chapter 4 ecology ex1

Tolerance

The ability of an organism to endure environmental variation without moving, maintaining function within a range of conditions.

Avoidance

Strategies (behavioral or physiological) to avoid unfavorable environmental conditions.

Physiological ecology

The study of how organisms interact with the physical environment to influence survival and persistence.

Potential distribution

The geographic range that could be occupied given the physical environment alone.

Actual distribution

The realized geographic range of a species, limited by factors such as dispersal, disturbance, and competition.

Limiting factor

A factor that limits a species’ distribution, survival, or reproduction (e.g., frost).

Climate envelope

The range of climatic conditions under which a species can occur.

Acclimatization

Short-term, reversible adjustments to stress through behavior or physiology.

Adaptation

Genetic changes via natural selection that make a population better suited to its environment over generations.

Ecotype

A population adapted to a unique environment.

Hypoxia

Low oxygen availability, typical at high altitude.

High-altitude adaptation

Physiological changes (e.g., increased red blood cells, larger lungs) that enable survival at high elevation.

Thermoneutral zone

The ambient temperature range within which metabolic rate is at a minimum and passive thermoregulation suffices.

Lower critical temperature

The ambient temperature below which metabolic heat production must increase to maintain body temperature.

Endotherm

An organism that primarily uses internal metabolic heat to regulate body temperature.

Ectotherm

An organism whose body temperature mainly reflects the external environment and heat exchange with it.

Homeotherm

An organism that maintains a relatively constant body temperature.

Poikilotherm

An organism whose body temperature varies with the environment.

Torpor

A short-term, dramatic reduction in metabolic rate to conserve energy.

Daily torpor

Daily bouts of torpor, typically used to reduce energy loss at night.

Hibernation

Prolonged torpor across seasons to conserve energy when resources are scarce.

Denning

A state of energy conservation with only a slight temperature decrease (e.g., bears).

Mesotherm

An organism that generates some internal heat but does not maintain a constant body temperature.

Stomata

Pores on leaf surfaces that regulate gas exchange and water loss.

Guard cells

Cells that flank stomata and control their opening and closing.

Pubescence

Hairy leaf surfaces that reduce water loss and reflect excess radiation.

Osmosis

Movement of water across a semipermeable membrane toward higher solute concentration.

Hypoosmotic

An environment with lower solute concentration than the cell, causing water to move into the cell.

Hyperosmotic

An environment with higher solute concentration than the cell, causing water to exit the cell.

Isoosmotic

Solute concentrations are equal between cell and environment; net water movement is minimal.

Isosmotic (marine organisms)

Marine organisms whose body fluids are isosmotic with seawater.

Osmotic adjustment

Physiological changes that alter solute concentrations to balance water relations under osmotic stress.

Transpiration

Water loss from plant leaves via stomata, driving water movement through the plant.

Evapotranspiration

Total water loss from a plant–environment system, combining evaporation and plant transpiration.

Water potential

The sum of osmotic, pressure, and matric potentials that drives water movement.

Osmotic potential (Psi_o)

Solute potential; negative value indicating attraction of water to solutes.

Pressure potential (Psi_p)

Pressure contribution to water potential; positive in turgid cells.

Matric potential (Psi_m)

Water potential due to water’s adhesion to surfaces (negative values in soils).</

Soil texture

The composition of soil (e.g., sand vs. clay) that affects water storage and drainage.

Sand

Coarse soil with large pore spaces and high hydraulic conductivity; stores less water than clay.

Clay

Fine soil with small pores and high water-holding capacity but low drainage.

Hydraulic conductivity

Rate at which water moves through soil or porous media.

Solar radiation (SR)

Energy from the sun that drives heat and photosynthesis.

Infrared radiation (IR)

Longwave radiation emitted by surfaces; part of heat exchange.

Latent heat transfer

Heat transfer associated with phase change of water (evaporation/condensation).

Conduction

Heat transfer through direct molecular contact between substances.

Convection

Heat transfer via moving fluids (air or water).

Energy balance

The balance between energy gained and energy lost by an organism or system.

Energy gradients

Differences in energy states that drive processes like water movement and heat exchange.