The individuals that belong to the same species and live in a given area at a particular time.
All the populations of organisms within a given area.
The study of the factors that cause populations to increase or decrease.
Population size (N)
The total number of individuals within a defined area at a given time.
The total number of individuals per unit area at a given time.
A description of how individuals are distributed with respect to one another.
The ratio of males to females in a population.
A description of how many individuals fit into a particular age categories in a population.
A resource that a population cannot live without and that occurs in quantities lower than the population would require to increase in size.
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 (K)
The limit of how many individuals in a population the environment can sustain.
A factor that has the same effect on an individual's probability of survival and the amount of reproduction at any population size.
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 death of the individual or its offspring during the same period.
Intrinsic growth rate (r)
The maximum potential for growth of a population under the ideal conditions with unlimited resources.
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).
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.
The shape of the logistic growth model when graphed.
When a population becomes larger than the environment's carrying capacity.
A rapid decline in a population due to death.
A species with a low intrinsic growth rate that causes the population to increase slowly until it reaches carrying capacity.
A species that has a high intrinsic growth rate, which often leads to population overshoots and die-offs.
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.
Strips of natural habitat that connect populations.
A group of spatially distinct populations that are connected by occasional movements of individuals between them.
When individuals with similar genotypes - typically relatives - breed with each other and produce offspring that have an impaired ability to survive and reproduce.
The study of interactions between species.
The relationship between two species that live in close association with each other.
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.
When two species divide a resource based on differences on their behavior or morphology.
An interaction in which one animal typically kills and consumes another animal.
A specialized type of predator that lays eggs inside other organisms - referred to as its host.
An interaction in which one organism lives on or in another organism.
A parasite that causes disease in its host.
An interaction in which an animal consumes a producer.
An interaction between two species that increases the chances of survival or reproduction for both species.
A relationship between species in which one species benefits and the other species is neither harmed or helped.
A species that plays a far more important role in its community than its relative abundance might suggest.
A keystone species that creates or maintains habitat for other species.
The predictable replacement of one group of species by another group of species over time.
Ecological succession occurring on surfaces that are initially devoid of soil.
The succession of plant life that occurs in areas that have been disturbed but have not lost their soil.
A species that can colonize new areas rapidly and grow well in the future.
Theory of island biogeography
A theory that demonstrates the dual importance of habitat size and distance in determining species richness.
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