1. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings PowerPoint Lectures for Biology: Concepts and Connections, Fifth Edition – Campbell, Reece, Taylor, and Simon Lectures by Chris Romero Chapter 18 The Evolution of Animal Diversity

2. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 18.21 Mammals are amniotes that have hair and produce milk Mammals are endothermic amniotes with –Hair, which insulates their bodies –Mammary glands, which produce milk

3. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Mammals In addition to having hair and the ability to nourish their young with milk, all mammals –breathe air. –have four-chambered hearts. –are endotherms that generate their body heat internally.

4. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Evolution of Mammals –Mammalian fossils are characterized by a lower jaw with a large, teeth-bearing bone connected directly to the skull by a joint, and distinctive features of the limbs and the backbone.

5. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Evolution of Mammals Mammals are descended from ancient reptiles. Ancestors of modern mammals diverged from ancient reptiles during the Carboniferous Period. For millions of years, various mammal-like reptiles lived alongside other reptile groups.

6. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Form and Function in Mammals –The mammalian body has adapted in varied ways to a great many habitats.

7. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Body Temperature Control –Mammals are endotherms. –A high rate of metabolism helps mammals generate body heat. –Mammals have external body hair that helps them keep warm. –Subcutaneous fat, which is a layer of fat located beneath the skin, also helps conserve body heat. Form and Function in Mammals

8. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Many mammals have sweat glands that help cool the body. –If its body temperature gets too high, the mammal sweats. –Evaporation of sweat then cools the body. –Some mammals pant to cool down. Form and Function in Mammals

9. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The ability of mammals to regulate their body heat from within is an example of homeostasis. Homeostasis is the steady state physiological condition of the body, i.e. temperature, water balance, nutrient balance…etc (refer to C. 20) Form and Function in Mammals

10. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Feeding –Because of its high metabolic rate, a mammal must eat a lot of food to maintain homeostasis. –Some mammals are herbivores. Some mammals are carnivores. Some mammals, including humans, are omnivores. –Certain whales are filter feeders. Form and Function in Mammals

11. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings A mammal’s digestive tract breaks down and absorbs the type of food that it eats. Carnivores have a short intestine because enzymes quickly digest meat. Herbivores have a longer intestine because tough, fibrous plant tissues take longer to digest. Form and Function in Mammals

12. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Cows have a stomach chamber called the rumen, in which swallowed plant food is stored and processed. It contains bacteria that digest the cellulose of plant tissues. Form and Function in Mammals

13. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Respiration –All mammals use lungs to breathe. –A diaphragm is a large, flat muscle at the bottom of a mammal’s chest cavity that helps in breathing. Form and Function in Mammals

14. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings When an animal inhales, chest muscles lift the rib cage up and out. The diaphragm pulls the chest cavity down. The combined actions of the chest muscles and diaphragm increase the volume of the chest cavity. The increase in volume pulls air into the lungs. Form and Function in Mammals

15. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings When an animal exhales, chest muscles lower the rib cage. The diaphragm relaxes, and the volume of the chest cavity decreases. Air is then pushed out of the lungs. Form and Function in Mammals

16. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Circulation –The mammalian circulatory system has two loops and a four-chambered heart. –The right side of the heart receives oxygen- poor blood from the body and pumps it to the lungs. –The left side receives oxygen-rich blood from the lungs and pumps it to the rest of the body. Form and Function in Mammals

17. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Mammalian heart Right atrium Right ventricle Left atrium Left ventricle Complete division Form and Function in Mammals

18. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Excretion –Kidneys extract nitrogenous wastes from the blood in the form of urea. –Urea, other wastes, and water combine to form urine. –From the kidneys, urine flows to a urinary bladder, where it is stored until it is eliminated. Form and Function in Mammals

19. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The kidneys of mammals help maintain homeostasis by filtering urea from the blood, as well as by excreting excess water or retaining needed water. Form and Function in Mammals

20. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The kidneys control the amount of water in the body. This enables mammals to live in many habitats in which they could not otherwise survive. Form and Function in Mammals

21. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Response –Mammals have well-developed brains with three main parts: cerebrum—controls thinking and learning cerebellum—controls muscular coordination medulla oblongata—regulates involuntary body functions Form and Function in Mammals

22. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Mammalian Brain Form and Function in Mammals

23. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The cerebrum has a well-developed outer layer called the cerebral cortex, which is the center of thinking and other complex behaviors. Some behaviors, such as reading, are possible only with the human cerebral cortex. Mammals other than humans also exhibit complex behaviors. Form and Function in Mammals

24. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Chemical Controls –Mammals have endocrine glands that regulate body activities by releasing hormones. –Hormones are substances produced in one part of an organism that affect another part of the same organism. –Hormones are carried by the blood to the organs that they affect. Form and Function in Mammals

25. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Fighting Disease –The immune system helps protect animals from disease. –Barriers, such as the skin, prevent pathogens from entering the body. –Specialized cells and chemicals recognize and destroy pathogens. Form and Function in Mammals

26. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Movement –Mammals have backbones that flex vertically and side to side. –Shoulder and pelvic girdles are streamlined and flexible, permitting both front and hind limbs to move in many ways. –Variations in limb bones and muscles permit a variety of movements. Form and Function in Mammals

27. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Monkey Mole Seal Bat Horse The limbs and digits (fingers and toes) of many mammals are adapted to their particular way of life. Note the variety of lengths and shapes of the limb bones. Homologous bones are the same color in all the drawings. Form and Function in Mammals

28. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Reproduction –Mammals reproduce by internal fertilization. –The male deposits sperm inside the reproductive tract of the female, where fertilization occurs. –All newborn mammals feed on their mother’s milk. Form and Function in Mammals

29. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Young mammals need care from one or both parents when they are born and for a long time afterward. Parental care ensures that young will survive and reproduce. The duration and intensity of parental care varies among different species. Form and Function in Mammals

30. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Some mammal species, such as lions, live in groups in which the young may be cared for by adults other than the parents. Group living provides young mammals with complex social interaction among adults and juveniles. Form and Function in Mammals

31. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Diversity of Mammals The three groups of living mammals are: – monotremes – marsupials – placentals

32. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Monotremes and Marsupials Monotremes Monotremes lay eggs. Monotremes share two notable characteristics with reptiles: –The digestive, reproductive, and urinary systems all open into a cloaca. –Females lay soft-shelled eggs that incubate outside the body.

33. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Monotremes and Marsupials Marsupials Marsupials bear live young, but at a very early stage of development. Young marsupials complete their development in an external pouch. When marsupials reproduce, the fertilized egg develops into an embryo inside the mother's reproductive tract.

34. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Monotremes and Marsupials Once born, the embryo crawls across its mother's fur and attaches to a nipple. Nipples are located in a pouch called the marsupium on the outside of the mother's body. The embryo spends several months attached to the nipple. The young marsupial will drink milk until it grows enough to survive on its own.

35. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Placental Mammals –Placental mammals are named for an internal structure called the placenta, which forms when the embryo's tissues join with tissues from within the mother's body. –In placental mammals, nutrients, oxygen, carbon dioxide, and wastes are exchanged efficiently between embryo and mother through the placenta.