Section 1
Section 1
The Reptilian Body
Focus Objectives
Overview Before beginning this section review with your students the objectives listed in the Student Edition. In this section, students will learn how reptiles are welladapted to life on land. Terrestrial adaptations include a strong skeleton, watertight skin covered with scales, watertight eggs, larger lungs with greater surface area, internal fertilization, and a partially divided heart.
● Describe the key characteristics of reptiles. 8C ● Relate a reptile’s ectothermic metabolism to its activity 7B 11A TAKS 3 level. ● Summarize the adaptations that enable reptiles to live on land. 7B TAKS 3
Key Terms amniotic egg oviparous ovoviviparous
Bellringer Ask students to design a survival capsule for themselves. The capsule can only be 1.5 m high by 1 m wide. The capsule will not be opened for three weeks. Nothing, other than gasses, can pass through the wall of the capsule. What should the capsule contain? Ask students to compare their capsule with the amniotic egg described in this section.
www.scilinks.org Topic: Characteristics of Reptiles Keyword: HX4038
Key Characteristics of Reptiles Many people react with fear or repulsion when they see a snake slither across a yard or field. But snakes and their reptile relatives are important members of most ecosystems, and they kill large numbers of insect pests and small rodents. It’s true that some reptiles—venomous snakes and crocodilians (crocodiles and alligators) —are dangerous. Most reptiles, however, live quietly and go about their business, preferring to avoid humans. Members of class Reptilia live throughout the world in a wide variety of habitats, except in the coldest regions, where it is impossible for ectotherms to survive. Reptiles share certain fundamental characteristics, features they retain from the time when reptiles replaced amphibians as the dominant terrestrial vertebrates. Figure 1 summarizes these key features. Reptiles have a strong, bony skeleton, and most have two pairs of limbs, although snakes and some lizards are legless. The legs of reptiles are positioned more directly under their body than are the limbs of amphibians. Thus, reptiles can move more easily on land than amphibians can. Unlike amphibians, reptiles have toes with claws, which are used for climbing and digging. Claws also enable reptiles to get a good grip on the ground, allowing many reptiles to run quickly for short distances. The nervous system of a reptile is very similar to that of an amphibian. Like their dinosaur ancestors, modern reptiles have a brain that is small in relation to their body. For example, an alligator about 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 behaviors, including elaborate courtship.
TAKS 1 Bio/IPC 2C, 2D
Motivate Activity Favorite Reptile Have each student draw a picture of his or her favorite reptile. Have volunteers share their drawings with the class and tell why they chose their particular reptile. Lead a discussion of how reptiles are viewed in popular culture. LS Visual Bio 3F
Figure 1 Characteristics of living reptiles. This male anole is extending his dewlap, a display used during courtship and when defending territory.
Key Features of Reptiles • Strong, bony skeleton and toes with claws • 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
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Chapter Resource File pp. 772–773 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, 11A TEKS Bio/IPC 2C Teacher Edition TAKS Obj 1 Bio/IPC 2C, 2D TAKS Obj 3 Bio 7B TEKS Bio 3F, 7B, 11A TEKS Bio/IPC 2C, 2D
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Chapter 34 • Reptiles and Birds
• Lesson Plan GENERAL • Directed Reading • Active Reading GENERAL • Data Sheet for Data Lab GENERAL • Data Sheet for Quick Lab GENERAL
Planner CD-ROM • Reading Organizers • Reading Strategies • Basic Skills Worksheets Reading a Thermometer Temperature Conversions
Ectothermic Metabolism Reptiles’ ectothermic metabolism is too slow to generate enough heat to warm their bodies, so they must absorb heat from their surroundings. As a result, a reptile’s body temperature is largely determined by the temperature of its environment. Many reptiles regulate their temperature behaviorally, by basking in the sun to warm up or seeking shade to cool down. Figure 2 shows that a lizard can maintain a relatively constant body temperature throughout the day by moving between sunlight and shade. At very low temperatures, most reptiles become sluggish and unable to function. Intolerance of cold generally limits their geographical range and, in temperate climates, forces them to remain inactive through the winter.
Temperature (°C)
Resting in shade
Activity Basking
READING SKILL
Returns to den
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Emerges 30 from den 25 20 15
Air temperature
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Lizard's body temperature
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Sunrise
12
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Noon
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Sunset
Time of day
Identifying Ectotherms
TAKS 1
Temperature (°C)
The body temperature of all animals changes during the course of a day. How it changes can help you identify an animal as an ectotherm or an endotherm. 2C 11A
0100010110 011101010 0010010001001 1100100100010 0000101001001 1101010100100 0101010010010
Body Temperatures of Two Animals Species A
Background
Species B
Identifying Ectotherms
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TAKS 1 Bio/IPC 2C; Bio 11A 12 A.M.
6 A.M.
12 P.M.
0100010110 011101010 0010010001001 1100100100010 0000101001001 1101010100100 0101010010010
6 P.M.
4. Propose a reason why the ectotherm’s body temperature is highest at this time.
5. Predict what the endotherm’s graph line would look like if it were extended to show body temperature between 6 P.M. and midnight.
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TT Bellringer TT Key Features of Reptiles TT Changes in Lizard Body Temperature TT Reptilian Heart Structure
Have students draw a graph that depicts the changes in human body temperature for a 24-hour period. (The graph should show that the human body remains at about 37˚C for the entire day.) Then ask them to compare their graphs to the one for the lizard’s body temperature in Figure 2. Ask: Why are the graphs different? (The lizard depends on external sources for heat, so its body temperature tracks the temperature of the environment. Humans produce their own heat, so body temperature is not dependent on environmental temperature changes.) LS Visual
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3. Identify the time of day the animal you identified as an ectotherm reaches its highest body temperature.
Transparencies
Using the Figure
TAKS 1 Bio/IPC 2C, 2D; TAKS 3 Bio 7B
Air
Time of day
2. Identify the time of day the animal you identified as an ectotherm reaches its lowest body temperature.
Interactive Reading Assign Chapter 34 of the Holt Biology Guided Audio CD Program to help students achieve greater success in reading the chapter.
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Analysis 1. Analyze the data and determine which animal species, A or B, is most likely an ectotherm. Explain your reasoning.
GENERAL
BUILDER
Figure 2 Body temperature in a lizard. A lizard may regulate its body temperature by moving repeatedly between sun and shade.
Changes in Lizard Body Temperature
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Teach
Skills Acquired Analyzing data, interpreting graphs, predicting patterns
Teacher’s Notes Remind students that ecto- refers to “outside,” endo- refers to “within,” and therm refers to “heat.” Hence, ectotherm means “outside heat” and endotherm means “heat within.”
Answers to Analysis
MISCONCEPTION
ALERT
Cold-blooded Emphasize that the terms ectothermic and coldblooded are not synonyms, although they are often mistakenly used that way. Many reptiles experience body temperatures as high as or higher than human body temperature. For example, the body temperature of the desert iguana in western North America regularly reaches 42°C (108°F), which would be fatal for a human. TAKS 1 Bio/IPC 2D
1. Species A (yellow curve) probably is an ectotherm. Its temperature increases during the day, when the air temperature 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 from its value at 6 P.M. to its value at 12 A.M.
Chapter 34 • Reptiles and Birds
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Water Retention
Teach, continued continued Modeling Watertight Skin
TAKS 1 BioIPC 2B, 2C, 2D; TAKS 3 Bio 7B
Skills Acquired Calculating, analyzing data, inferring conclusions Teacher’s Notes Be sure to have students wipe the pan of the scale clean between weighings. Place an incandescent lamp on each table to simulate a desert environment.
Reviewing Information Reread the bulleted list of key features of reptiles in Figure 1. Then write them down on a separate piece of paper, leaving room to write notes about each characteristic. As you read, summarize how the information relates to a particular characteristic.
Amphibians such as frogs cannot be considered fully terrestrial because they lose too much water through their skin. Amphibians must stay moist to avoid dehydration, and their method of reproduction requires a moist environment. Reptiles have evolutionary adaptations that free them from the water requirements of amphibians.
Watertight Skin Terrestrial animals face a serious problem of water loss as water evaporates through their skin. Modern reptiles have evolved a skin made of light, flexible scales. These scales overlap and form a protective, almost watertight skin that minimizes water loss, as shown in Figure 3.
Figure 3 Reptilian scales. The scales of a reptile’s skin form a tight seal that retains moisture within the reptile’s body.
Answers to Analysis 1. The mass of the skinless grape should decrease. The mass of the intact grape should stay the same. 2. The skin prevents water from evaporating from an intact grape, so the grape’s weight does not change. Without its skin, a grape loses water and becomes lighter. 3. The skinless grape represents an amphibian’s skin. The intact grape represents a reptile’s skin. 4. Watertight skin, as in the intact grape, prevents water loss. This allows an animal to survive in dry environments. Most amphibians, like the skinless grape, would dry up if out of water or moist environment for an extended period of time.
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 2B 2C 2D 7B different types of skin. Materials
TAKS 1, TAKS 3
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 an open Petri dish.
3. Wait 15 minutes, and then find and record the mass of each grape again.
2. Using forceps, peel the skin from the second grape. Find and record the mass of the peeled grape. Then place it in the same Petri dish, but do not let the two grapes touch.
1. Calculate the difference between the original and final masses of each grape.
Analysis
2. Propose an explanation for any changes in mass you observed.
3. Determine which grape represents an amphibian’s skin and which represents a reptile’s skin. 4. Describe how a watertight skin is an adaptation to terrestrial life. Include information you have learned in this lab in your explanation.
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did you know? pp. 774–775 Student Edition TAKS Obj 1 Bio/IPC 2B, 2C, 2D TAKS Obj 3 Bio 7B TAKS 3 Bio 12E TEKS Bio 7B, 12C, 12E TEKS Bio/IPC 2B, 2C, 2D Teacher Edition TAKS Obj 1 Bio/IPC 2B, 2C, 2D TAKS Obj 3 Bio 7B, 12B, 12E TAKS Obj 5 IPC 6B TEKS Bio 3F, 7B, 12B, 12C, 12E TEKS Bio/IPC 2B, 2C, 2D, 3C TEKS IPC 6B
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Introduced Species Cause Problems In the western United States, the tansy ragwort plant is poisonous to cattle. The cinnabar moth, whose larvae eat the tansy ragwort, was introduced into the region to control this plant. However, the larvae accumulate toxins that kill the northern alligator lizards that prey on the larvae. Populations of these lizards may be at risk in certain areas of the west. TAKS 3 Bio 12B; Bio/IPC 3C; Bio 3F
Chapter 34 • Reptiles and Birds
IPC Benchmark Review To prepare students for the TAKS and accompany the discussion of thermoregulation in reptiles, have students review Convection, Conduction, and Radiation, TAKS 5 IPC 6B on p. 1063 of the IPC Refresher in the Texas Assessment Appendix of this book.
Watertight Eggs For a reptile living on dry land, reproduction presents another serious water-loss problem. Without a watery environment, both sperm and eggs will dry out. A reptile’s fertilized eggs need a moist environment 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 the second problem. An amniotic egg contains both a water supply and a 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 does not dry out, even in very dry habitats. Most reptiles, all birds, and three species of mammals reproduce by means of amniotic eggs with shells. (Other mammals produce amniotic eggs, but the embryo develops within the female’s uterus rather than within a shell. You will learn about the development of these eggs in a later chapter.) The formation of amniotic eggs with shells suggests that these three groups of animals evolved from a common ancestor.
Trouble for Turtles in Texas TAKS 3 Bio 12E; Bio 12C
Teaching Strategies • Show students a map of Texas and trace the flow of the Guadalupe River. Ask students to locate cities that are near the river. Then have students locate Canyon Lake. • Tell students that in Cagle’s map turtle, a turtle’s sex is determined by the temperature during which it was incubated. When temperatures are higher than 30.5ºC, female turtles are produced; when it is lower than 28ºC, male turtles are produced.
Trouble for Turtles in Texas TAKS 3
T
he Guadalupe River in southern Texas is home to several threatened and endangered species. Another may soon be added to the list: Cagle’s map turtle, Graptemys caglei. First discovered in 1974, this reptile at one time had a larger range than it does today. It is now thought to exist only in the Guadalupe River. Although the turtle is not yet considered threatened or endangered, it has been listed as a protected species in Texas. Cagle’s map turtles rarely leave the water except to lay eggs. The females eat clams and aquatic snails. The males eat insect larvae, which are usually found in pools and in rocky areas with riffles.
A Changing Environment The Guadalupe River winds through a part of Texas that has a rapidly growing human population with an increasing demand for water. Some parts of the river attract so many recreational visi-
tors that water quality and shoreline habitat are being degraded. Clearing of forests along the river for building construction could further lower the river’s water quality and change its flow. Numerous dams already interrupt the flow of the river, and two additional dams have been proposed. Dams cause riffles to disappear and allow silt to cover rocks, making it harder for turtles to find food.
Monitoring the Situation Researchers at West Texas A&M University in Canyon have been studying the ecology of Cagle’s map turtle for more than 20 years. The data they have collected show how the turtle is faring in different areas. For example, turtle populations now are greatly reduced in Canyon Lake, a reservoir in the upper portion of the river. Further work by the researchers will focus on the turtles’ water flow requirements and habitat
characteristics. Knowing what water flows the turtles need may allow scientists to recommend when and how much water should be released from the dams. Learning more about the turtles’ preferred habitat, such as the size of rocks they use most, will help people identify sections of the river that may have to be preserved. Changes such as these, the researchers believe, are needed to keep Cagle’s map turtle from becoming a threatened species.
www.scilinks.org Topic: Texas Reptiles Keyword: HXX4023
Discussion • How do humans affect the habitat of the Cagle’s map turtle? (Humans disrupt turtle habitat by drawing water from the river, using the river for recreation, building dams, and developing areas along the river.) • Even though they spend most of their life in the water, Cagle’s map turtles lay their eggs on land. Why don’t their eggs dry out? (Turtles lay amniotic eggs. Amniotic eggs have a food and water supply so that they don’t dry out.) • Male and female turtles eat different things. What do you think would be a benefit of this strategy? (It might decrease competition for food.)
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Activity Green Turtles Tour the Atlantic Green turtles migrate more than 2,000 km (1,250 mi) from the waters off Brazil to the beaches of Ascension Island in the central Atlantic Ocean. A female green turtle will lay her eggs on the same beach where she hatched. Scientists do not yet know for certain how she finds her birthplace. Bio 12C
Comparing Eggs Using field guides, books, and Internet resources, have students research the eggs of birds, reptiles, and amphibians. Ask each student to make life-size, full-color drawings of several types of eggs on small pieces of paper. When students are finished, assemble the drawings into three large posters for comparison: The Eggs of Amphibians, The Eggs of Reptiles, and The Eggs of Birds. LS Interpersonal
TAKS 1 Bio/IPC 2C, 2D; TAKS 3 Bio 7B
Chapter 34 • Reptiles and Birds
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Respiration Because most reptiles are far more active than amphibians, they have greater metabolic requirements for oxygen. Their bodies meet this demand in several ways.
Teach, continued continued Teaching Tip
Lungs
Surface Area Ask students which melts faster—multiple cubes of ice or a single block of ice of the same weight? Lead students into a discussion of the importance of surface area in living things. Relate the cubes of ice to alveoli in the lungs.
A reptile’s scaly skin does not permit gas exchange, so reptiles cannot use their skin as an additional respiratory surface, as many amphibians can. However, the lungs of most reptiles have many internal folds, as shown in Figure 4. These folds greatly increase the respiratory surface area of a reptile’s lungs. In addition, reptiles have strong muscles attached to their rib cage. The action of these muscles helps to move air into and out of the lungs, increasing the lungs’ efficiency.
LS Verbal TAKS 4 IPC 9D
SKILL
BUILDER
GENERAL
Math Skills Ask students to find the surface area of an 8 mL cube and the combined surface area of eight 1 mL cubes. Remind students that the surface 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 has two-centimeter sides and a 1-mL cube has one-centimeter sides. (Although the overall volume is the same, the 8-mL cube has a surface area of 24 cm2 and eight 1-mL cubes have a combined surface area of 48 cm2.)
Figure 4 Reptilian lungs. The lungs of reptiles contain numerous internal folds.
Figure 5 Reptilian heart. In most reptiles, the ventricle of the heart is partly divided by a septum.
Heart Recall that the ventricle of the amphibian heart is not divided by a septum. Oxygen-poor blood and oxygen-rich blood mix somewhat in the amphibian’s ventricle. In most reptiles, however, the septum extends into the ventricle, partly dividing it into right and left halves, as shown in Figure 5. The septum enables a much better, but still incomplete, separation of oxygen-rich and oxygen-poor blood. As a result, oxygen is delivered to the body cells more efficiently than in amphibians. Unlike most reptiles, crocodilians have a heart with a completely divided ventricle that consists of two pumping chambers. This arrangement fully separates the lung circulation from the body circulation. Thus, the delivery of oxygen throughout the body is further improved in these animals.
Reptilian Heart Structure
LS Logical
Group Activity Oxygen-poor blood from the body enters the right atrium. Oxygen-rich blood from the lungs enters the left atrium.
Local Snakes Use a field guide to determine what kinds of snakes are found in your area. Have groups research these snakes and report to the class on the snakes’ habitat, range, reproduction, behavior, feeding habits, and any other relevant information.
1
To body Right atrium
Incomplete septum
TAKS 1 Bio/IPC 2C, 2D; Bio 8B
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SOCIAL STUDIES CONNECTION
Snakes in Literature Throughout history, many cultures have used snakes in literary, cultural, and religious settings, such as The Bible, and in stories such as the Greek myth of Medusa. Even children’s stories like Aladdin and The Jungle Book include snakes. Snakes are often portrayed as evil, coldblooded animals. Have students research this phenomenon in literature and write an essay on whether the reputation of the snake is deserved. TAKS 1 Bio/IPC 2D
Chapter 34 • Reptiles and Birds
To body To lungs From lungs Left atrium
Right half of ventricle
LS Verbal Co-op Learning
pp. 776–777 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, 11A TEKS 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, 11A TEKS Bio/IPC 2C, 2D TEKS IPC 9D
An incomplete septum partly divides the ventricle. Thus, there is less mixing of oxygen-rich and oxygen-poor blood than there is in the amphibian heart.
2
From body
Left half of ventricle
Arteries carry oxygen-rich blood from the left half of the ventricle to the body and oxygen-poor blood from the right half of the ventricle to the lungs.
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Reproduction Unlike the eggs of most amphibians, reptilian eggs are fertilized within the female, a process called internal fertilization. The male reptile introduces his semen directly into the female’s body. The semen contains sperm and fluid secretions. Internal fertilization protects the gametes from drying out, even though the adult animals are fully terrestrial. Many reptiles are oviparous (oh VIHP urh uhs), meaning the young hatch from eggs, as shown in Figure 6. In most cases, the eggs are not protected by the parents. Most snakes and lizards, all turtles and tortoises, and all crocodilians are oviparous. All birds and three species of mammals are also oviparous. Some species of snakes and lizards are ovoviviparous , which means the female retains the eggs within her body until shortly before 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 ovoviviparous reptiles, the eggs are less vulnerable to predators.
The term ovoviviparous comes from three different Latin words: ovum, meaning “egg,” vivus, meaning “alive,” and parere, meaning “to bring forth or bear.”
Figure 6 Reproduction. Sea turtles hatch from eggs buried on sandy beaches. The eggs of some species of snakes are incubated within the female’s body, and the young are born live.
Close Reteaching Have students pair up and list each of the seven key features of reptiles, which are given in Figure 1, on individual index cards. On the back of each card, have them write a one-word clue to identify the characteristic on the front of the card. Ask students to shuffle the cards and turn them so only the clue words are showing. Have one student choose a card at random and read the clue word. His or her partner should respond with the key characteristic. If the student answers correctly, his or her partner should set the card aside. Students should continue the game until all of the cards are set aside. Students should then switch roles and repeat the process. LS Interpersonal Co-op Learning
TAKS 2 Bio 8C
Quiz Sea turtles
Hatchling snakes
Section 1 Review Identify seven characteristics of reptiles.
8C
Describe how the ectothermic nature of reptiles 11A influences their physical activity and feeding habits. Summarize the skin and egg adaptations that
allow reptiles to live on land.
7B
Critical Thinking Forming Reasoned Opinions Data show that an animal’s tempera-
ture changes over the course of a day. A student asserts that this proves the animal is an ectotherm. What must the student consider before 2C 11A making such a claim?
Describe how reptiles meet their need for more 10A oxygen than amphibians require. TAKS Test Prep If a lizard’s internal temperature sensors detect a decrease in body temperature, the lizard can maintain 11A homeostasis by A speeding up its metabolism. B slowing its metabolism. C basking in the sunshine. D resting in the shade.
TAKS 2 Bio 8C, 10A; TAKS 3 Bio 7B
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Answers to Section Review 1. strong, bony skeletons, and toes with claws; ectothermic metabolism; dry scaly skin, almost watertight; amniotic eggs; well-developed lungs; partly or completely divided ventricle; internal fertilization TAKS 2 Bio 8C 2. Because they are ectotherms, reptiles must thermoregulate behaviorally. They can be physically active and hunt for food only when their body temperature is within a certain critical range. Bio 11A 3. The almost watertight skin and amniotic eggs of reptiles minimize water loss on land. TAKS 3 Bio 7B
GENERAL
True or False: 1. As in most amphibians, fertilization in reptiles is external. (False. Fertilization is internal, an adaptation to life on land.) TAKS 2 Bio 8C 2. The heart of most reptiles only partially separates blood from the lungs and blood from the body. (True. Except in crocodilians, freshly oxygenated blood mixes in the heart with oxygendepleted blood.)
4. The student would need to compare the animal’s temperature changes to changes in the environmental temperature. TAKS 1 Bio/IPC 2C; Bio 11A
5. In contrast to amphibians, reptiles have welldeveloped lungs with alveoli, as well as strong rib muscles. Bio 11A 6. A. Incorrect. Ectotherms cannot alter their metabolism to maintain homeostasis. B. Incorrect. A slower metabolism would not increase body temperature. C. Correct. Ectotherms maintain body temperature by basking. D. Incorrect. Resting in the shade would not increase body temperature. Bio 11A
Alternative Assessment
GENERAL
Have teams of students write brief descriptions of what they think are the five most important things they have learned about reptiles. Have teams present their descriptions to the class, with each team member participating in the presentation. LS Verbal Co-op Learning
TAKS 2 Bio 8C
Chapter 34 • Reptiles and Birds
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Section 2
Section 2
Today’s Reptiles
Focus Objectives
Overview Before beginning this section review with your students the objectives listed in the Student Edition. In this section, students are introduced to the orders of the reptiles, one of the most diverse classes of terrestrial vertebrates. Students will also learn the distinguishing characteristics of all the orders.
Bellringer Ask students to list as many reptiles as they can. Then, have them indicate which reptiles on their list are closely related. After reading the section, have students make corrections and add any missing groups of reptiles to their lists. (Students should indicate that snakes and lizards are related, turtles and tortoises are related, and that crocodiles and alligators are related. Students are probably unfamiliar with the tuataras.) TAKS 2 Bio 8C; Bio 8B
Lizards and Snakes
● Compare the four living orders of reptiles. 8C TAKS 2
You’ve probably walked by a snake or lizard without even knowing it was there. Most are quiet, and their coloration often conceals them from view. Even if you visited the jungles of South America, ● Describe the timber rattle7B you might not notice an anaconda unless it moved. What’s an anasnake’s adaptations for locating and capturing prey. TAKS 3 conda? It’s the world’s largest snake, frequently reaching 5 m (about 16 ft) in length. The largest anaconda ever found was twice that ● Compare the parental care long. Very large anacondas have been known to prey on jaguars. of crocodilians with that of After such a meal, the anaconda may not eat again for up to a year. other reptiles. 8B Snakes and lizards belong to order Squamata. A distinguishing characteristic of this order is a lower jaw that is only loosely conKey Terms nected to the skull. This allows the mouth to open wide enough to carapace accommodate large prey and explains how an anaconda can swalplastron low a jaguar. This ability is a contributing factor to the success of snakes and most lizards as predators.
Lizards Common lizards include iguanas, chameleons, geckos, anoles, and horned lizards (often mistakenly called “horny toads”). A few species of lizards are herbivores, but most are carnivores. Most lizards are small, measuring less than 30 cm (1 ft) in length, but lizards that belong to the monitor family can be quite large. The Komodo dragon of Indonesia, shown in Figure 7, is the largest monitor lizard. It can be up to 3 m (10 ft) in length and weigh up to 125 kg (275 lb). The tail of some species of lizards, such as the gecko shown in Figure 7, breaks off easily when seized by a predator, allowing the lizard to escape. Lizards can regenerate a new tail, but it does not have any vertebrae in it.
Motivate Demonstration
GENERAL
Obtain a picture of a skink, and cover its body so that only its head shows. Ask students if the animal is a lizard or a snake. Then reveal the rest of the animal, pointing out how similar some lizards are to snakes. Ask students how to tell a lizard from a snake. (Most lizards have legs and external ears, a pectoral girdle, and many have movable eyelids. Snakes lack these features.) LS Visual TAKS 2 Bio 8C; Bio 8B
Gecko
Figure 7 Lizards. Geckos are small reptiles, rarely exceeding 24 cm (10 in.) in length. The Komodo dragon is the world’s largest lizard. Komodo dragon
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Chapter Resource File
pp. 778–779 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 8C TAKS Obj 3 Bio 12B TEKS Bio 8B, 8C, 12B TEKS Bio/IPC 3C
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Chapter 34 • Reptiles and Birds
• Lesson Plans GENERAL • Directed Reading • Active Reading GENERAL
Transparencies TT TT TT TT TT
Bellringer External Structures of Snakes Internal Structures of Snakes Orders of Living Reptiles Orders of Extinct Reptiles
Planner CD-ROM • Reading Organizers • Reading Strategies • Occupational Application Worksheet: Emergency Medical Technician GENERAL
Snakes Snakes probably evolved from lizards during the Cretaceous period. The close relationship between lizards and snakes is reflected in their many similarities. In fact, it is often difficult to distinguish the legless species of lizards from snakes. Snakes lack movable eyelids and external ears, as do several species of lizards. Also, both snakes and lizards molt periodically, shedding their outer layers of skin. Body Structure The skeleton of snakes is unique. Most snakes have no trace of a pectoral girdle (the supporting bones for the bones of the forelimbs), which is found even in legless lizards. The snake’s jaw is very flexible because it has five points of movement. (Your jaw, in contrast, has only one movement point.) One of these points is the chin, where the halves of the lower jaw are connected by an elastic ligament. This ligament permits the lower jaw to spread apart when a large meal is being swallowed. The African egg-eating snake, shown in Figure 8, can swallow eggs that are much larger than its head in a process that can take an hour or more. Feeding While many snakes simply seize their prey and swallow it
whole, some snakes use other methods to subdue their prey. Many very large snakes, such as anacondas, boas, and pythons, are constrictors, as are some smaller species, such as king snakes. Constrictors wrap their body around their prey, gradually squeezing tighter and tighter until the prey suffocates. The snakes then swallow 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 families of snakes, only four are venomous: (1) cobras, kraits, and coral snakes; (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 the victim through grooved or hollow teeth. The African boomslang and twig snakes produce venom but do not inject it. Instead, they bite their prey with fangs located at the back of their mouth. Grooved teeth direct the venom into their victim’s wound. You can read more about the biology of snakes in Up Close: Timber Rattlesnake, on the following pages.
Real Life
Teach
Need a lizard? TAKS 3 Instead of calling an exterminator to rid their homes of unwanted pests, some adventuresome homeowners keep a Tokay gecko. This gecko preys voraciously on mice and insects and is very efficient at ridding a home of these pests. Finding Information Investigate the pros and cons of using geckos for pest control. Who should try this method and who should avoid it?
Real Life Answer TAKS 3
Bio 12B
People who have other pets that might harass a gecko, such as a cat or a dog, should not try to use geckos for pest control.
Teaching Tip
Figure 8 Snake feeding. Snakes have flexible jaws that allow them to swallow prey much larger than their head.
Dangerous Snakes Ask students what venomous snake is the most dangerous in the world. Record their responses. (examples: king cobra, sea snake, coral snake, and Australian tiger snake) Ask why a particular species is considered more dangerous than others. Tell them that many different venomous snakes are touted as the “most dangerous snake alive,” or the “most poisonous snake on Earth.” Point out that several factors determine how “dangerous” a snake is. Among these factors are the toxicity of its venom, the type of venom (hemolytic or neurotoxic), and the amount of venom a bite victim receives. In India, there are about 900,000 snakebites each year, resulting in about 9,000 deaths. Many of these bites are delivered by the aggressive king cobra, which is frequently encountered by India’s large human population. LS Verbal Bio/IPC 3C
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MEDICINE CONNECTION
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 than the heart. • Get medical help.
Medical professionals are nearly unanimous in their 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
Chapter 34 • Reptiles and Birds
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Up Close Up Close
Timber Rattlesnake TAKS 2, TAKS 3
Timber Rattlesnake TAKS 2 Bio 8C, 10A; TAKS 3 Bio 7B; Bio 12C
Teaching Strategies Help students understand the rattlesnake’s ability to sense its prey in the dark by using a warm object such as a heating pad. Place the heating pad on a table and allow it to warm the surface. Remove the heating pad and have students move their hands above the tabletop without touching the table itself. They should be able to feel the heat radiating from the warmed spot. Have students determine how close their hands must be to detect the heat. Inform them that a rattlesnake can locate warm prey from a distance of 1 m (39 in.). These snakes, however, sense heat with their pit organs, not through their skin. On a sheet of paper, have students list each major heading in the Up Close feature. After they read each section, have them hypothesize how that particular feature of the timber rattlesnake is an adaptation for survival. Then have students exchange papers with a partner and read their partner’s paper, noting how their partner may have identified a different survival value for some of the features.
●
Scientific name: Crotalus horridus
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Size: Typically 90–150 cm (36–60 in.) long; maximum 189 cm (74 in.)
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Range: Eastern and central United States, from northern New York to northern Florida and west, to central Texas
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Habitat: Prefers thick brush, dense woodland, or swamp
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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
▲
External Structures Rattle
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.
Eye
Pit organ Between each eye and nostril of the rattlesnake is an organ
Nostril
▼
that can detect infrared radiation. The snake can locate a warm-bodied Pit organ
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.
780 MISCONCEPTION
ALERT
pp. 780–781 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, 12C TEKS Bio/IPC 2D, 3C
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GENERAL
Slimy Snakes Contact a local nature center, zoo, or herpetological society to arrange for a live, non-poisonous snake and handler to visit the class. Have students make a list of some of their preconceptions about snakes. For instance, many students believe that a snake’s skin is slimy, like that of a frog. Another misconception is that the tongue of
Chapter 34 • Reptiles and Birds
a snake is poisonous, and that snakes will attack people for no reason. Show the class a live snake, and allow students to touch and examine the snake. Help to dispel misconceptions by discussing possible origins for such fears. Remain sensitive to the fact that many people will continue to fear snakes. TAKS 1 Bio/IPC 2D
Internal Structures Jacobson’s organs
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
Jacobson’s organs Flicking its forked tongue into the air, the rattlesnake takes in chemical samples from the environment. These chemicals are transferred to two depressions in the roof of the mouth called Jacobson’s organs, which detect the odor of the chemicals. The snake uses these organs to follow
Fang
Venom gland
hemorrhaging. Modified salivary glands in the upper jaw produce the venom.
▼
Venom glands The timber rattle-
the scent trail of prey. Tongue
Stomach
Small intestine Trachea Esophagus
Gallbladder
Right lung Left lung
Pancreas
Internal anatomy
Heart
The internal organs are elongated, matching the snake’s body shape. The left lung is nonfunctional. Large intestine
Up Close Timber Rattlesnake Discussion • Explain why it would be easier for a timber rattlesnake to kill a mouse than a lizard at night. (The mouse is an endotherm and the pit viper’s heat-sensitive pits can detect its body heat. The lizard is an ectotherm and would not necessarily be warmer than its surroundings.) • What is the advantage to a rattlesnake of announcing its presence to other animals by rattling? (Answers may vary but may include that by rattling the snake keeps large mammals, such as cattle, from stepping on it.) • How is an ovoviviparous snake, such as the timber rattlesnake, different from a viviparous snake in the way developing embryos are sustained? (Ovoviviparous mothers supply no nutrients to the developing young, while viviparous mothers do.)
Liver
Kidneys
Cloaca ▼ Testes
▼ Spine
Reproductive structures This male rattlesnake
Spine The rattlesnake’s spine is
produces sperm in his testes. Female timber rattlesnakes
made up of several hundred ver-
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
tebrae, each with its own pair of attached ribs. It provides the framework for thousands of muscles that
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.
manipulate not only the skeleton but also the snake’s skin, causing the overlapping scales to extend or lie flat.
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did you know? Triple-jointed Jaws The tiny snakes called threadsnakes have triple-jointed jaws. When a threadsnake burrows into the nests of ants or other social insects, parts of its lower jaw rotate like a pair of swinging doors. It is thought that this action helps the snake to eat quickly and escape injury or death from ant stings.
Venomous Snakes About 99 percent of venomous snakebites in the United States are from pit vipers. About 8,000 snakebites occur in the United States each year, and around 9 to 15 victims die. Every state except Maine, Alaska, and Hawaii is home to at least one poisonous snake species.
TAKS 3 Bio 7B; Bio 12C
Bio /IPC 3C
Chapter 34 • Reptiles and Birds
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Other Orders of Reptiles The remaining orders of living reptiles contain far fewer species than the order Squamata does. There are about 250 species of turtles (which generally live in water) and tortoises (which live on land), all classified in the order Chelonia. The order Crocodilia is composed of 25 species of large, aquatic reptiles. The order Rhynchocephalia (RING koh seh FAY lee uh) contains only two species of tuataras.
Teach, continued continued Using the Figure
GENERAL
Point out in Figure 10 that a turtle’s shoulders lie within its rib cage. Students should recognize that their own shoulders are outside of their ribs. Tell students that a turtle is attached to its shell and cannot crawl out of it, as cartoon turtles often do. LS Visual TAKS 3 Bio 7B
SKILL
Turtles and Tortoises
BUILDER
Writing Skills Have students imagine that they are the first person from their country to see a turtle. Ask students to write a description of a turtle, for an audience that has never seen a turtle before. Encourage them to be both descriptive and accurate. LS Verbal
Figure 9 Turtle and tortoise. Like other sea turtles, this green sea turtle (top) spends virtually its entire life in the sea. The Galápagos tortoise (bottom) spends its life on land.
TAKS 1 Bio/IPC 2D
Turtles and tortoises, shown in Figure 9, differ from other reptiles in that their bodies are encased within a hard, bony, protective shell. Many of them can pull their head and legs into the shell for effective protection from predators. While most tortoises have a dome-shaped shell, water-dwelling turtles have a streamlined, diskshaped shell that permits rapid maneuvering in water. Turtles and tortoises lack teeth but have jaws covered by sharp plates, which form powerful beaks. Many are herbivores but some, such as the snapping turtle, are aggressive carnivores. Today’s turtles and tortoises differ little from the earliest known turtle fossils, which date to more than 200 million years ago. This evolutionary stability may reflect the adaptive aspects of their basic shell-covered body structure. The shell is made of fused plates of bone covered with horny shields or tough, leathery skin. In either case, the shell consists of two basic parts. The carapace is the dorsal (top) part of the shell, and the plastron is the ventral (bottom) portion. The vertebrae and ribs of most species are fused to the inside of the carapace, as shown in Figure 10. The shell provides the support for all muscle attachments in the torso.
Teaching Tip Endangered Crocodilians Tell students that although crocodilians are fierce predators, many of the 25 species of crocodilians are endangered or threatened. Overhunting of crocodilians for their hides, which are used to make leather goods, is the primary cause of their decline. TAKS 3 Bio 12B; Bio/IPC 3C
Crocodiles and Alligators
Figure 10 Turtle interior. In this ventral view, a turtle’s plastron has been removed to show the relationship of the vertebral column, ribs, pelvis, and pectoral girdle to the carapace.
Of all the living reptiles, the crocodilians are most closely related to the dinosaurs. In addition to crocodiles and alligators, shown in Figure 11, the order Crocodilia includes the alligator-like caimans and the long-snouted gavial. Crocodilians are aggressive carnivores. Some are quite large. American alligators can reach 5.5 m (18 ft) in length, and Nile crocodiles can reach 6 m (20 ft) in length and weigh 750 kg (1,650 lb). Crocodilians generally capture prey by stealth, often floating just beneath the water’s surface near the shore. When an animal comes to the water to drink, the crocodilian explodes out of the water and seizes its prey. The crocodilian then hauls the prey back into the water to be drowned and eaten. The bodies of crocodilians are well adapted for this form of hunting. Their eyes are high on the sides of the head, and their nostrils are on top of the snout. As a result, they can see and breathe while lying nearly submerged in the water. Crocodilians have a very strong neck and an enormous mouth studded
782 Cultural pp. 782–783 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, 10A TAKS Obj 3 Bio 7B, 12B TEKS Bio 7B, 8B, 8C, 10A, 11B, 12B, 12C TEKS Bio/IPC 2D, 3C
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Awareness
Turtle Myths The turtle appears as a central character in mythologies from around the world. An ancient Chinese myth describes how the turtle Kwei created the universe. The Chinese Book of Rites names the turtle as one of the four benevolent spirit animals. Hindu myths from India describe the world as being supported by four elephants standing on a turtle’s back. And in North America, several native cultures imagined the world as an island on the back of a great turtle. Bio/IPC 3C
Chapter 34 • Reptiles and Birds
did you know? Alligators’ Sounds Alligators are unusual among reptiles in being able to make definite vocalizations. The male alligator bellows loudly during mating season. Vocal sacs on each 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 time to open the nest. Hatchlings also have a distress call they use to alert their mother if they feel threatened. TAKS 3 Bio 7B; Bio 12C
Australian crocodiles
Close Reteaching Write the following words or phrases on the board: lizards and snakes, turtles and tortoises, crocodiles and alligators, and tuataras. Have students copy them, leaving space for additional information. Have students write distinguishing traits of each group in the appropriate spaces without using their textbooks. (lizards and snakes-lower jaw has loose connection to skull, no pectoral girdle in snakes, molt periodically, may lack eyelids; turtles and tortoises-hard shell, lack teeth, jaws have a powerful beak; crocodiles and alligators-long snout, eyes high on head, nostrils on top of head, large mouth with sharp teeth; tuataraslizardlike, active at night) When the students have finished their work, have them share their results with a partner, recording any characteristics they omitted but their partner identified. LS Verbal Co-op Learning
American alligator
with sharp teeth. A valve in the back of the mouth prevents water from entering the lungs when crocodilians feed underwater. Unlike other living reptiles, crocodilians care for their young after hatching. For instance, a female American alligator builds a nest of rotting vegetation for her eggs. After the eggs hatch, the mother may tear open the nest to free the hatchlings. The young alligators remain under her protection for up to a year.
Figure 11 Crocodilians. In general, the snouts of alligators are shorter and broader than those of crocodiles.
Tuataras The two living species of tuataras are members of the genus Sphenodon and are native to New Zealand. Sphenodon punctatus, the more common species, is shown in Figure 12. Tuataras are lizardlike reptiles up to 70 cm (2 ft) long. Unlike most reptiles, tuataras are most active at low temperatures. They burrow or bask in the sun during the day and feed on insects, worms, and other small animals at night. Tuataras are sometimes called living fossils because they have survived almost unchanged for 150 million years. Since the arrival of humans in New Zealand about 1,000 years ago, the tuatara’s range has diminished, and their numbers are declining.
TAKS 2 Bio 8C; TAKS 3 Bio 7B; Bio/IPC 2D; Bio 8B
Figure 12 Tuatara. Tuataras live on only a few small islands in New Zealand.
Quiz
Section 2 Review Describe the characteristics shared by lizards 8C and snakes. Describe the function of two different organs 7B that help snakes locate their prey. Summarize the ways turtles and tortoises differ
from other reptiles.
8B 10A 11B
Compare the parental care shown by alligators
with that shown by most other reptiles.
8B
Critical Thinking Recognizing Relationships
How does the position of a crocodile’s nostrils and 11B eyes relate to its method of hunting? TAKS Test Prep The pit organ of a rattle11B snake is sensitive to A airborne chemicals. B faint sounds. C ground vibrations. D infrared radiation.
characteristics with snakes are the ________ (lizards) TAKS 2 Bio 8C 2. Unlike other reptiles, ________ care for their young after they hatch. (crocodilians) TAKS 2 Bio 8C 3. The shells of turtles and tortoises consist of a plastron on the underside and a ________, which fuses with the rib cage. (carapace) TAKS 3 Bio 7B
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Answers to Section Review 1. Snakes and lizards both have scaly skin and molt periodically. Their lower jaw is loosely connected to the skull. TAKS 2 Bio 8C 2. Jacobson’s organs, located in the roof of the mouth, detect microscopic airborne particles, which the brain interprets as scent. Pit vipers use their pit organs to detect heat. TAKS 3 Bio 7B 3. Their bodies are encased in a protective shell, and they lack teeth. TAKS 2 Bio 10A; Bio 8B, 11B 4. Alligators and other crocodilians are the only reptiles to care for their young. Some alligators build nests for their young and care for them for up to a year after they hatch. Bio 8B
GENERAL
1. The reptiles that share the most
5. The crocodile is able to keep most of its body submerged and hidden while still being able to breathe and look for prey. Bio 11B 6. A. Incorrect. The Jacobson’s organs in the roof of the mouth are sensitive to airborne chemicals. B. Incorrect. Snakes lack ears and do not hear faint sounds. C. Incorrect. Snakes can feel ground vibrations through their bodies, not the pit organs. D. Correct. Using pit organs, warm-blooded animals can be found even in the dark. Bio 11B
Alternative Assessment Assign students to work in groups of three. Each group will research the reptiles of an assigned continent. For each reptile, include the following: order, appearance (drawing), size, diet, habitat, range, and status (common, rare, threatened, or endangered). When groups have finished their research and drawings, the entire collection can be assembled on a large mural of the continents. Ask a local elementary school to display the mural. LS Interpersonal Co-op Learning
TAKS 2 Bio 8C
Chapter 34 • Reptiles and Birds
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Section 3
Characteristics and Diversity of Birds
Section 3
Focus Overview Before beginning this section review with your students the objectives listed in the Student Edition. In this section, students will summarize the key features of birds. These include several reptile-like characteristics, such as amniotic eggs and scale-covered feet and legs. Unique adaptations include feathers for flight and insulation, a strong yet very lightweight skeleton, a highly efficient respiratory system and completely divided heart. These features allow flight for nearly all birds. Students will also examine the highly variable beaks and feet of birds, which allow different species to make use of a range of diets and habitats.
Key Characteristics of Birds
Objectives
Why do people use the expression “free as a bird”? Most likely it ● Summarize the key characteristics of birds. 8C TAKS 2 comes from a bird’s ability to fly seemingly wherever it wishes. Through human history, the gift of flight has been celebrated in stories, poetry, and songs. But there is more to birds than flight; in fact, some species of birds can’t fly. The birds you see today are the modern members of class Aves. ● Summarize how a bird’s Unlike their reptilian relatives, birds lack teeth and have a tail that lungs and heart are adapted is greatly reduced in length. But they do retain some reptilian 7B 10A for high efficiency. TAKS 2, characteristics. For instance, birds lay amniotic eggs that are very ● Relate the structure of a TAKS 3 similar to those of reptiles, and the feet and legs of birds are bird’s feet and beak to its covered with scales. Other characteristics unique to birds distin7B 11B habits and diet. guish them from all other animals. The most obvious is the TAKS 3 presence of feathers and the modification of the forelimbs into Key Terms wings. Figure 13 lists some distinguishing features of birds. To contour feather learn more about the anatomy and habits of one bird, see Up preen gland Close: Bald Eagle later in this section. ● Describe how a bird’s feathers and bone structure aid flight. 7B TAKS 3
down feather
Feathers Feathers are modified reptilian scales that develop from tiny pits, called follicles, in the skin. Just as snakes and lizards replace their skin by molting, birds molt and replace their feathers. However, few birds shed all of their feathers at one time. Birds have two main types of feathers: contour feathers and down feathers. Contour feathers cover the bird’s body and give adult birds their shape. Specialized contour feathers, called flight feathers, are found on a bird’s wings and tail. These feathers help provide lift for flight. As shown in Figure 14, a contour feather has many branches called barbs. Each barb has many projections, called
Bellringer Ask students to list the unique adaptations of birds that allow them to fly. TAKS 3 Bio 7B
www.scilinks.org Topic: Characteristics of Birds Keyword: HX4036
Motivate Demonstration Bring a feather to class and ask students what kind of animal it is from. When students answer “a bird,” ask them to think of any bird that does not have feathers. (There are none.) Ask them if they can think of any living animals that have feathers but are not considered birds. (no) Emphasize that having feathers is a unique classification characteristic for the class Aves. LS Visual TAKS 2 Bio 8C; Bio 8B
Characteristics of Birds
Figure 13 Characteristics of birds. Like most birds, this tern 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
784 Transparencies
Chapter Resource File pp. 784–785 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 8C TAKS Obj 3 Bio 7B, 12B TEKS Bio 3D, 7B, 8B, 8C TEKS Bio/IPC 2D
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Chapter 34 • Reptiles and Birds
• Lesson Plan GENERAL • Directed Reading • Active Reading GENERAL • Data Sheet for Math Lab
GENERAL
Planner CD-ROM • Reading Organizers • Reading Strategies • Supplemental Reading Guide Through a Window
TT TT TT TT TT TT
Bellringer Characteristics of Birds Contour Feather Structure Avian Skeleton Avian Heart Structure Avian Lung Structure
Figure 14 Contour feather The structure of a contour feather helps create a smooth, aerodynamic surface, aiding flight.
Teach
Vane
READING SKILL
BUILDER
Barb
Shaft
Barbule
Paired Summarizing After students have read silently about birds, have pairs of students summarize what they have read without looking at the textbook. One student should listen without interrupting but should be prepared to point out any inaccuracies in the summary, and to add any ideas that were left out. Students may refer to the textbook during this clarification process. You may want to pair ELL students with native English Language Learners English speakers.
Hook
barbules, that are equipped with microscopic hooks. These hooks link the barbs to one another, giving the feather a continuous surface and a sturdy but flexible shape. With use, the connections become undone. 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 called a preen gland which secretes oil. When a bird preens, it spreads the oil over its feathers, cleaning and waterproofing them. Down feathers cover the body of young birds and are found beneath the contour feathers of adults. Their soft, fluffy structure provides good insulation for the bird, helping the bird conserve body heat. Feathers are important for other reasons too. Their coloration may be protective (as camouflage) or may be important in the selection of a mate. For example, the feathers of some birds allow them to blend in with their surroundings. In other species, the males develop special plumage during the breeding season.
Teaching Tip
Figure 15 Avian skeleton. A bird’s large, keeled attachment point for flight muscles, while its fused collarbones (wishbone) help absorb the stresses of flight.
Strong, Lightweight Skeleton If you have ever picked up a bird, such as a parakeet, you may have been surprised at how light it was compared to a mammal of a similar size. This is because the bones of birds are thin and hollow. Many of the bones are fused, making a bird’s skeleton more rigid than a reptile’s. The fused sections form a sturdy frame that anchors muscles during flight. The power for flight (or for swimming underwater in the case of some birds, like penguins) comes from large breast muscles that can make up 30 percent of a bird’s body weight. These muscles stretch from the wing to the breastbone. The breastbone is greatly enlarged and bears a prominent keel for muscle attachment, as illustrated in Figure 15. Muscles also attach to the fused collarbones (wishbone). No other living vertebrates have a keeled breastbone or fused collarbones.
TAKS 2 Bio 8C; Bio 8B
TAKS 1 Bio/IPC 2D; TAKS 3 Bio 7B
Demonstration
Fused collarbones Keeled breastbone
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Career Veterinarian When most people think of a veterinarian, they think of a “dog or cat doctor.” Many students will know that veterinarians also treat livestock. However, most people probably do not know that veterinarians also treat birds and reptiles. Have students investigate the training required to become a veterinarian, and have them find out where vet schools are located in your region of the country. LS Verbal Bio 3D
GENERAL
Preening Birds often sit and preen their feathers. Students have probably observed this behavior. Have students hypothesize about the function of preening and the reason that birds spend so much time doing it. After a period of discussion, point out that when birds preen, they smooth out and clean their feathers, making them more aerodynamic. Also note that birds spread oil from a gland near the base of their tail to waterproof the feathers and make them more resistant to breakage, much the way hair conditioner works. LS Logical
MISCONCEPTION
ALERT
Bird Nests Children who find bird nests are often warned not to touch them. The children are told, “the mother won’t return to the nest if you touch it.” In reality, most birds have a very poor sense of smell and probably would not know if their nest had been touched by a human (exceptions are flightless birds, ducks, and vultures). To compensate, many birds have keen vision and hearing. LS Interpersonal TAKS 3 Bio 7B
GENERAL
Bring cooked, cleaned chicken bones to class for students to examine. Cut a few bones in half so students can see the hollow structure. If you have a wishbone, allow students to pull it gently to note its flexibility. The cartilage keel on the breast of a chicken is also interesting to examine because it provides an attachment surface for flight muscles. LS Visual TAKS 3 Bio 7B
Chapter 34 • Reptiles and Birds
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Endothermic Metabolism Interpreting Graphics After studying Figure 18, use your own words to summarize how one breath of air circulates through a bird’s lungs. Remember to include both the inhalation and the exhalation cycle.
Teach, continued continued Teaching Tip Heat Source The high temperature of birds is a by-product of their rapid metabolism. You may wish to use the analogy of a car engine for metabolism. If the engine is running, heat is produced. The faster the engine is running, the more heat is produced. Ectothermic reptiles are like cars whose engines run very slowly all the time, producing little heat. In contrast, birds (and mammals) keep their engines running at high speed all of the time, producing much heat. TAKS 3 Bio 7B
www.scilinks.org Topic: Texas Songbirds Keyword: HXX4021
Completely Divided Ventricle As in crocodilians, the ventricle of birds is completely divided by a septum, as shown in Figure 16. Oxygen-rich and oxygen-poor blood are kept separate, meaning that oxygen is delivered to the body cells more efficiently. The sinus venosus, which is a prominent part of the fish heart, is not a separate chamber of the heart in birds (or mammals). However, a small amount of tissue from it remains in the wall of the right atrium. This tissue is the point of origin of the heartbeat and is known as the heart’s pacemaker.
Highly Efficient Lungs
IPC Benchmark Mini-Lesson Biology/IPC Skills TAKS 5 IPC 4B Investigate and describe applications of Newton's laws. Newton’s second law states that the amount of force acting on an object is equal to the object’s mass multiplied by its acceleration. Furthermore, an object’s momentum is the product of its mass and velocity. This helps explain one of the principles of flight. Bird’s wings have a special shape called an airfoil and airplane wings mimic this shape. As a mass of air passes over a wing it’s path is bent downward, thereby changing its momentum. Changes in the momentum of the air result in changes on the forces acting on the wing. The amount of lift on a wing depends on the amount and velocity of the air being diverted downward. For more lift, the wing can either divert more air—the mass—or increase the downward velocity of the air. Activity: Have students build paper airplanes that have airfoil wings. Then test them outside to see if their designs were successful.
Birds are endotherms; that is, they generate enough heat through metabolism to maintain a high body temperature. Birds maintain body temperatures ranging from 40°C to 42°C (104°F to 108°F), which is significantly higher than the body temperature of most mammals. 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.
Figure 16 Avian heart. A bird’s heart has a complete septum.
Birds such as the geese shown in Figure 17 use a considerable amount of energy when they fly. Since birds often fly for long periods of time, their cellular demand for energy exceeds that of even the most active mammals. How do birds get the energy they need? Recall that reptiles meet their increased need for oxygen with lungs 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 be improved just by increasing its surface area. Another way to
Avian Heart Structure Oxygen-poor blood from the body enters the right atrium. The right atrium pumps this blood to the right ventricle.
1
To body From body
Oxygen-rich blood from the lungs enters the left atrium, which pumps it to the left ventricle.
3
To lungs From lungs Left atrium
Right atrium
Left ventricle Complete septum
Right ventricle
2
The right ventricle pumps the oxygen-poor blood to the lungs.
From body
The left ventricle pumps the oxygen-rich blood to the body.
4
786 Cultural
Awareness
pp. 786–787 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 4B TEKS Bio 7A, 7B, 12C TEKS Bio/IPC 2C, 2D, 3C TEKS IPC 4B
786
Eagle Feathers The only people in North America who can legally own eagle feathers are Native Americans. The eagle is so highly valued by tribes throughout the United States that its feathers must be earned through personal sacrifice, and then they may be used only in special ceremonies. For instance, if a
Chapter 34 • Reptiles and Birds
Winnebago pow-wow dancer accidentally drops an eagle feather during a performance, the dance is stopped until the feather is purified by an elder and then reclaimed by the dancer, who is not allowed to dance again for a year. Bio/IPC 3C
increase the efficiency of a lung is to have air pass over its respiratory surface in one direction only, just as water flows over a fish’s gills in one direction. This is what happens in birds. One-way air flow is possible in birds because they have air sacs connected to their lungs, as shown in Figure 18. There is no gas exchange in the air sacs. They simply act as holding tanks. There are two important advantages to oneway air flow. First, the lungs are exposed only to air that is almost fully oxygenated, increasing the amount of oxygen transported to the body cells. Second, the flow of blood in the lungs runs in a different direction than the flow of air does. Unlike the flow of water and blood in fish gills, the flow of air and blood in bird lungs are not completely opposite (countercurrent). Nevertheless, the difference in direction does increase oxygen absorption. These three characteristics—endothermic metabolism, a completely divided ventricle, and highly efficient lungs—provide the energy a bird needs for takeoff and sustained flight. They enable a hummingbird to flap its wings rapidly (20–80 beats per second) as it hovers by a flower. They also permit migrating birds to fly thousands of kilometers without stopping. One species of shorebirds called the lesser yellowlegs flies across the open ocean from Massachusetts to Martinique in the West Indies. Incredibly, some of these birds 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 birds take advantage of upward air movements that lift them.
Teaching Tip
White or Dark Meat? The dark color of some chicken meat is partly due to the presence of myoglobin, a hemoglobin-related molecule that helps provide oxygen to muscles that must contract vigorously and repeatedly. Ask students why a duck has dark breast meat but a chicken has white breast meat. (The duck flies long distances, but the chicken does not.) Ask what chickens usually use for locomotion and what color that meat is. (They usually use their legs to walk, and the legs contain dark meat.)
Figure 17 Flight. These barnacle geese expend an enormous amount of energy during take off and flight.
TAKS 3 Bio 7B; Bio 12C
Activity Origin of Birds Ask students to identify the living reptiles that are most closely related to birds. (crocodilians) Have them name two characteristics that crocodilians and birds share. (a heart with completely divided ventricle, parental care of young, amniotic eggs, and vocalization) Have students research recent fossil discoveries that have changed views on the origin of birds. LS Verbal
Figure 18 Avian respiration. A single breath of air stays in a bird’s respiratory system for two cycles of inhalation and exhalation.
Avian Lung Structure Right lung Inhalation
Trachea
GENERAL
inhalation, most of the 1 During 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.
TAKS 1 Bio/IPC 2C, 2D; TAKS 3 Bio 7A (grade 11 only), 7B
Anterior air sacs
Posterior air sacs
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
Exhalation
787
did you know? Brood Parasites The brown-headed cowbird is a brood parasite. A female brown-headed cowbird will fly to a nest full of eggs, roll one or two eggs out, and lay the same number as the number she has displaced. When the owner of the nest returns, it will incubate all the eggs, including the cowbird’s. The cowbird eggs often have a shorter incubation time and hatch before
the eggs of the incubating species. Therefore, the cowbird nestlings are fed first and get a head start in their development over the other chicks in the nest. Cowbird nestlings may even eject the nestlings of the incubating species, thereby eliminating competition for food. TAKS 3 Bio 7B; Bio 12C
Chapter 34 • Reptiles and Birds
787
Up Close Up Close
Bald Eagle
Bald Eagle TAKS 2 Bio 8C, 10A;
TAKS 3 Bio 7B, 12B; Bio 3F
Scientific name: Haliaeetus leucocephalus
●
Size: Wingspan is typically over 2 m (6.5 ft), and body weight 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
External Structures 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.
▲ Eye
▼ Feathers
Feathers The body of the bald eagle is covered with feathers everywhere except the feet and the beak, which are bare.
Nostril
Both sexes develop the characteristic white head and neck at maturity.
▼ Beak
Grasping feet The bald eagle
Beak The beak is mas-
has large feet and talons—the hind
sive, with an elongated,
talon may be 5 cm (2 in.) long. The talons are used to snatch fish from the water while the eagle is flying.
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
When the muscles of the legs contract, the tendons in the lower legs are pulled, and the talons lock together around the fish.
788
pp. 788–789 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, 12B TEKS Bio/IPC 2D
788
●
▲
Teaching Strategies • The largest bald eagle nests in North America were found in Vermillion, Ohio— 3.7 m (12 ft) deep, 2.6 m (8.5 ft) in diameter, and weighing 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 called an aerie. • After World War II, the numbers of bald eagles in the lower 48 states fell drastically because of the widespread use of the pesticide DDT. Because DDT breaks down very slowly, it accumulates in the food chain and causes the eggshells of bald eagles and many other birds to become thin and fragile. Affected eggs break when a parent attempts to incubate them. In 1972, the use of DDT was banned in the United States. By 1978, fewer than 500 breeding pairs of bald eagles remained in the United States outside Alaska. A slow recovery of the eagles began, and by the summer of 1999, six states had removed bald eagles from the endangered species list. • Show students a picture of a large but immature bald eagle and ask them what kind of bird it is. Point out that the bald eagle does not get its white head and tail until its fourth or fifth year of life.
TAKS 2, TAKS 3
Chapter 34 • Reptiles and Birds
Transparencies TT TT TT TT
External Structures of Birds Internal Structures of Birds Avian Adaptations Major Orders of Birds
Talon
Internal Structures Brain In the ratio of brain size to body size, birds rank
Up Close Cerebrum
Cerebellum
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.
Bald Eagle
Medulla oblongata
Discussion • Identify three differences between the internal structures of the timber rattlesnake and the bald eagle. (The rattlesnake has one functional lung, lacks air sacs, has neither a crop nor a gizzard, has venom-producing glands, and does not have hollow bones.) • Would the heat-sensitive pits of the timber rattlesnake be an effective way of sensing prey for a bald eagle? (No, the rattlesnake’s pits are sensitive only to nearby heat sources, and the bald eagle spots its prey from great distances.)
Optic lobe
▲ Brain
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 concenLeft lung trated into a harmless white paste. Left ovary The uric acid travels to the cloaca and is eliminated. Kidney
Esophagus
▼
Trachea Air sac
Crop
• Why might it be a disadvantage for an eagle to have a urinary bladder? (Urine contains a greater amount of water, which is heavy. The extra weight would be a disadvantage in flight.) • Why might teeth be a disadvantage to a bird? (Teeth are heavy and require heavy jaws.)
Small intestine Heart
Large intestine Liver
Pancreas
▼ Gizzard
Digestive system Large meals are temporarily stored in ▼ Cloaca
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.
LS Visual
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.
Activity
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.
789
GENERAL
Eagle Eyes Eagles have much better vision than humans do. To simulate how much better, tape a worksheet on the wall and have students stand about 3 m away and try to read it. Then have them move 1 m away and read the worksheet. Tell them that an eagle could see the paper at 3 m as well as humans can at 1 m. TAKS 1 Bio/IPC 2D; TAKS 3 Bio 7B
Chapter 34 • Reptiles and Birds
789
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 approximately 5,300 species and are by far the largest group of terrestrial vertebrates. Birds are adapted for different ways of life, and you can tell a great deal about the habits and diet of a bird by examining its beak (bill), legs, and feet. Carnivorous birds such as hawks have curved talons for seizing prey and a sharp beak for tearing apart their meal. The beaks of ducks are flat for shoveling through water or mud, and their webbed feet enable them to swim. Finches are seed eaters, and their short, thick beak is adapted for crushing seeds while their curved toes enable them to cling to branches. Other birds, such the penguins shown in Figure 19, are flightless, 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 the birds live in, as shown in Table 1. Some birds are more highly specialized than others, and many birds are highly flexible in their eating habits. The song sparrow, for example, has a strong bill that it uses in winter to crack hard seeds. In summer, the sparrow uses its bill to catch soft-bodied insects.
Teach, continued continued Teaching Tip
GENERAL
Reptiles and Birds Have students make a three-column chart like the one in the Graphic Organizer shown at the bottom of this page. They should use the information on birds in Section 3 and the material on reptiles in Sections 1 and 2. Students should use the following characteristics for both reptiles and birds: type of body covering, type of heart, mode of reproduction, type of metabolism, and parental care of offspring. LS Visual TAKS 2 Bio 8C, 10A; TAKS 3 Bio 7B
Figure 19 Penguin. The penguin’s wings are adapted for swimming rather than flying.
Teaching Tip Introduced Pests House sparrows and European starlings are two common birds that may be familiar to students. Inform students that these two species were introduced into the United States from Europe. Both species have become serious pests. These exotic species out compete native songbirds for food and nesting sites. In fact, they are thought to be at least partly responsible for the decline in the numbers of bluebirds. Bio/IPC 3C
Table 1 Avian Adaptations Type of bird
Beak adaptations
Foot adaptations
Songbirds (e.g., cardinal, robin)
Perching: Toes can cling to branches; one toe points backward
Seed-cracking: Short, thick, strong beak
Insect-catching: Long, slender beak for probing
Hummingbirds
Probing: Thin, slightly curved beak for inserting into flowers to sip nectar
Hovering: Legs so small the bird cannot walk on the ground; tiny feet
790
Graphic Organizer Use this graphic organizer with Teaching Tip: Reptiles and Birds. pp. 790–791 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, 12C TEKS Bio/IPC 2C, 2D, 3C
790
Chapter 34 • Reptiles and Birds
Characteristic Body covering Type of heart Reproduction Metabolism Parental care
Reptiles
Birds
Scaly skin Partially or completely divided ventricle Oviparous or ovoviviparous Ectothermic Little or none
Feathers Completely divided ventricle Oviparous Endothermic Until offspring can fly
Beak adaptations
Type of bird Woodpeckers
Drilling: Strong, chisel-like beak
Foot adaptations
Using the Table
Grasping: Feet with two toes pointing forward and two pointing backward
Parrots
Cracking, tearing: Short, stout, hooked beak used to crack seeds and nuts and to tear vegetation
Climbing/grasping: Strong toes, two pointing forward, two pointing backward; adapted for perching, climbing, and holding food
Birds of prey
Tearing: Curved, pointed beak for pulling apart prey
Grasping: Powerful, curved talons for seizing and gripping prey
Have students pair up. Instruct the students to cover the two columns on the right side of Table 1 with a sheet of paper. Have one student uncover the Beak adaptations column, choose one, and read the description. The other student should try to identify the type of bird whose beak is described. This process should continue until the second student has correctly identified each bird. The students should then switch roles and repeat the process using the Foot adaptations column. LS Verbal TAKS 2 Bio/IPC 2C, 2D; TAKS 3 Bio 7B
Ducks
Sieving: Long, flattened, rounded bill
Demonstration Show students pictures of several different types of birds. Be sure to include some with distinctly different beaks and feet. A typical assortment would be: woodpecker, heron, pelican, grosbeak, chickadee, goose, and hummingbird. Ask students to examine the different types of beaks and feet and to hypothesize about each bird’s habitat and diet. LS Visual
Swimming: Three toes linked by webs for improved swimming
TAKS 3 Bio 7B; Bio 12C
Group Activity Long-legged waders
Fishing: Long, slender, spear-shaped beak for fishing Wading: Long legs; toes spread out over a large area to support bird on soft surfaces
791
Trends in Ornithology Researchers around the country have been monitoring bird populations each year to determine long-term trends. One apparent trend: of the 42 bird species that are listed as threatened or endangered, 22 are associated with wetlands. The trend holds true for other animals as well. Have students research the threatened and endangered birds in your area. In their reports, students should discuss the probable causes of decline, as well as plans for species recovery. Bio/IPC 3C
REAL WORLD CONNECTION
Birding (once called birdwatching) has been described as the second-favorite outdoor activity in the United States, after gardening. Invite a local naturalist or member of a nearby chapter of the Audubon Society to visit your classroom and discuss tips on how to attract and identify backyard birds. Make a list of local birds and show slides of each bird to your class. Slides can be purchased from many sources, including the Cornell University Laboratory of Ornithology.
Avian Adaptations Divide the class into small groups, and assign each group a particular feeding strategy and bird habitat. Have each group use a field guide to identify five species of birds that share the assigned feeding strategy and habitat. Students should then use drawings or written descriptions to demonstrate the similarities in beaks, feet, and behavior among birds with similar lifestyles. Have each group share its findings with the entire class. LS Visual Co-op Learning TAKS 1 Bio/IPC 2C, 2D; TAKS 3 Bio 7B; Bio 12C
Bio/IPC 3C; Bio 8C
Chapter 34 • Reptiles and Birds
791
Other Adaptations
x 2+ 6x
76
0 2
5
-7-0
Calculating Average Bone Density TAKS 1 Bio/IPC 2C, 2D; TAKS 3 Bio 7B
Skills Acquired Analyzing data, calculating
8 0 2
493 x 2+ 6x
5
Calculating Average Bone Density
-7-0 <
493
<
18
There are many groups of birds, each of which is adapted to its particular living conditions. For example, gulls and terns have streamlined bodies that are adapted for flying over the water in search of fish. Owls’ excellent low-light vision enables them to survive as nocturnal hunters. For a list of the orders of birds, see “Classification in Kingdoms and Domains” in the Appendix.
Teacher’s Notes After students read the explanatory paragraph, have them glance at the data and predict which animal has the higher average bone density.
2C 2D 7B
TAKS 1, TAKS 3
Background Density is the ratio of the mass of an object to its volume. Several teams of students determined the density of bones from two different animals. You can use their data to practice calculating average bone density.
DATA TABLE Bone type
Answers to Analysis 1. Animal 1: 1.3 g/cm3; Animal 2: 2.0 g/cm3 2. A certain amount of variation is normal in biological systems. 3. Animal 1
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
9.0 g/cm3 sum of the densities 3.0 g/cm3 3 number of samples
Analysis
Close
1. Calculate the average bone density for each of the two animals in the data table. Express your answer in grams per cubic centimeter.
Reteaching Have each student develop ten questions for this section, and use the questions in a review game. LS Interpersonal
Quiz
2. Critical Thinking Evaluating Methods Why is it important to analyze several samples and obtain the average of your data?
MATH TAKS Obj 10, 8.14A, 8.15A, 8.16B
TAKS 1 Bio/IPC 2C, 2D
GENERAL
Section 3 Review
True or False: 1. Birds are ectotherms. (False. Birds are endotherms.) TAKS 3 Bio 7B; Bio 8B, 12C 2. Birds have a two-way airflow during respiration. (False. Birds have a one-way airflow.) TAKS 3 Bio 7B; Bio 8B, 12C
Identify the adaptations of birds for
Critical Thinking Evaluating Hypotheses
flight.
A student examines a bird that has delicate, perching feet with long, slender toes. Its beak is small but slightly long and pointed. The student concludes that the bird is a seed-eating songbird. 3A 7B Do you agree? Explain your reasoning.
7B
Summarize how birds obtain the energy
necessary for flight.
7B 10A
Relate the bald eagle’s methods of hunting and 7B 11B feeding to its external body features.
TAKS Test Prep Which structure is part of the excretory, digestive, and reproductive systems 10B of a bird? A kidney C gizzard B cloaca D ovary
pp. 792–793 Student Edition TAKS Obj 1 Bio/IPC 2C, 2D TAKS Obj 1 IPC 3A TAKS Obj 2 Bio 10A, 10B TAKS Obj 3 Bio 7B Math TAKS Obj 10, 8.14A, 8.15A, 8.16B TEKS Bio 3A, 7B, 10A, 10B, 11B TEKS Bio/IPC 2C, 2D TEKS IPC 3A Teacher Edition TAKS Obj 1 Bio/IPC 2C, 2D TAKS Obj 1 IPC 3A TAKS Obj 2 Bio 8C, 10A, 10B TAKS Obj 3 Bio 7B TEKS Bio 3A, 7B, 8B, 8C, 10A, 10B, 11B, 12C TEKS Bio/IPC 2C, 2D TEKS IPC 3A
792
3. Critical Thinking Drawing Conclusions Based on your answer to item 1, which of the two animals is more likely to be a bird?
792
Answers to Section Review 1. forelimbs modified as wings; feathers; streamlined shape; lightweight bones, endothermic metabolism; highly efficient lungs; heart with completely divided ventricle TAKS 3 Bio 7B 2. An endothermic body and a rapid metabolism provide the energy necessary for flight. TAKS 2 Bio 10A; TAKS 3 Bio 7B
3. The bald eagle has strong feet with sharp talons for grabbing prey, and a massive, hooked beak for tearing prey into pieces it can eat. TAKS 3 Bio 7B; Bio 11B
4. The small, pointed beak indicates that it is not a seedeater because seedeaters have thick beaks for crushing seeds. The foot structure, however,
Chapter 34 • Reptiles and Birds
is consistent with the songbird anatomy. TAKS 1 IPC 3A; TAKS 3 Bio 7B; Bio 3A
5.
A. Incorrect. The kidneys play an important excretory role in birds, but are not closely associated with the other systems. B. Correct. The cloaca is an opening that allows wastes to leave the body. In females, it also allows sperm to enter the body and fertilized eggs to leave the body. C. Incorrect. The gizzard is the second part of the stomach that helps to grind food; it is not part of the excretory or reproductive systems. D. Incorrect. The ovary is a reproductive organ; it is not part of the digestive or excretory systems. TAKS 2 Bio 10B (grade 11 only)
Study
CHAPTER HIGHLIGHTS
ZONE Key Concepts
Alternative Assessment
Key Terms Section 1
1 The Reptilian Body
amniotic egg (775) oviparous (777) ovoviviparous (777)
●
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.
GENERAL
Have each student use the red and blue subheadings in this chapter to create questions based on each subheading, and then correctly answer it. For example, “Reptiles Share Several Key Characteristics,” could become “What key characteristics do reptiles share?” LS Verbal TAKS 1 Bio/IPC 2C, 2D; TAKS 2 Bio 8C; TAKS 3 Bio 7B; Bio 12C
Chapter Resource File
2 Today’s Reptiles
Section 2
●
Snakes and lizards (order Squamata) share many characteristics, such as periodic molting, but snakes have no legs.
carapace (782) plastron (782)
●
The shells of turtles and tortoises (order Chelonia) are made of fused plates of bone covered with horny shields or leathery skin.
●
Unlike other reptiles, crocodilians (order Crocodilia), care for their young after hatching. They also have a completely divided ventricle.
●
There are only two species of tuataras (order Rhynchocephalia).
• Science Skills Worksheet GENERAL • Critical Thinking Worksheet • Test Prep Pretest GENERAL • Chapter Test GENERAL
Section 3
3 Characteristics and Diversity of Birds ●
Birds are endotherms. Their high rate of metabolism helps them meet the large energy requirements for flight.
●
A bird’s contour feathers give the bird its shape and aid flight. Its down feathers provide insulation.
●
The bones of birds are thin and hollow, and many of them are fused; all are adaptations for flight.
●
One-way airflow through the lungs provides the large amounts of oxygen birds need for flight.
●
The ventricle of the bird heart is completely divided by a septum.
contour feather (784) preen gland (785) down feather (785)
793
Answer to Concept Map The following is one possible answer to Performance Zone item 15 on the following page. birds
Reptiles are
are
ectotherms
are
Ovoviviparous
such as
Snakes
Lizards
Tuataras
which have a
3-chambered heart
which are
Oviparous
and have
and have
Turtles
Crocodilians which have a
endotherms
Scales
Feathers and have a
4-chambered heart
Chapter 34 • Reptiles and Birds
793
Performance ZONE
CHAPTER 34
ANSWERS
9. Snakes differ from lizards in that snakes
Using Key Terms
Using Key Terms
do not have a. lungs. b. kidneys.
1. All of the following reptiles belong to the
1. b Bio 8B 2. a TAKS 3 Bio 7B 3. a TAKS 3 Bio 7B 4. a TAKS 3 Bio 7B 5. a. Oviparous animals lay eggs. In ovoviviparous animals, embryos develop within eggs inside the mother’s body. These eggs hatch within the mother, giving the appearance of live birth. b. Contour feathers are large and allow the bird to fly. Down feathers are small and fluffy; they are found under the contour feathers and function only to insulate.
Understanding Key Ideas 6. b TAKS 3 Bio 7B 7. b TAKS 2 Bio 10A 8. a TAKS 2 Bio 10A 9. c TAKS 3 Bio 7B 10. a TAKS 2 Bio 10A 11. d TAKS 2 Bio 8C; Bio 8B 12. d TAKS 3 Bio 7B 13. d TAKS 3 Bio 7B 14. The dams cause riffles, which contain insects that male turtles feed on, to disappear. Thus, turtles may not be able to find adequate food to survive in dammed areas. TAKS 3 Bio 7B 15. One possible answer to the concept map is found at the bottom of the Study Zone page. Bio 3E
order Crocodilia, except 8B a. alligators. c. crocodiles. b. tuataras. d. gavials.
7B
c. a pectoral girdle. d. a flexible jaw.
10. Jacobson’s organs are involved in the
sense of 10A a. smell. b. hearing.
2. The two basic parts of a turtle’s shell
are the 7B a. carapace and plastron. b. septum and amnion. c. chorion and allantois. d. keratin and cloaca.
c. sight. d. touch.
11. Which group of living reptiles is most
closely related to birds? 8B 8C a. snakes c. rhynchocephalians b. turtles d. crocodilians
3. The eggs of reptiles and birds are
12. The feathers of most birds are well
described as 7B a. amniotic. b. oviparous. c. ovoviviparous. d. externally fertilized. 7B 4. The preen gland a. secretes oil. b. senses chemicals. c. stimulates egg production. d. causes a change in body temperature.
adapted for 7B 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 of
a bird adapted for a. wading. b. grasping.
7B
c. perching. d. swimming.
5. For each pair of terms, explain the
differences in their meanings. a. oviparous, ovoviviparous b. contour feather, down feather
Understanding Key Ideas 6. Which is not an adaptation of reptiles
for life on land? 7B a. watertight skin b. external fertilization c. amniotic egg d. 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 a. b. c. d.
reptiles, fertilization 10A is internal. is external. always occurs in water. does not occur.
794
Assignment Guide Section 1 2 3 pp. 794–795 Review and Assess TAKS Obj 1 Bio/IPC 2A, 2B, 2C, 2D TAKS Obj 2 Bio 8C, 10A TAKS Obj 3 Bio 7B TEKS Bio 3E, 7B, 8B, 8C, 10A, 12C TEKS Bio/IPC 2A, 2B, 2C, 2D
794
CHAPTER REVIEW
Chapter 34 • Reptiles and Birds
Questions 3, 5a, 6–8, 14, 19, 22 1–3, 9–11, 14–16, 19 3, 4, 5b, 11, 12–15, 17, 18, 20, 21
10A
14.
In what ways might the damming of the Guadalupe River affect the ability of Cage’s map turtle to find food? 7B
15.
Concept Mapping Construct a concept map that describes the characteristics of both reptiles and birds. Include the following terms in your map: ectotherm, endotherm, oviparous, ovoviviparous, scales, feathers, three-chambered heart, and four-chambered heart. 3E
Critical Thinking
Alternative Assessment
Critical Thinking
16. Forming Hypotheses Many viviparous
20. Applying Information Design and build a
16. Because the young are carried inside the body, they receive some heat as a result of the mother’s muscular movements and basking behavior.
snakes and lizards live in cold climates. Why might viviparity be advantageous in such environments? 2A 7B
bird feeder. Place the feeder where it can be easily observed. Keep a journal of your observations to share with your class. 2A 2B 2D
17. Predicting Outcomes How might having
21. Being a Team Member and Communicating
a three-chambered heart, like that of most reptiles, affect a hummingbird in flight? 10A 18. Recognizing Logical Connections How
might a long period of parental care be related to the number of offspring an animal produces? 10A 19. Forming a Hypothesis When a piece
of a lizard’s tail breaks off, the separated portion may wiggle about forcefully. How might this adaptation be an advantage for the lizard? 2C 7B
Work with two or three of your classmates to find out what kinds of birds are common in your area. Select at least six birds to explore in depth and research the following: its habitat, its food, its beak and foot adaptations, and where it winters. Present the information you gathered in an illustrated guide. Make copies of your guide available 2A 2B 2C 2D for interested students. 22. Organizing Information Create a habitat in
a terrarium for a small lizard, and observe the lizard’s behavior. Make a labeled drawing of the environment you create, and keep a journal of your observations.
TAKS Test Prep The chart below shows the normal ranges of body temperature in five groups of reptiles. Use the chart and your knowledge of science to answer questions 1–3.
Tuataras Turtles Lizards Snakes Crocodilians
2. If a bar showing the body temperature
range of birds were added to this chart, the bar for birds would partially overlap with 12C the bar for F lizards. H crocodilians. G tuataras. J turtles.
10
20
30
40
50
Body temperature (°C)
1. Which groups could probably best
tolerate the temperature extremes found in deserts? 2C A Turtles, snakes, and crocodilians B Turtles, lizards, and snakes C Tuataras, turtles, and snakes D Tuataras and crocodilians
2. F. Correct. Although birds are endotherms with a very small temperature range, their range overlaps with lizards, the only reptile with temperatures above 40ºC. G. Incorrect. Tuataras do not have body temperatures as warm as birds, which have temperatures of 40ºC–42ºC. H. Incorrect. Crocodilians do not have body temperatures as warm as birds. J. Incorrect. Turtles do not have body temperatures as warm as birds. Bio 12C
Alternative Assessment
2C the 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. Students should research both seeds and feeder types to predict which birds will be attracted. TAKS 1 Bio/IPC 2A, 2B, 2D
21. Answers will vary depending on birds chosen. Students should acknowledge their sources and include an illustration of each bird. TAKS 1 Bio/IPC 2A, 2B, 2C, 2D 22. Students should research what type of food and habitat is appropriate for the lizard they choose and set up their terrarium accordingly.
Test When a question refers to a graph, study the data plotted on the graph to determine any trends or anomalies before you try to answer the question.
795 3. A. Incorrect. While crocodilians have a greater body temperature than tuataras, the ranges of body temperatures are about the same for both. B. Correct. According to this data, turtles and snakes have a body temperature range of about 9ºC–38ºC. C. Incorrect. Lizards often have a higher body temperature than tuataras but their temperature ranges overlap. D. Incorrect. The lowest body temperature for a crocodilian is higher than the highest body temperature for a tuatara. TAKS 1 Bio/IPC 2C
17. Because it mixes oxygen-rich and oxygen-poor blood, a threechambered heart would not distribute enough oxygen to the hummingbird’s muscles to sustain flight. TAKS 2 Bio 10A 18. Animals that invest a long period of parental care typically have fewer offspring than animals with little or no parental care, but the offspring that are cared for are more likely to live to adulthood. In both cases, only a small number of offspring survive to breeding age. TAKS 2 Bio 10A 19. Predators are distracted by the wiggling tail part, which gives the lizard time to escape. TAKS 1 Bio/IPC 2C; TAKS 3 Bio 7B
3. Which of these statements is supported by
0
TAKS 1 Bio/IPC 2A; TAKS 3 Bio 7B
1.
A.Incorrect. Crocodilians are not tolerant of the low temperatures sometimes found in deserts. B. Correct. Turtles, lizards, and snakes are able to tolerate both the low and high temperatures often found in deserts. C. Incorrect. Tuataras are not able to tolerate the high heat of the desert. D. Incorrect. Tuataras are not able to tolerate the high heat of the desert, and crocodilians are not tolerant of the low temperatures sometimes found in deserts. TAKS 1 Bio/IPC 2C
Chapter 34 • Reptiles and Birds
795
