Exotics thermoregulation SDL Flashcards
Define homeotherm
organism that maintains its body temp at a constant level by its metabolic activity
e.g., birds and mammals
Define poikilotherm
Organism that cannot regulate its body temp except by behavioural means
e.g., snakes, frogs
What are the advantages and disadvantages of homeotherms
Advantages:
- can regulate own body temp
- efficient body use
- more efficient enzyme activity as they function in specific temp range
Disadvantages:
- cannot survive in extreme temps
What are the pros and cons of poikilotherms
Pros:
- dont use energy to maintain temp
- dont need to feed each day as energy is not used in temp regulation
Cons:
- rely heavily on external temp to survive
What is normal bird temp?
39-43 degrees
Why is normal temp of birds and rabbits higher than others?
higher metabolic rate
more activity
What is metachromatism?
colour change of reptiles
How can metachromatism be used in thermoregulation?
by becoming a darker colour when cold => retain more heat
Becoming lighter => skin reflect light to prevent overheating
What cells in lizard skin enable them to use metachromatism in thermoregulation?
melanophores (contain melanin)
Describe the behavioural adaptations used by frogs to prevent freezing in cold weather
seek insulated hiding spots
may bury themselves in mud
Describe the physiological adaptations of frogs to prevent freezing in cold weather
Produce anti-freeze like compounds e.g., glucose, urea which lowers the freezing point of their bodily fluids preventing ice formation within their cells
What strategies do birds use to lose heat in hot weather?
Extending wings
elevate scapula feather to expose skin at back of neck
Shade seeking
Bathing
Why do birds have poor tolerance for high temps?
no sweat glands
Why do birds rely on behavioural adaptations to stay warm?
no brown adipose fat (used to burn calories to produce heat)
What strategies do birds use to conserve heat in cold weather?
Fluffing feathers to create insulating layer of air
Tucking legs and bill into feather to minimise exposed surface area
Roosting together to share body heat
Sunbathing
Shivering
Reduce metabolic rate
Find sheltered microhabitats such as tree cavities
Feather preening (well maintained feather provide better insulation)
Describe the cardiovascular adaptations of birds for thermoregulation
In heat:
- can shunt blood away from left ventricle to legs to aid heat loss
In cold - countercurrent heat exchange in aquatic and wading birds:
- cold blood flowing up from foot cools blood flowing towards foot
- warm blood flowing down to feet warm up cold blood travelling up
- decreases temp gradient between water and arriving blood so heat exchange is slower
Describe the respiratory strategies for thermoregulation in birds
Birds can lose heat by
- evaporation and dissipation from oral mucosa by thermal panting and gular fluttering
- dissipation of heat via air sacs when running and flying
What is non-shivering thermogenesis?
increase in metabolic heat production not association with muscle activity
Why are small mammals prone to heat stress?
large surface area:volume ration => heat is lost quickly
What behavioural strategies do small mammas use to thermoregulate
adjust activity patterns e.g., active during cool times, sleep when its hot
Burrowing to preserve heat in the cold or find shady spot when its too hot
Changes in thickness of fur coat
Describe cardiovascular adaptations of small mammals for thermoregulation
Vasoconstriction and vasodilation
ateriovenous shunting
countercurrent exchange
In tails, ears, face, paws
What is the response to low temps by hamsters?
Enter torpor (state of physical inactivity/temporary hibernation)
Decreases metabolic rate, hypothermia, bradycardia, bradypnoea
