported by your data?Explain.
ERROR ANALYSIS
Experiment Form a hypothesis regardingsnail behavior when given a choice betweenlight and dark conditions. Design and carryout an experiment to test your hypothesis.
Web Links To find out more about animal behavior, visitca.bdol.glencoe.com/animal_behavior
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Tracking Sea Turtles
The Florida green turtle (Chelonia mydas mydas)is an endangered species that nests on sandy
beaches. It is found in temperate and tropicalwaters, including the southeastern coast of theUnited States. Like other sea turtles, the Floridagreen turtle spends virtually all of its life at sea;however, adult females visit beaches severaltimes a year to lay their eggs.
Studying sea turtles presents a challengebecause they spend so little time on land.Research is most easily conducted on the beach,where the nesting behavior of the females can bedirectly observed. These observations have pro-vided important information about how to pro-tect the nesting sites from human disturbance orpredation. But more information about theFlorida green turtle is needed because protectingan endangered species requires knowing whatenvironmental factors are crucial to its survival.
Tagging To study these animals, researchers affixa small plastic or metal tag onto the flipper of acaptured turtle. The tag is etched with an identifi-cation number. If the animal is captured again, thedate and location are shared with other turtleresearchers. But even when a tagged turtle isrecaptured, the route the animal took to movefrom one location to another remains unknown.
Satellite tracking Recent improvements insatellite telemetry are making it possible forresearchers to keep much better track of individualturtles as they swim from place to place. A trans-mitter the size of a small, portable cassette playeris attached to the shell behind the turtle’s neck.The battery-powered transmitter will work for sixto ten months before it falls off. When the turtlecomes to the surface to breathe, the transmitterbroadcasts data in the form of a digital signal to anorbiting communications satellite. The satellitetransmits the data to a receiving station on Earth.
The digital signal con-tains information aboutthe turtle’s latitude and lon-gitude, the number of dives itmade in the past 24 hours, the length of its mostrecent dive, and the temperature of the water. Byplotting the location of data transmissions on amap, researchers can track the direction andspeed in which the animal is moving.
Problems with satellite tracking Sometimes atransmitter stops working after just a few weeks,and there are problems with the data itself.Increasingly accurate information will becomeavailable as the technology improves and as moreturtles are included in satellite tracking efforts.
Think Critically Telemetry data from a Floridagreen turtle indicate the animal has spent the pastseveral days in an offshore location characterizedby coral reefs and seagrass meadows. Past teleme-try data from other green turtles indicate thatthese animals periodically interrupt their travels tostop at this location and at other coral reefs andseagrass meadows. Form a hypothesis that couldexplain this behavior. How could you test yourhypothesis?
To find out more about sea turtle migration,visit
876 ANIMAL BEHAVIOR
Florida green turtle
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(t)Doug Perrine/DRK Photo, (inset)Andrew G. Woods/Photo Researchers
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Section 33.1
Section 33.2
Key Concepts■ Behavior is anything an animal does in
response to a stimulus. ■ Many behaviors have adaptive value and
are shaped by natural selection.■ Innate behavior is inherited. Innate behav-
iors include fixed-action patterns, auto-matic responses and instincts.
■ Automatic responses include reflexes andfight-or-flight responses.
■ An instinct is a complex pattern of innatebehaviors.
■ Behaviors such as courtship rituals, displaysof aggressive behavior, territoriality, domi-nance hierarchies, hibernation, and migra-tion are all forms of instinctive behavior.
■ Pecking order is an exampleof a dominance hierarchy.
Vocabularyaggressive behavior
(p. 864)behavior (p. 859)circadian rhythm
(p. 865)courtship behavior
(p. 862)dominance hierarchy
(p. 864)estivation (p. 866)fight-or-flight response
(p. 861)hibernation (p. 866)innate behavior (p. 861)instinct (p. 862)migration (p. 865)reflex (p. 861)territory (p. 863)
Innate Behavior
Key Concepts■ Learning takes place when behavior
changes through practice or experience.■ Learned behavior has adaptive value.■ Learning includes habituation, imprinting,
trial and error, and classical conditioning.■ The most complex type of learning is
learning by insight.■ Some animals use language, whereas most
communicate by either visual, auditory, orchemical signals.
Vocabularycommunication (p. 872)classical conditioning
(p. 871)habituation (p. 869)imprinting (p. 869)insight (p. 871)language (p. 873)motivation (p. 870)trial-and-error learning
(p. 870)
LearnedBehavior
STUDY GUIDESTUDY GUIDE
CHAPTER 33 ASSESSMENT 877Jacana/Photo Researchers
To help you review ani-mal behavior, use the OrganizationalStudy Fold on page 868.
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Review the Chapter 33 vocabulary words listed inthe Study Guide on page 877. Match the wordswith the definitions below.
1. innate behavior by which animals form asocial ranking within a group in which someindividuals are more subordinate than others;usually has one top-ranking individual
2. learned behavior in which an animal, at aspecific critical time of its life, forms a socialattachment to another object
3. complex innate behavior pattern that beginswhen an animal recognizes a stimulus andperforms an action until all parts of thebehavior have been formed
4. type of learning in which an animal uses previ-ous experiences to respond to a new situation
5. physical space an animal defends againstother members of its species; may contain ananimal’s breeding area, feeding area, potentialmates, or all three
6. Your adult dog is chewing on a bone when apuppy approaches. Your dog growls at thepuppy. What type of behavior is your dogexhibiting?A. conditioning C. habituationB. aggressive behavior D. fighting
7. Animals with behavior that makes themmore successful at surviving and reproduc-ing tend to produce more ________.A. offspring C. territoryB. aggression D. eggs
8. When a toad flips out its tongue to catch aninsect flying past, it is exhibiting ________.A. learned behavior C. territorialityB. courtship behavior D. innate behavior
9. Caribou are ________ when they move fromtheir winter homes in the forests to the tun-dra for the summer.A. hibernating C. migratingB. imprinting D. learning
10. Establishing ________ reduces the need foraggressive behavior among members of thesame species.A. reflexes C. territoriesB. conditioning D. habituation
11. Your cat exhibits ________ when it runs forits food dish upon hearing the can opener. A. insight C. habituationB. conditioning D. imprinting
12. Open Ended Explain the result of naturalselection in animal behavior.
13. Open Ended Explain how Ivan Pavlov used scientific methods to study classicalconditioning.
14. Recognize Cause and Effect When CharlesDarwin visited the Galápagos Islands in1835, he was amazed that the animals wouldallow him to touch them. Hypothesize whythey were not afraid.
15. Compare and Contrast Ducklings display analarm reaction when a model of a hawk isflown over their heads and no alarm reactionwhen a model of a goose is flown over theirheads. After several days, neither model causesany reaction. Compare the effects of the twomodels during the first two days with theeffects of the same models two weeks later.
16. Visit to investigate bee
behavior and communication. Include historicdiscoveries about how bees communicate withother members of the hive as to where a newfood source is. Also include the results of themost recent research about how bees measurethe distance to a food source. Present theresults of your research to your class in theform of a poster or multimedia presentation.
REAL WORLD BIOCHALLENGE
878 CHAPTER 33 ASSESSMENT
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17. Concept MapComplete the concept map by using the following vocabulary terms: innate behavior, imprinting, habituation, conditioning, insight.
CHAPTER 33 ASSESSMENT 879
2.
3. 4.
5.
such as
and learned behavior1.includesAnimal
behavior
Ave
rag
e %
co
rrec
t
Days after training
Recognition of Sheep Faces by Other Sheep100
75
50
25
075–200 201–400 401–600 601–800
Perc
enta
ge
of
sin
ger
s
Direction of migration and year
Percentage of Whales Singing Old and New Song100
80
60
40
20
0 S1995 N1996 S1996 N1997 S1997 N1998
Old song Combination New song
N North S South
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Multiple ChoiceStudy the graph and answer questions 18–19.
18. The recognition of sheep faces by othersheep can be described as ________.A. more than 75% correct even after 800 daysB. less than 50% correct after 400 daysC. remembering 80 sheep after 800 daysD. remembering 800 sheep after 80 days
19. The ability of sheep to recognize faces maybe an adaptation to ________.A. escaping predatorsB. living in a herdC. finding foodD. cold climate
On the east coast of Australia, humpback whalessing the same song while they migrate north andsouth. Use the graph to answer questions 20–21.
20. In 1996, ________.A. all whales sang the old songB. all whales sang the new songC. one or two whales sang a new songD. no migration occurred
21. By 1998, all whales sang ________.A. the new songB. the old songC. the old and new songsD. the intermediate song
Constructed Response/Grid InRecord your answers on your answer document.
22. Open Ended Some bird species give differing calls depending on the source of alarm. Otherbirds of the same species either scan the ground or the sky in response to the calls. Infer what thebirds may be communicating.
23. Open Ended What would be the advantage of a dominance hierarchy in members of a speciesthat are not defending a territory?
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VertebratesLike all chordates, vertebrates have a notochord, pharyngeal pouches, a
dorsal hollow nerve cord, and postanal tail. However, in vertebratesthe notochord is replaced during development by a backbone. Allvertebrates are bilaterally symmetrical coelomate animals that have anendoskeleton, a closed circulatory system, an efficient respiratory system,and a complex brain and nervous system.
FishesSize ranges: Largest: Whale shark, length, 15 m; smallest: Dwarf goby, length, 1 cmDistribution: Freshwater, saltwater, and estuarine habitats worldwideUnusual adaptations: Electric eels can deliver an electrical charge of 650 volts, which stuns or kills their prey. Some deep-seafishes have their own bioluminescent lures tohelp capture prey.Longest-lived: Lake sturgeon, 80 yearsNumbers of species:Class Myxini—hagfishes, 43 species Class Cephalaspidomorphi—lampreys, 17 speciesClass Chondrichthyes—cartilaginous fishes,850 speciesClass Osteichthyes—bony fishes, 18 007 species
880 BIODIGEST UNIT 9 REVIEW
Cartilaginous fishes such as this whitetip reef sharkhave internal fertilization. In some species of cartilagi-nous fishes, development of fertilized eggs is external;other species give live birth to well-developed young.
FishesAll fishes are ectotherms, animals with body
temperatures dependent upon an external heatsource. Fishes have two-chambered hearts andbreathe through gills. Fishes are grouped into fourdifferent classes.
Two Classes of Jawless FishesLampreys and hagfishes make up the two
classes of jawless fishes. Jawless fishes haveendoskeletons made of cartilage, like sharks andrays, but they do not have jaws.
Cartilaginous FishesSharks, skates, and rays are cartilaginous fishes.
Fossil evidence shows that jaws first evolved inthese fishes. Cartilaginous fishes have endoskele-tons made of cartilage, paired fins, and a lateralline system that enables them to detect movementand vibrations in water.
Bony FishesMost fish species belong to the bony fishes.
All bony fishes have a bony skeleton, gills, pairedfins, flattened bony scales, and a lateral line sys-tem. Bony fishes breathe by drawing water intotheir mouths, then passing it over gills where gasexchange occurs. They adjust their depth in thewater by regulating the amount of gas that dif-fuses out of their blood into a swim bladder. Mostbony fishes fertilize their eggs externally and leavethe survival of the offspring to chance.
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AmphibiansSize ranges: Largest: Goliath frog, length,30 cm; Chinese giant salamander, length,1.8 m; Smallest frog: Psyllophryne didactyla,length, 9.8 mmDistribution: Tropical and temperate regions worldwideNumbers of species:Class Amphibia
Order Anura—frogs and toads, 3700species
Order Caudata—salamanders and newts,369 species
Order Apoda—legless caecilians, 168species
Vertebrates
The tympanic membrane, or eardrum, is located behind and belowthe frog’s eye. It transmits vibrations from the air or water to thefrog’s inner ear.
Caecilians are long, limbless amphibians adapted for burrowingand living underground.
Like other amphibians, salamanders have smooth, moist skin and lack true claws on their toes. Salaman-ders are carnivorous, feeding on insects, worms, andsmall mollusks.
VERTEBRATES 881
AmphibiansAmphibians are ectothermic vertebrates with
three-chambered hearts, lungs, and thin, moistskin. Although they have lungs, most gas exchangein amphibians is carried out through the skin. Asadults, the majority of amphibians live on land,however, many of these species rely on water forreproduction. Most amphibians go through meta-morphosis, in which the young hatch into tadpoles,which gradually lose their tails and gills as theydevelop legs, lungs, and other adult structures.
Amphibian ClassificationAmphibians are classified into three orders:
Anura, frogs and toads; Caudata, salamanders and newts; and Apoda, legless caecilians. Frogsand toads have vocal cords that can produce awide range of sounds. Frogs have thin, smooth,moist skin and toads have thick, bumpy skin withpoison glands. Salamanders have long, slenderbodies with a neck and tail. Caecilians are amphib-ians with long, wormlike bodies and no legs.
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Reptiles were the first group of vertebrates to live entirely onland. They evolved a thick, scaly skin that prevented water
loss from body tissues. They evolved strong skeletons, with limbspositioned somewhat underneath their bodies. These limbsenabled them to move quickly on land, avoiding or seeking thesun as their body temperatures demanded. But perhaps their mostimportant adaptation to life on land was the development of theamniotic egg.
Protecting the embryo An amniotic egg encloses the embryo inamniotic fluid; provides the yolk, a source of food for the embryo;and surrounds both the embryo and yolk with membranes and atough, leathery shell. These structures in the egg help prevent
The Amniotic Egg
Nile crocodile hatchling
All crocodilians have astrong, muscular jaw andteeth that are in sockets.Crocodiles generally havea narrower snout in com-parison with alligators.
Vertebrates
882
Constrictors, such as this emer-ald tree boa, hold prey withtheir mouths, then wrap coilsaround the prey’s body. Thesnake tightens its coils, pre-venting inhalation, and theprey suffocates.
ReptilesReptiles are ectotherms with dry, scaly skin and
clawed toes. They include snakes, lizards, turtles,crocodiles, and alligators. With the exception ofsnakes, all reptiles have four legs that are posi-tioned somewhat underneath their bodies. Mostreptiles have a three-chambered heart, but
crocodilians have a four-chambered heart in whichoxygenated blood is kept entirely separate fromblood without oxygen. The scaly skin of reptilesreduces the loss of body moisture on land, butscales also prevent the skin from absorbing orreleasing gases to the air. Reptiles are entirelydependent upon lungs for this essential gasexchange.
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ReptilesSize ranges: Largest: Anaconda snake, length, 9 m; Leatherback turtle, mass, 680 kg; smallest: Thread snake, length, 1.3 cmDistribution: Temperate and tropical forests,deserts, and grasslands, and freshwater, salt-water, and estuarine habitats worldwideReptile that causes most human death:King cobra, 7500 deaths per yearNumbers of species:Class Reptilia
Order Squamata—snakes and lizards, 6800species
Order Chelonia—turtles, 250 speciesOrder Crocodilia—crocodiles and alligators,
25 speciesOrder Rhynchocephalia—tuataras,
2 species
Vertebrates
dehydration and injury to the embryo as it devel-ops on land. Most reptiles lay their eggs in pro-tected places beneath sand, soil, gravel, or bark.
Membranes inside the egg Membranes foundinside the amniotic egg include the amnion, thechorion, and the allantois. The amnion is a mem-brane filled with fluid that surrounds the develop-ing embryo. The embryo’s nitrogenous wastes areexcreted into a membranous sac called the allan-tois. The chorion surrounds the yolk, allantois,amnion, and embryo. With this egg, reptiles donot need water for reproduction. The evolution ofthe amniotic egg completed the move oftetrapods from water to land.
All turtles, including this olive ridley, a marinespecies, lay eggs in nests they dig in the ground.After the eggs are laid, the female turtle coversthem and leaves.
The shell of a turtle consists of bony plates covered withhorny shields. A turtle can pull
its head and legs into theshell to protect itself againstpredators.
Albumin
YolkChorion
Amnion
Embryo
Allantois
Egg shell883
Internal FertilizationAll reptiles have internal fertilization and most
species lay eggs. The development of the amnioticegg enabled reptiles to move away from adependence upon water for reproduction. Theamniotic egg provides nourishment to the embryoand protects it from drying out as it develops.
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BirdsBirds are the only class of animals with feathers.
Feathers, which are lightweight, modified scales,help insulate birds and enable them to fly. Birdshave forelimbs that are modified into wings. Likereptiles, birds have scales on their feet and clawedtoes; unlike reptiles, they are endotherms, animalsthat maintain a constant body temperature.Endotherms must eat frequently to provide theenergy needed for producing body heat.
Bird Flight
The male peacock displays its tail feathers to attract the femalepeahen. Feathers keep birds warm, streamline them for flight,and are often important in courtship or camouflage.
Peregrine falcon
Vertebrates
884
Penguins are flightless birds with wings and feet modi-fied for swimming. A thick layer of insulating fat helpskeep these penguins warm in the cold antarctic climatein which they live. This young emperor penguin mayreach a height of 1 m and weigh nearly 34 kg.
Bird FlightBirds have bones with cross braces that provide
support for strong flight muscles. Birds also have afour-chambered heart and a unique respiratorysystem in which oxygen is available during bothinhalation and exhalation.
W hat selection pressure may have resulted in bird flight?Maybe an early bird’s need to escape from a predator
caused it to run so fast its feet left the ground. Whatever causedbirds to evolve an ability to fly, there must first have been adapta-tions that made flight possible. What are some of these adapta-tions? A bird that flies has a body that is lighter than that of ananimal of equal size because it has little fat and air sacs through-out its body. It also has a beak instead of a heavy jaw with teeth,and its legs are made mostly of skin, bone, and tendons.
Efficient respiration Birds receive oxygenated air when theybreathe in as well as when they breathe out. Air sacs enable birdsto get more oxygen because 75 percent of the air inhaled by a
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BirdsSize ranges: Largest: Ostrich, height, 2.4 m,mass, 156 kg; smallest: Bee hummingbird,length, 57 mm, mass, 1.5 gDistribution: Worldwide in all habitats.Widest wingspan: Wandering albatross, 3.7 mFastest flyer: White-throated spinetail swift,171 kphLargest egg: Ostrich, length, 13.5 cm, mass,1.5 kgLongest yearly migration: Arctic tern, 40 000 kmNumbers of species:Class Aves—8600 species in 27 present-dayorders:
Order Passeriformes—perching song birds,5200 species
Order Ciconiiformes—herons, bitterns,ibises, 114 species
Order Anseriformes—swans, ducks, geese,150 species
Order Falconiformes—eagles, hawks, falcons, 288 species
Vertebrates
The cedar waxwing isfound in openwoodlands,orchards, andbackyards acrossthe UnitedStates. Theyspend most ofthe year in flocks,descending uponorchards and eat-ing until the fruitis gone.
Although some birds lay their eggs on the ground orrocks, most birds do construct some type of nest intowhich eggs are laid. Bald eagles build the largest nests,some of which are 2 m across and 2 tons in mass.
Arctic tern
885
bird passes directly into posterior air sacs rather than into itslungs. When a bird exhales, oxygenated air in the sacs passesinto its lungs, then into anterior air sacs and out through thetrachea. This one-way flow of air provides the oxygen that birdsneed to power flight muscles.
Wings adapted for flight Flight is also supportedby feathers that streamline a bird’s body and shapethe wings. Wing shape and size determine the typeof flight a bird is capable of. Birds that fly through the branches
of trees in a forest, such as finches, have elliptically shapedwings adapted to quick changes of direction. Wings of swallowsand terns have shapes that sweep back and taper to a slendertip, promoting high speed in open areas. The broad wings ofhawks, eagles, and owls provide strong lift and slow speeds.These birds are predators that carry prey while in flight.
Nest Builders Like reptiles, birds lay amniotic eggs. Unlike
reptiles, birds incubate their eggs in nests, keepingeggs warm until the young birds hatch.
(t)Wayne Lankinen/DRK Photo, (c)David Hosking/Photo Researchers, (b)O. Newman/O.S.F./Animals Animals
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Both birds and mammals are endotherms. Endotherms haveinternal processes that maintain a constant body tempera-
ture. Just as a thermostat controls the temperature of your home,internal processes cool endotherms if they are too warm, andwarm them if they are too cool, thus maintaining homeostasis.
Adaptations A variety of adaptations enables mammals tomaintain body temperature. Hair helps many mammals conserveheat. The thick coat of a polar bear is an adaptation to living in a cold climate. Small ears and an accumulation of body fat underthe skin also help prevent heat loss. Small ears have less surfacearea than large ears from which body heat can escape.
Endothermy
Female mammals, suchas this moose, feed theiryoung milk secretedfrom mammary glands.Mammals often care fortheir young until theybecome adults.
Polar bear
Vertebrates
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MammalsMammals are endotherms that are named for
their mammary glands, which produce milk tofeed their young. Most mammals have hair thathelps insulate their bodies and sweat glands thathelp keep them cool. Mammals need a high levelof energy for maintaining body temperature andhigh speeds of locomotion. An efficient four-chambered heart and the muscular diaphragmbeneath the lungs help to deliver the necessaryoxygen for these activities.
Mammal DiversityAll mammals have internal fertilization, and the
young begin development inside the mother’suterus. But from that point, developmental pat-terns in mammals diverge. Mammals are classifiedinto three groups. Monotremes are mammals thatlay eggs. Marsupials are mammals in which theyoung complete a second stage of developmentafter birth in a pouch made of skin and hair onthe outside of the mother’s body. Placental mam-mals carry their young inside the uterus untildevelopment is nearly complete.
(t)Stephen J. Krasemann/DRK Photo, (b)Johnny Johnson/Animals Animals
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Vertebrates
Hibernation Many rodents hibernate duringperiods of extreme cold. During hibernation, thebody temperature lowers. For example, when thesurrounding temperature drops to about 0°C, aground squirrel’s temperature drops to 2°C, and it goes into hibernation, which conserves the
animal’s energy.
Estivation In hot desert environments, wherewater is limited, some small rodents survive without
drinking. They obtain enough water from the foodsthey eat. Other desert mammals, such as the fennec fox,
have large ears that aid in heat loss. During periods of intenseheat, some desert mammals go into a state of reduced metabolismcalled estivation. As a result, the animal’s body temperature is low-ered and energy is conserved.
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MammalsSize ranges: Largest: Blue whale, length, 30 m, mass, 190 metric tons; smallest: Etruscan shrew, length, 6 cm, mass, 1.5 gDistribution: Worldwide in all habitatsFastest: Cheetah, 110 kphLongest-lived: Asiatic elephant, 80 years;humans, up to 120 yearsNumbers of species:Class Mammalia
Order Monotremata—egg-laying mam-mals, 3 species
Order Marsupialia—pouched mammals, 280 species
Orders of Placental Mammals—4120species
Grazing animals, such as this horse, rely on incisors tocut grasses and molars to grind and crush their food.Horses, like many other herbivores, lack canine teeth.
Carnivores, such as wolves, have canine teeth thatpierce food. Humans, who are omnivores, have inci-sors, canines, premolars, and molars in order toprocess many different kinds of food.
Fennec fox
Mammal TeethMammals can be classified by the number and
type of teeth they have. All mammals have diversi-fied teeth used for different purposes. Incisors areused to cut food. Canines—long, pointed teeth—are used to stab or hold food. Molars and premolarshave flat surfaces with ridges and are used to grindand chew food. By examining an animal’s teeth, sci-entists can hypothesize what type of consumer it is.
(t)Porterfield-Chickering/Photo Researchers, (b)Jacana Scientific Control/Photo Researchers
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888 UNIT 9 STANDARDIZED TEST PRACTICE
Multiple Choice
Use the information in the table to answer questions 1 and 2.
1. The bellies of male stickleback fish turn brightred during breeding season. In an experimentto test for triggers of aggressive behavior, sev-eral models were presented to live fish. Basedon the results presented in the table, what canyou conclude about the triggers for aggressivebehavior in these fish?A. Aggressive behavior is exhibited when the
fish recognizes another fish.B. Aggressive behavior is exhibited when the
fish sees any type of foreign object.C. Aggressive behavior is exhibited when the
fish recognizes the red belly.D. There is no pattern for aggressive behavior.
2. What is the independent variable in this experiment?A. the live fish used in the experimentB. the frequency of attacksC. the models of fish used in the experimentD. There is no independent variable.
Use the information below and your knowledge ofscience to answer questions 3 and 4.
3. The best description of the relationshipbetween body mass and total metabolic rate inanimals is ________.A. as body mass increases, total metabolic rate
decreasesB. as body mass increases, total metabolic rate
stays the sameC. as total metabolic rate decreases, body mass
decreasesD. as body mass increases, total metabolic rate
increases
4. Which title is appropriate for this graph?A. The Relationship Between Metabolic Rate
and Body SizeB. The Effect of Metabolic Rate on Body SizeC. The Relationship Between Metabolic Rate
and Life SpanD. The Effect of Body Size on Metabolic Rate
5. The arctic fox lives further north than anyother terrestrial mammal. The polar climatethat occurs above the arctic circle is primarilydue to which of the following?A. frequent El Niño eventsB. intensity of solar radiation at Earth’s sur-
face decreases as latitude increasesC. ocean currents flow from north to southD. ocean currents flow from south to north
Tota
l met
abo
lic r
ate
(wat
ts)
Body mass (kg)
0.01
0.1
1
10
100
1000
0.1 1 10 100 1000 10 000
Elephant
Horse
CowMan
WomanGoat
Dog
CatChicken
Dove
Mouse
If it Looks Too Good To Be True . . .
Beware of answer choices that seem obvious.Remember that only one answer choice of theseveral that you’re offered for each question iscorrect. Check each answer carefully beforefinally selecting it.
Behavior of Male Stickleback Fish
Model Description Frequency of Attack
Fish-shaped with Lowno red belly
Fish-shaped with Higha red belly
Lump of wax with Highred stripe at bottom
Standards Practice
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Use the diagram below to answer questions 6 and 7.
6. What effects could a drastic decline in theinsect population have?A. The numbers of shrew and sparrows will
increase.B. The owls will eat more mice.C. The numbers of shrew and sparrows will
remain the same.D. The number of rats will increase.
7. Which organism would be considered the toppredator in this food web?A. shrew C. mouseB. insect D. owl
8. Fossil evidence has led scientists to believe thatmodern birds evolved directly from ________.A. early reptilesB. therapod dinosaursC. amphibiansD. mammals
Use the graph to answer questions 9–11.
The graph shows the percentage of each gender inoffspring of live-bearing lizards kept at differenttemperatures during gestation.
9. Which temperature(s) yielded the closest ratioof male and female offspring?A. 25°C C. 32°CB. 30°C D. all of the above
10. If a lizard had been kept at 28°C, predict whatpercentage of the offspring would be female.A. 100 C. 50B. 70 D. 35
Perc
enta
ge
of
mal
e/fe
mal
e o
ffsp
rin
g 100
80
60
40
20
25°C 30°C 32°CTemperature
Male
Female
Owls
Mice Rats
Shrew
Insects
Plants
Sparrows
UNIT 9 STANDARDIZED TEST PRACTICE 889
Constructed Response/Grid InRecord your answers or fill in the bubbles on your answer document using the correct place value.
11. Grid In If four lizards were born in the group at 30°C, how many of them would most likely be male?12. Open Ended The egg case of a certain species of skate looks like a thin, leathery pod about 5 cm long
with each of the four corners ending in a small, curved spike. Form a hypothesis that explains the func-tion of these spikes.
13. Open Ended Tiny particles have been found in the hair of a prehistoric woolly mammoth frozen inthe permafrost of Siberia. The particles were of mosses, grasses, beetles, and mites. Make an inferenceabout the environment in which this woolly mammoth lived.
14. Open Ended Wild western-lowland gorillas have been observed in the water making spectacularsplash displays. Biologists hypothesize that the gorillas are using water to communicate. Infer what thegorillas may be communicating when they splash.
15. Open Ended The skin of a frog secretes mucus when it is injured or infected with microbes. Form ahypothesis about the function of the mucus and design an experiment to test your hypothesis.
ca.bdol.glencoe.com/standardized_test
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