Lecture 15: Physiological Ecology Flashcards
Physiology
how organisms acquire energy
core concepts of physiological ecology
- ranges of tolerance
- organisms = complex chemical reactions
- reactions occur at optimal temperature and osmotic conditions
- many mechanisms for homeostasis have evolved to challenge hostile environments
- maintenance of homeostasis requires energy and is limited by constraints and tradeoffs
biodiversity
diversity of morphologies and behaviours (even within a species)
Organisms in similar environments have similar…
physiologies because of convergent evolution
How are an organism’s tolerance levels tested?
Scientists look at critical temperatures—the point at which the animal loses some critical function (walking, flying, etc)
Thermal tolerance breadth
number of degrees between maximum and minimum temperature organism can tolerate
Why do animals from equatorial regions have lower thermal tolerance breadth?
Temperature is largely invariable near the equator (seasonality is not really a thing because solar radiation is fairly constant).
poikilotherms
coldblooded
- lack physiological means to regulate their body temp HOWEVER they often compensate with behavioural means (basking or burrowing) ex. snakes, mole rats, frogs
homeotherms
warm blooded
- have to keep body within certain range ex. birds, mammals
Modes of heat gain or loss
- radiation
- conduction (direct contact)
- convection (heat transfer by moving fluid ex. air/water)
- evaporation
- redistribution - homeotherms tend to redistribute heat from core to appendages
Why does size matter for heat balance?
Heat can only be shed through surface area. Larger animals are better at retaining heat than smaller animals because as size increases, ratio of SA to volume decreases.
SA determines . . . . and volume provides . . . ?
- equilibration rate (to environment)
- inertia
Bergmann’s rule
homeotherms tend to be larger at higher latitudes where it’s colder
ex. bears, woodrats, elephants (they’re huge but still smaller than wooly mammoths were)
Animal with maximum SA to volume ratio
Chrysopelen gliding snake (found in warm tropics)
- COMPLETELY flat, looks like a ribbon
Animal with minimum SA to volume ratio
American Pika (found high in mountains) - basically a ball of fur with tiny ears