Population Ecology and Interactions Vocabulary

Vocabulary terms and definitions related to population ecology, density factors, ecological methods, interactions, symbiosis, and succession from Life Sciences notes.

Population

A group of organisms of the same species which occupy the same habitat, at a particular time, and are able to produce viable offspring.

Natality

The increase in a population owing to new offspring being added to the population.

Mortality

The death of individuals in a population.

Immigration

The movement of organisms into a new area.

Emigration

The movement of organisms out of an area.

Environmental resistance

The limits on population growth determined by the carrying capacity of the environment when available resources begin to limit growth.

Density independent factors

Abiotic factors that affect population size regardless of how many individuals are in the population, such as earthquakes, droughts, and floods.

Density dependent factors

Factors that affect population size when the population reaches a certain density, causing increased competition and stress on resources like food, space, water, and shelter.

Lag phase

The initial period of population growth in a new habitat where organisms adapt, mature, and begin to reproduce slowly.

Geometric phase

The phase of rapid exponential population growth due to little or no environmental resistance; also known as the logarithmic phase.

Stationary phase

The phase of population growth where numbers level out and stabilise at the carrying capacity; also known as the equilibrium phase.

Death phase

The phase where a population decreases because the environment can no longer support it due to factors like severe drought or disease; also known as the extinction phase.

Carrying capacity

The maximum number of individuals of a species that a specific habitat can support on a sustainable basis.

Total count (census)

A direct population counting method that involves counting every individual in the population.

Mark-recapture method

An indirect method used to estimate animal population sizes by capturing, marking, releasing, and recapturing individuals.

Petersen Index

The mathematical formula $\text{N} = \frac{\text{C} \times \text{M}}{\text{R}}$ used to estimate total population size based on mark-recapture data.

Quadrat method

An indirect sampling method using a square frame to count organisms in small sample sections to estimate total population size over a given area.

Predator

An animal that hunts down living prey, kills it, and eats it.

Prey

An animal that is hunted, killed, and eaten by a predator.

Intraspecific competition

Competition between individuals of the same species for a limited resource.

Interspecific competition

Competition between individuals of different species for the same limited resources in a shared habitat.

Competitive Exclusion Principle

The ecological principle stating that two organisms cannot use the same resources in the same ecological niche and coexist indefinitely.

Resource partitioning

An evolutionary mechanism where different species in the same habitat avoid direct competition by using different resources or using resources in different ways or times.

Stratification

The vertical layering of vegetation in a forest ecosystem based on light requirements for photosynthesis.

Temporal partitioning

A form of resource partitioning where competing species hunt or utilise resources at different times of the day or night.

Symbiosis

An interdependent relationship between two different species of organisms living in close association.

Mutualism

A symbiotic relationship in which both organisms involved benefit from the interaction.

Commensalism

A symbiotic relationship in which one partner benefits and the other partner is unaffected.

Parasitism

A symbiotic relationship in which one organism benefits at the expense of another organism (the host), which is harmed.

Social organisation

A population structure where individuals live and work together to increase the survival rate of the whole group.

Ecological succession

The gradual process of change in the structure and function of ecological communities over time.

Primary succession

Ecological succession that begins in a brand-new, completely barren habitat lacking existing topsoil or vegetation.

Pioneer species

The first species, such as mosses and lichens, to colonise a barren environment during primary succession.

Climax community

A stable and mature plant and animal community that remains unchanged unless climatic conditions change.

Secondary succession

Ecological succession occurring in an area where existing vegetation was destroyed or cleared, but topsoil remains.