Lec 15:Animal ecophysiology

Question 1

Core ideas in physiological ecology

Answer 1

Ranges of tolerance ultimately limit distribution
* Organisms are complex chemical reactions
* Reactions occur (enzymes function) best at optimum temperature and osmotic conditions, where fitness is maximized
* Many mechanisms for homeostasis have evolved to challenge hostile environments
* Maintenance of homeostasis requires energy and is often limited by constraints and tradeoffs

Question 2

Temperate animals also tolerate a wider range of temperatures than tropical animals. Why?

Answer 2

Remember:
seasonal temperature variation is low near the equator and increases with latitude

Question 3

Poikilotherms :
What are thy and how do they balance heat

Answer 3

(most reptiles, amphibians, fish, invertebrates) lack physiological means to deviate from environmental temperature (although they use behavioural means): their temperatures fluctuate

Because maintaining a constant internal temperature requires energy, poikilotherms have lower energy requirements than similarly sized homeotherms

Question 4

How do homeotherms balance heat

Answer 4

Homeotherms must regulate heat balance to keep internal temperature within a narrow range: many traits contribute

Question 5

Modes of heat gain or loss

Answer 5

• Radiation—heat transfer by electromagnetic radiation
• Conduction—transfer by direct contact with substrate (e.g., feet lose heat to ground)
• Convection—heat transfer mediated by moving fluid (usually air or water)
• Evaporation—efficient cooling from wet surfaces
• Redistribution—circulatory system redistributes heat among body parts, esp. core to appendages

Question 6

Bergmann’s rule

Answer 6

Homeotherms tend to be larger at higher latitudes (colder)

Question 7

Allen’s rule:

Answer 7

Homeotherms tend to have smaller appendages at higher, colder latitudes

Question 8

Countercurrent circulation

Answer 8

Arteries and veins should be appressed in appendages to conserve heat; separated in appendages designed to shed heat
* Countercurrent flow maintains gradient, so heat is always flowing from outgoing blood to incoming blood

Question 9

Two reasons why natural selection produces deeply imperfect organisms

Answer 9

• Trade-offs
• Being good at x may necessarily imply being bad at y
• Constraints
• Selection builds on what is already there, especially existing developmental programs
• Tinkering, yes; fundamentally fresh redesign, no

Question 10

What mechanisms of heat gain/loss do animals have?

Answer 10

Insulation
Hair and feathers can provide adjustable insulation
blubber
fur
evaporative cooling