Metabolism & Thermal Biology

Standard Metabolic Rate

• Rate of oxygen needed to sustain life

• O2 needed to maintain ATP levels to run all basal processes

• Effected by temp!!

What doent SMR take into account

• reproduction

• major growth

• running around

SMR is heavily impacted by

temperature

Most biological processes have ___ range, because

optimal temperature

all processes are driven by protein and enzymes which can only work in certain environments and temperatures

Organisms can change ____ based on the activities they are doing

temperature

Thermoregulation rules

• all processes are temp dependent

• higher body temp = more food to keep SMR

• logical that org wants stable body temp

Thermoregulation

• relatively same temp no matter the surrounding temp

• stable body temp

Thermoconformance

• change in air temp = change in body temp

• incremental change in both

Poikolotherms

• variable body temp

• as ambient rises so does body temp

• “cold blooded”

Homeotherms

• stable body temp

• no fluctuations as temp changes

• “warm blooded”

why is warm blooded and cold blooded incorrect

sometimes cold blooded have warmer blood that warm blooded, they could also be colder as they change with the environment

Ectotherms:

get energy from their surroundings, basking in sunlight

metabolic rate proportional to body temp

• no neural control

Endotherms:

• depend on internal metabolic processes to generate body heat

metabolic rate not always proportional

• constant in thermoneutral zone

• increases beyond critical temps

• Metabolism counters heat loss in/below thermonetural zone

• as air temp increases, body temp stays stable bc metabolism goes down

Inaccuracies btw Ecto & Endo

not about temperature but about the SOURCE of the energy used for thermoregulation

• not that temp varies

Benthic fish

• ectotherms

• homeotherms because environment doesn’t change

  • environment temp doesn’t change, so neither does the fish body temp

dfifficulties and exceptions

• reptiles are normally ectotherms

• some female snakes will heat eggs by increasing body metabolism

Heterothermy occurs when

endotherms show wide swings

Nightime torpor

• body temp drops to 1 degree above ambient

• extreme cold climates

• artic ground squirrels to -2.9 C

• not enough food to maintain body temp all the time

• temporal heterothermy

• warms up when the sun comes back up

• Facultative torpor

• birds flying long distances

• drop temps to make sure energy stores last the flight

• hummingbirds

• vampire bats

Seasonal Torpor

• true hibernation

• comatose state for days/week at a time

• mostly in smaller endotherms

• NOT BEARS

  • larger things need more energy to be heated

Torpor

• larger mammals do not experience true torpor

  • can lower body temp some

• true torpor saves a lot of energy

• substantial cost to heat

Energy cost of arousal

energy cost that the organism needs to pay off to get back up to body temperature

• massive bear would require an insane amount of energy

• small squirrel would be fine

Enodtherms vs Ectotherms

• endo has a higher baseline metabolism

  • 5-10 x

• Endo have increased insulation

  • hair fur feathers fat

• endo contol metabolism neurally

  • when the outside temp go up the metabolic rate gets slowed down and vv

• ecto will do more behavior to change temp

if all the metabolism stops

the org dies 💀

Insulation

• increased volume of insulation can prevent the loss of heat through conductance

• fluffing/shedding of fur

• increased blubber

  • keeping blood further away from the environment