Endotherms Flashcards
What are endotherms?
An organism that is able to regulate its own body temperature
What is the issue with a larger sa:v
Lose heat more rapidly
Small bodies
Substances with a low conductivity have what?
High insulation
Why does fur & feathers have low conductivity?
They trap air between them (provide good insulation)
Why is fur invaluable to small mammals in cold climates?
Impractical to have very thick/long fur
What is meant by ‘thermal windows’?
Many large, furred animals have shorter fur on underparts, particularly legs & feet
How is the colour of mammal’s fur determined?
- The need for camouflage or mimicry
- Display
- Thermoregulation
What is the thermal neutral zone?
Range of temperatures over which an endothermic animal can maintain a constant temp without a change in heat production
What is the lower critical temperature?
The point at which heat production is increased to prevent a drop in Tb
What is the upper critical temperature?
The point at which an endothermic needs to actively invoke cooling measures (e.g. panting)
What are the 3 trends in the thermal neutral zones of different animals?
- The lower the critical temp of high latitude + polar species is lower than tropical species
- The width of thermoneutral zone is usually larger in high latitude + polar species
- The conductance’s of cold-adapted species are generally lower (because of good insulation)
What are the 2 forms of heat production?
- Shivering
- Non-shivering thermogenesis (NST)
What is non-shivering thermogenesis?
- Doesn’t involve muscles
- Brown fat (brown adipose tissue BAT), usually located in anterior parts of body + vital organs, is capable of very high rates of metabolism
- We don’t have brown fat (other than when a baby, in between shoulder blades)
What is hibernation?
A state of minimal activity + metabolic depression
Why do animals hibernate?
- Keeping warm in cold is energy-expensive
- Food is limiting
- Finding food is energy-expensive
What is the difference between torpor and hibernation?
- Torpor is generally shorter (often daily basis) + hibernating is a long period (months)
- Requires more energy to arouse from torpor than it does hibernation
What is nocturnal hypothermia?
Allowing body temp to drop but up to 10°C overnight
Why do larger mammals not use torpor or hibernation?
- Lower SA:V ratio, conserve body heat much better
- Lose heat relatively slowly
- Warming back up is too energetically expensive
What is regional heterothermy?
- Extremities have little/no insulation + lose heat rapidly to cold air/substrate
- blood flowing into these extremities is cooled rapidly
- if cool blood re-entered body, animal would rapidly lose heat from its core
- Some species defend core temp b allowing temp of extremities to fall
- E.g. Arctic foxes
Why do some animals arouse periodically (torpor)?
Recent evidence:
- High rates of water loss (replenish water supply)
What is an issue with allowing limb temp to drop close to freezing?
Animal fats become hard + brittle at low temps
What is used to keep leather supple at low temps?
Neatsfoot oil from hooves of cold-adapted animals
