BIO 320 EXAM 2 QUESTIONS AND
ANSWERS 100% CORRECT.
Describe all processes by which organisms exchange heat with their environment. -
ANSWERRadiation, Conduction, Convection, Evaporation
Radiation - ANSWER*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 - ANSWER*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)
Convection - ANSWER*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)
Evaporation - ANSWER*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 - ANSWERMaintain constant temperature conditions within the cells.
Poikilotherms - ANSWERDoes not have constant body temperatures.
Ectotherms - ANSWER*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 - ANSWER*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 - ANSWERAεT^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 - ANSWER(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 - ANSWERhA(T_b-T_a)
*Tb=temp of body surface
*Ta=temp of air/water
*A=surface area in contact with fluid
*h=convection coefficient (shape of organism and movement of fluid that determines
rate of heat flux by convenction)
*larger h means larger heat flux
Evaporation Equation - ANSWERcA(e_w-e_a)
*eW=vapor pressure of water in body
*eA=vapor pressure in the air
*A=surface area where water can evaporate
*c= constant that converts water loss to heat loss
*Evaporation requires water concentration of the body to exceed that of air. When the
air has less water than the body, the pressure generated in body exceeds that of water
in the air so water molecules push their way into air as vapor.
Freshwater Osmoregulation - ANSWER*Freshwater animals have higher solute conc in
their tissues than surrounding water.
ANSWERS 100% CORRECT.
Describe all processes by which organisms exchange heat with their environment. -
ANSWERRadiation, Conduction, Convection, Evaporation
Radiation - ANSWER*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 - ANSWER*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)
Convection - ANSWER*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)
Evaporation - ANSWER*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 - ANSWERMaintain constant temperature conditions within the cells.
Poikilotherms - ANSWERDoes not have constant body temperatures.
Ectotherms - ANSWER*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 - ANSWER*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 - ANSWERAεT^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 - ANSWER(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 - ANSWERhA(T_b-T_a)
*Tb=temp of body surface
*Ta=temp of air/water
*A=surface area in contact with fluid
*h=convection coefficient (shape of organism and movement of fluid that determines
rate of heat flux by convenction)
*larger h means larger heat flux
Evaporation Equation - ANSWERcA(e_w-e_a)
*eW=vapor pressure of water in body
*eA=vapor pressure in the air
*A=surface area where water can evaporate
*c= constant that converts water loss to heat loss
*Evaporation requires water concentration of the body to exceed that of air. When the
air has less water than the body, the pressure generated in body exceeds that of water
in the air so water molecules push their way into air as vapor.
Freshwater Osmoregulation - ANSWER*Freshwater animals have higher solute conc in
their tissues than surrounding water.
