Population Ecology

These flashcards cover fundamental concepts of population ecology, including definitions, sampling methods, growth patterns, survivorship curves, and regulation mechanisms.

Population

All the organisms belonging to the same species that live within a designated area and can interact, breed, and have offspring.

Population Density

The number of individuals per unit area or volume, expressed as $n/\text{unit area}$.

Mark-recapture method

A sampling technique where individuals are trapped, marked with a tag, released, and later recaptured to estimate total population size.

Active Sampling

A method where a researcher actively looks for organisms, such as using netting for insects or drag nets in water.

Quadrat

A square that encases an area within a habitat, typically used to sample plant species or slow-moving animal species.

Transect sampling

A method of collecting data by moving along a straight line through an area and recording observations.

Passive Sampling

A method where traps, such as mist nets, drift nets, or pitfall traps, are set to catch organisms.

Pitfall traps

Containers buried in the ground to catch small animals such as insects, spiders, amphibians, and reptiles.

Notching

A marking method where a notch is made on the scute or shell of some reptiles.

Immigration

The influx of new individuals into a population from other areas.

Emigration

The movement of individuals out of a population.

Dispersion

The pattern of spacing among individuals within the geographic boundaries of a population.

Random dispersion

A pattern where the position of each individual is independent of others and spacing is unpredictable, occurring in the absence of strong attraction or repulsion.

Clumped dispersion

A pattern where individuals aggregate in patches, often influenced by soil conditions, microenvironments, or mating interactions.

Uniform dispersion

A pattern where individuals are evenly spaced, often resulting from territoriality or chemical inhibition of competitors.

Biotic potential

The unrestricted growth of a population where every member survives and produces offspring, resulting in maximum growth.

Resistance factors

Also called limiting factors, these are things that directly or indirectly reduce population size, such as predators, disease, or competition.

Density-dependent limiting factors

Factors that alter population growth based on the density of the population, usually biotic in nature, such as waste accumulation or invasive species.

Interspecific competition

Competition that occurs between members of different species.

Intraspecific competition

Competition between organisms of the same species.

Density-independent limiting factors

Abiotic factors, such as natural disasters, fires, or pollution, that affect population growth rate regardless of the population's density.

Exponential growth

Growth characterized by a $J$-shaped curve where the rate increases over time because of unlimited resources and no environmental limitations.

Logistic growth

Growth characterized by an $S$-shaped curve where resources are limited and growth rate decreases as the population approaches carrying capacity.

Carrying Capacity ($K$)

The maximum population size that a particular environment can support indefinitely.

Minimum Viable Population ($MVP$)

The smallest population size at which a population can exist without facing extinction due to inbreeding, disasters, or limiting factors.

Cyclical oscillations

Regular cycles of population increase (boom) and decrease (bust) typically driven by species interactions or density-dependent factors.

Demography

The study of vital statistics of populations, particularly birth rates and death rates, and how they change over time.

Type I Survivorship Curve

A curve reflecting low death rates in early and middle life with a steep drop in older age groups, typical of humans and large mammals.

Type II Survivorship Curve

A curve reflecting constant mortality over an organism's life span, seen in rodents and some invertebrates.

Type III Survivorship Curve

A curve reflecting very high death rates early in life followed by a flattening for the few survivors, typical of organisms that provide little parental care.

$K$-selected species

Niche specialists adapted to stable environments that mature later, produce fewer offspring, and provide high levels of parental care.

$r$-selected species

Niche generalists adapted to changing environments that mature quickly, produce many offspring, and provide little parental care.

Top-down regulation

The control of population size due to pressures from the top trophic level, such as predation and natural disasters.

Bottom-up regulation

The control of population size due to factors at the bottom of a trophic pyramid, such as nutrients, water, sunlight, and habitat.