biob34 mod 3

thermal strategy

behavioural, biochemical, and physiological responses ensuring body temp is within acceptable range

ambient temp (Ta)

temp of animal surroundings; most important environmental influence on animal thermal strategy

tolerance

body temp varies with ambient temp; ectotherms

regulation

body temp does not vary with ambient temp; endotherms

heat flux (Q)

rate of heat transfer from hot to cold; form of power measured in watts or J/s

total thermal energy

sum of metabolic rate, conduction, convection, radiation, evaporation

convection

transfer of thermal energy between object and moving external medium; rate of heat exchange dep on thermal gradient, liquid flow rate, fluid conductivity

radiation

emission of emr; usually from sun

basking

dark color enhance heat absorption

evaporation

water absorb thermal energy from surfaces when evaporating; amount of heat loss dep on volume of water and heat of vaporization; salt increase heat of vaporization

conduction

transfer of thermal energy from one medium to another through direct contact; thermal conductivity varies with material type and geometry

insulation

layer of material reducing thermal exchange; can be internal (under skin) or external (on body surface); effectiveness largely dep on thickness

bergmann’s rule

“animals living in colder climates tend to be larger”

allen’s rule

“animals living in colder climates tend to have smaller extremities”

poikilotherm

variable body temp

homeotherm

stable body temp

ectotherm

environment determines body temp; req ability regulate thermogenesis and heat exchange with environment; futile cycles

endotherm

animal generates internal heat to maintain body temp; high metabolic rate to increase heat production; can retain enough heat to elevate body temp above ambient temp

thermoneutral zone (tnz)

optimal temp range for physiological process; minimal metabolic rate

upper critical temp (uct)

higher temp than tnz; metabolic rate increases as animal physiologically respond to prevent overheating

lower critical temp (lct)

lower than tnz; metabolic rate increases as animal physiologically respond to increase heat production

preferred temp

ambient/body temp for optimal poikilotherm physiological func

incipient lethal temp

ambient temp when half of poikilotherm animals die

range of tolerance

ambient temp range between upper incipient lethal temp and lower incipient lethal temp

eurytherm

poikilotherms tolerating wide range of ambient temp; occupy more thermal niches

stenotherm

poikilotherms tolerating narrow range of ambient temp; occupy less thermal niches

regional heterotherms

body temp varies in diff body regions

futile cycling

two opposing enzymes activated simultaneously

homeoviscous adaptation

maintain membrane fluidity at diff temp by changing membrane lipid and cholesterol content; shorter unsaturated fatty acid chains increase fluidity

psychrotroph

animals thriving at low temp; has cold adapted enzymes; vulnerable to temp dep denaturation

freeze tolerance

animals freeze tissue in controlled ways

freeze avoidance

animals prevent ice crystal formation with behavioural and physiological mechanisms

antifreeze macromolecules

proteins or glycoproteins that decrease freezing point by binding to small ice crystals and disrupting ice crystal formation

hypothalamus

controls rate of heat production and dissipation using cns and pns sensors

shivering thermogenesis

unique to bird and mammals; uncontrolled myofiber contractions generating heat; no net muscle work; prevents muscle from performing other func; glycogen use dominates at high intensities

brown adipose tissue (bat)

nonshivering thermogenesis for small mammals and newborns in cold climates; more mitochondria than white adipocytes; produce uncoupling protein 1 (ucp1) uncoupling mitochondrial ets and protein pumping for atp synthesis; futile cycle of fatty acid oxidation to release heat; activated by sympathetic nervous input

torpor

daily changes in body temp; duration predicts energy savings

shallow torpor

save energy with reduced metabolic rate at regulated moderate temp; does not strongly track ambient temp

deep torpor

save energy with reduced metabolic rate at minimum body temp that ambient temp allows; does strongly track ambient temp