Ch 40 – Animal Form & Function

1. Ch 40 – Animal Form & Function

2. Form & function • Evolution of Animal size & shape • Constrained by physical forces • Convergent evolution • i.e. fusiform shape for aquatic animals Seal Penguin

3. Exchange with Environment Mouth Gastrovascular cavity • All cells need access to aqueous environment • Why? • How do surface area & volume relate to exchange of materials? Exchange Exchange Exchange 0.1 mm 1 mm (a) Single cell (b) Two layers of cells

4. More complex animals – have highly folded internal surfaces for maximum exchange Villi Advantages of a complex body: Protection Sensory organs Better able to deal with environmental changes

5. Gas Exchange & Alveoli

6. Nutrition/ Microvilli http://www.youtube.com/watch?v=AJ1wKsmBPvA

7. Excretion/Nephron http://www.youtube.com/watch?v=glu0dzK4dbU

8. Circulation/Heart

9. Organization of body plan • Cells  Tissues  Organs  Organ systems • What coordinates & controls the systems?

10. Feedback control helps maintain a stable environment • regulator – animal that uses internal mechanisms to control internal environment • conformer – animal that allows internal environment to change in response to external variable

11. Homeostasis • -maintain a “steady state” or internal balance regardless of external environment • In humans, body temperature, blood pH, and glucose concentration are each maintained at a constant level • For a given variable, fluctuations above or below a set point serve as a stimulus • - sensor detects & triggers response

12. Negative feedback – • Control that reduces the original stimulus; maintains homeostasis by returning to “normal range”

13. Positive feedback • Control mechanism that amplifies the stimulus (is not used for maintenance of homeostasis)

14. Alterations in homeostasis • Set points and normal ranges can change with age or show cyclic variation • In animals and plants, a circadian rhythm governs physiological changes that occur roughly every 24 hours • Homeostasis can adjust to changes in external environment, a process called acclimatization

17. Thermoregulation: an example of homeostasis • the process by which animals maintain an internal temperature within a tolerable range

18. Endothermy and Ectothermy • Endothermic animals generate heat by metabolism; birds and mammals are endotherms, some insects • (have more stable temperature in a changing environment) • Ectothermic animals gain heat from external sources; ectotherms include most invertebrates, fishes, amphibians, and nonavianreptiles • (tolerate larger range of temperatures)

19. Balancing heat gain & heat loss • Organisms exchange heat by four physical processes:

20. Adaptations for heat regulation • Insulation • - major thermoregulatory adaptation in mammals and birds • Skin, feathers, fur, and blubber reduce heat flow between an animal and its environment • The integumentary system is frequently involved in regulation • - skin, hair, nails

21. Circulatory adaptations • Regulation of blood flow near the body surface significantly affects thermoregulation • Many endotherms and some ectotherms can alter the amount of blood flowing between the body core and the skin • Vasodilation - blood flow in the skin increases, facilitating heat loss • Vasoconstriction - blood flow in the skin decreases, lowering heat loss

22. Circulatory adaptations Countercurrent heat exchange – in many birds & mammals, also sharks, dolphins • Warm blood from arteries is used to warm blood in adjacent veins • allows for transfer of heat to colder blood coming from extremities

24. Circulatory adaptations • Evaporative heat loss – • water absorbs heat when it evaporates, so heat is carried away from surface by water vapor • Adaptations: sweat glands, birds with pouch with blood vessels in mouth

25. Behavioral responses • move to warmer or cooler area • move closer together • Some insects have specific postures for thermoregulation

26. Adjusting metabolic heat production • Thermogenesis: • - adjustment of metabolic heat production to maintain body temperature • - increased by muscle activity such as moving or shivering • - Nonshiveringthermogenesis takes place when hormones cause mitochondria to increase their metabolic activity (heat vs. ATP) • - Some ectotherms can also shiver to increase body temperature

27. Acclimatization in Thermoregulation • Birds and mammals can vary their insulation to acclimatize to seasonal temperature changes • When temperatures are subzero, some ectotherms produce “antifreeze” compounds to prevent ice formation in their cells

28. Thermoregulation is controlled by a region of the brain called the hypothalamus • The hypothalamus triggers heat loss or heat generating mechanisms • Fever is the result of a change to the set point for a biological thermostat – helps fight infection.

29. Bioenergetics • - the overall flow and transformation of energy in an animal • - determines how much food an animal needs and it relates to an animal’s size, activity, and environment • Ectotherms use less energy than endotherms

30. Metabolic rate is the amount of energy an animal uses in a unit of time How can metabolic rate be measured?

31. Influences on metabolic rate Size – rate is proportional to body mass, smaller animals have higher metabolic rate per gram than larger animals

32. Activity & metabolic rate • Activity greatly affects metabolic rate for endotherms and ectotherms • In general, the maximum metabolic rate an animal can sustain is inversely related to the duration of the activity • Endotherms – high energy strategy, can have intense, long-duration activity • Ectotherms – low energy strategy,usually incapable of intense activity over long periods

33. Energy budgets Reproduction – high energy cost strategies: seasonal reproduction, life history strategy – i.e. diapause (in insects)

34. Torpor & Energy conservation • Torpor – physiological state of decreased activity -small mammals & birds – daily torpor (i.e. bats feed at night, torpor in day) • Hibernation – body’s thermostat is turned down in winter, due to cold & food scarcity (seasonal response) • Estivation – summer torpor – due to high temp & scarce water supplies

35. bear hibernation • http://animal.discovery.com/tv-shows/animal-planet-presents/videos/natural-world-bear-hibernation.htm • Thermoregulation in animals (4:08) • http://www.youtube.com/watch?v=NJEBfl_LKno