Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Unit 1: What is Biology? Unit 2: Ecology Unit 3: The Life of a Cell Unit 4: Genetics Unit 5: Change Through Time Unit 6: Viruses, Bacteria, Protists, and Fungi Unit 7: Plants Unit 8: Invertebrates Unit 9: Vertebrates Unit 10: The Human Body Unit 1: What is Biology? Chapter 1: Biology: The Study of Life Unit 2: Ecology Chapter 2: Principles of Ecology Chapter 3: Communities and Biomes Chapter 4: Population Biology Chapter 5: Biological Diversity and Conservation Unit 3: The Life of a Cell Chapter 6: The Chemistry of Life Chapter 7: A View of the Cell Chapter 8: Cellular Transport and the Cell Cycle Chapter 9: Energy in a Cell Unit 4: Genetics Chapter 10: Mendel and Meiosis Chapter 11: DNA and Genes Chapter 12: Patterns of Heredity and Human Genetics Chapter 13: Genetic Technology Unit 5: Change Through Time Chapter 14: The History of Life Chapter 15: The Theory of Evolution Chapter 16: Primate Evolution Chapter 17: Organizing Life’s Diversity Unit 6: Viruses, Bacteria, Protists, and Fungi Chapter 18: Viruses and Bacteria Chapter 19: Protists Chapter 20: Fungi Unit 7: Plants Chapter 21: Chapter 22: Chapter 23: Chapter 24: What Is a Plant? The Diversity of Plants Plant Structure and Function Reproduction in Plants Unit 8: Invertebrates Chapter 25: What Is an Animal? Chapter 26: Sponges, Cnidarians, Flatworms, and Roundworms Chapter 27: Mollusks and Segmented Worms Chapter 28: Arthropods Chapter 29: Echinoderms and Invertebrate Chordates Unit 9: Vertebrates Chapter 30: Fishes and Amphibians Chapter 31: Reptiles and Birds Chapter 32: Mammals Chapter 33: Animal Behavior Unit 10: The Human Body Chapter 34: Protection, Support, and Locomotion Chapter 35: The Digestive and Endocrine Systems Chapter 36: The Nervous System Chapter 37: Respiration, Circulation, and Excretion Chapter 38: Reproduction and Development Chapter 39: Immunity from Disease Vertebrates Fishes and Amphibians Reptiles and Birds Mammals Animal Behavior Chapter 32 Mammals 32.1: Mammal Characteristics 32.1: Section Check 32.2: Diversity of Mammals 32.2: Section Check Chapter 32 Summary Chapter 32 Assessment 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. Section Objectives: • Distinguish mammalian characteristics. • Explain how the characteristics of mammals enable them to adapt to most habitats on Earth. What is a mammal? • Mammals, like birds, are endotherms. What is a mammal? • They have hair and produce milk to nurse their young. • Mammals also have diaphragms, fourchambered hearts, specialized teeth, modified limbs, and highly developed brains. Mammals have hair • Like feathers, mammalian hair, made out of the protein keratin, is also thought to have evolved from scales. Mammals have hair • The arrangement of hair provides insulation and waterproofing and thereby conserves body heat. Mammals have hair • 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. • Panting releases water from the nose and mouth, which results in a loss of body heat. Mammals have hair • Sweat glands help regulate body temperature by secreting moisture onto the surface of the skin. • As the moisture evaporates, it transfers heat from the body to the surrounding air. Mammals nurse their young • Mammals have several types of glands, which are a group of cells that secrete fluids. • They include glands that produce saliva, sweat, oil, digestive enzymes, hormones, milk, and scent. Mammals nurse their young • Mammals also feed their young from mammary glands, possibly modified sweat glands, which produce and secrete milk, a liquid that is rich in fats, sugars, proteins, minerals, and vitamins. Mammals nurse their young • Mammals nurse their young until they are able to digest and absorb nutrients from solid foods. Respiration and circulation in mammals • The mammals’ diaphragm helps expand the chest cavity to aid the flow of oxygen into their lungs. Position of ribs when exhaling Position of ribs when inhaling Lungs when exhaling Lungs when inhaling Position of diaphragm when inhaling Position of diaphragm when exhaling Respiration and circulation in mammals • A diaphragm is the sheet of muscle located beneath the lungs that separates the chest cavity from the abdominal cavity, where other organs are located. Position of diaphragm when inhaling Position of diaphragm when exhaling Respiration and circulation in mammals • Mammals have four-chambered hearts in which oxygenated blood is kept entirely separate from deoxygenated blood. Right atrium Right ventricle Left atrium Left ventricle Respiration and circulation in mammals • Circulation also removes waste products from cells and helps regulate body temperature. • Blood helps keep a constant cellular environment, which maintains homeostasis. Most mammals have specialized teeth • Mammals with teeth have different kinds that are adapted to the type of food the animal eats. Most mammals have specialized teeth • The pointed incisors of moles grasp and hold small prey. • The chisel-like incisors of beavers are modified for gnawing. Most mammals have specialized teeth • A lion’s canines puncture and tear the flesh of its prey. Most mammals have specialized teeth • Premolars and molars are used for slicing or shearing, crushing, and grinding. Most mammals have specialized teeth • Many hoofed mammals have an adaptation called cud chewing that enables the cellulose in plant cell walls to be broken down into nutrients they can absorb and use. • When plant material is swallowed, it moves into the first two of four pouches in the stomach where cellulose in the cell walls is broken down by bacteria. Most mammals have specialized teeth • The partially digested food, called cud, is repeatedly brought back up into the mouth. Most mammals have specialized teeth • After more chewing, the cud is swallowed again and when the food particles are small enough they are passed to the other stomach areas, where digestion continues. Mammals have modified limbs • Mammal limbs are adapted for a variety of methods of food gathering. • Primates, for example, use their opposable thumb to grasp objects—including fruits and other foods. Mammals can learn • Mammals can accomplish complex behaviors, such as learning and remembering what they have learned. Mammals can learn • Primates, including humans, are perhaps the most intelligent animals. Mammals can learn • Chimpanzees, for example, can use tools, work machines, and use sign language to communicate with humans. Mammals can learn Motor area Cerebrum Sensory area Speech area Language area Vision area Taste area General interpretation area Intellect, learning, and personality Balance area Hearing area Brain stem Cerebellum A Mammal Question 1 What two characteristics do mammals have that no other animal has? Answer All mammals have hair and produce milk to nurse their young. Question 2 What do scientists believe mammalian hair evolved from? A. feathers B. scales C. skin D. keratin The answer is B. Like feathers, hair also is made out of keratin which leads scientists to believe that hair evolved from scales. Question 3 How do a mammal’s teeth help it obtain food? Mammals have teeth that are adapted to the type of food they eat. Canine teeth puncture and tear the flesh of prey. Premolars and molars are used for slicing, shearing, and crushing while incisors are used for gnawing and grasping. Question 4 Which of the following helps a mammal take in large amounts of oxygen? A. glands B. heart C. teeth D. diaphragm The answer is D, diaphragm. Diaphragm Heart Glands Teeth Hair Mammary glands Section Objectives: • Distinguish among the three groups of living mammals. • Compare reproduction in egg-laying, pouched, and placental mammals. Mammal Classification • 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. Placental mammals: A great success • The uterus is a hollow, muscular organ in which offspring develop. • Nourishment of the young inside the uterus occurs through an organ called the placenta which develops during pregnancy. Placental mammals: A great success • The time during which placental mammals develop inside the uterus is called gestation. • Development inside the mother’s body ensures that the offspring are protected from predators and the environment during the early stages of development. Pouched mammals: The marsupials • A marsupial is a mammal in which the young have a short period of development within the mother’s body, followed by a period of development inside a pouch made of skin and hair on the outside of the mother’s body. Pouched mammals: The marsupials • Most marsupials are found in Australia and surrounding islands. • Scientists have found fossil marsupials on the continents that once made up Gondwana. • These fossils support the idea that marsupials originated in South America, moved across Antarctica, and populated Australia before Gondwana broke up. Monotremes: The egg layers • The duck-billed platypus is a monotreme, a mammal that reproduces by laying eggs. • Spiny anteaters, also called echidnas, belong to this subclass as well. Monotremes: The egg layers • Monotremes are found only in Australia, Tasmania, and New Guinea. • Only three species of monotremes are alive today. Monotremes: The egg layers • 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. Monotremes: The egg layers • The platypus has webbed front feet for swimming through water, but it also has sharp claws on its front and hind feet for digging and burrowing into the soil. • Much of its body is covered with thick, brown fur. Monotremes: The egg layers • The spiny anteater has course, brown hair, and its back and sides are covered with sharp spines that it can erect for defensive purposes when threatened by enemies. Origins of Mammals • The first placental mammals appeared in the fossils record about 125 million years ago. • Scientists trace the origins of placental mammals from a group of mouse-sized animals to a group of reptilian ancestors called therapsids. Origins of Mammals • Therapsids had features of both reptiles and mammals. • They existed between 270 and 180 million years ago. Origins of Mammals • The mass extinction of the dinosaurs at the end of the Mesozoic Era, along with the breaking apart of Pangaea and changes in climate, opened up new niches for early mammals to fill. • The Cenozoic Era is sometimes called the golden age of mammals because of the dramatic increase in their numbers and diversity. Origins of Mammals Artiodactyls Cetaceans 220 species 79 species Carnivores 270 species Primates Rodents 230 species 2000 species Chiropterans 925 species Perissodactyls 270 species Insectivores 375 species Placental mammals 4400 species 2 species Marsupials Therapsids mammal-like reptiles Proboscids 280 species Reptiles Amphibians Fishes Invertebrates Species numbers are approximate and subject to change pending discoveries or extinctions. Monotremes 3 species Question 1 Which of the following is NOT an example of a placental mammal? A. kangaroo B. human C. dog D. fox The answer is A. A kangaroo is a marsupial. Question 2 What three events allowed mammals to fill new niches? Answer The mass extinction of the Mesozoic Era, the break up of Pangaea, and changes in climate opened up new niches for early mammals to fill. Question 3 What is the difference between a monotreme and a marsupial? Monotremes reproduce by laying eggs. A marsupial’s young begins development within the body but complete its development outside the body in a pouch made of skin and hair. Mammal Characteristics • Mammals are endotherms giving them the ability to maintain a fairly constant body temperature. • Hair is present on all mammals at some point in their lives. • Mammals feed their young from modified sweat glands called mammary glands. Mammal Characteristics • 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. Diversity of Mammals • Mammals are classified into three subclasses—placentals, marsupials, and monotremes—based on how they reproduce. • Placental mammals carry young inside the uterus until their body systems are fully functional. Nourishment inside the uterus occurs through an organ called the placenta. Diversity of Mammals • 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. Question 1 How many groups are mammals classified into? A. one B. two C. three D. four The answer is C. Mammals are classified as placental, marsupial, or as monotremes. Question 2 Of the teeth shown, which set would most likely be used by an animal that feeds on grass. A. B. C. D. The answer is A. This skull contains primarily molars and premolars which are used to crush and grind food. Question 3 What role do zoos play in the preservation of endangered species? Answer Zoos use captive breeding programs to increase populations of animals, educate the public, conduct research, and provide professional training for staff. Question 4 Which organ in this mammal is responsible for keeping oxygenated and deoxygenated blood separate? The heart enables mammals to keep oxygenated and deoxygenated blood separate. This helps them maintain their high metabolism. Heart Question 5 Which of the following is one way that mammals cool off? A. by swimming B. by shedding C. by panting D. by hibernating The answer is C. Mammals cool off by panting and through the action of sweat glands. Question 6 Why are mammals considered to be one of the most successful groups of organisms? Mammals are capable of accomplishing complex behaviors such as learning and remembering what they have learned. Mammals also guard their young and teach them the skills they need to survive on their own. Question 7 While walking through the forest, you find an animal skull. You notice that the teeth in the skull are primarily pointed and long. What can you infer about the diet of the animal? The animal was most likely a carnivore. Long, pointed incisors and canines are used to stab and tear flesh. Photo Credits • Digital Stock • PhotoDisc • Bill Tarpenning/USDA • Digital Vision • Alton Biggs To advance to the next item or next page click on any of the following keys: mouse, space bar, enter, down or forward arrow. Click on this icon to return to the table of contents Click on this icon to return to the previous slide Click on this icon to move to the next slide Click on this icon to open the resources file. End of Chapter 32 Show