Thermoregulation. Learning Objectives 2/13/08. Distinguish between the thermoregulators classified as endotherms and ectotherms, homeotherms, heterotherms, and poikilotherms Describe the adaptive advantage(s) of endothermy
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Ectotherm (ecto = “outside”) - An animal that derives body temperature from an external heat source.
Endotherm (endo = “inside”) - An animal that derives body temperature from internal heat production.
Note: These terms relate to the source of body heat, not whether the animals are capable of regulating body temperature.
Why is body temperature homeostasis important?
What must be true in order for an endotherm to maintain temperature homeostasis?
Poikilotherm (poikilo =“varied”) - body temperature approximates the ambient temperature. Not capable of controlling body temperature as ambient temperature varies. What is the adaptive advantage here?
Heterotherm(hetero = “different”) - regulates body temperature when active, but allows body temperature to fluctuate with the environment when inactive.
Homeotherm (homeo = “same”) - controls body temperature, keeping it relatively constant as ambient temperature varies.
These terms relate to whether or not the animal is capable of controlling body temperature.
Describe the advantage to temperature homeostasis from the fact that animal bodies are made mostly of water.
Heat Exchange Between an Animal and its Environment
See Fig. 41.15
Lizard Behavioral Thermoregulation
Heat Exchange in Appendages
See Fig. 41.20
Leg of a bird or mammal
Flipper of a seal or whale
Which mechanism of heat transfer is operating here?
Control of Conductance by Regional Heterothermy
Cold-climate homeotherms can allow their appendages to cool to reduce heat loss.
Countercurrent heat exchange occurs between warm out-flowing blood in a central artery and cold in-flowing blood in surrounding veins.
What organ serves as the controlcenter to regulate these organs?
Why are there both cold and hot
thermoreceptors in the body?
See p. 916
How does the behavior of the cell membrane change with temperature?
How does the chemical make-up influence this behavior?
Wood frog in summer
Wood frog, frozen
The “winter” frog is in cardiac arrest, & has 65% of its body water frozen.
If ECF water freezes, what would happen to ICF water?