BSES 36 - POPULATION ECOLOGY

POPULATION

All the individuals of a species that live in the same geographic area and are able to interact and interbreed.

RANGE

The geographic area where a species or one of its populations can be found.

POPULATION DISTRIBUTION

The location and spacing of individuals within their range.

CLUMPED DISTRIBUTION

A distribution in which individuals are found in groups or patches within the habitat.

RANDOM DISTRIBUTION

A distribution in which individuals are spread out over the environment irregularly, with no discernible pattern.

UNIFORM DISTRIBUTION

A distribution in which individuals are spaced evenly, perhaps due to territorial behavior or mechanisms for suppressing the growth of nearby individuals.

POPULATION DYNAMICS

Changes over time in population size and composition.

MINIMUM VIABLE POPULATION

The smallest number of individuals that would still allow a population to be able to persist or grow, ensuring long-term survival.

CARRYING CAPACITY (K)

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

POPULATION DENSITY

The number of individuals per unit area.

POPULATION GROWTH RATE

The change in population size over time that takes into account the number of births and deaths as well as immigration and emigration numbers.

GROWTH FACTORS

Resources individuals need to survive and reproduce that allow a population to grow in

number.

RESISTANCE FACTORS

Things that directly (predators, disease) or indirectly (competitors) reduce population size.

BIOTIC POTENTIAL (R)

The maximum rate at which the population can grow due to births if each member of the population survives and reproduces.

EXPONENTIAL GROWTH

The kind of growth in which a population becomes proportionally larger each breeding cycle; produces a J curve when plotted over time.

LOGISTIC GROWTH

The kind of growth in which population size increases rapidly at first but then slows down as the population becomes larger; produces an S-shaped curve when plotted over

time.

DENSITY-DEPENDENT FACTORS

Factors, such as predation or disease, whose impact on a population is influenced by the

size of that population.

DENSITY-INDEPENDENT FACTORS

Factors, such as a storm or an avalanche, whose impact on a population is not related to

population size.

LIFE-HISTORY STRATEGIES

Biological characteristics of a species, such as life span and fecundity, that influence how quickly a population can potentially increase in number.

R-SELECTED SPECIES

Species that have a high biotic potential and that share other characteristics, such as short life span, early maturity, and high fecundity.

K-SELECTED SPECIES

Species that have a low biotic potential and that share characteristics such as long life span, late maturity, and low fecundity; generally show logistic population growth.

BOTTOM-UP REGULATION

Population sizes in a community are limited primarily by availability of resources that enhance growth and survival of organisms lower on the food chain.

TOP-DOWN REGULATION

Population sizes in a community are limited primarily by predation from organisms at the top of the food chain.

TROPHIC CASCADE

Top-down effects from the presence or absence of a top predator that propagate all the way down a food chain to the ecosystem’s plant communities.