Unit 4 Flashcards
(12 cards)
Metabolic rates
- overall rate of energy use
— can be measured as O2 consumption - effected by many factors
— ex. Body temp (chemical reactions in animal body speeds up or slow downs with changing temps)
Endotherms
Generates internal heat to maintain body temp
Ectotherms
Environment determines body temp
Homeotherm
Stable body temp (balance heat loss/gain)
Poikilotherm
Variable body temp
Maintaining optimal body temp
-ectotherms and endotherms can regulate temp through behaviour
— orienting towards/away from sun
— seeking shelter/breeze
- endotherms use behavior as first line of defense against thermal stress
— ex. Penguins huddling
Blood flow to the body affects heat exchange
-normal/cool body temp
— constriction of arterials to reduce blood flow to surface skin
-high body temp
— decrease constriction of arterioles
— vessels dilate and blood directed to skin surface
- heat loss from unexpected extremities
— ex. Toucans beak
Shivering thermogenesis
-skeletal muscles pull against each other
- ATP converted to ADP (heat is released)
Non shivering thermogenesis (heat production)
-occurs in mammals and some birds
- brown adipose tissue
— type of fat that produces heat
— cold sympathetic nervous system activates BAT
—breaks down fat and blood sugar molecules to crate heat
Heat conservation (endotherms)
- evolutionary adaptions
— large body size
— reduced extremities
-insulation
— fur and feathers trap air
Avoiding overheating
- evaporative cooling
— direct contact with water
— sweating or panting - heat windows
— rabbit ears
Endotherms vs ectotherms: which is better?
Benefits of ectotherms
- lower metabolic rates
- less time foraging
- expend little on thermoregulagion
—can invest on growth and reproduction
Costs of ectotherms
- limited ability to regulate body temp
- limits activity (duration and seasons)
- limits geographic distribution
- limits Bursts of high activity
