LECTURE 9 CH 9 ADAPTATION TO LIFE IN VARYING ENVIRONMENTS
Temporal and spatial heterogeneity
Biological activity relates to varying environmental conditions
Possible responses to heterogeneity
1) Avoid variable environment
A) Change in activity space or time
Select microhabitats to optimize energy budgets
B) Migrate
C) Store resources during favorable conditions
D) Dormancy
2)Alter environment so it is favorable
3) Change phenotype to better match environment
Phenotype = genotype + environment
Vary phenotype if environment changes
Phenotypic plasticity
Environmentally-induced variation in phenotype
An evolved trait
May differ among populations
Phenotypic responses to a variable environment
a) Acclimation
Short-term change (reversible) shift in range of physiological tolerances
Involves changes in enzyme structure
Critical (lethal) temperature depends on acclimation temperature
No acclimation if no range in environment conditions
b) Acclimitization
Change in response to seasonal (predictable) environmental change
c) Developmental response (non-reversible) to persistent variation in environmt.
Response to varying environment during growth
4) Regulation (homeostasis)
Maintain steady conditions against an external gradient
Regulators vs. conformers
Endotherms vs. ectotherms
Advantages/ disadvantages of regulation
Homeostasis is energetically expensive; but allows optimal use of enzymes
Partial homeostasis: reset internal temperature control while in torpor
Food supplies
Vary in space and in time
Optimal foraging theory: costs/benefits
When, where, how long, what: choices to make about feeding
Central place foraging: animals tied to particular place
Risk-sensitive foraging: value of feeding area reduced by risks (e.g. predation)
Prey choice
Prey quality varies
Consume a mixed diet
Complementarity of amino acids
Avoid large doses of plant toxins