Animal Ecophysiology Flashcards
Physiological ecology
Physiologists study how organisms acquire
energy and nutrients and tolerate physical
conditions
* Ecologists study how organisms deal with
their environment and how the environment
limits where they live
* Physiological ecology or “ecophysiology” is
simply the study of physiology in the context
of an organism’s ecology
Core ideas in physiological ecology
Ranges of tolerance (Lectures 1 & 2) 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
Organisms as adaptive solutions
to environmental challenges
An organism’s physiology reflects the climate
and other conditions to which the organism is
adapted
* Different environments lead to different
solutions (i.e., different physiologies)
* Similar environments often lead to similar
adaptations (even in different taxa, a
phenomenon called convergent evolution)
* Example: Animals that live in cold places
tolerate colder temperatures than animals
that live in warm places
Temperate animals
tolerate a
wider range of temperatures than
tropical animals
- seasonal
temperature
variation is
low near the
equator and
increases
with latitude
Poikilotherms
(most reptiles, amphibians, fish,
invertebrates) lack physiological means to
deviate from environmental temperature
(although they use behavioural means): their
temperatures fluctuate
Homeotherms
must regulate heat balance to
keep internal temperature within a narrow range:
many traits contribute, therefore, homeotherms require more energy
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
Size matters to heat balance
Homeostasis and surface area:volume (SA:V)
ratio
* Surface area determines equilibration rate
* Volume provides the inertia
Bergmann’s rule:
Homeotherms tend to be
larger at higher latitudes (colder)
Shape matters:
Sometimes SA is needed for function
* Sometimes particular shapes are needed for
function
* Tradeoffs and adaptive compromises
Allen’s rule
Homeotherms tend to have smaller
appendages at higher, colder latitudes
Insulation
Fur
Blubber
Feathers
Convective
cooling enhanced by vascularization
Countercurrent
circulation to limbs conserves heat
* 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
Other heat loss mechanisms
Evaporation - cooling by evaporating water to cool hot air
Behavioural - finding shade
Weasel
Well suited body for warm environments, but lives in a cold region, it therefore has a fast metabolism but this is expensive since it requires more energy, but their bodies are good for hunting
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
