7_Population distribution, abundance, and dynamics_BI370

Population

A group of individuals of the same species living in the same area and interacting.

Metapopulation

A group of populations that are linked through dispersal.

Population density

The number of individuals per unit area.

Census

The total count of individuals in a population.

Clumped dispersion

Individuals aggregate in patches due to resource availability.

Uniform dispersion

Individuals are evenly spaced, often due to territoriality.

Random dispersion

The placement of individuals is independent of one another.

Endemic species

Species that occur in one location and nowhere else.

Carrying capacity

The maximum number of individuals an environment can support.

Exponential growth

A growth pattern where individuals reproduce at a constant rate, forming a J-shaped curve. Occurs when a population reaches a new area.

Logistic growth

Population growth that slows as it approaches the carrying capacity.

Density-dependent factors

Change in intensity based on population density (disease, competition, territoriality, intrinsic factors, predation)

Density-independent factors

Do not change with a population’s density (fire, storms, drought)

Trophic cascade

A series of alternating effects in an ecosystem following changes in apex predator abundance.

Demographic stochasticity

Random variations in population sizes due to survival and reproduction chance.

Environmental stochasticity

Random environmental changes that impact population dynamics.

Inbreeding

Mating between closely related individuals that increases the risk of genetic defects.

Genetic drift

Random changes in allele frequencies in a population, affecting genetic diversity.

Extinction vortex

A positive feedback loop where declining populations lead to further risks of extinction.

Dispersal

The movement of individuals from one population to another.

Source populations

Populations that provide immigrants to other populations.

Sink populations

Populations that accept immigrants.

Consensus population size

An estimate of the total number of individuals in a population.

Mark-recapture method

A technique used to estimate population size by capturing, marking, and recapturing individuals.

Colonization rate

The rate at which unoccupied patches are colonized by individuals.

Extinction rate

The rate at which populations go extinct.

Bottom-up influences

Increases in NPP will increase all trophic levels above.

Top-down influences

Factors that affect a population in alternating (±/-) starting from the top predators.

Historical factors

Past events that have influenced current species distributions.

Delayed density dependence

A lag between changes in conditions and density responses.

Genetic drift

allele frequencies in a population change due to random sampling of organisms, especially affecting small populations.