1. Homeostasis

2. Regulating vs Conforming
Difference between regulating and conforming
Why is regulation more energy expensive than
conforming?

3. Adaptation needs to outweigh the needs of the body
more than the benefits of the body

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. Thermoregulation
Temperature affects a lot of things
- Proteins
- Membranes
- What else?

6. Four physical processes of heat gain and loss
Conduction
Convection
Radiation
Evaporation

7. What is a wind chill effect?

8. Endothermy vs Ectothermy
Define endotherm/ ectotherm
True or false: ectotherms are always cold-blooded.

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. Disadvantage of endothermy
Thermoregulators invest more energy in their
activity than conformers, thus, increasing the energy
intake of regulators.

11. Question: why is ectothermy a good strategy in living
in a new environment?

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. 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. Mechanisms of temperature control
Mammals/ birds
 Constant heat loss
 Constant heat production
 Nonshivering thermogenesis vs shivering thermogenesis

15. Nonshivering thermogenesis (NST)
Hormones- inc metabolic activity of mitochondria
rather than production of ATP
Brown fat
Insulation
Blubber

16. Panting and evaporative cooling
Increase rate of heat exchange

17. How does fur/hair help in insulation?

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. FIshes
Mostly are conformers
Endothermic fishes use countercurrent heat
exchange system
Presence of special heat generating organs

20. Invertebrates
Aquatic invertebrates- mainly thermoconformers
Terrestrial invertebrates- same as vertebrate
ectotherms
Flying insects- smallest endotherms

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. Thermostat
Controls temperature
Warm receptors- indicate inc in temp
Cold receptors- indicate dec in temp
What kind of mechanisms will each receptor
activate?

23. Below normal range?
Above normal range?

24. Acclimation vs acclimatization
Acclimation- laboratory
Acclimatization- natural environment

25. Antifreeze- used by ectotherms in sub-zero
environment
Proteins- e.g. Heat shock proteins

26. Torpor
Physiological state of low activity and low
metabolism
Hibernation vs winter sleep
Estivation
Daily torpor

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. 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. 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. 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. 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. 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. 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. Stenohaline- animals that cannot tolerate broad
change in solute concentration
Euryhaline- animals that can tolerate substantial
change in external osmolarity, e.g. salmon