Chapter 40

1. Chapter 40 Basic Principles of Animal Form and Function

2. What you need to know… • The 4 types of tissues and their general functions. • The importance of homeostasis and examples. • How feedback systems control homeostasis, and one example of positive feedback and one example of negative feedback.

3. Figure 40.1 • Animals inhabit almost every part of the biosphere • Despite their amazing diversity • All animals face a similar set of problems, including how to nourish themselves • The comparative study of animals reveals that form and function are closely correlated

4. 40.1 Basic Principles of Animal Form and Function • Physical laws and the need to exchange materials with the environment • Place certain limits on the range of animal forms • The ability to perform certain actions • Depends on an animal’s shape and size

5. Evolutionary convergence • Reflects different species’ independent adaptation to a similar environmental challenge (a) Tuna (b) Shark (c) Penguin (d) Dolphin Figure 40.2a–e (e) Seal

6. Exchange with the Environment • An animal’s size and shape • Have a direct effect on how the animal exchanges energy and materials with its surroundings • Exchange with the environment occurs as substances dissolved in the aqueous medium • Diffuse and are transported across the cells’ plasma membranes

7. Diffusion (a) Single cell Example of Form and Function • A single-celled protist living in water • Has a sufficient surface area of plasma membrane to service its entire volume of cytoplasm Figure 40.3a

8. Example of Form and Function • Multicellular organisms with a sac body plan • Have body walls that are only two cells thick, facilitating diffusion of materials Mouth Gastrovascular cavity Diffusion Diffusion Figure 40.3b (b) Two cell layers

9. Levels of Organization • Tissues – groups of cells that have a common structure and function • Organs – functional units of tissues • Organ Systems – groups of organs that work together (ex. Digestive, circulatory, or excretory systems)

10. Lumen of stomach Mucosa. The mucosa is an epithelial layer that lines the lumen. Submucosa. The submucosa is a matrix of connective tissue that contains blood vessels and nerves. Muscularis. The muscularis consistsmainly of smooth muscle tissue. Serosa. External to the muscularis is the serosa,a thin layer of connective and epithelial tissue. 0.2 mm • In some organs • The tissues are arranged in layers Figure 40.6

11. Types of Tissues • 4 Types of tissues • Epithelial tissue • Connective tissue • Muscle tissue • Nervous tissue

12. Epithelial Tissue • Covers the outside of the body and lines organs and cavities within the body • Contains cells that are closely joined

13. Connective Tissue • Functions mainly to bind and support other tissues • Contains sparsely packed cells scattered throughout an extracellular matrix

14. Muscle Tissue • Is composed of long cells called muscle fibers capable of contracting in response to nerve signals • Is divided in the vertebrate body into three types: skeletal, cardiac, and smooth

15. Nervous Tissue • Senses stimuli and transmits signals throughout the animal, including to other neurons (nerve cells), glands, muscles, and the brain.

16. Organ Systems in Mammals

17. 2 Systems that Specialize Coordination and Control • For survival, tissues, organs, and organ systems must act in a coordinated way: • 2 Systems specialize in this: • Endocrine system – chem. Signals called hormones = released. Each hormone cause specific effects • Nervous system (neurons) – transmit info between specific locations

18. 40.2 Feedback control loops maintain homeostasis • The internal environment of vertebrates • Is called the interstitial fluid, and is very different from the external environment • Homeostasis - a balance between external changes and the animal’s internal control mechanisms that oppose the changes

19. Response No heat produced Heater turned off Room temperature decreases Set point Too hot Set point Too cold Set point Control center: thermostat Room temperature increases Heater turned on Response Heat produced Homeostatic Control • Functions by having a set point (like a body temp to maintain) • It has sensors to detect any stimulus above or below the set point • A physiological response helps return the body to its set point

20. Homeostatic Control Systems • Negative feedback systems (most) – • Where buildup of the end product of the system shuts the system off • Ex. In response to exercise, the body temp rises, which initiates sweating to cool the body

21. Homeostatic Control Systems • Positive feedback systems • involves a change in some variable that triggers mechanisms to amplify the change • Ex. During birth, pressure of the baby’s head against receptors near the opening of the uterus stimulates greater uterine contractions, which cause greater pressure against the uterine opening, which heightens the contractions and so forth

22. 40.3 Homestatic processes for thermoregulation • Thermoregulation • process by which animals maintain an internal temperature within a tolerable range • 2 Types of regulation • Endotherms – (such as mammals and birds) – warmed mostly by heat generated by metabolism • Ectotherms – (such as most invertebrates, fishes, amphibians, and reptiles) – generate relatively little metabolic heat, gaining most of their heat from external sources

23. 40 River otter (endotherm) 30 Body temperature (°C) 20 Largemouth bass (ectotherm) 10 0 10 20 30 40 Ambient (environmental) temperature (°C) Ectoderms • In general, ectotherms • Tolerate greater variation in internal temperature than endotherms Figure 40.12

24. Endoderms • Endothermy is more energetically expensive than ectothermy • But buffers animals’ internal temperatures against external fluctuations • And enables the animals to maintain a high level of aerobic metabolism

25. Radiation is the emission of electromagnetic waves by all objects warmer than absolute zero. Radiation can transfer heat between objects that are not in direct contact, as when a lizard absorbs heat radiating from the sun. Evaporation is the removal of heat from the surface of a liquid that is losing some of its molecules as gas. Evaporation of water from a lizard’s moist surfaces that are exposed to the environment has a strong cooling effect. Conduction is the direct transfer of thermal motion (heat) between molecules of objects in direct contact with each other, as when a lizard sits on a hot rock. Convection is the transfer of heat by the movement of air or liquid past a surface, as when a breeze contributes to heat loss from a lizard’s dry skin, or blood moves heat from the body core to the extremities. Modes of Heat Exchange • Organisms exchange heat by four physical processes Figure 40.13

26. Balancing Heat Loss and Gain • Thermoregulation involves physiological and behavioral adjustments • That balance heat gain and loss • Examples include • Insulation • Vasodilation • Vasocontriction • Countercurrent Exchange

27. Balancing Heat Loss and Gain • Insulation • Reduces the flow of heat between an animal and its environment • May include feathers, fur, or blubber • In vasodilation • Blood flow in the skin increases, facilitating heat loss • In vasoconstriction • Blood flow in the skin decreases, lowering heat loss

28. Arteries carrying warm blood down the legs of a goose or the flippers of a dolphin are in close contact with veins conveying cool blood in the opposite direction, back toward the trunk of the body. This arrangement facilitates heat transfer from arteries to veins (black arrows) along the entire length of the blood vessels. Pacific bottlenose dolphin 1 Canada goose Blood flow Near the end of the leg or flipper, where arterial blood has been cooled to far below the animal’s core temperature, the artery can still transfer heat to the even colder blood of an adjacent vein. The venous blood continues to absorb heat as it passes warmer and warmer arterial blood traveling in the opposite direction. 1 Artery Vein Vein 2 Artery 35°C 3 33° 3 30º 27º 20º 18º 2 10º 9º In the flippers of a dolphin, each artery is surrounded by several veins in a countercurrent arrangement, allowing efficient heat exchange between arterial and venous blood. As the venous blood approaches the center of the body, it is almost as warm as the body core, minimizing the heat lost as a result of supplying blood to body parts immersed in cold water. 2 3 Countercurrent Exhange • Many marine mammals and birds • Have arrangements of blood vessels called countercurrent heat exchangers that are important for reducing heat loss • Antiparallel blood vessels going from the middle of the body where the blood is warm to the extremities 3 1 Figure 40.15

29. 21º 23º 25º 27º 29º 31º Body cavity Skin Artery Vein Blood vessels in gills Capillary network within muscle Heart Artery and vein under the skin Dorsal aorta Countercurrent Heat Exhange • Some specialized bony fishes and sharks • Also possess countercurrent heat exchangers (a) Bluefin tuna. Unlike most fishes, the bluefin tuna maintains temperatures in its main swimming muscles that are much higher than the surrounding water (colors indicate swimming muscles cut in transverse section). These temperatures were recorded for a tuna in 19°C water. (b) Great white shark. Like the bluefin tuna, the great white shark has a countercurrent heat exchanger in its swimming muscles that reduces the loss of metabolic heat. All bony fishes and sharks lose heat to the surrounding water when their blood passes through the gills. However, endothermic sharks have a small dorsal aorta, and as a result, relatively little cold blood from the gills goes directly to the core of the body. Instead, most of the blood leaving the gills is conveyed via large arteries just under the skin, keeping cool blood away from the body core. As shown in the enlargement, small arteries carrying cool blood inward from the large arteries under the skin are paralleled by small veins carrying warm blood outward from the inner body. This countercurrent flow retains heat in the muscles. Figure 40.16a, b

30. Countercurrent Heat Exchange • Many endothermic insects • Have countercurrent heat exchangers that help maintain a high temperature in the thorax Figure 40.17

31. Adjustment to Changing Temperatures • In a process known as acclimatization • Many animals can adjust to a new range of environmental temperatures over a period of days or weeks

32. Torpor and Energy Conservation • Torpor • Is an adaptation that enables animals to save energy while avoiding difficult and dangerous conditions • Is a physiological state in which activity is low and metabolism decreases

33. Hibernation is long-term torpor • That is an adaptation to winter cold and food scarcity during which the animal’s body temperature declines Additional metabolism that would be necessary to stay active in winter 200 Actual metabolism 100 Figure 40.22 Metabolic rate (kcal per day) 0 Arousals 35 Body temperature 30 25 20 Temperature (°C) 15 10 5 0 Outside temperature Burrow temperature -5 -10 -15 June August October December February April

34. Estivation, or summer torpor • Enables animals to survive long periods of high temperatures and scarce water supplies • Daily torpor • Is exhibited by many small mammals and birds and seems to be adapted to their feeding patterns