Large organisms heat and cool less quickly than

smaller organisms

Heat content is a function of

Heat exchange is a function of

volume

surface area

Temp. of organisms is determined by exchanges of

thermal energy(heat) with the external environment

*heat produced by metabolims

Heat Balance Equation: Generalized Equation

H= SR + IR_in - IR_out +/- H_conv +/- H_cond - H_evap + H_met

Plant Balance Equation:

H= SR + IR_in - IR_out +/- H_conv +/- H_cond - H_evap

Organisms influence their temp. by modifying gains and losses via

1. Acute responses occurs within individual plants

2. Phenotypic acclimatization within individual plants

3. Evolutionary adaptation occurs across generations

Plants can alter

- evapotranspirational water loss

- leaf surface reflective properties

- leaf orientation to the sun

- leaf surface roughness

Thermal Adaptation

Thermal Acclimatization

Plants used: Brittlebush

Endothermy

*sources of heat

organism to maintain a stable body temperature through metabolic processes.

* predominant source of heat

Ectothermy

*sources of heat

regulate their body temperature using external sources, such as sunlight or ambient temperature

* outside env is their heat

Homeothermy

*body temp

maintain a stable internal body temperature, even when the external temperature varies

to sustain: heat must be lost in the same rate it is gained

Poikilothermy

*body temp

organism that cannot regulate its body temperature except by behavioral means such as basking or burrowing.

Most Fish: Generalized Equation

H= - H_conv +/- H_cond

Terrestrial Ectotherms

H= SR + IR_in - IR_out +/- H_conv +/- H_cond - H_evap

H_met dropped due to not producing heat fast enough

Terrestrial Endotherms

H= SR + IR_in - IR_out +/- H_conv +/- H_cond - H_evap + H_met

Endotherms can maintain high and constant body temps but

Endothermic homeothermy has a high energetic price

Temp regulation and thermal ecology are inseparable from energy metabolism

Ectotherms can not use what to thermoregulate?

metabolism

Endo and ectothermy are not

strict alternatives

Skipjack tuna use muscle activity and heat exchange to

maintain a body temp 14 C

Terrestrial ectotherms can move between heat sources and heat sinks using

Ex. Lizards

behavioral thermoregulation

Insects have a high concentration of glycerol, a chemical that

*similar to antifreeze proteins that fishes have as well

lowers the freezing point of body fluids

Wood frogs (Rana Sylvatica) and some other species of frogs tolerate

tolerate freezing

Metabolic rate depends on

external temp & S/V ratio

Heat loss is faster in the

cold

* endothermy is non-sustainable due to this and may enter torpor under cold conditions

Benefits of enedothermy

_ independence from env temp

- range expansion to high latitude and alitude

- high capacity to sustain physical activity

Characteristics of Endothermy

- Thermoneutral zone

_ Low critical temp

Thermoneutral zone

a constant basal metabolic rate can be maintained

Lower critical temp

* lower in Arctic mammals than tropical mammals

heat loss > metabolic production; body temp drops and heat increases

Torpor

* long periods are possible for animals that can store enough energy

* also related to hiberation

state of physical or mental inactivity; lethargy.

Small endothemrs undego daily torpor to

survive cold nights