section 1 the reptilian body - jourdanton isd · section 1 the reptilian body ... reptiles have a...
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OverviewBefore beginning this sectionreview with your students theobjectives listed in the StudentEdition. In this section, studentswill learn how reptiles are well-adapted to life on land. Terrestrialadaptations include a strong skeleton, watertight skin coveredwith scales, watertight eggs, largerlungs with greater surface area,internal fertilization, and a partiallydivided heart.
Ask students to design a survivalcapsule for themselves. The capsulecan only be 1.5 m high by 1 m wide.The capsule will not be opened forthree weeks. Nothing, other thangasses, can pass through the wall ofthe capsule. What should the capsulecontain? Ask students to comparetheir capsule with the amniotic eggdescribed in this section.
ActivityFavorite Reptile Have each stu-dent draw a picture of his or herfavorite reptile. Have volunteersshare their drawings with the classand tell why they chose their par-ticular reptile. Lead a discussion ofhow reptiles are viewed in popularculture. Visual Bio 3FLS
MotivateMotivate
TAKS 1 Bio/IPC 2C, 2D
Bellringer
FocusFocus
Section 1
772 Chapter 34 • Reptiles and Birds
• Reading Organizers• Reading Strategies• Basic Skills Worksheets
Reading a ThermometerTemperature Conversions
Planner CD-ROM
• Lesson Plan• Directed Reading• Active Reading• Data Sheet for Data Lab• Data Sheet for Quick Lab GENERAL
GENERAL
GENERAL
GENERAL
Chapter Resource File
Section 1 The Reptilian Body
Key Characteristics of ReptilesMany people react with fear or repulsion when they see a snakeslither across a yard or field. But snakes and their reptile relativesare important members of most ecosystems, and they kill largenumbers of insect pests and small rodents. It’s true that some rep-tiles—venomous snakes and crocodilians (crocodiles and alligators)—are dangerous. Most reptiles, however, live quietly and go abouttheir business, preferring to avoid humans.
Members of class Reptilia live throughout the world in a wide vari-ety of habitats, except in the coldest regions, where it is impossiblefor ectotherms to survive. Reptiles share certain fundamental char-acteristics, features they retain from the time when reptiles replacedamphibians as the dominant terrestrial vertebrates. Figure 1 summa-rizes these key features.
Reptiles have a strong, bony skeleton, and most have two pairs oflimbs, although snakes and some lizards are legless. The legs of rep-tiles are positioned more directly under their body than are thelimbs of amphibians. Thus, reptiles can move more easily on landthan amphibians can. Unlike amphibians, reptiles have toes withclaws, which are used for climbing and digging. Claws also enablereptiles to get a good grip on the ground, allowing many reptiles torun quickly for short distances.
The nervous system of a reptile is very similar to that of anamphibian. Like their dinosaur ancestors, modern reptiles have abrain that is small in relation to their body. For example, an alligatorabout 2.5 m (8 ft) long has a brain that is about the size of a walnut.Despite this small brain size, reptiles are capable of complex behav-iors, including elaborate courtship.
Objectives● Describe the key character-
istics of reptiles.
● Relate a reptile’s ectothermicmetabolism to its activitylevel.
● Summarize the adaptationsthat enable reptiles to live on land.
Key Terms
amniotic eggoviparousovoviviparous
www.scilinks.orgTopic: Characteristics
of ReptilesKeyword: HX4038
Figure 1 Characteristicsof living reptiles. This maleanole is extending his dewlap,a display used during court-ship and when defendingterritory.
• Strong, bony skeleton and toes withclaws
• Ectothermic metabolism• Dry, scaly skin, almost
watertight• Amniotic eggs, almost
watertight• Respiration through well-developed
lungs• Ventricle of heart partly divided by a
septum• Internal fertilization
Key Features of Reptiles
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7B
7B 11A
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Student Edition TAKS Obj 1 Bio/IPC 2C TAKS Obj 2 Bio 4B TAKS Obj 2 Bio 8C TAKS Obj 2 Bio 10A TAKS Obj 3 Bio 7B TEKS Bio 4B, 7B, 8C, 10A, 11ATEKS Bio/IPC 2C
Teacher Edition TAKS Obj 1 Bio/IPC 2C, 2D TAKS Obj 3 Bio 7B TEKS Bio 3F, 7B, 11ATEKS Bio/IPC 2C, 2D
pp. 772–773
TAKS 3
TAKS 3
Interactive Reading AssignChapter 34 of the Holt BiologyGuided Audio CD Program to helpstudents achieve greater success inreading the chapter.
Using the FigureHave students draw a graph thatdepicts the changes in human bodytemperature for a 24-hour period.(The graph should show that thehuman body remains at about 37˚Cfor the entire day.) Then ask them tocompare their graphs to the one forthe lizard’s body temperature inFigure 2. Ask: Why are the graphsdifferent? (The lizard depends onexternal sources for heat, so its bodytemperature tracks the temperatureof the environment. Humans producetheir own heat, so body temperatureis not dependent on environmentaltemperature changes.) VisualTAKS 1 Bio/IPC 2C, 2D; TAKS 3 Bio 7B
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GENERALSKILLBUILDER
READINGREADING
TeachTeach
Chapter 34 • Reptiles and Birds 773
IdentifyingEctothermsSkills AcquiredAnalyzing data,interpreting graphs,predicting patterns
Teacher’s Notes Remind students that ecto- refersto “outside,” endo- refers to“within,” and therm refers to“heat.” Hence, ectotherm means“outside heat” and endothermmeans “heat within.”
Answers to Analysis1. Species A (yellow curve)
probably is an ectotherm. Itstemperature increases duringthe day, when the air tempera-ture increases.
2. around 12 A.M.3. around 12 P.M.4. It has been exposed to
sunlight-warmed air since early in the morning.
5. It would decline steadily fromits value at 6 P.M. to its valueat 12 A.M.
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MISCONCEPTION ALERT
Cold-blooded Emphasize that the termsectothermic and coldblooded are not syn-onyms, although they are often mistakenlyused that way. Many reptiles experiencebody temperatures as high as or higher than human body temperature. For exam-ple, the body temperature of the desertiguana in western North America regularlyreaches 42°C (108°F), which would be fatalfor a human. TAKS 1 Bio/IPC 2D
Transparencies
TT BellringerTT Key Features of ReptilesTT Changes in Lizard Body
TemperatureTT Reptilian Heart Structure
Ectothermic MetabolismReptiles’ ectothermic metabolism is too slow to generate enoughheat to warm their bodies, so they must absorb heat from their sur-roundings. As a result, a reptile’s body temperature is largely deter-mined by the temperature of its environment. Many reptiles regulatetheir temperature behaviorally, by basking in the sun to warm up orseeking shade to cool down. Figure 2 shows that a lizard can main-tain a relatively constant body temperature throughout the day bymoving between sunlight and shade. At very low temperatures, mostreptiles become sluggish and unable to function. Intolerance of coldgenerally limits their geographical range and, in temperate climates,forces them to remain inactive through the winter.
Figure 2 Body temperature in a lizard. Alizard may regulate its bodytemperature by moving repeat-edly between sun and shade.
Tem
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ture
(°C
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5 6 7 8 94 11 12 1 2 310 5 6 7 840
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20
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5
15
25
35
Time of daySunrise Noon Sunset
Changes in Lizard Body Temperature
Emergesfromden
Basking Activity Returns
to denResting in
shade
Lizard's bodytemperature
Air temperature
Analysis
1. Analyze the data and deter-mine which animal species, A or B, is most likely an ecto-therm. Explain your reasoning.
2. Identify the time of day theanimal you identified as anectotherm reaches its lowestbody temperature.
3. Identify the time of day the animal you identified as an ectothermreaches its highest body temperature.
4. Propose a reason why theectotherm’s body temperatureis highest at this time.
5. Predict what the endo-therm’s graph line would looklike if it were extended to show body temperaturebetween 6 P.M. and midnight.
Identifying EctothermsBackground
The body temperature of all animalschanges during the course of a day. How itchanges can help you identify an animal asan ectotherm or an endotherm.
010001011001110101000100100010011100100100010000010100100111010101001000101010010010
Tem
pera
ture
(°C
)
10
20
30
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6 A.M.12 A.M. 12 P.M. 6 P.M.
Time of day
Body Temperatures of Two Animals
Species A Species B Air
2C 11A
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Teach, continuedTeach, continued
774 Chapter 34 • Reptiles and Birds
ModelingWatertight SkinSkills AcquiredCalculating, analyzingdata, inferring conclusions
Teacher’s Notes Be sure to have students wipethe pan of the scale cleanbetween weighings. Place anincandescent lamp on eachtable to simulate a desert environment.
Answers to Analysis1. The mass of the skinless grape
should decrease. The mass ofthe intact grape should stay the same.
2. The skin prevents water fromevaporating from an intactgrape, so the grape’s weightdoes not change. Without itsskin, a grape loses water andbecomes lighter.
3. The skinless grape representsan amphibian’s skin. Theintact grape represents a reptile’s skin.
4. Watertight skin, as in theintact grape, prevents waterloss. This allows an animal tosurvive in dry environments.Most amphibians, like theskinless grape, would dry up if out of water or moist envi-ronment for an extendedperiod of time.
did you know?Introduced Species Cause Problems In thewestern United States, the tansy ragwort plantis poisonous to cattle. The cinnabar moth,whose larvae eat the tansy ragwort, was intro-duced into the region to control this plant.However, the larvae accumulate toxins that killthe northern alligator lizards that prey on thelarvae. Populations of these lizards may be atrisk in certain areas of the west.TAKS 3 Bio 12B; Bio/IPC 3C; Bio 3F
Water RetentionAmphibians such as frogs cannot be considered fully terrestrialbecause they lose too much water through their skin. Amphibians muststay moist to avoid dehydration, and their method of reproductionrequires a moist environment. Reptiles have evolutionary adap-tations that free them from the water requirements of amphibians.
Watertight SkinTerrestrial animals face a serious problem of water loss as waterevaporates through their skin. Modern reptiles have evolved a skinmade of light, flexible scales. These scales overlap and form a pro-tective, almost watertight skin that minimizes water loss, as shownin Figure 3.
Reviewing InformationReread the bulleted list ofkey features of reptiles inFigure 1. Then write themdown on a separate piece of paper, leaving room towrite notes about eachcharacteristic. As you read,summarize how the informa-tion relates to a particularcharacteristic.
Figure 3 Reptilian scales.The scales of a reptile’s skin form a tight seal thatretains moisture within thereptile’s body.
Modeling Watertight Skin Scales make a reptile’s skin almost watertight. This is one of reptiles’ adaptations to terrestrial life. You can use grapes to model and compare water loss in different types of skin.
Materials
forceps, 2 grapes, balance, Petri dish
Procedure
1. Find the mass of one grape,and record it in a data table.Then place the grape in anopen Petri dish.
2. Using forceps, peel the skin from the second grape.Find and record the mass ofthe peeled grape. Then placeit in the same Petri dish, butdo not let the two grapestouch.
3. Wait 15 minutes, and thenfind and record the mass ofeach grape again.
Analysis
1. Calculate the differencebetween the original and finalmasses of each grape.
2. Propose an explanation forany changes in mass youobserved.
3. Determine which graperepresents an amphibian’sskin and which represents areptile’s skin.
4. Describe how a watertightskin is an adaptation to ter-restrial life. Include informa-tion you have learned in thislab in your explanation.
2B 2C 2D 7B
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TAKS 1 BioIPC 2B, 2C, 2D; TAKS 3 Bio 7B
Student Edition TAKS Obj 1 Bio/IPC 2B, 2C, 2D TAKS Obj 3 Bio 7B TAKS 3 Bio 12ETEKS Bio 7B, 12C, 12ETEKS Bio/IPC 2B, 2C, 2D
Teacher Edition TAKS Obj 1 Bio/IPC 2B, 2C, 2D TAKS Obj 3 Bio 7B, 12B, 12ETAKS Obj 5 IPC 6BTEKS Bio 3F, 7B, 12B, 12C, 12ETEKS Bio/IPC 2B, 2C, 2D, 3CTEKS IPC 6B
pp. 774–775
IPC Benchmark Review
To prepare students for the TAKS and accompany thediscussion of thermoregulation in reptiles, have stu-dents review Convection, Conduction, and Radiation,TAKS 5 IPC 6B on p. 1063 of the IPC Refresher in theTexas Assessment Appendix of this book.
TAKS 1, TAKS 3
Green Turtles Tour the Atlantic Green turtles migrate more than 2,000 km (1,250 mi)from the waters off Brazil to the beaches ofAscension Island in the central Atlantic Ocean.A female green turtle will lay her eggs on thesame beach where she hatched. Scientists donot yet know for certain how she finds herbirthplace. Bio 12C
ActivityComparing Eggs Using fieldguides, books, and Internetresources, have students researchthe eggs of birds, reptiles, andamphibians. Ask each student tomake life-size, full-color drawingsof several types of eggs on smallpieces of paper. When students arefinished, assemble the drawingsinto three large posters forcomparison: The Eggs ofAmphibians, The Eggs of Reptiles,and The Eggs of Birds.
InterpersonalTAKS 1 Bio/IPC 2C, 2D; TAKS 3 Bio 7BLS
Chapter 34 • Reptiles and Birds 775
Trouble for Turtles inTexasTeaching Strategies• Show students a map of Texas
and trace the flow of theGuadalupe River. Ask stu-dents to locate cities that arenear the river. Then havestudents locate Canyon Lake.
• Tell students that in Cagle’smap turtle, a turtle’s sex isdetermined by the tempera-ture during which it was incu-bated. When temperatures arehigher than 30.5ºC, femaleturtles are produced; when itis lower than 28ºC, maleturtles are produced.
Discussion• How do humans affect the
habitat of the Cagle’s mapturtle? (Humans disrupt turtlehabitat by drawing water fromthe river, using the river forrecreation, building dams, anddeveloping areas along the river.)
• Even though they spend mostof their life in the water,Cagle’s map turtles lay theireggs on land. Why don’t theireggs dry out? (Turtles layamniotic eggs. Amniotic eggshave a food and water supplyso that they don’t dry out.)
• Male and female turtles eatdifferent things. What do youthink would be a benefit ofthis strategy? (It mightdecrease competition for food.)
Watertight EggsFor a reptile living on dry land, reproduction presents another seri-ous water-loss problem. Without a watery environment, both spermand eggs will dry out. A reptile’s fertilized eggs need a moist envi-ronment in which to develop. As you will read later in this chapter,the first problem is overcome by internal fertilization.
The nature of a reptile’s amniotic (am nee AHT ic) egg solves thesecond problem. An contains both a water supply anda food supply and is key to a reptile’s success as a terrestrial animal.Because the egg’s tough shell makes it essentially watertight, it doesnot dry out, even in very dry habitats. Most reptiles, all birds, andthree species of mammals reproduce by means of amniotic eggs withshells. (Other mammals produce amniotic eggs, but the embryodevelops within the female’s uterus rather than within a shell. Youwill learn about the development of these eggs in a later chapter.) Theformation of amniotic eggs with shells suggests that these threegroups of animals evolved from a common ancestor.
amniotic egg
The Guadalupe River in south-ern Texas is home to several
threatened and endangeredspecies. Another may soon beadded to the list: Cagle’s mapturtle, Graptemys caglei. Firstdiscovered in 1974, this reptile atone time had a larger range thanit does today. It is now thought toexist only in the Guadalupe River.Although the turtle is not yetconsidered threatened or endan-gered, it has been listed as aprotected species in Texas.
Cagle’s map turtles rarely leavethe water except to lay eggs. Thefemales eat clams and aquaticsnails. The males eat insect larvae,which are usually found in poolsand in rocky areas with riffles.
A Changing EnvironmentThe Guadalupe River windsthrough a part of Texas that has arapidly growing human populationwith an increasing demand forwater. Some parts of the riverattract so many recreational visi-
tors that water quality and shore-line habitat are being degraded.Clearing of forests along the riverfor building construction couldfurther lower the river’s waterquality and change its flow.Numerous dams already interruptthe flow of the river, and two addi-tional dams have been proposed.Dams cause riffles to disappearand allow silt to cover rocks, mak-ing it harder for turtles to find food.
Monitoring the SituationResearchers at West Texas A&MUniversity in Canyon have beenstudying the ecology of Cagle’smap turtle for more than 20 years.The data they have collectedshow how the turtle is faring indifferent areas. For example, tur-tle populations now are greatlyreduced in Canyon Lake, a reser-voir in the upper portion of theriver.
Further work by the researcherswill focus on the turtles’ waterflow requirements and habitat
characteristics. Knowing whatwater flows the turtles need mayallow scientists to recommendwhen and how much watershould be released from thedams. Learning more about theturtles’ preferred habitat, such asthe size of rocks they use most,will help people identify sectionsof the river that may have to bepreserved. Changes such asthese, the researchers believe,are needed to keep Cagle’s mapturtle from becoming a threat-ened species.
www.scilinks.orgTopic: Texas ReptilesKeyword: HXX4023
Trouble for Turtles in Texas
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TAKS 3
Teaching TipSurface Area Ask students whichmelts faster—multiple cubes of iceor a single block of ice of the sameweight? Lead students into a dis-cussion of the importance of sur-face area in living things. Relate thecubes of ice to alveoli in the lungs.
Verbal
Math Skills Ask students to findthe surface area of an 8 mL cube andthe combined surface area of eight 1mL cubes. Remind students that thesurface area of a cube is found by l � w � 6 (where l � length, w �width, and 6 � the number of sides).Point out that an 8-mL cube hastwo-centimeter sides and a 1-mLcube has one-centimeter sides.(Although the overall volume is thesame, the 8-mL cube has a surface areaof 24 cm2 and eight 1-mL cubes have acombined surface area of 48 cm2.)
Logical
Group ActivityLocal Snakes Use a field guide todetermine what kinds of snakesare found in your area. Havegroups research these snakes andreport to the class on the snakes’habitat, range, reproduction,behavior, feeding habits, and anyother relevant information.
Verbal
TAKS 1 Bio/IPC 2C, 2D; Bio 8B
Co-op LearningLS
LS
GENERALBUILDERSKILL
TAKS 4 IPC 9DLS
Teach, continuedTeach, continued
776 Chapter 34 • Reptiles and Birds
Snakes in Literature Throughout history,many cultures have used snakes in literary,cultural, and religious settings, such as TheBible, and in stories such as the Greek mythof Medusa. Even children’s stories likeAladdin and The Jungle Book include snakes.Snakes are often portrayed as evil, cold-blooded animals. Have students research thisphenomenon in literature and write an essayon whether the reputation of the snake isdeserved. TAKS 1 Bio/IPC 2D
SOCIAL STUDIESSOCIAL STUDIESCONNECTIONCONNECTION
Respiration Because most reptiles are far more active than amphibians, theyhave greater metabolic requirements for oxygen. Their bodies meetthis demand in several ways.
LungsA reptile’s scaly skin does not permit gas exchange, so reptiles can-not use their skin as an additional respiratory surface, as manyamphibians can. However, the lungs of most reptiles have manyinternal folds, as shown in Figure 4. These folds greatly increase therespiratory surface area of a reptile’s lungs. In addition, reptileshave strong muscles attached to their rib cage. The action of thesemuscles helps to move air into and out of the lungs, increasing thelungs’ efficiency.
HeartRecall that the ventricle of the amphibian heart is not divided by aseptum. Oxygen-poor blood and oxygen-rich blood mix somewhatin the amphibian’s ventricle. In most reptiles, however, the septumextends into the ventricle, partly dividing it into right and lefthalves, as shown in Figure 5. The septum enables a much better, butstill incomplete, separation of oxygen-rich and oxygen-poor blood.As a result, oxygen is delivered to the body cells more efficientlythan in amphibians.
Unlike most reptiles, crocodilians have a heart with a com-pletely divided ventricle that consists of two pumping chambers.This arrangement fully separates the lung circulation from thebody circulation. Thus, the delivery of oxygen throughout thebody is further improved in these animals.
Figure 4 Reptilian lungs.The lungs of reptiles containnumerous internal folds.
Figure 5 Reptilian heart.In most reptiles, the ventricleof the heart is partly divided bya septum.
Reptilian Heart Structure
Rightatrium
From body To body
To body
Righthalf of
ventricle Lefthalf of
ventricle
Leftatrium
Fromlungs
To lungs
Incompleteseptum
Oxygen-poor blood from the bodyenters the right atrium. Oxygen-rich
blood from the lungs enters the left atrium.
1
An incomplete septum partlydivides the ventricle. Thus,
there is less mixing of oxygen-richand oxygen-poor blood than there isin the amphibian heart.
2
Arteries carry oxygen-richblood from the left half of
the ventricle to the body andoxygen-poor blood from the righthalf of the ventricle to the lungs.
3
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Student Edition TAKS Obj 1 Bio/IPC 2C TAKS Obj 2 Bio 8C TAKS Obj 2 Bio 10A TAKS Obj 3 Bio 7B TEKS Bio 7B, 8C, 10A, 11ATEKS Bio/IPC 2C
Teacher Edition TAKS Obj 1 Bio/IPC 2C, 2D TAKS Obj 2 Bio 8C, 10A TAKS Obj 3 Bio 7B TAKS Obj 4 IPC 9D TEKS Bio 7B, 8B, 8C, 10A, 11ATEKS Bio/IPC 2C, 2DTEKS IPC 9D
pp. 776–777
Answers to Section Review
1. strong, bony skeletons, and toes with claws;ectothermic metabolism; dry scaly skin, almostwatertight; amniotic eggs; well-developedlungs; partly or completely divided ventricle;internal fertilization
2. Because they are ectotherms, reptiles must thermoregulate behaviorally. They can be physically active and hunt for food only whentheir body temperature is within a certain critical range.
3. The almost watertight skin and amniotic eggsof reptiles minimize water loss on land.TAKS 3 Bio 7B
Bio 11A
TAKS 2 Bio 8C
ReteachingHave students pair up and list eachof the seven key features of reptiles,which are given in Figure 1, onindividual index cards. On the backof each card, have them write aone-word clue to identify the char-acteristic on the front of the card.Ask students to shuffle the cardsand turn them so only the cluewords are showing. Have one stu-dent choose a card at random andread the clue word. His or her part-ner should respond with the keycharacteristic. If the studentanswers correctly, his or her part-ner should set the card aside.Students should continue the gameuntil all of the cards are set aside.Students should then switch rolesand repeat the process.
Interpersonal
QuizTrue or False:
1. As in most amphibians, fertiliza-tion in reptiles is external. (False.Fertilization is internal, an adapta-tion to life on land.)
2.The heart of most reptiles onlypartially separates blood fromthe lungs and blood from thebody. (True. Except in crocodil-ians, freshly oxygenated bloodmixes in the heart with oxygen-depleted blood.)
AlternativeAssessmentHave teams of students write briefdescriptions of what they think arethe five most important things theyhave learned about reptiles. Haveteams present their descriptions tothe class, with each team memberparticipating in the presentation.
Verbal
TAKS 2 Bio 8C
Co-op LearningLS
GENERAL
TAKS 2 Bio 8C, 10A; TAKS 3 Bio 7B
TAKS 2 Bio 8C
GENERAL
TAKS 2 Bio 8C
Co-op LearningLS
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Chapter 34 • Reptiles and Birds 777
ReproductionUnlike the eggs of most amphibians, reptilian eggs are fertilizedwithin the female, a process called internal fertilization. The malereptile introduces his semen directly into the female’s body. Thesemen contains sperm and fluid secretions. Internal fertilizationprotects the gametes from drying out, even though the adult ani-mals are fully terrestrial.
Many reptiles are (oh VIHP urh uhs), meaning theyoung hatch from eggs, as shown in Figure 6. In most cases, theeggs are not protected by the parents. Most snakes and lizards, allturtles and tortoises, and all crocodilians are oviparous. All birdsand three species of mammals are also oviparous.
Some species of snakes and lizards are , whichmeans the female retains the eggs within her body until shortlybefore hatching, or the eggs may hatch within the female’s body.Although the embryos receive water and oxygen from the female,their nourishment comes from the yolk sac. The offspring of a snake,shown in Figure 6, are born able to fend for themselves. In ovovivip-arous reptiles, the eggs are less vulnerable to predators.
ovoviviparous
oviparous
Figure 6 Reproduction.Sea turtles hatch from eggsburied on sandy beaches. The eggs of some species ofsnakes are incubated withinthe female’s body, and theyoung are born live.
Sea turtles Hatchling snakes
Section 1 Review
Identify seven characteristics of reptiles. 8C
Describe how the ectothermic nature of reptilesinfluences their physical activity and feeding habits.
Summarize the skin and egg adaptations thatallow reptiles to live on land. 7B
Critical Thinking Forming ReasonedOpinions Data show that an animal’s tempera-ture changes over the course of a day. A studentasserts that this proves the animal is an ecto-therm. What must the student consider beforemaking such a claim? 2C 11A
Describe how reptiles meet their need for moreoxygen than amphibians require. 10A
If a lizard’s internal temperature sensors detect a decrease in bodytemperature, the lizard can maintain homeostasis by 11A
A speeding up its metabolism.B slowing its metabolism.C basking in the sunshine. D resting in the shade.
TAKS Test PrepTAKS Test Prep
The term ovoviviparouscomes from three differentLatin words: ovum, meaning“egg,” vivus, meaning“alive,” and parere, mean-ing “to bring forth or bear.”
11A
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4. The student would need to compare theanimal’s temperature changes to changes in theenvironmental temperature.
5. In contrast to amphibians, reptiles have well-developed lungs with alveoli, as well as strongrib muscles.
6. A. Incorrect. Ectotherms cannotalter their metabolism to maintain homeostasis. B. Incorrect. A slower metabolism would not increase body temperature. C. Correct.Ectotherms maintain body temperature bybasking. D. Incorrect. Resting in the shadewould not increase body temperature. Bio 11A
Bio 11A
TAKS 1 Bio/IPC 2C; Bio 11A
OverviewBefore beginning this sectionreview with your students theobjectives listed in the StudentEdition. In this section, students areintroduced to the orders of the rep-tiles, one of the most diverse classesof terrestrial vertebrates. Studentswill also learn the distinguishingcharacteristics of all the orders.
Ask students to list as manyreptiles as they can. Then, havethem indicate which reptiles ontheir list are closely related. Afterreading the section, have studentsmake corrections and add anymissing groups of reptiles to theirlists. (Students should indicate thatsnakes and lizards are related, turtlesand tortoises are related, and thatcrocodiles and alligators are related.Students are probably unfamiliar withthe tuataras.)
DemonstrationObtain a picture of a skink, andcover its body so that only its headshows. Ask students if the animal isa lizard or a snake. Then reveal therest of the animal, pointing outhow similar some lizards are tosnakes. Ask students how to tell alizard from a snake. (Most lizardshave legs and external ears, a pec-toral girdle, and many have movableeyelids. Snakes lack these features.)
Visual TAKS 2 Bio 8C; Bio 8BLS
GENERAL
MotivateMotivate
TAKS 2 Bio 8C; Bio 8B
Bellringer
FocusFocus
Section 2
778 Chapter 34 • Reptiles and Birds
• Lesson Plans• Directed Reading• Active Reading GENERAL
GENERAL
Chapter Resource File• Reading Organizers• Reading Strategies• Occupational Application Worksheet:
Emergency MedicalTechnician GENERAL
Planner CD-ROM
Transparencies
TT BellringerTT External Structures of SnakesTT Internal Structures of SnakesTT Orders of Living ReptilesTT Orders of Extinct Reptiles
Section 2 Today’s Reptiles
Lizards and Snakes You’ve probably walked by a snake or lizard without even knowingit was there. Most are quiet, and their coloration often concealsthem from view. Even if you visited the jungles of South America,you might not notice an anaconda unless it moved. What’s an ana-conda? It’s the world’s largest snake, frequently reaching 5 m (about16 ft) in length. The largest anaconda ever found was twice thatlong. Very large anacondas have been known to prey on jaguars.After such a meal, the anaconda may not eat again for up to a year.
Snakes and lizards belong to order Squamata. A distinguishingcharacteristic of this order is a lower jaw that is only loosely con-nected to the skull. This allows the mouth to open wide enough toaccommodate large prey and explains how an anaconda can swal-low a jaguar. This ability is a contributing factor to the success ofsnakes and most lizards as predators.
LizardsCommon lizards include iguanas, chameleons, geckos, anoles, andhorned lizards (often mistakenly called “horny toads”). A few speciesof lizards are herbivores, but most are carnivores. Most lizards aresmall, measuring less than 30 cm (1 ft) in length, but lizards thatbelong to the monitor family can be quite large. The Komodo dragonof Indonesia, shown in Figure 7, is the largest monitor lizard. It canbe up to 3 m (10 ft) in length and weigh up to 125 kg (275 lb). Thetail of some species of lizards, such as the gecko shown in Figure 7,breaks off easily when seized by a predator, allowing the lizard toescape. Lizards can regenerate a new tail, but it does not have anyvertebrae in it.
Objectives● Compare the four living
orders of reptiles.
● Describe the timber rattle-snake’s adaptations forlocating and capturing prey.
● Compare the parental careof crocodilians with that ofother reptiles.
Key Terms
carapaceplastron
Figure 7 Lizards. Geckosare small reptiles, rarelyexceeding 24 cm (10 in.) inlength. The Komodo dragon isthe world’s largest lizard.
Komodo dragon
Gecko
8C
8B
7B
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Student Edition TAKS Obj 2 Bio 8C TAKS Obj 3 Bio 7B TAKS Obj 3 Bio 12B TEKS Bio 7B, 8C, 12B
Teacher Edition TAKS Obj 2 Bio 8CTAKS Obj 3 Bio 12BTEKS Bio 8B, 8C, 12BTEKS Bio/IPC 3C
pp. 778–779
TAKS 2
TAKS 3
Teaching TipDangerous Snakes Ask studentswhat venomous snake is the mostdangerous in the world. Recordtheir responses. (examples: kingcobra, sea snake, coral snake, andAustralian tiger snake) Ask why aparticular species is consideredmore dangerous than others. Tellthem that many different venomoussnakes are touted as the “most dan-gerous snake alive,” or the “mostpoisonous snake on Earth.” Pointout that several factors determinehow “dangerous” a snake is.Among these factors are the toxic-ity of its venom, the type of venom(hemolytic or neurotoxic), and theamount of venom a bite victimreceives. In India, there are about900,000 snakebites each year,resulting in about 9,000 deaths.Many of these bites are deliveredby the aggressive king cobra, whichis frequently encountered by India’slarge human population. VerbalBio/IPC 3C
LS
TeachTeach
Chapter 34 • Reptiles and Birds 779
Answer
People who have other pets thatmight harass a gecko, such as acat or a dog, should not try touse geckos for pest control.
TAKS 3 Bio 12B
Real Life
MEDICINEMEDICINECONNECTIONCONNECTION
Medical professionals are nearly unanimous intheir views of what not to do for snakebite:
• No ice or any other type of cooling on the bite
• No tourniquets
• No electric shock
• No incisions in the wound Bio/IPC 3C
The American Red Cross recommends the following first-aid treatment for snakebite:
• Wash the bite with soap and water.
• Immobilize the area and keep it lower thanthe heart.
• Get medical help.
SnakesSnakes probably evolved from lizards during the Cretaceous period.The close relationship between lizards and snakes is reflected intheir many similarities. In fact, it is often difficult to distinguish thelegless species of lizards from snakes. Snakes lack movable eyelidsand external ears, as do several species of lizards. Also, both snakesand lizards molt periodically, shedding their outer layers of skin.
Body Structure The skeleton of snakes is unique. Most snakes haveno trace of a pectoral girdle (the supporting bones for the bones ofthe forelimbs), which is found even in legless lizards. The snake’sjaw is very flexible because it has five points of movement. (Yourjaw, in contrast, has only one movement point.) One of these pointsis the chin, where the halves of the lower jaw are connected by anelastic ligament. This ligament permits the lower jaw to spreadapart when a large meal is being swallowed. The African egg-eatingsnake, shown in Figure 8, can swallow eggs that are much largerthan its head in a process that can take an hour or more.
Feeding While many snakes simply seize their prey and swallow itwhole, some snakes use other methods to subdue their prey. Manyvery large snakes, such as anacondas, boas, and pythons, are con-strictors, as are some smaller species, such as king snakes.Constrictors wrap their body around their prey, gradually squeezingtighter and tighter until the prey suffocates. The snakes then swal-low their prey whole, even if the prey is very large. Like all snakes,constrictors have no teeth that are suited for cutting and chewing.
Some snakes kill their prey with venom (poison). Of the 13 fami-lies of snakes, only four are venomous: (1) cobras, kraits, and coralsnakes; (2) sea snakes; (3) adders and vipers; and (4) rattlesnakes,water moccasins, and copperheads. In most venomous snakes,modified salivary glands produce a venom that is injected into thevictim through grooved or hollow teeth. The African boomslangand twig snakes produce venom but do not inject it. Instead, theybite their prey with fangs located at the back of their mouth.Grooved teeth direct the venom into their victim’s wound. You canread more about the biology of snakes in Up Close: Timber Rattle-snake, on the following pages.
Real LifeNeed a lizard? Instead of calling anexterminator to rid theirhomes of unwanted pests,some adventuresomehomeowners keep a Tokaygecko. This gecko preysvoraciously on mice andinsects and is very efficientat ridding a home of these pests. Finding Information Investigate the pros andcons of using geckos forpest control. Who shouldtry this method and whoshould avoid it?
Figure 8 Snake feeding.Snakes have flexible jaws thatallow them to swallow preymuch larger than their head.
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TAKS 3
780 Chapter 34 • Reptiles and Birds
MISCONCEPTION ALERT
Slimy Snakes Contact a local nature center,zoo, or herpetological society to arrange for alive, non-poisonous snake and handler tovisit the class. Have students make a list ofsome of their preconceptions about snakes.For instance, many students believe that asnake’s skin is slimy, like that of a frog.Another misconception is that the tongue of
a snake is poisonous, and that snakes willattack people for no reason. Show the class alive snake, and allow students to touch andexamine the snake. Help to dispel misconcep-tions by discussing possible origins for suchfears. Remain sensitive to the fact that manypeople will continue to fear snakes.TAKS 1 Bio/IPC 2D
GENERAL
Timber Rattlesnake
Teaching Strategies Help students understand therattlesnake’s ability to sense itsprey in the dark by using awarm object such as a heatingpad. Place the heating pad on atable and allow it to warm thesurface. Remove the heatingpad and have students movetheir hands above the tabletopwithout touching the tableitself. They should be able tofeel the heat radiating from thewarmed spot. Have studentsdetermine how close theirhands must be to detect theheat. Inform them that a rat-tlesnake can locate warm preyfrom a distance of 1 m (39 in.).These snakes, however, senseheat with their pit organs, notthrough their skin.On a sheet of paper, have stu-dents list each major headingin the Up Close feature. Afterthey read each section, havethem hypothesize how thatparticular feature of the timberrattlesnake is an adaptation forsurvival. Then have studentsexchange papers with a partnerand read their partner’s paper,noting how their partner mayhave identified a different survival value for some of the features.
TAKS 2 Bio 8C, 10A; TAKS 3 Bio 7B; Bio 12C
Up Close
External Structures
Up CloseTimber Rattlesnake
Scientific name: Crotalus horridus
Size: Typically 90–150 cm (36–60 in.) long; maximum 189 cm (74 in.)
Range: Eastern and central United States, from northern New York to northern Florida and west, to central Texas
Habitat: Prefers thick brush, dense woodland, or swamp
Diet: Primarily small mammals
●
●
●
●
●
Rattle The rattle typically consists of 5 to 7 interlocking rings
made of keratin, a protein. When shaken, it produces a rattling
sound that serves as a warning. Contrary to popular belief, the
snake does not add a rattle each year. Instead, each time the
snake sheds its skin during molting, a new ring is added
to the base of the rattle. The more rapidly the snake
grows, the more rattles it accumulates during a
given time. This is why the number of rattles
a snake has increases with the size
of the snake.
Pit organ Between each eye and nostril of the rattlesnake is an organ
that can detect infrared radiation. The snake can locate a warm-bodied
animal in a cool, nighttime environment by detecting the difference in
infrared radiation emitted by the animal and the cooler background. Thus,
a rattlesnake can hunt in total darkness.
Rattle
Pit organ ▼
▲
Eye
Nostril
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TAKS 2, TAKS 3
Student Edition TAKS Obj 2 Bio 8C, 10A TAKS Obj 3 Bio 7B TEKS Bio 7B, 8C, 10A, 12C
Teacher Edition TAKS Obj 1 Bio/IPC 2D TAKS Obj 2 Bio 8C, 10A TAKS Obj 3 Bio 7B TEKS Bio 7B, 8C, 10A, 12CTEKS Bio/IPC 2D, 3C
pp. 780–781
Venomous Snakes About 99 percent ofvenomous snakebites in the United States arefrom pit vipers. About 8,000 snakebitesoccur in the United States each year, andaround 9 to 15 victims die. Every stateexcept Maine, Alaska, and Hawaii is hometo at least one poisonous snake species.Bio /IPC 3C
Chapter 34 • Reptiles and Birds 781
Timber RattlesnakeDiscussion • Explain why it would be eas-
ier for a timber rattlesnake tokill a mouse than a lizard atnight. (The mouse is anendotherm and the pit viper’sheat-sensitive pits can detectits body heat. The lizard is anectotherm and would not nec-essarily be warmer than itssurroundings.)
• What is the advantage to arattlesnake of announcing itspresence to other animals byrattling? (Answers may varybut may include that by rat-tling the snake keeps largemammals, such as cattle, fromstepping on it.)
• How is an ovoviviparoussnake, such as the timber rat-tlesnake, different from aviviparous snake in the waydeveloping embryos are sus-tained? (Ovoviviparous mothers supply no nutrients to the developing young, whileviviparous mothers do.)
Up Close
did you know?Triple-jointed Jaws The tiny snakes calledthreadsnakes have triple-jointed jaws. When athreadsnake burrows into the nests of ants orother social insects, parts of its lower jaw rotatelike a pair of swinging doors. It is thought thatthis action helps the snake to eat quickly andescape injury or death from ant stings.TAKS 3 Bio 7B; Bio 12C
Internal Structures
Venom glands The timber rattle-
snake has hollow upper front teeth,
or fangs. When the rattlesnake
strikes, these hinged fangs swing
forward from the roof of the mouth
and inject venom deep into the prey.
The venom contains hemotoxins,
proteins that attack the circulatory
system, destroying red blood
cells and causing internal
hemorrhaging. Modified salivary
glands in the upper jaw produce
the venom.
Jacobson’s organs Flicking its
forked tongue into the air, the rattle-
snake takes in chemical samples
from the environment. These chemi-
cals are transferred to two depres-
sions in the roof of the mouth called
Jacobson’s organs, which detect
the odor of the chemicals. The
snake uses these organs to follow
the scent trail of prey.
Reproductive structures This male rattlesnake
produces sperm in his testes. Female timber rattlesnakes
are ovoviviparous. A female carries her fertilized eggs in her
body while they develop. Each egg has a thin membrane
through which water and oxygen pass from the mother to
the embryo. All nourishment is provided by the egg’s yolk.
After the eggs hatch in the mother’s body, the live young
are ejected and must fend for themselves.
Spine The rattlesnake’s spine is
made up of several hundred ver-
tebrae, each with its own pair of
attached ribs. It provides the frame-
work for thousands of muscles that
manipulate not only the skeleton but
also the snake’s skin, causing the
overlapping scales to extend or lie flat.
Internal anatomyThe internal organs are
elongated, matching the
snake’s body shape. The
left lung is nonfunctional.
Jacobson’s organs ▼
Fang
Tongue
TracheaEsophagus
Venomgland
▼Heart
Cloaca
Left lung
Right lung
Stomach
Small intestine
Large intestine
Kidneys
Liver
Gallbladder
Pancreas
▼ Testes ▼ Spine
781
Using the FigurePoint out in Figure 10 that a turtle’sshoulders lie within its rib cage.Students should recognize that theirown shoulders are outside of theirribs. Tell students that a turtle isattached to its shell and cannotcrawl out of it, as cartoon turtlesoften do. Visual
Writing Skills Have studentsimagine that they are the first per-son from their country to see aturtle. Ask students to write adescription of a turtle, for an audi-ence that has never seen a turtlebefore. Encourage them to be bothdescriptive and accurate. Verbal
Teaching TipEndangered Crocodilians Tellstudents that although crocodiliansare fierce predators, many of the 25species of crocodilians are endan-gered or threatened. Overhuntingof crocodilians for their hides,which are used to make leathergoods, is the primary cause of theirdecline. TAKS 3 Bio 12B; Bio/IPC 3C
TAKS 1 Bio/IPC 2DLS
BUILDERSKILL
TAKS 3 Bio 7BLS
GENERAL
Teach, continuedTeach, continued
782 Chapter 34 • Reptiles and Birds
did you know?Alligators’ Sounds Alligators are unusualamong reptiles in being able to make definitevocalizations. The male alligator bellowsloudly during mating season. Vocal sacs oneach side of his throat inflate when he calls.When alligators hatch from their buried eggs,they make a sound that is almost like a bark.The sound signals their mother that it is timeto open the nest. Hatchlings also have a dis-tress call they use to alert their mother if theyfeel threatened. TAKS 3 Bio 7B; Bio 12C
CulturalAwarenessCulturalAwareness
Turtle Myths The turtle appears as a cen-tral character in mythologies from aroundthe world. An ancient Chinese mythdescribes how the turtle Kwei created theuniverse. The Chinese Book of Rites namesthe turtle as one of the four benevolentspirit animals. Hindu myths from Indiadescribe the world as being supported byfour elephants standing on a turtle’s back.And in North America, several native cul-tures imagined the world as an island on theback of a great turtle. Bio/IPC 3C
Other Orders of Reptiles The remaining orders of living reptiles contain far fewer species thanthe order Squamata does. There are about 250 species of turtles(which generally live in water) and tortoises (which live on land), allclassified in the order Chelonia. The order Crocodilia is composed of25 species of large, aquatic reptiles. The order Rhynchocephalia(RING koh seh FAY lee uh) contains only two species of tuataras.
Turtles and TortoisesTurtles and tortoises, shown in Figure 9, differ from other reptilesin that their bodies are encased within a hard, bony, protectiveshell. Many of them can pull their head and legs into the shell foreffective protection from predators. While most tortoises have adome-shaped shell, water-dwelling turtles have a streamlined, disk-shaped shell that permits rapid maneuvering in water. Turtles andtortoises lack teeth but have jaws covered by sharp plates, whichform powerful beaks. Many are herbivores but some, such as thesnapping turtle, are aggressive carnivores.
Today’s turtles and tortoises differ little from the earliest knownturtle fossils, which date to more than 200 million years ago. Thisevolutionary stability may reflect the adaptive aspects of their basicshell-covered body structure. The shell is made of fused plates ofbone covered with horny shields or tough, leathery skin. In eithercase, the shell consists of two basic parts. The is the dor-sal (top) part of the shell, and the is the ventral (bottom)portion. The vertebrae and ribs of most species are fused to theinside of the carapace, as shown in Figure 10. The shell provides thesupport for all muscle attachments in the torso.
Crocodiles and AlligatorsOf all the living reptiles, the crocodilians are mostclosely related to the dinosaurs. In addition tocrocodiles and alligators, shown in Figure 11, theorder Crocodilia includes the alligator-likecaimans and the long-snouted gavial. Crocodiliansare aggressive carnivores. Some are quite large.American alligators can reach 5.5 m (18 ft) inlength, and Nile crocodiles can reach 6 m (20 ft) inlength and weigh 750 kg (1,650 lb). Crocodiliansgenerally capture prey by stealth, often floating
just beneath the water’s surface near the shore. When an animalcomes to the water to drink, the crocodilian explodes out of the waterand seizes its prey. The crocodilian then hauls the prey back into thewater to be drowned and eaten. The bodies of crocodilians are welladapted for this form of hunting. Their eyes are high on the sides ofthe head, and their nostrils are on top of the snout. As a result, theycan see and breathe while lying nearly submerged in the water. Croc-odilians have a very strong neck and an enormous mouth studded
plastroncarapace
Figure 9 Turtle andtortoise. Like other seaturtles, this green sea turtle(top) spends virtually its entirelife in the sea. The Galápagostortoise (bottom) spends its lifeon land.
Figure 10 Turtle interior.In this ventral view, a turtle’splastron has been removed toshow the relationship of thevertebral column, ribs, pelvis,and pectoral girdle to the carapace.
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Student Edition TAKS Obj 2 Bio 8C TAKS Obj 2 Bio 10A TAKS Obj 3 Bio 7B TAKS Obj 3 Bio 12B TEKS Bio 7B, 8B, 8C, 10A, 11B, 12B
Teacher Edition TAKS Obj 1 Bio/IPC 2D TAKS Obj 2 Bio 8C, 10ATAKS Obj 3 Bio 7B, 12B TEKS Bio 7B, 8B, 8C, 10A, 11B,12B, 12CTEKS Bio/IPC 2D, 3C
pp. 782–783
Answers to Section Review
1. Snakes and lizards both have scaly skin andmolt periodically. Their lower jaw is looselyconnected to the skull.
2. Jacobson’s organs, located in the roof of themouth, detect microscopic airborne particles,which the brain interprets as scent. Pit vipersuse their pit organs to detect heat.
3. Their bodies are encased in a protective shell,and they lack teeth.
4. Alligators and other crocodilians are the onlyreptiles to care for their young. Some alligatorsbuild nests for their young and care for themfor up to a year after they hatch. Bio 8B
TAKS 2 Bio 10A; Bio 8B, 11B
TAKS 3 Bio 7B
TAKS 2 Bio 8C
5. The crocodile is able to keep most of its bodysubmerged and hidden while still being able tobreathe and look for prey.
6. A. Incorrect. The Jacobson’sorgans in the roof of the mouth are sensitive toairborne chemicals. B. Incorrect. Snakes lackears and do not hear faint sounds. C. Incorrect.Snakes can feel ground vibrations throughtheir bodies, not the pit organs. D. Correct.Using pit organs, warm-blooded animals canbe found even in the dark. Bio 11B
Bio 11B
ReteachingWrite the following words orphrases on the board: lizards andsnakes, turtles and tortoises, croco-diles and alligators, and tuataras.Have students copy them, leavingspace for additional information.Have students write distinguishingtraits of each group in the appro-priate spaces without using theirtextbooks. (lizards and snakes-lowerjaw has loose connection to skull, nopectoral girdle in snakes, molt peri-odically, may lack eyelids; turtles andtortoises-hard shell, lack teeth, jawshave a powerful beak; crocodiles andalligators-long snout, eyes high onhead, nostrils on top of head, largemouth with sharp teeth; tuataras-lizardlike, active at night) When thestudents have finished their work,have them share their results with apartner, recording any characteris-tics they omitted but their partneridentified. Verbal
Quiz1. The reptiles that share the most
characteristics with snakes arethe ________ (lizards)
2.Unlike other reptiles, ________care for their young after theyhatch. (crocodilians)
3. The shells of turtles and tortoisesconsist of a plastron on theunderside and a ________, whichfuses with the rib cage. (carapace)
AlternativeAssessmentAssign students to work in groupsof three. Each group will researchthe reptiles of an assigned conti-nent. For each reptile, include thefollowing: order, appearance(drawing), size, diet, habitat, range,and status (common, rare, threat-ened, or endangered). When groupshave finished their research anddrawings, the entire collection canbe assembled on a large mural ofthe continents. Ask a local elemen-tary school to display the mural.
Interpersonal
TAKS 2 Bio 8C
Co-op LearningLS
TAKS 3 Bio 7B
TAKS 2 Bio 8C
TAKS 2 Bio 8C
GENERAL
Co-op LearningLS
CloseClose
Chapter 34 • Reptiles and Birds 783
with sharp teeth. A valve in the back of the mouth pre-vents water from entering the lungs when crocodiliansfeed underwater.
Unlike other living reptiles, crocodilians care fortheir young after hatching. For instance, a femaleAmerican alligator builds a nest of rotting vegetationfor her eggs. After the eggs hatch, the mother may tearopen the nest to free the hatchlings. The young alliga-tors remain under her protection for up to a year.
TuatarasThe two living species of tuataras are members of thegenus Sphenodon and are native to New Zealand.Sphenodon punctatus, the more common species, isshown in Figure 12. Tuataras are lizardlike reptiles upto 70 cm (2 ft) long. Unlike most reptiles, tuataras aremost active at low temperatures. They burrow or baskin the sun during the day and feed on insects, worms,and other small animals at night. Tuataras are some-times called living fossils because they have survivedalmost unchanged for 150 million years. Since thearrival of humans in New Zealand about 1,000 yearsago, the tuatara’s range has diminished, and theirnumbers are declining.
Figure 11 Crocodilians. In general, thesnouts of alligators are shorter and broaderthan those of crocodiles.
American alligator
Australian crocodiles
Figure 12 Tuatara. Tuataras live on only a few small islands in New Zealand.
Section 2 Review
Describe the characteristics shared by lizardsand snakes. 8C
Describe the function of two different organsthat help snakes locate their prey. 7B
Summarize the ways turtles and tortoises differfrom other reptiles. 8B 10A 11B
Compare the parental care shown by alligatorswith that shown by most other reptiles. 8B
Critical Thinking Recognizing RelationshipsHow does the position of a crocodile’s nostrils andeyes relate to its method of hunting? 11B
The pit organ of a rattle-snake is sensitive to A airborne chemicals.B faint sounds.C ground vibrations.D infrared radiation.
TAKS Test PrepTAKS Test Prep11B
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TAKS 2 Bio 8C; TAKS 3 Bio 7B; Bio/IPC 2D; Bio 8B
OverviewBefore beginning this sectionreview with your students theobjectives listed in the StudentEdition. In this section, students willsummarize the key features of birds.These include several reptile-likecharacteristics, such as amniotic eggs and scale-covered feet and legs.Unique adaptations include feathersfor flight and insulation, a strong yetvery lightweight skeleton, a highlyefficient respiratory system and completely divided heart. These fea-tures allow flight for nearly all birds.Students will also examine the highlyvariable beaks and feet of birds,which allow different species tomake use of a range of diets andhabitats.
Ask students to list the unique adap-tations of birds that allow them tofly.
DemonstrationBring a feather to class and askstudents what kind of animal it isfrom. When students answer “abird,” ask them to think of anybird that does not have feathers.(There are none.) Ask them if theycan think of any living animals thathave feathers but are not consid-ered birds. (no) Emphasize thathaving feathers is a unique classifi-cation characteristic for the classAves. Visual TAKS 2 Bio 8C; Bio 8BLS
MotivateMotivate
TAKS 3 Bio 7B
Bellringer
FocusFocus
Section 3
784 Chapter 34 • Reptiles and Birds
• Lesson Plan• Directed Reading• Active Reading• Data Sheet for Math Lab GENERAL
GENERAL
GENERAL
Chapter Resource File
• Reading Organizers• Reading Strategies • Supplemental Reading Guide
Through a Window
Planner CD-ROM
Transparencies
TT BellringerTT Characteristics of BirdsTT Contour Feather StructureTT Avian SkeletonTT Avian Heart StructureTT Avian Lung Structure
Section 3 Characteristics andDiversity of Birds
Key Characteristics of BirdsWhy do people use the expression “free as a bird”? Most likely itcomes from a bird’s ability to fly seemingly wherever it wishes.Through human history, the gift of flight has been celebrated in sto-ries, poetry, and songs. But there is more to birds than flight; infact, some species of birds can’t fly.
The birds you see today are the modern members of class Aves.Unlike their reptilian relatives, birds lack teeth and have a tail thatis greatly reduced in length. But they do retain some reptiliancharacteristics. For instance, birds lay amniotic eggs that are verysimilar to those of reptiles, and the feet and legs of birds arecovered with scales. Other characteristics unique to birds distin-guish them from all other animals. The most obvious is thepresence of feathers and the modification of the forelimbs intowings. Figure 13 lists some distinguishing features of birds. Tolearn more about the anatomy and habits of one bird, see UpClose: Bald Eagle later in this section.
FeathersFeathers are modified reptilian scales that develop from tiny pits,called follicles, in the skin. Just as snakes and lizards replace theirskin by molting, birds molt and replace their feathers. However, fewbirds shed all of their feathers at one time.
Birds have two main types of feathers: contour feathers anddown feathers. cover the bird’s body and giveadult birds their shape. Specialized contour feathers, called flightfeathers, are found on a bird’s wings and tail. These feathers helpprovide lift for flight. As shown in Figure 14, a contour feather hasmany branches called barbs. Each barb has many projections, called
Contour feathers
Objectives● Summarize the key charac-
teristics of birds.
● Describe how a bird’sfeathers and bone structureaid flight.
● Summarize how a bird’slungs and heart are adaptedfor high efficiency.
● Relate the structure of abird’s feet and beak to itshabits and diet.
Key Terms
contour featherpreen glanddown feather
www.scilinks.orgTopic: Characteristics
of BirdsKeyword: HX4036
Figure 13 Characteristicsof birds. Like most birds, thistern is well adapted to flight.
• Forelimbs modified into wings• Body covered with feathers• Lightweight bones• Endothermic metabolism• Super-efficient respiratory
system• Heart with completely
divided ventricle
Characteristics of Birds
8C
7B
7B 10A
7B 11B
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Student Edition TAKS Obj 2 Bio 8C TAKS Obj 2 Bio 10A TAKS Obj 3 Bio 7B TEKS Bio 7B, 8C, 10A, 11B
Teacher Edition TAKS Obj 1 Bio/IPC 2D TAKS Obj 2 Bio 8CTAKS Obj 3 Bio 7B, 12B TEKS Bio 3D, 7B, 8B, 8CTEKS Bio/IPC 2D
pp. 784–785
TAKS 2
TAKS 3
TAKS 3
TAKS 2,TAKS 3
Paired Summarizing Afterstudents have read silently aboutbirds, have pairs of students sum-marize what they have read withoutlooking at the textbook. One studentshould listen without interruptingbut should be prepared to point outany inaccuracies in the summary, andto add any ideas that were left out.Students may refer to the textbookduring this clarification process. You may want to pair ELL stu-dents with native English speakers.
Teaching TipPreening Birds often sit and preentheir feathers. Students have proba-bly observed this behavior. Havestudents hypothesize about thefunction of preening and the reasonthat birds spend so much time doingit. After a period of discussion,point out that when birds preen,they smooth out and clean theirfeathers, making them more aerody-namic. Also note that birds spreadoil from a gland near the base oftheir tail to waterproof the feathersand make them more resistant tobreakage, much the way hair condi-tioner works. Logical
DemonstrationBring cooked, cleaned chickenbones to class for students to exam-ine. Cut a few bones in half so stu-dents can see the hollow structure.If you have a wishbone, allow stu-dents to pull it gently to note itsflexibility. The cartilage keel on thebreast of a chicken is also interest-ing to examine because it providesan attachment surface for flightmuscles. Visual TAKS 3 Bio 7BLS
GENERAL
TAKS 1 Bio/IPC 2D; TAKS 3 Bio 7BLS
GENERAL
TAKS 2 Bio 8C; Bio 8B
SKILLBUILDER
READINGREADING
TeachTeach
Chapter 34 • Reptiles and Birds 785
MISCONCEPTION ALERT
Bird Nests Children who find bird nestsare often warned not to touch them. Thechildren are told, “the mother won’t returnto the nest if you touch it.” In reality, mostbirds have a very poor sense of smell andprobably would not know if their nest hadbeen touched by a human (exceptions areflightless birds, ducks, and vultures). Tocompensate, many birds have keen visionand hearing. Interpersonal TAKS 3 Bio 7BLS
English Language Learners
CareerCareerVeterinarian When most people think of aveterinarian, they think of a “dog or cat doctor.” Many students will know that veteri-narians also treat livestock. However, mostpeople probably do not know that veterinari-ans also treat birds and reptiles. Have studentsinvestigate the training required to become aveterinarian, and have them find out where vet schools are located in your region of the country. Verbal Bio 3DLS
Shaft
Vane
Barb Barbule Hook
barbules, that are equipped with microscopic hooks. These hooks linkthe barbs to one another, giving the feather a continuous surface anda sturdy but flexible shape. With use, the connections becomeundone. When you see a bird pulling its feathers through its beak, it is relinking these connections. This process is called preening.Preening also serves another function. Most birds have a gland calleda which secretes oil. When a bird preens, it spreads theoil over its feathers, cleaning and waterproofing them.
cover the body of young birds and are foundbeneath the contour feathers of adults. Their soft, fluffy structureprovides good insulation for the bird, helping the bird conserve body heat.
Feathers are important for other reasons too. Their colorationmay be protective (as camouflage) or may be important in the selec-tion of a mate. For example, the feathers of some birds allow themto blend in with their surroundings. In other species, the malesdevelop special plumage during the breeding season.
Strong, Lightweight SkeletonIf you have ever picked up a bird, such as a para-keet, you may have been surprised at how light itwas compared to a mammal of a similar size. Thisis because the bones of birds are thin and hollow.Many of the bones are fused, making a bird’s skel-eton more rigid than a reptile’s. The fused sectionsform a sturdy frame that anchors muscles duringflight. The power for flight (or for swimmingunderwater in the case of some birds, like pen-guins) comes from large breast muscles that canmake up 30 percent of a bird’s body weight. Thesemuscles stretch from the wing to the breastbone.The breastbone is greatly enlarged and bears aprominent keel for muscle attachment, as illus-trated in Figure 15. Muscles also attach to the fusedcollarbones (wishbone). No other living vertebrateshave a keeled breastbone or fused collarbones.
Down feathers
preen gland
The structure of a contour feather helps create a smooth, aerodynamic surface, aiding flight.
Figure 14 Contour feather
Fused collarbones
Keeled breastbone
Figure 15 Avian skeleton.A bird’s large, keeled attach-ment point for flight muscles,while its fused collarbones(wishbone) help absorb thestresses of flight.
785
Teaching TipHeat Source The high tempera-ture of birds is a by-product oftheir rapid metabolism. You maywish to use the analogy of a carengine for metabolism. If theengine is running, heat is produced.The faster the engine is running,the more heat is produced.Ectothermic reptiles are like carswhose engines run very slowly allthe time, producing little heat. Incontrast, birds (and mammals)keep their engines running at highspeed all of the time, producingmuch heat. TAKS 3 Bio 7B
Teach, continuedTeach, continued
786 Chapter 34 • Reptiles and Birds
CulturalAwarenessCulturalAwareness
Eagle Feathers The only people in NorthAmerica who can legally own eagle feathersare Native Americans. The eagle is so highlyvalued by tribes throughout the United Statesthat its feathers must be earned through per-sonal sacrifice, and then they may be used onlyin special ceremonies. For instance, if a
Winnebago pow-wow dancer accidentallydrops an eagle feather during a performance,the dance is stopped until the feather is purifiedby an elder and then reclaimed by the dancer,who is not allowed to dance again for a year.Bio/IPC 3C
From body
From body
To body
To lungsFromlungs
Leftatrium
Leftventricle
Rightventricle
Rightatrium
Completeseptum
Oxygen-rich blood from thelungs enters the left atrium,
which pumps it to the left ventricle.
3
The left ventricle pumps the oxygen-rich blood to
the body.
4The right ventricle pumps theoxygen-poor blood to the lungs.2
Oxygen-poor blood from the body entersthe right atrium. The right atrium pumps
this blood to the right ventricle.
1
Avian Heart Structure
Endothermic MetabolismBirds are endotherms; that is, they generate enough heat throughmetabolism to maintain a high body temperature. Birds maintainbody temperatures ranging from 40°C to 42°C (104°F to 108°F),which is significantly higher than the body temperature of mostmammals. For comparison, your body temperature is 37°C (98°F).These high temperatures are due to a high rate of metabolism,which satisfies the increased energy requirements of flight.
Completely Divided VentricleAs in crocodilians, the ventricle of birds is completely divided by aseptum, as shown in Figure 16. Oxygen-rich and oxygen-poor bloodare kept separate, meaning that oxygen is delivered to the body cellsmore efficiently. The sinus venosus, which is a prominent part ofthe fish heart, is not a separate chamber of the heart in birds (ormammals). However, a small amount of tissue from it remains inthe wall of the right atrium. This tissue is the point of origin of theheartbeat and is known as the heart’s pacemaker.
Highly Efficient LungsBirds such as the geese shown in Figure 17 use a considerableamount of energy when they fly. Since birds often fly for long pe-riods of time, their cellular demand for energy exceeds that of eventhe most active mammals. How do birds get the energy they need?
Recall that reptiles meet their increased need for oxygen withlungs that have a larger surface area than the lungs of amphibians.But there is a limit to how much the efficiency of a lung can beimproved just by increasing its surface area. Another way to
Interpreting GraphicsAfter studying Figure 18, useyour own words to summa-rize how one breath of aircirculates through a bird’slungs. Remember to includeboth the inhalation and theexhalation cycle.
Figure 16 Avian heart.A bird’s heart has a complete septum.
www.scilinks.orgTopic: Texas SongbirdsKeyword: HXX4021
786
IPC BenchmarkMini-Lesson
Biology/IPC Skills TAKS 5 IPC 4BInvestigate and describe applications of Newton's laws.Newton’s second law states that theamount of force acting on an object isequal to the object’s mass multiplied byits acceleration. Furthermore, anobject’s momentum is the product of itsmass and velocity. This helps explainone of the principles of flight. Bird’swings have a special shape called anairfoil and airplane wings mimic thisshape. As a mass of air passes over awing it’s path is bent downward,thereby changing its momentum.Changes in the momentum of the airresult in changes on the forces actingon the wing. The amount of lift on awing depends on the amount andvelocity of the air being diverteddownward. For more lift, the wing caneither divert more air—the mass—orincrease the downward velocity of theair. Activity: Have students build paperairplanes that have airfoil wings. Thentest them outside to see if their designswere successful.
Student Edition TAKS Obj 2 Bio 10A TAKS Obj 3 Bio 7B TEKS Bio 7B,10A
Teacher Edition TAKS Obj 1 Bio/IPC 2C, 2D TAKS Obj 3 Bio 7A, 7B TAKS Obj 5 IPC 4BTEKS Bio 7A, 7B, 12CTEKS Bio/IPC 2C, 2D, 3CTEKS IPC 4B
pp. 786–787
the eggs of the incubating species. Therefore, thecowbird nestlings are fed first and get a headstart in their development over the other chicksin the nest. Cowbird nestlings may even ejectthe nestlings of the incubating species, therebyeliminating competition for food.TAKS 3 Bio 7B; Bio 12C
Teaching TipWhite or Dark Meat? The darkcolor of some chicken meat is partlydue to the presence of myoglobin, ahemoglobin-related molecule thathelps provide oxygen to musclesthat must contract vigorously andrepeatedly. Ask students why aduck has dark breast meat but achicken has white breast meat. (Theduck flies long distances, but thechicken does not.) Ask what chick-ens usually use for locomotion andwhat color that meat is. (They usu-ally use their legs to walk, and thelegs contain dark meat.)
Activity Origin of Birds Ask students toidentify the living reptiles that aremost closely related to birds. (crocodilians) Have them name twocharacteristics that crocodiliansand birds share. (a heart with com-pletely divided ventricle, parentalcare of young, amniotic eggs, andvocalization) Have studentsresearch recent fossil discoveriesthat have changed views on theorigin of birds. VerbalTAKS 1 Bio/IPC 2C, 2D; TAKS 3 Bio 7A(grade 11 only), 7B
LS
TAKS 3 Bio 7B; Bio 12C
GENERAL
Chapter 34 • Reptiles and Birds 787
did you know?Brood Parasites The brown-headed cowbirdis a brood parasite. A female brown-headedcowbird will fly to a nest full of eggs, roll one ortwo eggs out, and lay the same number as thenumber she has displaced. When the owner ofthe nest returns, it will incubate all the eggs,including the cowbird’s. The cowbird eggs oftenhave a shorter incubation time and hatch before
increase the efficiency of a lung is to have airpass over its respiratory surface in one direc-tion only, just as water flows over a fish’s gills inone direction. This is what happens in birds.One-way air flow is possible in birds becausethey have air sacs connected to their lungs, asshown in Figure 18. There is no gas exchange inthe air sacs. They simply act as holding tanks.
There are two important advantages to one-way air flow. First, the lungs are exposed only toair that is almost fully oxygenated, increasingthe amount of oxygen transported to the bodycells. Second, the flow of blood in the lungsruns in a different direction than the flow of air does. Unlike theflow of water and blood in fish gills, the flow of air and blood in birdlungs are not completely opposite (countercurrent). Nevertheless,the difference in direction does increase oxygen absorption.
These three characteristics—endothermic metabolism, a com-pletely divided ventricle, and highly efficient lungs—provide theenergy a bird needs for takeoff and sustained flight. They enable ahummingbird to flap its wings rapidly (20–80 beats per second) as ithovers by a flower. They also permit migrating birds to fly thou-sands of kilometers without stopping. One species of shorebirdscalled the lesser yellowlegs flies across the open ocean from Massa-chusetts to Martinique in the West Indies. Incredibly, some of thesebirds cover this distance of 3,220 km (about 2,000 mi) in less than 6 days. Note, however, that many birds, such as gulls and vultures,remain aloft for long periods of time using little energy. These birdstake advantage of upward air movements that lift them.
Avian Lung Structure
During inhalation, most of the fresh air (yellow) inhaled is pulled into the posterior air sacs.At the same time, stale air (green) from the previous inhalation is pulled into the anterior air sacs.
1
During exhalation, fresh air (yellow) from the posterior air sacs enters the lungs. At the same time, stale air (green) from the previous inhalation moves from the anterior air sacs out of the body.
2
Inhalation
Exhalation
Right lung
Trachea
Posterior air sacs Anterior air sacs
Figure 18 Avianrespiration. A single breathof air stays in a bird’s respi-ratory system for two cyclesof inhalation and exhalation.
Figure 17 Flight. Thesebarnacle geese expend anenormous amount of energyduring take off and flight.
787
788 Chapter 34 • Reptiles and Birds
Bald EagleTeaching Strategies• The largest bald eagle nests
in North America werefound in Vermillion, Ohio—3.7 m (12 ft) deep, 2.6 m(8.5 ft) in diameter, andweighing 1,800 kg (2 tons)-and in Florida—6.1 m (20 ft)deep and 2.9 m (9.5 ft)across. An eagle nest is calledan aerie.
• After World War II, the num-bers of bald eagles in thelower 48 states fell drasticallybecause of the widespread useof the pesticide DDT. BecauseDDT breaks down veryslowly, it accumulates in thefood chain and causes theeggshells of bald eagles andmany other birds to becomethin and fragile. Affected eggsbreak when a parent attemptsto incubate them. In 1972,the use of DDT was bannedin the United States. By 1978,fewer than 500 breeding pairsof bald eagles remained in theUnited States outside Alaska.A slow recovery of the eaglesbegan, and by the summer of1999, six states had removedbald eagles from the endan-gered species list.
• Show students a picture of alarge but immature baldeagle and ask them whatkind of bird it is. Point outthat the bald eagle does notget its white head and tailuntil its fourth or fifth yearof life.
Up Close
Transparencies
TT External Structures of BirdsTT Internal Structures of BirdsTT Avian AdaptationsTT Major Orders of Birds
External Structures
Up CloseBald Eagle
Scientific name: Haliaeetus leucocephalus
Size: Wingspan is typically over 2 m (6.5 ft), and bodyweight often exceeds 7 kg (15 lb)
Range: Nearly all of North America, from Florida to northern Alaska
Habitat: Forested areas near water that have tall trees for perching and nesting
Diet: Fish, small mammals, birds, carrion
●
●
●
●
●
Eyes Vision is a bald
eagle’s most important
sense. The bird’s keen
eyesight allows it to see
prey at great distances.
Its visual acuity is 3–4
times higher than ours.
Feathers The body of
the bald eagle is covered
with feathers everywhere
except the feet and the
beak, which are bare.
Both sexes develop the
characteristic white head
and neck at maturity.
Grasping feet The bald eagle
has large feet and talons—the hind
talon may be 5 cm (2 in.) long. The
talons are used to snatch fish from
the water while the eagle is flying.
When the muscles of the legs
contract, the tendons in the lower
legs are pulled, and the talons
lock together around the fish.
Beak The beak is mas-
sive, with an elongated,
sharp, downward-curving
tip. Because they have no
teeth, bald eagles do not
chew their food. Instead,
they use their beak to tear
their prey into portions
that they swallow whole.
Grasping feet
▼ Feathers
▲
▼ Beak
▲ Eye
Nostril
Talon
788
TAKS 2 Bio 8C, 10A; TAKS 3 Bio 7B, 12B; Bio 3F
Student Edition TAKS Obj 2 Bio 8C, 10A TAKS Obj 3 Bio 7B, 12B TEKS Bio 3F, 7B, 8C, 10A, 12B
Teacher Edition TAKS Obj 1 Bio/IPC 2D TAKS Obj 2 Bio 8C, 10A TAKS Obj 3 Bio 7B, 12B TEKS Bio 3F, 7B, 8C, 10A, 12BTEKS Bio/IPC 2D
pp. 788–789
TAKS 2, TAKS 3
ActivityEagle Eyes Eagles have much better vision than humans do. Tosimulate how much better, tape aworksheet on the wall and havestudents stand about 3 m away andtry to read it. Then have themmove 1 m away and read the work-sheet. Tell them that an eagle couldsee the paper at 3 m as well ashumans can at 1 m.TAKS 1 Bio/IPC 2D; TAKS 3 Bio 7B
GENERAL
Chapter 34 • Reptiles and Birds 789
Bald EagleDiscussion• Identify three differences
between the internal struc-tures of the timber rattlesnakeand the bald eagle. (The rat-tlesnake has one functionallung, lacks air sacs, has neithera crop nor a gizzard, hasvenom-producing glands, anddoes not have hollow bones.)
• Would the heat-sensitive pitsof the timber rattlesnake bean effective way of sensingprey for a bald eagle? (No, therattlesnake’s pits are sensitiveonly to nearby heat sources,and the bald eagle spots itsprey from great distances.)
• Why might it be a disadvan-tage for an eagle to have aurinary bladder? (Urine con-tains a greater amount ofwater, which is heavy. Theextra weight would be a disad-vantage in flight.)
• Why might teeth be a disad-vantage to a bird? (Teeth areheavy and require heavy jaws.)
VisualLS
Up CloseInternal Structures
Brain In the ratio of brain size to body size, birds rank
second among vertebrates, behind only mammals. The
large cerebellum receives and integrates information from
the muscles, eyes, and inner ears. This makes possible the
precise control of movement and balance necessary for flight.
The optic lobe is large because it processes input from the
eagle’s most important sense organs—the eyes. The
cerebrum performs many functions, including evaluation of
sensory information, control of behavior, and learning.
Excretory system The excretory system is
efficient and lightweight. It does not store waste
liquids in a bladder. Instead, the bald eagle
(and other birds) converts its nitrogenous
wastes to uric acid, which is concen-
trated into a harmless white paste.
The uric acid travels to the
cloaca and is eliminated.
Cloaca The cloaca is a common
collecting chamber for the excretory,
digestive, and reproductive systems.
As fertilized eggs travel down the
female eagle’s oviduct, egg white,
membranes, and the shell are added.
The completed egg then passes
into the cloaca and out of the
female’s body.
Digestive system Large
meals are temporarily stored in
the crop, the expandable
lower portion of the esophagus.
The food then passes into a
two-chamber stomach. In the
first chamber, stomach acids
begin breaking down the food.
The partially digested food is
then passed to the second
chamber, the gizzard, where
it is ground and crushed.
Undigested material is
eliminated through the cloaca.
Medulla oblongata Optic lobe
Cerebellum Cerebrum
Liver
▼ Gizzard
Crop
Esophagus
Small intestine
Large intestine
▼ Kidney
Left ovary
▼ Cloaca
Pancreas
Left lung
▲ Brain
Trachea
Air sac
Heart
789
Teaching TipReptiles and Birds Have studentsmake a three-column chart like theone in the Graphic Organizershown at the bottom of this page.They should use the information onbirds in Section 3 and the materialon reptiles in Sections 1 and 2.Students should use the followingcharacteristics for both reptiles andbirds: type of body covering, typeof heart, mode of reproduction,type of metabolism, and parentalcare of offspring. Visual
Teaching TipIntroduced Pests House spar-rows and European starlings aretwo common birds that may befamiliar to students. Inform stu-dents that these two species wereintroduced into the United Statesfrom Europe. Both species havebecome serious pests. These exoticspecies out compete native song-birds for food and nesting sites. Infact, they are thought to be at leastpartly responsible for the decline inthe numbers of bluebirds. Bio/IPC 3C
TAKS 2 Bio 8C, 10A; TAKS 3 Bio 7BLS
GENERAL
Teach, continuedTeach, continued
790 Chapter 34 • Reptiles and Birds
Graphic Organizer
Use this graphic organizer with Teaching Tip: Reptiles and Birds.
Characteristic Reptiles Birds
Body covering Scaly skin Feathers
Type of heart Partially or completely Completely divided divided ventricle ventricle
Reproduction Oviparous or ovoviviparous Oviparous
Metabolism Ectothermic Endothermic
Parental care Little or none Until offspring can fly
Adaptations of Birds While there is great diversity among the 28 orders of birds,60 percent of all bird species belong to order Passeriformes.These birds, also know as the songbirds, number approxi-mately 5,300 species and are by far the largest group of ter-restrial vertebrates. Birds are adapted for different ways oflife, and you can tell a great deal about the habits and diet ofa bird by examining its beak (bill), legs, and feet. Carnivorousbirds such as hawks have curved talons for seizing prey anda sharp beak for tearing apart their meal. The beaks of ducksare flat for shoveling through water or mud, and theirwebbed feet enable them to swim. Finches are seed eaters,and their short, thick beak is adapted for crushing seedswhile their curved toes enable them to cling to branches.Other birds, such the penguins shown in Figure 19, are flight-less, and their wings and feet are modified for swimming.
During the evolutionary history of birds, their beaks, legs,and feet have been adapted to the particular environment thebirds live in, as shown in Table 1. Some birds are more highlyspecialized than others, and many birds are highly flexible intheir eating habits. The song sparrow, for example, has astrong bill that it uses in winter to crack hard seeds. In sum-mer, the sparrow uses its bill to catch soft-bodied insects.
Figure 19 Penguin. Thepenguin’s wings are adaptedfor swimming rather than flying.
Type of bird Beak adaptations Foot adaptations
Songbirds (e.g., cardinal, robin)Seed-cracking:Short, thick,strong beak
Insect-catching:Long, slenderbeak for probing
Hovering: Legs so small the bird cannot walk on the ground;tiny feet
Perching: Toes can cling tobranches; one toe points backward
Probing: Thin, slightly curved beakfor inserting into flowers to sip nectar
Hummingbirds
Table 1 Avian Adaptations
790
Student Edition TAKS Obj 2 Bio 8C TAKS Obj 3 Bio 7B TEKS Bio 7B, 8C
Teacher Edition TAKS Obj 1 Bio/IPC 2C, 2D TAKS Obj 2 Bio 8C, 10A TAKS Obj 3 Bio 7B TEKS Bio 7B, 8C, 10A, 12CTEKS Bio/IPC 2C, 2D, 3C
pp. 790–791
Trends in OrnithologyResearchers around the country have beenmonitoring bird populations each year todetermine long-term trends. One apparenttrend: of the 42 bird species that are listed asthreatened or endangered, 22 are associatedwith wetlands. The trend holds true for otheranimals as well. Have students research thethreatened and endangered birds in your area.In their reports, students should discuss theprobable causes of decline, as well as plans forspecies recovery. Bio/IPC 3C
Using the TableHave students pair up. Instruct thestudents to cover the two columnson the right side of Table 1 with asheet of paper. Have one studentuncover the Beak adaptations col-umn, choose one, and read thedescription. The other studentshould try to identify the type ofbird whose beak is described. Thisprocess should continue until thesecond student has correctly identi-fied each bird. The students shouldthen switch roles and repeat theprocess using the Foot adaptationscolumn. Verbal
DemonstrationShow students pictures of severaldifferent types of birds. Be sureto include some with distinctlydifferent beaks and feet. A typicalassortment would be: woodpecker,heron, pelican, grosbeak, chick-adee, goose, and hummingbird.Ask students to examine the differ-ent types of beaks and feet and tohypothesize about each bird’s habi-tat and diet. Visual
Group Activity Avian Adaptations Divide theclass into small groups, and assigneach group a particular feedingstrategy and bird habitat. Have eachgroup use a field guide to identifyfive species of birds that share theassigned feeding strategy andhabitat. Students should then usedrawings or written descriptions todemonstrate the similarities in beaks,feet, and behavior among birds withsimilar lifestyles. Have each groupshare its findings with the entireclass. Visual
TAKS 3 Bio 7B; Bio 12CTAKS 1 Bio/IPC 2C, 2D;
Co-op LearningLS
TAKS 3 Bio 7B; Bio 12CLS
TAKS 2 Bio/IPC 2C, 2D; TAKS 3 Bio 7BLS
Chapter 34 • Reptiles and Birds 791
Birding (once called birdwatching) has beendescribed as the second-favorite outdooractivity in the United States, after gardening.Invite a local naturalist or member of anearby chapter of the Audubon Society tovisit your classroom and discuss tips on howto attract and identify backyard birds. Makea list of local birds and show slides of eachbird to your class. Slides can be purchasedfrom many sources, including the CornellUniversity Laboratory of Ornithology.Bio/IPC 3C; Bio 8C
REAL WORLDREAL WORLDCONNECTIONCONNECTION
Type of bird Beak adaptations Foot adaptations
Sieving: Long, flattened, rounded bill Swimming: Three toes linked bywebs for improved swimming
Woodpeckers Drilling: Strong, chisel-like beak Grasping: Feet with two toespointing forward and two pointingbackward
Parrots Cracking, tearing: Short, stout,hooked beak used to crack seedsand nuts and to tear vegetation
Climbing/grasping: Strong toes,two pointing forward, two pointingbackward; adapted for perching,climbing, and holding food
Grasping: Powerful, curved talonsfor seizing and gripping prey
Tearing: Curved, pointed beak forpulling apart prey
Birds of prey
Ducks
Long-legged waders Fishing: Long, slender, spear-shapedbeak for fishing
Wading: Longlegs; toesspread out overa large area tosupport bird onsoft surfaces
791
ReteachingHave each student develop tenquestions for this section, and usethe questions in a review game.
Interpersonal
QuizTrue or False:
1. Birds are ectotherms. (False. Birdsare endotherms.)
2.Birds have a two-way airflow dur-ing respiration. (False. Birds have aone-way airflow.) TAKS 3 Bio 7B; Bio 8B, 12C
TAKS 3 Bio 7B; Bio 8B, 12C
GENERAL
TAKS 1 Bio/IPC 2C, 2DLS
CloseClose
Answers to Section Review
1. forelimbs modified as wings; feathers; stream-lined shape; lightweight bones, endothermicmetabolism; highly efficient lungs; heart withcompletely divided ventricle
2. An endothermic body and a rapid metabolismprovide the energy necessary for flight.
3. The bald eagle has strong feet with sharp talonsfor grabbing prey, and a massive, hooked beakfor tearing prey into pieces it can eat.
4. The small, pointed beak indicates that it is nota seedeater because seedeaters have thick beaksfor crushing seeds. The foot structure, however,
TAKS 3 Bio 7B; Bio 11B
TAKS 2 Bio 10A; TAKS 3 Bio 7B
TAKS 3 Bio 7B
is consistent with the songbird anatomy.
5. A. Incorrect. The kidneys playan important excretory role in birds, but arenot closely associated with the other systems.B. Correct. The cloaca is an opening thatallows wastes to leave the body. In females, italso allows sperm to enter the body and fertil-ized eggs to leave the body. C. Incorrect. Thegizzard is the second part of the stomach thathelps to grind food; it is not part of the excre-tory or reproductive systems. D. Incorrect. Theovary is a reproductive organ; it is not part ofthe digestive or excretory systems.TAKS 2 Bio 10B (grade 11 only)
TAKS 1 IPC 3A; TAKS 3 Bio 7B; Bio 3A
792 Chapter 34 • Reptiles and Birds
CalculatingAverage BoneDensitySkills AcquiredAnalyzing data,calculating
Teacher’s Notes After students read the explana-tory paragraph, have themglance at the data and predictwhich animal has the higheraverage bone density.
Answers to Analysis1. Animal 1: 1.3 g/cm3;
Animal 2: 2.0 g/cm3
2. A certain amount of variationis normal in biological systems.
3. Animal 1
<x + 6x - 7 - 02
18
49376
0
52
Other AdaptationsThere are many groups of birds, each of which is adapted to its par-ticular living conditions. For example, gulls and terns have stream-lined bodies that are adapted for flying over the water in search offish. Owls’ excellent low-light vision enables them to survive as noc-turnal hunters. For a list of the orders of birds, see “Classificationin Kingdoms and Domains” in the Appendix.
Analysis
1. Calculate the average bonedensity for each of the twoanimals in the data table.Express your answer in gramsper cubic centimeter.
2. Critical ThinkingEvaluating MethodsWhy is it important to analyzeseveral samples and obtainthe average of your data?
3. Critical Thinking DrawingConclusions Based on youranswer to item 1, which of thetwo animals is more likely tobe a bird?
Calculating Average Bone DensityBackground
Density is the ratio of the mass of an object to its volume. Several teams of studentsdetermined the density of bones from two different animals. You can use their data to practice calculating average bone density.
<x + 6x - 7 - 02
8
493 0
52
DATA TABLE
Bone type Team 1 Team 2 Team 3 Team 4
Animal 1 1.6 g/cm3 1.0 g/cm3 1.2 g/cm3 1.4 g/cm3
Animal 2 2.3 g/cm3 1.8 g/cm3 1.8 g/cm3 2.1 g/cm3
1. Add the densities of one bone type. For example, if three bone samples have densities of 3.0, 3.1, and 2.9 g/cm3, their sum would be 9.0 g/cm3.
2. Divide the sum of the densities by the number of samples.
Average density � � � 3.0 g/cm39.0 g/cm3
3sum of the densitiesnumber of samples
Identify the adaptations of birds for flight. 7B
Summarize how birds obtain the energynecessary for flight. 7B 10A
Relate the bald eagle’s methods of hunting andfeeding to its external body features. 7B 11B
Critical Thinking Evaluating HypothesesA student examines a bird that has delicate,perching feet with long, slender toes. Its beak issmall but slightly long and pointed. The studentconcludes that the bird is a seed-eating songbird.Do you agree? Explain your reasoning. 3A 7B
Which structure is part of theexcretory, digestive, and reproductive systems of a bird? 10B
A kidney C gizzardB cloaca D ovary
TAKS Test PrepTAKS Test Prep
Section 3 Review
2C 2D 7B
792
TAKS 1 Bio/IPC 2C, 2D;TAKS 3 Bio 7B
Student Edition TAKS Obj 1 Bio/IPC 2C, 2DTAKS Obj 1 IPC 3ATAKS Obj 2 Bio 10A, 10B TAKS Obj 3 Bio 7B Math TAKS Obj 10, 8.14A, 8.15A,8.16BTEKS Bio 3A, 7B, 10A, 10B, 11BTEKS Bio/IPC 2C, 2DTEKS IPC 3A
Teacher Edition TAKS Obj 1 Bio/IPC 2C, 2D TAKS Obj 1 IPC 3ATAKS Obj 2 Bio 8C, 10A, 10B TAKS Obj 3 Bio 7BTEKS Bio 3A, 7B, 8B, 8C, 10A, 10B,11B, 12CTEKS Bio/IPC 2C, 2DTEKS IPC 3A
pp. 792–793
TAKS 1, TAKS 3
MATH TAKS Obj 10, 8.14A, 8.15A, 8.16B
AlternativeAssessmentHave each student use the red andblue subheadings in this chapter tocreate questions based on each sub-heading, and then correctly answerit. For example, “Reptiles ShareSeveral Key Characteristics,” couldbecome “What key characteristicsdo reptiles share?” Verbal
TAKS 3 Bio 7B; Bio 12CTAKS 1 Bio/IPC 2C, 2D; TAKS 2 Bio 8C;
LS
GENERAL
Chapter 34 • Reptiles and Birds 793
• Science Skills Worksheet• Critical Thinking Worksheet• Test Prep Pretest• Chapter Test GENERAL
GENERAL
GENERAL
Chapter Resource File
which have a
Lizards
ectotherms
Reptiles
3-chambered heart 4-chambered heart
Tuataras
endotherms
TurtlesSnakes Crocodilians
which have a
Ovoviviparous Oviparous
Scales
and have
areare which areare
and have
Feathers
and have a
such as
birds
Answer to Concept MapThe following is one possible answer to Performance Zone item 15 on the following page.
Key Concepts
Study CHAPTER HIGHLIGHTS
ZONEKey Terms
Section 1amniotic egg (775)oviparous (777)ovoviviparous (777)
Section 2carapace (782)plastron (782)
Section 3contour feather (784)preen gland (785)down feather (785)
The Reptilian Body
● Reptiles have a strong, bony skeleton. ● Reptiles are ectothermic.● Reptiles have nearly watertight skin and eggs, both of which
enable them to be terrestrial animals.● Reptiles have paired lungs that have a greater surface area
for gas exchange than the lungs of amphibians.● Reptiles have a double-loop circulatory system. Most have
a ventricle that is partly divided into right and left halves,resulting in incomplete separation of oxygen-rich and oxygen-poor blood.
● Reptilian fertilization is internal.
Today’s Reptiles
● Snakes and lizards (order Squamata) share many character-istics, such as periodic molting, but snakes have no legs.
● The shells of turtles and tortoises (order Chelonia) are made of fused plates of bone covered with horny shields orleathery skin.
● Unlike other reptiles, crocodilians (order Crocodilia), care for their young after hatching. They also have a completelydivided ventricle.
● There are only two species of tuataras (order Rhynchocephalia).
Characteristics and Diversity of Birds
● Birds are endotherms. Their high rate of metabolism helpsthem meet the large energy requirements for flight.
● A bird’s contour feathers give the bird its shape and aidflight. Its down feathers provide insulation.
● The bones of birds are thin and hollow, and many of themare fused; all are adaptations for flight.
● One-way airflow through the lungs provides the largeamounts of oxygen birds need for flight.
● The ventricle of the bird heart is completely divided by a septum.
3
2
1
793
ANSWERS
Using Key Terms
1. b2. a3. a4. a5. a. Oviparous animals lay eggs. In
ovoviviparous animals,embryos develop within eggsinside the mother’s body.These eggs hatch within themother, giving the appearanceof live birth.
b. Contour feathers are large andallow the bird to fly. Downfeathers are small and fluffy;they are found under the con-tour feathers and functiononly to insulate.
Understanding Key Ideas
6. b7. b8. a9. c
10. a11. d12. d13. d14. The dams cause riffles, which
contain insects that male turtlesfeed on, to disappear. Thus, tur-tles may not be able to find adequate food to survive indammed areas.
15. One possible answer to the con-cept map is found at the bottomof the Study Zone page. Bio 3E
TAKS 3 Bio 7B
TAKS 3 Bio 7BTAKS 3 Bio 7BTAKS 2 Bio 8C; Bio 8BTAKS 2 Bio 10ATAKS 3 Bio 7BTAKS 2 Bio 10ATAKS 2 Bio 10ATAKS 3 Bio 7B
TAKS 3 Bio 7BTAKS 3 Bio 7BTAKS 3 Bio 7BBio 8B
Section Questions1 3, 5a, 6–8, 14, 19, 222 1–3, 9–11, 14–16, 193 3, 4, 5b, 11, 12–15, 17, 18, 20, 21
Assignment Guide
794 Chapter 34 • Reptiles and Birds
CHAPTER 34
Using Key Terms1. All of the following reptiles belong to the
order Crocodilia, except a. alligators. c. crocodiles.b. tuataras. d. gavials.
2. The two basic parts of a turtle’s shell are thea. carapace and plastron.b. septum and amnion.c. chorion and allantois.d. keratin and cloaca.
3. The eggs of reptiles and birds aredescribed as a. amniotic.b. oviparous.c. ovoviviparous.d. externally fertilized.
4. The preen gland a. secretes oil.b. senses chemicals.c. stimulates egg production.d. causes a change in body temperature.
5. For each pair of terms, explain thedifferences in their meanings.a. oviparous, ovoviviparousb. contour feather, down feather
Understanding Key Ideas6. Which is not an adaptation of reptiles
for life on land? a. watertight skinb. external fertilizationc. amniotic eggd. kidneys
7. The heart of most reptiles has a. no septum.b. a partly divided ventricle.c. a fully divided ventricle.d. two pumping chambers.
8. In reptiles, fertilization a. is internal.b. is external.c. always occurs in water.d. does not occur.
9. Snakes differ from lizards in that snakesdo not have a. lungs. c. a pectoral girdle.b. kidneys. d. a flexible jaw.
10. Jacobson’s organs are involved in the sense of a. smell. c. sight.b. hearing. d. touch.
11. Which group of living reptiles is mostclosely related to birds? a. snakes c. rhynchocephaliansb. turtles d. crocodilians
12. The feathers of most birds are well adapted for a. swimming and repelling water.b. expelling heat and feeding.c. flying and conducting heat.d. flying and insulating.
13. The foot illustrated below is most likely ofa bird adapted for a. wading. c. perching.b. grasping. d. swimming.
14. In what ways might the damming of the Guadalupe River affect the ability of Cage’s map turtle tofind food?
15. Concept Mapping Construct a con-cept map that describes the characteristicsof both reptiles and birds. Include the fol-lowing terms in your map: ectotherm,endotherm, oviparous, ovoviviparous,scales, feathers, three-chambered heart, andfour-chambered heart.
PerformanceZONE
CHAPTER REVIEW
8B
7B
7B
7B
7B
10A
8B 8C
7B
7B
7B
3E
7B
10A
10A
794
Review and AssessTAKS Obj 1 Bio/IPC 2A, 2B, 2C, 2DTAKS Obj 2 Bio 8C, 10ATAKS Obj 3 Bio 7B TEKS Bio 3E, 7B, 8B, 8C, 10A, 12CTEKS Bio/IPC 2A, 2B, 2C, 2D
pp. 794–795
Critical Thinking
16. Because the young are carriedinside the body, they receive someheat as a result of the mother’smuscular movements and baskingbehavior.
17. Because it mixes oxygen-rich andoxygen-poor blood, a three-chambered heart would notdistribute enough oxygen to thehummingbird’s muscles to sustainflight.
18. Animals that invest a long periodof parental care typically havefewer offspring than animals withlittle or no parental care, but theoffspring that are cared for aremore likely to live to adulthood.In both cases, only a small number of offspring survive tobreeding age.
19. Predators are distracted by thewiggling tail part, which gives thelizard time to escape.
Alternative Assessment
20. Students should research bothseeds and feeder types to predictwhich birds will be attracted.
21. Answers will vary depending onbirds chosen. Students shouldacknowledge their sources andinclude an illustration of eachbird.
22. Students should research whattype of food and habitat isappropriate for the lizard theychoose and set up their terrariumaccordingly.
1. A.Incorrect.Crocodilians are not tolerant ofthe low temperatures sometimesfound in deserts. B. Correct.Turtles, lizards, and snakes areable to tolerate both the low andhigh temperatures often found indeserts. C. Incorrect. Tuataras arenot able to tolerate the high heatof the desert. D. Incorrect.Tuataras are not able to toleratethe high heat of the desert, andcrocodilians are not tolerant of thelow temperatures sometimes foundin deserts. TAKS 1 Bio/IPC 2C
TAKS 1 Bio/IPC 2A, 2B, 2C, 2D
TAKS 1 Bio/IPC 2A, 2B, 2D
TAKS 1 Bio/IPC 2C; TAKS 3 Bio 7B
TAKS 2 Bio 10A
TAKS 2 Bio 10A
TAKS 1 Bio/IPC 2A; TAKS 3 Bio 7B
2. F. Correct. Although birds are endothermswith a very small temperature range, theirrange overlaps with lizards, the only reptilewith temperatures above 40ºC. G. Incorrect.Tuataras do not have body temperatures aswarm as birds, which have temperatures of40ºC–42ºC. H. Incorrect. Crocodilians do nothave body temperatures as warm as birds.J. Incorrect. Turtles do not have body tem-peratures as warm as birds. Bio 12C
3. A. Incorrect. While crocodilians have agreater body temperature than tuataras, theranges of body temperatures are about thesame for both. B. Correct. According to thisdata, turtles and snakes have a body tempera-ture range of about 9ºC–38ºC. C. Incorrect.Lizards often have a higher body temperaturethan tuataras but their temperature rangesoverlap. D. Incorrect. The lowest body tem-perature for a crocodilian is higher than thehighest body temperature for a tuatara.TAKS 1 Bio/IPC 2C
Chapter 34 • Reptiles and Birds 795
Test
Critical Thinking16. Forming Hypotheses Many viviparous
snakes and lizards live in cold climates.Why might viviparity be advantageous insuch environments?
17. Predicting Outcomes How might having a three-chambered heart, like that of most reptiles, affect a hummingbird in flight?
18. Recognizing Logical Connections Howmight a long period of parental care berelated to the number of offspring ananimal produces?
19. Forming a Hypothesis When a piece of a lizard’s tail breaks off, the separatedportion may wiggle about forcefully. Howmight this adaptation be an advantage forthe lizard?
Alternative Assessment20. Applying Information Design and build a
bird feeder. Place the feeder where it can beeasily observed. Keep a journal of your obser-vations to share with your class.
21. Being a Team Member and CommunicatingWork with two or three of your classmatesto find out what kinds of birds are commonin your area. Select at least six birds toexplore in depth and research the following:its habitat, its food, its beak and foot adap-tations, and where it winters. Present theinformation you gathered in an illustratedguide. Make copies of your guide availablefor interested students.
22. Organizing Information Create a habitat ina terrarium for a small lizard, and observethe lizard’s behavior. Make a labeled draw-ing of the environment you create, andkeep a journal of your observations.
TAKS Test PrepTAKS Test Prep
The chart below shows the normal ranges ofbody temperature in five groups of reptiles.Use the chart and your knowledge of science toanswer questions 1–3.
1. Which groups could probably best tolerate the temperature extremes found in deserts? A Turtles, snakes, and crocodiliansB Turtles, lizards, and snakes C Tuataras, turtles, and snakesD Tuataras and crocodilians
2. If a bar showing the body temperature range of birds were added to this chart, thebar for birds would partially overlap with the bar for F lizards. H crocodilians.G tuataras. J turtles.
3. Which of these statements is supported bythe data in the chart? A Crocodilians have a greater body
temperature range than tuataras.B Turtles and snakes have similar body
temperature ranges. C Lizards always have a higher body
temperature than tuataras.D Some tuataras can have a higher body
temperature than some crocodilians.
20 30 40 5010 0
TuatarasTurtlesLizardsSnakes
Crocodilians
Body temperature (°C)
10A
10A
2C
12C
2C
2A 7B
2C 7B
When a question refers to a graph, study the dataplotted on the graph to determine any trends oranomalies before you try to answer the question.
2A 2B 2D
2A 2B 2C 2D
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