Convection - *Transfer of heat by movement of liquids and gases (Molecules of air or water next
to warm surface gain energy and move away from surface)*When environment is cold, organism warms
it's boundary layer which reduces heat loss but current of air can disrupt layer and carry away heat by
...
BIO 320 EXAM 2
Convection - *Transfer of heat by movement of liquids and gases (Molecules of air or water next
to warm surface gain energy and move away from surface)*When environment is cold, organism warms
it's boundary layer which reduces heat loss but current of air can disrupt layer and carry away heat by
convection (wind chill)
Radiation - *Emission of electromagnetic energy by surface (i.e. sun)
*When objects are warmed by radiation, they emit lower-energy radiation as infrared light
*The temp of the radiating surface determines how rapidly an object loses energy by radiation to colder
parts of the environment.
Conduction - *Transfer of kinetic energy of heat between substances in contact (i.e. lizards lying
flat on rocks to warm)
*Rate of heat movement depends on 1) surface area 2) resistance to heat transfer 3) temp difference
*Greater surface area=greater surface for energy transfer (i.e. animals curling up in ball for warmth)
Evaporation - *Transformation of water from liquid to gas using heat energy
*Removes heat=cooling effect on organism
*Plants transpire/Animals breathing makes water evaporate from exposed gas exchange surfaces esp. in
higher temp.
Homeotherms - Maintain constant temperature conditions within the cells.
Poikilotherms - Does not have constant body temperatures.
Ectotherms - *Body temp largely determined by external environment
*Usually have low metabolic rates (reptiles, amphibians, plants, insects- those that cant generate or
retain heat to offset heat loss)*Ectotherms adjust temp by altering behavior (moving in/out of shade,
etc)
, Endotherms - *Generate enough metabolic heat to raise body temp higher than external
environment
*Most mammals/birds maintain body temp between 36°C-41°C, despite surrounding temp.
*Maintaining a higher body temp gives them more energy for activity like find food and escape.
*Sustaining internal conditions despite external difference requires a lot of work/energy
*Organisms make up for temp difference by generating metabolic heat or gaining through radiation,
conduction, or convection.
Radiation Equation - AεT^4 σ
*A=surface area of obj emitting radiation
*ε=defines how effectively obj radiates energy (0-1)
*T=temp of obj expressed in K
*σ=Boltzmann constant
*^Temp=exponential inc in radiation
*Organism emits radiation to and received radiation from environment. Hot organism in cold
environment will emit more than it gains, meaning radiation will cause body to cool.
*Organism w/ temp that equal environment will emit as much as it receives, canceling change.
Conduction Equation - (KA(Tb-Tg))/L
*Tb= temp of body surface
*Tg=temp of ground (or other solid)
*A=area of contact between organism & environment
*k=conductivity (how well solid conducts heat)
*Tb equals the temperature of the body surface *Tg equals the temperature of the ground (or another
solid).
*L=distance of heat transfer
*Surfaces like metals have high conductivity, meaning they transfer heat rapidly. Insulation such as fur or
feathers will increase the distance that heat must flux between an organism and its environment
Convection Equation - hA(T_b-T_a)
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