An organism’s adjustment of its physiology, morphology, or behavior to lessen the effect of an environmental change and minimize the associated stress.
adaptation
A physiological, morphological, or behavioral trait with an underlying genetic basis that enhances the survival and reproduction of its bearers in their environment.
avoidance
A response of an organism to stressful environmental conditions that lessens their effect through some behavior or physiological activity that minimizes exposure to the stress. Compare tolerance.
boundary layer
A zone close to a surface where a flow of fluid, usually air, encounters resistance and becomes turbulent.
cavitation
A disruption of the water column in the xylem of a plant that can occur under dry conditions when high tension (negative pressure potential) on the water in the xylem pulls air into it, or following freezing of water in the xylem, and coalescence of air bubbles when the ice melts.
ecotype
A population with adaptations to a unique environment.
ectotherm
An animal that regulates its body temperature primarily through energy exchange with its external environment. Compare endotherm.
endotherm
An animal that regulates its body temperature primarily through internal metabolic heat generation. Compare ectotherm.
geographic range
The entire geographic region over which a species is found.
gravitational potential
The energy associated with gravity.
lower critical temperature
The environmental temperature at which the heat loss of an endotherm is greater than its basal metabolic heat production, so that its body temperature begins to drop, triggering an increase in metabolic heat generation.
matric potential
The energy associated with attractive forces on the surfaces of large molecules inside cells or on the surfaces of soil particles.
osmotic adjustment
An acclimatization response to changing water availability in terrestrial and aquatic environments that involves changing the solute concentration, and thus the osmotic potential, of the cell.
osmotic potential
The energy associated with dissolved solutes.
pressure potential
The energy associated with the exertion of pressure.
pubescence
The presence of hairs on the surface of an organism.
resistance
The influence of a barrier on the movement of compounds such as water or CO2.
stomate
A pore in plant tissues, usually leaves, surrounded by specialized guard cells that control its opening and closing.
stress
An abiotic factor that results in a decrease in the rate of an important physiological process, thereby lowering the potential for an organism’s survival, growth, or reproduction.
thermoneutral zone
The range of environmental temperatures over which endotherms maintain a constant resting metabolic rate.
tolerance
The ability to survive stressful environmental conditions. Compare avoidance.
torpor
A state of dormancy in which endotherms drop their lower critical temperature and associated metabolic rate.
turgor pressure
Hydrostatic pressure that develops in a plant cell when water moves into it, following a gradient in water potential.
water potential
The overall energy status of water in a system; the sum of osmotic potential, gravitational potential, and matric potential.
