Thermoregulation
- Four mechanisms of heat transfer:
- Conduction: Heat gained or lost by direct contact
- Radiation: Heat gained from solar radiation or lost to cooler environments from the body via infrared radiation
- Convection: Heat lost via a moving fluid
- Evaporation: Heat lost from energy turning water from a liquid to a gas (no way to gain heat through this)
- Factors effecting heat transfer in animals:
- Size/Surface area: Smaller animals have a higher surface area to mass ratio which means they will gain and loose heat faster
- Amount of conductance: Influenced by the amount of insulation an animal has, the more insulation the less heat is lost
- Terrestrial creatures have to be more adapted to temperature extremes than aquatic tissues.
- The greater the difference in temperature between the environment and the body the greater the heat loss or gain
- Heat regulation mechanisms:
- Endothermic (warm-blooded): Body heat produced by metabolism, occurs in most mammals and birds, maintains a constant body temperature not dependent on the environment. May take advantage of behavioural mechanisms (huddling) and some increase insulation in cold seasons, both use less energy than increasing metabolism
- Heterothermic: Can be endothermic or ectothermic depending on conditions, occurs in bats, bees, moths, and hummingbirds, can undergo rapid and drastic changes in body temperature.
- Ectothermic (cold-blooded): Body heat gained from the environment through behavioural mechanisms, occurs in most fish, reptiles, amphibians, and invertebrates, body temperature is variable but still regulated
- Vasoconstriction of peripheral blood vessels helps reduce heat loss, and vasodilation encourages it
- Shivering uses muscles contractions to heat the body
- Sweating is evaporation which releases heat through the skin, most animals can not do this and pant instead
- Heterorthermic creatures can be endo or ectothermic based on conditions, species often practice nightly torpor. Ex. Hummingbirds, bats, bees, and moths