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  1. 1. Homeostasis
  2. 2. Regulating vs Conforming Difference between regulating and conforming Why is regulation more energy expensive than conforming?
  3. 3. Adaptation needs to outweigh the needs of the body more than the benefits of the body
  4. 4. Balances The natural environment is a system of balances  Law of thermodynamics Input and output should be equal  When will there be an imbalance?
  5. 5. Thermoregulation Temperature affects a lot of things - Proteins - Membranes - What else?
  6. 6. Four physical processes of heat gain and loss Conduction Convection Radiation Evaporation
  7. 7. What is a wind chill effect?
  8. 8. Endothermy vs Ectothermy Define endotherm/ ectotherm True or false: ectotherms are always cold-blooded.
  9. 9. Advantages of endothermy Longer vigorous activities than ectotherms  Sustained activity is only possible in endotherms  Thermal problems living in a terrestrial environment is resolved through endothermy; e.g. endotherms can live in below-freezing production- temperature that deactivate the metabolism of ectotherms
  10. 10. Disadvantage of endothermy Thermoregulators invest more energy in their activity than conformers, thus, increasing the energy intake of regulators.
  11. 11. Question: why is ectothermy a good strategy in living in a new environment?
  12. 12. Adaptation of animals that thermoregulate • Adjusting the rate of heat exchange between the animal and its surroundings • e.g. insulation such as feathers, fat • changes in the circulatory system- vasodilation/vasoconstriction • countercurrent heat exchange- arteries are in opposite direction that of veins in the extremities; heat exchange is determined by physiology or environment
  13. 13. Cooling through evaporative heat loss Behavioural response- posture or movement (migration/hibernation/estivation/winter sleep) Changing the rate of metabolic heat- applies only to endotherms
  14. 14. Mechanisms of temperature control Mammals/ birds  Constant heat loss  Constant heat production  Nonshivering thermogenesis vs shivering thermogenesis
  15. 15. Nonshivering thermogenesis (NST) Hormones- inc metabolic activity of mitochondria rather than production of ATP Brown fat Insulation Blubber
  16. 16. Panting and evaporative cooling Increase rate of heat exchange
  17. 17. How does fur/hair help in insulation?
  18. 18. Amphibians and Birds Movement is key to heat production Production of mucus to counter evaporative cooling Reptiles have scales that inc skin’s SA Vasoconstriction in extremities of marine iguana
  19. 19. FIshes Mostly are conformers Endothermic fishes use countercurrent heat exchange system Presence of special heat generating organs
  20. 20. Invertebrates Aquatic invertebrates- mainly thermoconformers Terrestrial invertebrates- same as vertebrate ectotherms Flying insects- smallest endotherms
  21. 21. Flying insects Generate heat through flight muscles Countercurrent exchange mechanisms  Shutdown mechanisms during hot weather Uses shivering in incubation Huddling Evaporative cooling fanning
  22. 22. Thermostat Controls temperature Warm receptors- indicate inc in temp Cold receptors- indicate dec in temp What kind of mechanisms will each receptor activate?
  23. 23. Below normal range? Above normal range?
  24. 24. Acclimation vs acclimatization Acclimation- laboratory Acclimatization- natural environment
  25. 25. Antifreeze- used by ectotherms in sub-zero environment Proteins- e.g. Heat shock proteins
  26. 26. Torpor Physiological state of low activity and low metabolism Hibernation vs winter sleep Estivation Daily torpor
  27. 27. Osmoregulation Functions in maintaining the composition of the cell’s cytoplasm Mostly done indirectly Open circulatory- uses hemolymph Close circulatory- use interstitial fluid Kidneys are specialized organs in maintaining the composition of the body’s fluid composition
  28. 28. Transport epithelia e.g. transport epithelium face the outside environment to release unwanted solutes but have tight junction in between cells to inhibit back flow; functions like the Casparian strip of plants
  29. 29. Ammonia Most common in aquatic animals Can easily pass through membranes via diffusion Invertebrates release ammonia all throughout the body Fish release ammonia in the form of ammonium ions through the gills (kidneys excrete only minimal amount) Freshwater fishes excrete NH4 ions but also take in Na ions through the gill epithelium to have a higher concentration of Na ions compared to the environment
  30. 30. Urea less toxic compared to ammonia Need less water in eliminating Used by mammals, adult amphibians, marine fishes and turtles Ammonia+CO2 Transported via the circulatory system and filtered in the kidneys
  31. 31. Can be transported in high concentration due to low toxicity Uses more energy Animal adaptation: amphibians in water excrete ammonia but excrete urea in land, what is the advantage of this lifestyle?
  32. 32. Uric Acid relatively nontoxic nitrogenous waste Insoluble in water and excreted as semisolid paste Advantage: low water loss Disadvantage: highly expensive Present in land snails, insects, birds, reptiles
  33. 33. Osmoconformers vs osmoregulators Osmoconformers- animals that have the same concentration of body fluid and of the external environment; live in relatively stable environment Osmoregulators- maintains the concentration of body fluid; body fluid is not isoosmotic with that of the environment
  34. 34. Stenohaline- animals that cannot tolerate broad change in solute concentration Euryhaline- animals that can tolerate substantial change in external osmolarity, e.g. salmon