Chapter 32: Mammals

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Mammals

What You’ll Learn ■ You will identify the characteristics of mammals. ■ You will compare and contrast three groups of living mammals and examine their relationships to their ancient ancestors.

Why It’s Important Mammals play a major role in most ecosystems on Earth because they are one of the most successful groups of animals. Humans are mammals, so studying mammal characteristics provides information about humans as well.

Understanding the Photo Giraffes are the tallest mammals. Newborn giraffes average 1.8 meters and can grow to be about 5.5 meters as adults. They have long legs and can run quickly—about 60 km/h. Their long legs, as well as their long necks, help them reach leaves in tall acacia trees.

Visit ca.bdol.glencoe.com to • study the entire chapter online • access Web Links for more information and activities on mammals • review content with the Interactive Tutor and self- check quizzes

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Mammal Characteristics 32.1

SECTION PREVIEW Objectives Mammals Make the following Foldable to help you identify Distinguish mammalian main characteristics of mammals. characteristics. Explain how the charac- STEP 1 STEP 2 teristics of mammals Fold a vertical Cut along every enable them to adapt to sheet of notebook paper fourth line of only the top layer most habitats on Earth. from side to side. to form tabs. Review Vocabulary metabolism: all of the chemical reactions that occur within an organism (p. 147) STEP 3 Label each tab. New Vocabulary gland mammary gland diaphragm

Find Main Ideas As you read Chapter 32, list the main characteristics of mammals on the tabs. As you learn about the main characteristics, write a benefit of the adaptation under the tab for each.

Physical What is a mammal? Science Mammals, like birds, are endotherms. The ability to maintain a fairly Connection constant body temperature enables mammals to live in almost every pos- Movement of sible environment on Earth. Mammals have important characteristics not heat through hair Compared to found in other animals. They have hair and produce milk to nurse their solids or liquids, young. Mammals also have diaphragms, four-chambered hearts, special- gases are poor ized teeth, modified limbs, and highly developed brains. conductors of heat. A layer of hair or fur on a Mammals have hair mammal’s skin contains many air Have you ever heard someone complain about a pet that is shedding pockets trapped its hair? There’s no doubt that such a pet is a mammal because hair is between the hair present on all mammals at some point in their lives. Like feathers, shafts. Because air is a poor heat mammalian hair, made out of the protein keratin, is also thought to conductor, heat have evolved from scales. The arrangement of hair provides insulation moves slowly through an air and waterproofing and thereby conserves body heat. If you have ever pocket. As a result, worn a wool sweater made from the hair of a sheep, you know how the rate at which warm wool can be on a cold day. As shown in Figure 32.1 on the next heat is lost by the mammal is page, hair also serves other functions. reduced. Although hair helps retain body heat, mammals also have internal feedback mechanisms that signal the body to cool off when it gets too warm. Mammals cool off by panting and through the action of sweat glands.

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Figure 32.1 B The black stripes of a tiger’s fur Hair helps maintain a constant body aid in camouflaging this beautiful temperature. It also serves a variety cat as it hunts for prey. of other purposes.

A The sharp, barb-tipped quills of a porcupine are a type of modified hair.

C The white patch of hair on the rump of the fleeing deer signals danger to other members of the herd.

Panting releases water from the nose You have already learned how sweat and mouth, which results in a loss of glands help keep a mammal cool. body heat. Sweat glands help regulate Mammals also feed their young body temperature by secreting mois- from mammary (MA muh ree) glands,

ture onto the surface of the skin. As the possibly modified sweat glands, which om McHugh/Photo Researchers

moisture evaporates, it transfers heat produce and secrete milk, a liquid that , (br)T from the body to the surrounding air. is rich in fats, sugars, proteins, miner-

als, and vitamins. Mammals nurse their DRK Photo Figure 32.2 Mammals nurse their young young until they are able to digest and lain/

Large mammals usually Chamber

Mammals have several types of absorb nutrients from solid foods. . have few young. Infer glands, which are a group of cells that Figure 32.2 shows that the number of l)M.C Why do mammals that secrete fluids. They include glands that young each mother has and the length , (b are prey for many predators tend to produce saliva, sweat, oil, digestive of time she nurses her young vary have larger litters? enzymes, hormones, milk, and scent. among species. asemann/DRK Photo Kr A An Indian rhinoceros usually has one calf at a time. . Calves begin to graze at two months of age. , (tr)Stephen J ynn/Photo Researchers , (tc)Renee L

B Mice have four to nine Dennis/Photo Researchers offspring in each litter, and up . to 17 litters a year. The young

nurse for just a few weeks. (tl)Nigel J

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Respiration and circulation in mammals Mammals need a high level of energy to maintain their endothermic metabolism. This energy level Compare and Contrast is sustained when large amounts of Anatomy of a Tooth Most mammals have nutrients and oxygen enter the body teeth. Teeth are adapted to a mammal’s diet. and reach the cells. The mammals’ diaphragm helps Procedure ! Examine a prepared longitudinal expand the chest cavity to aid the flow Longitudinal section view slide of a human tooth section of a of oxygen into their lungs. A under low-power magnification. canine tooth diaphragm (DI uh fram) is the sheet of CAUTION: Use caution when working muscle located beneath the lungs that with a microscope and slides. separates the chest cavity from the @ Locate the different areas—enamel, dentine, and pulp cav- abdominal cavity, where other organs ity—that form the tooth. Move the slide to see all areas. are located. Once in the lungs, oxygen # Diagram the tooth as it appears under low power. diffuses into the blood. As the chest cavity returns to its resting position, Analysis air is released. 1. Explain Most of the tooth you studied is composed of the root Mammals, like birds, have four- under the gums. How is the part chambered hearts in which oxygen- above the gum adapted to the ated blood is kept entirely separate diet of humans? from deoxygenated blood. This en- 2. Interpret Scientific sures that a good supply of nutrients Illustrations Examine the and oxygen are delivered to cells which diagrams of mammal skulls and supports their endothermic metabo- predict what kinds of food these mammals might eat based on lism. Circulation also removes waste the shape of their teeth. products from cells and helps regulate body temperature. Blood helps keep a constant cellular environment, which maintains homeostasis.

The pointed incisors of moles Most mammals have grasp and hold small prey. The chisel- Physical specialized teeth Science like incisors of beavers are modified Connection Teeth are a distinguishing feature for gnawing. A lion’s canines punc- Teeth as simple of most mammals. Although fishes ture and tear the flesh of its prey. machines Teeth and reptiles have teeth, their teeth are Premolars and molars are used for and chisels are relatively uniform and are used pri- slicing or shearing, crushing, and shaped like wedges. A wedge is a simple marily for tearing, grasping, and grinding. You can get a closer look at machine that holding prey. mammalian teeth in the MiniLab on increases an applied force and changes Mammals with teeth have different this page. By examining the teeth of a its direction. As a kinds that are adapted to the type of mammal, a scientist can determine result, a downward food the animal eats. Think of the dif- what kind of food it eats. force applied to a tooth is changed to ferent tools you might use to build a Many hoofed mammals have an a larger sideways piece of furniture, such as a chisel for adaptation called cud chewing that force. scraping or a saw for cutting. Like a enables the cellulose in plant cell cabinetmaker’s tools, teeth are shaped walls to be broken down into nutri- to match the types of jobs they do. ents they can absorb and use.

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Have you ever seen cows slowly chewing while lying in a pasture? When plant material is swallowed, it Analyze Information moves into the first two of four pouches in the stomach where cellu- Which animal has the longest digestive system? A mammal may be an herbivore, carnivore, or omnivore. Is there a rela- lose in the cell walls is broken down tionship between length of a mammal’s digestive tract and its by bacteria. The partially digested diet? Make a hypothesis as to what that correlation might be. food, called cud, is repeatedly brought back up into the mouth. After more Solve the Problem chewing, the cud is swallowed again The following data table provides general information on and when the food particles are small digestive tracts for several mammals. enough they are passed to the other Data Table stomach areas, where digestion con- tinues. You can learn more about Animal Length of Diet Animal Digestive Tract Category Mass digestion in mammals in the Problem- Koala 305 cm Herbivore 10 kg Solving Lab on this page. The various Dog 135 cm Carnivore 11 kg types of teeth in different mammals can be seen in Figure 32.3. Rabbit 272 cm Herbivore 9 kg Bobcat 145 cm Carnivore 12 kg Figure 32.3 Thinking Critically Mammal groups are distinguished by number and types of teeth. 1. Analyze What does the relationship between diet and digestive tract length appear to be? 2. Interpret Data Do the data support your hypothesis? Explain your answer. 3. Formulate a Hypothesis Explain the relationship between digestive tract length and difficulty in digesting food type. (Hint: Does cellulose take longer to digest?) 4. Conclude Was the mass of all animals relatively close when compared? Explain why mass is important.

A Bears, like humans, have incisors, canines, premolars, and molars. Bears and humans are omnivores.

B Carnivores, such as this tiger, have canine teeth that stab and pierce food, and premolars and molars adapted for chewing.

C Premolars and molars are the predominant teeth in horses and other herbivores. These crushing and grinding teeth are covered with hard enamel.

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Observe Mammal Skeletons Owls are predators. They feed on small mammals as well as on birds. After eating a meal, the tough indigestible parts of prey, such as bones, are regurgitated as pellets. The skeletons of a variety of small mammals can be studied by Owl pellet examining owl pellets.

Figure 32.4 Procedure The front limbs of ! Place an owl pellet onto a sheet of paper toweling. moles are powerful @ Use a forceps to remove a small amount of the outer and short, with large covering. claws that enable them to dig # Prepare a wet mount of this material and observe under through dirt. Bats low-, then high-power magnification. Diagram what you have elongated see. Use forceps to open the pellet and remove all bones finger bones that that are present. Look especially for skulls. (Note: Skulls support the flight may be small and certain parts, such as lower jaws, will be membranes of their wings. separated.) $ Identify mammalian skulls using diagrams A and B as a guide. Mammals have modified limbs % Attempt to reconstruct the skeleton for an entire animal. You may wish to glue the skeletal pieces onto a piece of Mammals have several adaptations cardboard. Dispose of materials appropriately. CAUTION: that help them meet their energy needs. Wash your hands after handling animal materials. For example, mammal limbs are A adapted for a variety of methods of food gathering. Recall that primates use their opposable thumb to grasp objects—including fruits and other Shrew foods. Figure 32.4 illustrates other B limb modifications in mammals. You can see the bones of mammal limbs and Vole other parts of mammalian skeletons in Analysis the MiniLab on this page. Refer to Figure 32.5 on the next page for a sum- 1. Understand What was the outer covering on the pellet? What does this tell you about the contents of the pellet? mary of mammalian characteristics. Explain. Mammals can learn 2. Interpret Data How many vole and shrew skulls were present in your pellet? One reason mammals are successful 3. Explain How were you able to differentiate the skulls of is that they guard their young fiercely these two mammals? and teach them survival skills. Mam- 4. Predict Are voles and shrews herbivores or carnivores mals can accomplish complex behav- based on appearance of their teeth? Explain. iors, such as learning and remembering what they have learned.

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A Mammal Figure 32.5 A red fox, a member of the dog family, can be found in open country and forests throughout the United States. Red foxes are active at night, and feed on insects, birds, rodents, rabbits, berries, and fruit. Critical Thinking Using the information given below, explain how a fox is able to maintain a constant body temperature.

Red fox B Diaphragm The diaphragm is a muscle that A Glands Most mammals helps the chest cavity expand have sweat, oil, mammary, C Heart The four-chambered heart of mam- to take in large amounts of mals enables them to keep oxygenated and and scent glands in their oxygen used to maintain the skin. Sweat glands help deoxygenated blood separate. This helps high metabolism of all mam- them maintain their high metabolism. mammals cool off. Oil mals. It separates the chest glands lubricate the hair and abdominal cavities. and skin. Foxes use their scent glands to mark new territories.

D Teeth A fox’s teeth indicate what it eats and how it gets food. Its canines are used to puncture and tear the flesh of prey. Its molars slice and crush the flesh before swallowing.

F Hair Dense, soft underhair insulates the fox by trapping warm air next to its body. The coarse, long guard hairs E Mammary glands Like all female mam- protect against wear and may be colored for camouflage. mals, a female fox nourishes her young The fox sheds its coat little by little during the summer. with milk from her mammary glands.

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Have you ever attended an aquarium show or watched a movie about per- forming dolphins and whales? Dol- phins exhibit a wide variety of learned Animal Trainer behaviors, including the behaviors per- f you seem to get along well formed for films or in aquarium shows. I with animals, consider a Primates, including humans, are career as an animal trainer. A perhaps the most intelligent animals. job as a trainer can be hard to Chimpanzees, for example, can use find, but fun and rewarding. tools, illustrated in Figure 32.6, work Skills for the Job machines, and use sign language Some animal trainers work in to communicate with humans. Mam- zoos or aquariums, teaching monkeys, malian intelligence is a result of com- parrots, seals, and other animals to perform plex nervous systems and highly specific behaviors. Some trainers work with race horses, and developed brains. The outer layer of a others teach police dogs to sniff out explosives or guide dogs to help people with physical limitations. Many trainers mammalian brain often is folded, begin as animal keepers. A position at a dog obedience forming ridges and grooves. These school may require only on-the-job experience, but if you ridges and grooves increase the want to train guide dogs, you must complete a three-year brain’s active surface area. course of study. To train dolphins at a large aquarium, you must have a two- or four-year degree in psychology or biol- Explain what ogy. If you want to narrate the shows, you must also be a enables mammals to be intelligent. good public speaker. For more careers in related fields, visit ca.bdol.glencoe.com/careers

Figure 32.6 A chimpanzee using a stick to get insects out of a tree trunk demonstrates that mammals other than humans are also intelligent enough to make and use tools.

Understanding Main Ideas Thinking Critically 1. Name four characteristics of mammals. 6. Suppose you are a mammal that feeds on pine 2. Describe three mammal adaptations for obtaining seeds and lives in a forest in a cold region. Describe and consuming food. the adaptations that would help you survive.

3. Identify and describe the relationship between SSKILLKILL RREVIEWEVIEW internal feedback mechanisms and the mainte- nance of body temperatures. 7. Observe and Infer On an archaeological dig, you find a skull about 5 cm long with two chisel- 4. How does intelligence benefit mammals? shaped front teeth and several flattened back 5. Explain how the interrelationship between teeth. Is this a skull from a mammal? Explain your respiration and circulation sustains a mammal’s answer. For more help, refer to Observe and Infer metabolism. in the Skill Handbook.

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Diversity of Mammals 32.2

SECTION PREVIEW Analyzing Mammalian Objectives Classification Distinguish among the Finding Main Ideas On a piece of three groups of living mammals. paper, construct an outline about mam- Compare reproduction in mal classification. Use the red and blue egg-laying, pouched, and titles in this section as a guideline. As placental mammals. you read the paragraphs that follow the Review Vocabulary titles, add important information and endangered species: a vocabulary words to your outline. species in which the number of individuals Example: falls so low that extinc- I. Mammal Classification tion is possible (p. 115) New Vocabulary A. Placental mammals placental mammal 1. uterus placenta B. Pouched mammals gestation 1. Plains of America with bison marsupial monotreme C. Monotremes therapsid 1. Use your outline to help you answer questions in the section assessment on page 851. For more help, refer to Outline in the Skill Handbook.

Mammal Classification Living in the United States, you are probably familiar with only one of the three subclasses, of the class Mammalia— placental mammals. Scientists place mammals into one of three subclasses based on their method of reproduction.

Placental mammals: A great success Placental mammals give birth to young that have developed inside the mother’s uterus until their body systems are fully functional and they can live independently of their mother’s body. Figure 32.7 The uterus (YEWT uh rus) is a hollow, muscular organ in which The length of gestation varies from offspring develop. Nourishment of the young inside the uterus species to species in placental mammals. occurs through an organ called the placenta (pluh SEN tuh), These raccoon kits were born after nine which develops during pregnancy. The placenta passes nutrients weeks of gestation. Gestation of mice is and oxygen to and removes wastes from the developing embryo. 21 days, whereas gestation for a rhinoceros is about 14 to 16 months. The time during which placental mammals develop inside the Hypothesize Why do larger mam- uterus is called gestation (jeh STAY shun). The kits shown in mals have longer gestation times? Figure 32.7 were born after a period of gestation.

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Figure 32.8 In Australia and Tasmania, many marsupials fill C The spotted cuscus of niches that are occupied by placental mammals Australia, a marsupial, on other continents. lives in trees. It is a solitary, nocturnal animal that eats fruit, A The giant ant- leaves, bark, insects, eater of Mexico, small mammals, a placental reptiles, and birds. mammal, has a long, sticky tongue that it uses to collect ants and termites from their nests.

B The numbat, a marsupial, lives in Australia. It has a D The ring tailed lemur, a placental mammal, long, sticky tongue that it lives in trees on the island of Madagascar. It uses to eat termites and ants. is active by day, and eats fruits, leaves, and occasionally insects.

Development inside the mother’s opossum. Most marsupials are found body is an adaptation that played a in Australia and surrounding islands. major role in the success of mammals. The theory of plate tectonics explains It ensures that the offspring are pro- why most marsupials are found in tected from predators and the envi- Australia today. Scientists have found ronment during the early stages of fossil marsupials on the continents development. that once made up Gondwana. These About 90 percent of all mammals fossils support the idea that marsupi- are placentals. You can learn more als originated in South America, about placental mammals on pages moved across Antarctica, and popu- 1086–1089 in the Focus On. lated Australia before Gondwana broke up. Pouched mammals: Ancestors of today’s marsupials gestation from The marsupials were able to populate the landmass the Latin word gestare, meaning Marsupials make up the second that became Australia without having “to bear”; Gesta- subclass of mammals. A marsupial to share the area with the competitive tion is time during (mar SEW pee uhl) is a mammal in placental mammals that evolved in which a placental mammal develops which the young have a short period other places. They successfully spread in a uterus. of development within the mother’s out and filled niches similar to those body, followed by a period of devel- that placental mammals filled in all opment inside a pouch made of skin other parts of the world, as you can and hair on the outside of the see in Figure 32.8. In fact, since mother’s body. You may have seen the humans introduced sheep, rabbits, only North American marsupial, the and other placental mammals to

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Figure 32.9 A Australia, many of the native marsu- Present-day mono- pial species have become threatened, tremes include one endangered, or even extinct. species of platypus and two species of echidnas. Infer why some mar- This echidna species is supials have become threatened in found only in Australia and nearby islands (A). Australia. The duck-billed platypus has several physical Monotremes: The egg layers features that seem to Do you think the animal shown belong to a variety of other animals (B). in Figure 32.9B is a mammal? It has hair and mammary glands, yet it lays eggs. The duck-billed platypus is a B monotreme (MA nuh treem), a mammal that reproduces by laying eggs. Figure 32.10 This diagram represents Artiodactyls the orders of mammals, 220 species Cetaceans 79 species gives the approximate species number, and shows their evolutionary relationships. Carnivores 270 species Rodents ANIMALS 2000 species

Primates 230 species

Chiropterans 925 species

Perissodactyls 18 species

Insectivores 375 species

Proboscids Placental 3 species mammals 4120 species

Therapsids mammal-like reptiles Marsupials 280 species

Reptiles Amphibians Fishes Monotremes Invertebrates 3 species

Species numbers are approximate and subject to change pending discoveries or extinctions.

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Spiny anteaters, also called echidnas, belong to this subclass as well. A Monotremes are found only in Aus- tralia, Tasmania, and New Guinea. One of the two species of spiny anteaters can be found only in New Guinea. Only three species of monotremes are alive today. B The platypus, a mostly aquatic animal, has a broad, flat tail, much like that of a beaver. Its rubbery snout resembles the bill of a duck. The platypus has webbed front feet for swimming through water, but it also Figure 32.11 has sharp claws on its front and hind in Figure 32.11A, to a group of (A) Eomaia is the oldest feet for digging and burrowing into reptilian ancestors called therapsids. placental mammal fossil the soil. Much of its body is covered Therapsids (ther AP sidz), represented discovered. Anatomical with thick, brown fur. in Figure 32.11B, had features of both evidence shows that it may have lived in trees. The spiny anteater has coarse, reptiles and mammals. They existed (B) Therapsids were the brown hair, and its back and sides are between 270 and 180 million years ago. ancestors of mammals. covered with sharp spines that it can The mass extinction of the dino- The lower jaw and mid- erect for defensive purposes when saurs at the end of the Mesozoic Era, dle ear bones of therap- threatened by enemies. From its along with the breaking apart of sids were like those of mouth, the anteater extends its long, Pangaea and changes in climate, reptiles. However, they had straighter legs than sticky tongue to catch insects. opened up new niches for early mam- reptiles and held them mals to fill. The appearance of flower- closer to the body. ing plants at the end of this era supplied Origins of Mammals new living areas, food sources, and Present-day mammal orders are shelter. Some mammals that moved shown in Figure 32.10. The first into the drier grasslands became fast- placental mammals appeared in the fos- running grazers, browsers, and preda- sil record about 125 million years ago. tors. The Cenozoic Era is sometimes Scientists trace the origins of placental called the golden age of mammals mammals from a group of mouse-sized because of the dramatic increase in animals, such as Eomaia represented their numbers and diversity.

Understanding Main Ideas America. Make a hypothesis about the presence 1. Describe the characteristics of placental mammals. or absence of marsupial species in Europe. How 2. Compare monotremes and marsupials. could you test your hypothesis?

3. Why are monotremes classified as mammals? SSKILLKILL RREVIEWEVIEW 4. What are therapsids and what is their relationship 6. Get the Big Picture You find a mammal fossil to mammals? and observe the following traits: hooves, flattened teeth, skeleton the size of a large dog. Thinking Critically What can you infer about its way of life? For 5. There are several marsupial species in South more help, refer to Get the Big Picture in the America, but only one species is native to North Skill Handbook.

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Adaptations in Breeds of Dogs

REPARATION Before You PPREPARATION ent & Donna Dannen/Photo Researchers Begin K Problem Dogs make great compan- ions. They provide their What adaptations are important to various breeds of dogs. owners with an opportu- nity to love and nurture Objectives another living thing. In In this BioLab, you will: return, they are loyal, ■ Observe the characteristics of dogs. offer protection to their ■ Record the adaptations of different dog breeds. owners, and are fun to ■ Use the Internet to collect and compare data from other have around. Dogs have students. been bred for a variety of ■ reasons. Some are working Compare and contrast the characteristics of breeds of dogs. dogs, such as herders, sporting dogs, sled dogs, Materials and guide dogs. Others access to the Internet have been bred for racing, while others are show Skill Handbook dogs. However, all of these If you need help with this lab, refer to the Skill Handbook. breeds have the same basic dog characteristics. PPROCEDUREROCEDURE 1. Make a copy of the data table. 2. Visit ca.bdol.glencoe.com/internet_lab to find links to sites that describe breeds of dogs. 3. Find pictures and descriptions of these dogs. Record the physical characteristics unique to each breed in the data table.

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Dogs Breed Physical Temperament Classification Characteristics Alaskan Malamute Australian Cattle Dog Collie German Shepherd Dog German Shorthaired Pointer Greyhound Labrador Retriever Old English Sheepdog Samoyed Siberian Husky Whippet

4. Record the temperaments of each breed in the data table. 5. Find links at ca.bdol.glencoe.com/internet_lab to find information on dogs that are classified as working dogs, herding dogs, sporting dogs, and hounds. 6. Record the classification of each breed in the data table.

Rough Collie

AANALYZENALYZE ANDAND CCONCLUDEONCLUDE

1. Compare and Contrast Alaskan Malamutes, Greyhounds, Samoyeds, Siberian Huskys, and Whippets are all built for running. How are they similar and how are they different? 2. Determine Which dogs would make good guide dogs? Why? Find this BioLab using the link below, and 3. Explain Why would a Collie make a good post the data tables provided for this activity. herder? Using the additional data from other stu- 4. Apply Assume you work for a local nursing dents on the Internet, analyze the combined home and are asked to find a dog that could data and complete your table. live in the home and be a good companion ca.bdol.glencoe.com/internet_lab and perhaps even help some of the residents. Go to ca.bdol.glencoe.com/internet_lab and select a breed of dog you think would be adapted for this work. Explain your reasoning.

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puzzles (such as fish stuffed into a block of ice for What should be the polar bears to dig out), slides, pools, and streams, as well as other items that simulate their natural role of modern zoos? environment.

Captive breeding oos were originally created for public enter- Ensuring a future for the Ztainment. They began as a result of people’s world’s animals has become as much a priority for interest in exotic animals. The animals were kept zoos as displaying them. Zoos use captive breeding in small cages with little attention given to their to increase their populations. The animals below needs. Soon, however, people began to realize the are results of captive breeding. Advances in captive animals needed more than food and basic shelter. breeding techniques, such as artificial insemination Zoos began providing better surroundings for the and in vitro fertilization, have drawn public atten- animals, and giving the public information about tion to the potential for rescuing species. In some animals and their natural habitat. cases, captive breeding has meant the difference between survival and extinction of a species. Modern zoos In modern zoos, animals are However, there is not enough room in zoos to rarely kept in tiny cages. During the 20th century, house many extra animals, and since some animals zoos began providing a new experience for visitors can be domesticated in as little as two generations, by replacing the bars and walls of cages with pro- few species can survive in the wild after being tective moats and larger animal areas. But space is raised for generations in captivity. Other limita- often limited so architects struggle to make exhibit tions of captive breeding include inbreeding areas look large and interesting to their inhabi- (which decreases the genetic diversity of the popu- tants and visitors. Many zoos also have enrichment lation), low fertility rates, lack of funding for pro- programs that provide animals with activities simi- grams, and diseases spread by contact with species lar to those they would participate in if they were not encountered in the wild. living in the wild. Zookeepers give animals games, Conservation Zoos also help preserve bio- diversity through public education, professional training, research and support of conservation efforts in the wild. Some zoos and wildlife con- servationists try to manage ecosystems and These tiger cubs and this wildlife populations through research, establish- black-footed ferret (inset) are results of captive ing natural preserves, maintaining genetically breeding in zoos. diverse captive-breeding programs, developing educational programs, and many other activities. Scientists realize that wildlife species cannot be ‘saved’ in the long term by protecting them exclusively in zoos. Without sustainable, wild populations each species will end up inbred, and will eventually face extinction.

Debate the Issue What should be the role of modern zoos? To find out more about modern zoos, visit ca.bdol.glencoe.com/biology_society

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STUDY GUIDE Section 32.1 Key Concepts Vocabulary Mammal ■ Mammals are endotherms giving them the diaphragm (p. 843) ability to maintain a fairly constant body gland (p. 842) mammary gland (p. 842) Characteristics temperature. ■ Hair is present on all mammals at some point in their lives. ■ Mammals feed their young from modified sweat glands called mammary glands. ■ Mammals with teeth have different kinds of teeth that are adapted to the type of food they eat. ■ Highly developed brains enable mammals to learn.

Section 32.2 Key Concepts Vocabulary ■ Mammals are classified into three gestation (p. 848) Diversity of subclasses—placentals, marsupials, marsupial (p. 849) monotreme (p. 850) Mammals and monotremes—based on how they placenta (p. 848) reproduce. placental mammal ■ Placental mammals carry young (p. 848) inside the uterus until their body therapsid (p. 851) uterus (p. 848) systems are fully functional. Nourishment inside the uterus occurs through an organ called the placenta. ■ Marsupials carry partially developed young in a pouch on the outside of the mother’s body. ■ Monotremes are egg-laying mammals found only in Australia, Tasmania, and New Guinea.

To help you review mammals, use the Organizational Study Fold on page 841.

ca.bdol.glencoe.com/vocabulary_puzzlemaker CHAPTER 32 ASSESSMENT 855 (tl)M.C. Chamberlain/DRK Photo; (tr)E. Hanumantha Rao/Photo Researchers; (b)Mickey Gibson/Animals Animals 0848-0857 C32S2 BDOL-829900 8/4/04 10:35 PM Page 856

11. Which type of teeth pictured below would be most suited for feeding on grasses? Review the Chapter 32 vocabulary words listed in A. C. the Study Guide on page 855. Match the words with the definitions below. 1. the hollow, muscular organ in which the offspring of placental mammals develop 2. a mammal that reproduces by laying eggs B. D. 3. organ that provides food and oxygen to and removes waste from the young inside the uterus of placental mammals 4. time during which placental mammals develop inside the uterus 12. Like bird feathers, mammalian hair probably evolved from ______. 5. in mammals, a sheet of muscles located A. teeth C. claws below the lungs that separates the chest B. scales D. setae cavity from the abdominal cavity 13. ______is a behavioral adaptation for cool- ing off a mammal’s body. A. Running C. Jogging 6. Which of the following is NOT a character- B. Panting D. Gnawing istic of mammals? A. endothermic B. three-chambered heart C. hair 14. Open Ended How does endothermy enable D. mammary glands mammals and birds to survive in the Arctic and in the Sahara of Africa? 7. Which of these is NOT an endothermic animal? 15. Open Ended Biologists hypothesize that the A. rattlesnake C. cat whiskers of harbor seals are sensitive to the B. penguin D. gorilla wakes their prey fish leave behind as they swim. Design an experiment to test this 8. Hair helps mammals by providing camou- hypothesis. flage and helping them to maintain ______. 16. Concept Map Complete the concept map A. evolution C. reproduction by using the following vocabulary terms: B. running speed D. body temperature marsupials, monotremes, placental mammals, placenta. 9. ______are examples of egg-laying mammals. Three groups of A. Numbats and lemurs B. Anteaters and shrews mammals C. Platypuses and spiny anteaters include D. Seals and whales

10. Which pair of terms is most closely related? 1. 2. 3. A. gland—secretion B. diaphragm—heart that have a that lay that have a C. placenta—Golgi bodies eggs D. gestation—molars pouch 4.

856 CHAPTER 32 ASSESSMENT ca.bdol.glencoe.com/chapter_test 0848-0857 C32S2 BDOL-829900 8/4/04 10:35 PM Page 857

educate the public about the grizzly bears’ physical appearance, habitat, feeding 17. REAL WORLD BIOCHALLENGE There habits, winter survival, management and are recovery efforts taking place in the restoration efforts, encounters with people, lower 48 states to save the grizzly bear and what to do when hiking and camping from extinction. In order for this to in grizzly bear country. Present your pam- happen, there must be support by the phlet to your class. public for endangered species protection. 18. Differentiate You find the skeleton of an Visit ca.bdol.glencoe.com to investigate animal. What features would indicate that it this problem. Prepare a pamphlet that will is a mammal rather than a reptile?

Multiple Choice There are only 80–120 wild ocelots left in the Documented United States. They are members of the cat family ocelot

that require a thorn-scrub habitat. They live in G south Texas, some are protected on the Laguna Laguna Atascosa Padre u Island l Atascosa National Wildlife Refuge and the Lower National Wildlife f Refuge o

f Rio Grande Valley National Wildlife Refuge. Laguna M Examine the map and answer questions 19–21. Madre e

c 19. o The best way to improve protection for South Padre endangered ocelots would be to ______. Island A. educate people to the needs of wild animals and their role in the ecosystem B. have a short hunting season C. discontinue agriculture Texas Lower Rio Grande Valley D. capture all ocelots and transport them to National Wildlife zoos Refuge

20. If ocelots disappear from south Texas, ______. 21. Ocelots are found in south Texas ______. A. this wild population will rise in the future A. exclusively on two wildlife refuges B. they can be easily replaced by zoo animals B. on wildlife refuges and areas outside the C. they will be extinct in the United States refuge D. their disappearance will not be a problem C. exclusively on South Padre Island for ecosystems since there are so few left D. only of the seashore of south Texas

Constructed Response/Grid In Record your answers on your answer document. 22. Open Ended How does the development of young inside a uterus enable mammals to adapt to environments that reptiles cannot? 23. Open Ended Mammals and insects are both considered to be extraordinarily successful animals. Explain the criteria used in both cases that give them this distinction.

ca.bdol.glencoe.com/standardized_test CHAPTER 32 ASSESSMENT 857