Friedland, Environmental Science for AP, 2e, Chapter 6

Age structure

A description of how many individuals fit into particular age categories in a population.

Carrying capacity (K?)

The limit of how many individuals in a -population the environment can sustain.

Commensalism

A relationship between species in which one species benefits and the other species is neither harmed nor helped.

Community

All of the populations of organisms within a given area.

Community ecology

The study of interactions between species.

Competition

The struggle of individuals to obtain a shared limiting resource.

Competitive exclusion principle

The principle stating that two species competing for the same limiting resource cannot coexist.

Corridor

Strips of natural habitat that connect populations.

Density-dependent factor

A factor that influences an individual's probability of survival and reproduction in a manner that depends on the size of the population.

Density-independent factor

A factor that has the same effect on an individual's probability of survival and the amount of reproduction at any population size.

Die-off

A rapid decline in a population due to death.

Ecological succession

The predictable replacement of one group of species by another group of species over time.

Ecosystem engineer

A keystone species that creates or maintains habitat for other species.

Exponential growth model (Nt = N0ert?)

A growth model that estimates a population's future size (Nt?) after a period of time (t?), based on the intrinsic growth rate (r?) and the number of reproducing individuals currently in the population (N0?).

Herbivory

An interaction in which an animal consumes a producer.

Inbreeding depression

When individuals with similar genotypes—typically relatives—breed with each other and produce offspring that have an impaired ability to survive and reproduce.

Intrinsic growth rate (r)

The maximum potential for growth of a population under ideal conditions with unlimited resources.

J-shaped curve

The curve of the exponential growth model when graphed.

K-selected species

A species with a low intrinsic growth rate that causes the population to increase slowly until it reaches carrying capacity.

Keystone species

A species that plays a far more important in its community than its relative abundance might suggest.

Limiting resource

A resource that a population cannot live without and that occurs in quantities lower than the population would require to increase in size.

Logistic growth model

A growth model that describes a -population whose growth is initially exponential, but slows as the population --approaches the carrying capacity of the environment.

Metapopulation

A group of spatially distinct populations that are connected by occasional movements of individuals between them.

Mutualism

An interaction between two species that increases the chances of survival or reproduction for both species.

Overshoot

When a population becomes larger than the environment's carrying capacity.

Parasitism

An interaction in which one organism lives on or in another organism.

Parasitoid

A specialized type of predator that lays eggs inside other organisms—referred to as its host.

Pathogen

Parasites that cause disease in their host.

Pioneer species

A species that can colonize new areas rapidly and grow well in full sunshine.

Population

The individuals that belong to the same species and live in a given area at a particular time.

Population density

The number of individuals per unit area at a given time.

Population distribution

A description of how -individuals are distributed with respect to one another.

Population ecology

The study of factors that cause populations to increase or decrease.

Population growth model

Mathematical -equations that can be used to predict population size at any -moment in time.

Population growth rate

The number of offspring an individual can produce in a given time period, minus the deaths of the individual or its offspring during the same period.

Population size (N?)

The total number of individuals within a -defined area at a given time.

Predation

An interaction in which one animal typically kills and consumes another animal.

Primary succession

Ecological succession occurring on surfaces that are initially devoid of soil.

r-selected species

A species that has a high intrinsic growth rate, which often leads to population overshoots and die-offs.

Resource partitioning

When two species divide a resource based on differences in their behavior or morphology.

S-shaped curve

The shape of the logistic growth model when graphed.

Secondary succession

The succession of plant life that occurs in areas that have been disturbed but have not lost their soil.

Sex ratio

The ratio of males to females in a population.

Survivorship curve

A graph that represents the distinct patterns of species survival as a function of age.

Symbiotic relationship

The relationship between two species that live in close association with each other.

Theory of island biogeography

A theory that demonstrates the dual importance of habitat size and distance in determining species richness.

Type I survivorship curve

A pattern of survival over time in which there is high survival throughout most of the life span, but then individuals start to die in large numbers as they approach old age.

Type II survivorship curve

A pattern of survival over time in which there is a relatively constant decline in survivorship throughout most of the life span.