Topic 3.1-3.5

Range of Tolerance

The limits to the abiotic conditions that a species can tolerate.

Fundamental Niche

The suite of abiotic conditions under which a species can survive, grow, and reproduce.

Realized Niche

The range of abiotic and biotic conditions under which a species actually lives.

Distribution

Areas of the world in which a species lives.

Niche Generalists

A species that can live under a wide range of abiotic or biotic conditions.

A species that is specialized to live in a specific habitat or to feed on a small group of species.

Mass Extinction

A large extinction of species in a relatively short period of time.

Population Growth Models

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.

intrinsic growth rate

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

exponential growth model

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)

J-shaped curve

The curve of the exponential growth model when graphed.

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.

S-shaped curve

The shape of the logistic growth model when graphed.

overshoot

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

die-off

A rapid decline in a population due to death.

K-selected species

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

r-selected species

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

survivorship curves

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

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.

type III survivorship curve

A pattern of survival over time in which there is low survivorship early in life with few individuals reaching adulthood.

corridors

Strips of natural habitat that connect populations.

metapopulation

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

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.

population

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

community

All of the populations of organisms within a given area.

population ecology.

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

Population size (N)

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

sex ratio

The ratio of males to females in a population.

age structure

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

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.

density-dependent factors

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

carrying capacity

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

K

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

density-independent factors

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