Thermoregulation in Endothermic and Ectothermic Animals

1. Endothermy and Ectothermy Ch. 6.7, Bush

2. Outline • Effects of temperature on life • Thermoregulation • Ecological aspects of thermoregulation

3. Outline • Effects of temperature on life • Thermoregulation • Ecological aspects of thermoregulation

4. Effects of extreme temperatures • Cold -- the effects of freezing • physical damage to structures caused by the formation of ice; the membrane bound structures are destroyed or damaged. • Heat • inadequate O2 supply for metabolic demands (especially in areas where O2 is low, such as water) • Heat and Cold • reduced activity or denaturation of proteins -- the inactivation of certain proteins with the result that metabolic pathways are distorted.

5. Optimal temperature for enzyme functioning

6. Body Temperature • Law of Tolerance: • for most requirements of life, there is an optimal quantity, above and below which the organism performs poorly • There is much variation in the range of temperatures that a species can tolerate

7. Outline • Effects of temperature on life • Thermoregulation • Ecological aspects of thermoregulation

8. Thermoregulation • maintenance of internal temperature within a range that allows cells to function efficiently • Two main types • ectothermy • endothermy

9. Endothermy versus ectothermy

10. Ectothermy • an animal that relies on external environment for temperature control instead of generating its own body heat • “cold-blooded” • e.g., invertebrates, reptiles, amphibians, and most fish • the majority of animals are ectotherms

11. Metabolism and temperature • ectotherms cannot move very much unless the ambient temperature allows • roughly, for each 10 degree increase in temperature, there is a 2.5 increase in metabolic activity

12. Ectothermy Desert iguanas are active only when ambient temperature is close to optimal for them

13. Ectothermic animals

14. Endothermy • a warm-blooded animal that controls its body temperature by producing its own heat through metabolism • evolved approximately 140 mya • E.g., birds, mammals, marsupial, some active fish like the great white shark and swordfish

15. Endothermic animals

16. Outline • Endothermy versus ectothermy • Behavioural adaptations to thermoregulation • Physiological adaptations to thermoregulation

17. Behavioural adaptations for thermoregulation • animals often bathe in water to cool off or bask in the sun to heat up

18. Shivering, sweating, and panting • honeybees survive harsh winters by clustering together and shivering, which generates metabolic heat • Inefficient – 75% of energy is lost in mechanical movement

19. Torpor • metabolism decreases • heart and respiratory system slow down • body temperature decreases • conserves energy when food supplies are low and environmental temps are extreme E.g., hummingbirds on cold nights

20. Hibernation • Long-term torpor • adaptation for winter cold and food scarcity • E.g., ground squirrels

21. Aestivation • summer torpor • adaptation for high temperatures and scarce water supplies • E.g., mud turtles, snails

22. Endothermy and the evolution of sleep? • evolutionary remnant of torpor of our ancestors • the body needs sleep in order to offset the high energy costs of endothermy: • When animals fall asleep their metabolic rates decrease by approximately ten percent

23. Colour and Posture • Change coloration (darker colors absorb more heat) • E.g., lizards, butterflies, crabs • Posture: • Change shape (flatten out to heat up quickly) • Orientation changes

24. Chemical adaptations • Many Canadian butterflies overwinter here and hibernate • they produce sugar-like substances as antifreeze • E.g., Mourning Cloak butterfly

25. Outline • Effects of temperature on life • Thermoregulation • Ecological aspects of thermoregulation

26. Advantages & Disadvantages of Endothermy • Advantages: • external temperature does not affect their performance • allows them to live in colder habitats • muscles can provide more sustained power • e.g., a horse can move for much longer periods than a crocodile can • Disadvantage: • energy expensive • an endotherm will have to eat much more than an ectotherm of equivalent size

27. Where can endotherms thrive? • Higher latitudes and deserts • Terrestrial environments have more variation in daily and seasonal temperature which contributes to more endotherms in terrestrial environments • endotherms (mammals and birds) generally outcompete ectotherms if they are after the same food source

28. Size and thermoregulation • Small mammals (such as mice and shrews) have a greater dependence on internally-generated heat than big mammals (such as elephants and hippos) • leads to: • presence of insulation (fur - large mammals generally have less hair) • voracious appetites of small mammals (a shrew eats more per unit body weight than an elephant does)

29. Surface area to volume ratios

30. Ectothermy vs. endothermy • Many more ectotherms are small in size versus endotherms • Ectotherms typically have no insulation • Posture is different

31. Where do ectotherms thrive? • Where food items are: • scarce • small • In environments low in O2

32. Ecosystem functioning and ectothermy • Production Efficiency: -can be seen as the ratio of assimilation between trophic levels = biomass of predator biomass of food species • Ectotherms are more efficient than endotherms (up to 15% versus 7%)

33. Thermoregulation and food chains • Endotherms are often the top predator in food chains • Food chains with lots of ectotherms are often longer in length

34. Summary • Endothermic animals regulate their body heat to stay within the optimal range for performance while the temperature of ectothermic animals fluctuates with that of the surrounding environment • Both endotherms and ectotherms have a variety of behavioural and physiological adaptations to deal with environmental extremes

36. Climate Ch. 4, Bush

37. Outline • Climate and ecology • Solar energy and air circulation • Oceanic influences • Cycles of climate change

38. Outline • Climate and ecology • Solar energy and air circulation • Oceanic influences • Cycles of climate change

39. Climate affects ecology

40. Temperature and precipitation

41. Outline • Climate and ecology • Solar energy and air circulation • Oceanic influences • Cycles of climate change

42. Solar energy • Solar energy distribution is not balanced across the globe in • intensity • constancy • Together, these differences explain the distribution of tropical and temperate climates

43. Intensity of Solar energy • Solar energy is more intense at lower latitudes (that is, closer to the equator) because: • the “footprint” of the beam of energy is smaller at tropical latitudes • beams have shorter passage through the atmosphere

44. Intensity of solar energy more energy per square meter in the tropics than at the poles

45. Differences in daylength

46. Differences in Day Length • caused by the constant tilt of Earth as it orbits around the sun • the reason why temperate environments have four seasons while tropical environments do not

47. Heat and air circulation • The disparity in energy input across the globe drives all our weather systems • This is because heat energy must flow from warm to cold

48. Hadley cells – the effect of heat transfer • Hot air rises and, as it rises, it cools • Cool air cannot hold as much moisture as heated air, so it rains • This cool, dry air must go somewhere so it pushes towards the poles, where it slows and descends • As it descends, it is warmed

49. Hadley cells

50. Hadley cells and climate • The downdraft of hot dry air causes the formation of the desert regions of Earth: E.g., Sahara Sonoran Australian Gobi Atacama