C4.1 Populations (SL)

Vocabulary flashcards covering key terms and definitions from the C4.1 Populations lecture, suitable for exam review.

Population

A group of organisms of the same species living in the same area at the same time, capable of interbreeding.

Community

All the different populations living together in a defined area and interacting with one another.

Habitat

The abiotic (physical) environment where an organism or population normally lives.

Ecosystem

A community and its abiotic environment considered together.

Natality

The birth rate; adds new individuals to a population and increases its size.

Mortality

The death rate; removes individuals from a population and decreases its size.

Immigration

The arrival of individuals into a population from outside, increasing population size.

Emigration

The departure of individuals from a population to another area, decreasing population size.

Reproductive isolation

The lack of interbreeding between different populations of the same species, distinguishing them as separate populations.

Sampling error

The difference between an estimated population size obtained from sampling and the true population size.

Random sampling

A sampling method in which sample points are chosen randomly to avoid bias in population estimates.

Systematic sampling

A sampling method where sample points are taken at regular intervals (e.g., along a transect) to study distribution patterns.

Quadrat

A square or rectangular frame of known area used to sample sessile organisms and estimate their density or percent cover.

Sessile organism

A non-motile organism, such as many plants or attached animals, suitable for quadrat sampling.

Transect

A straight line or path along which systematic samples are taken to study changes in distribution across an environmental gradient.

Capture-mark-release-recapture

A method for estimating population size of mobile species by capturing, marking, releasing, and later recapturing individuals.

Lincoln index

The equation M × N ÷ R used with mark-recapture data to estimate population size (M=marked initially, N=total recaptured, R=marked recaptured).

Carrying capacity (K)

The maximum number of individuals of a species that an environment can sustainably support.

r-selected species

Species characterized by high growth rates, early reproduction, low survivability, and large population fluctuations around carrying capacity.

K-selected species

Species with low reproductive rates, high survivability, and stable population sizes near carrying capacity.

Density-dependent factor

An environmental factor whose effect on a population varies with population density (e.g., food shortage, predation, disease).

Negative feedback (population)

A regulatory mechanism where rising population density increases environmental resistance, slowing growth and returning size toward carrying capacity.

Predation

A biological interaction in which a predator hunts, kills, and feeds on prey, influencing both populations.

Intraspecific competition

Competition among members of the same species for limited resources such as mates, territory, or food.

Cooperation

A beneficial interaction between members of the same species, such as pack hunting or colony foraging.

Sigmoid (S-shaped) growth curve

The typical population growth pattern with exponential, transitional, and plateau phases.

Exponential growth phase

Early stage of a growth curve when natality exceeds mortality and population size rises rapidly.

Transitional phase

Middle stage of a growth curve when resource limitation increases competition and growth rate slows.

Plateau phase

Late stage of a growth curve where natality equals mortality and population size stabilizes around carrying capacity.

Abiotic factor

A non-living environmental component (e.g., light, temperature) that can influence population size.

Biotic factor

A living component (e.g., predators, pathogens) that can influence population size.

Turbidity

The cloudiness of a liquid culture; used to estimate microbial growth such as yeast population size.

Standard deviation (sampling)

A statistical measure of spread around the mean number of individuals per sample, indicating evenness of population distribution.

Predator-prey relationship

A density-dependent interaction where predator and prey population sizes oscillate in response to each other (e.g., arctic fox and snowshoe hare).