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Population and Community Ecology
Transcript of Population and Community Ecology
Levels of complexity
A population is composed of all individuals that belong to the same species and live in a given area at a particular time.
A community incorporates all of the populations of organisms within a given area.
The study of factors that cause populations to increase or decrease is this science.
Population Size (N)
The total number of individuals withing a defined area at a given time
The number of individuals per unit area (or volume, in the case of aquatic organisms) 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.
Number of offspring an individual can produce in a given time period, minus the deaths of the individual or its offspring during the same time period
Intrinsic Growth Rate
Under the ideal conditions with unlimited resources, every population has a particular maximum potential for growth which is called this and denoted as "R"
Exponential Growth Model
When the population's future size after some period of time has passed can be estimated.
A description of how many individuals fit into particular age categories.
Factors Influencing Population Size
Density Dependent Facotors
Influence an individual's probability of survival and reporduction in a manner that depends on the size of the population.
The limit of population growth which slows if the population size increases to much where there are not enough resources to sustain. It is also known as "K."
Density Independent factors
These factors have the same effect on an individual's probability of survival and amount of reproduction at any population size.
When a curve on a graph is shaped like a "J"
Logistic Growth Model
Logistic Growth Model
Describes a population whose growth is initially exponential but, slows as the population approaches the carrying capacity of the environment.
When the logistic growth model is graphed and creates an "S" shape.
Variations of Logistic Growth Model
If there is less resources available than needed the population will experience an overshoot by becoming larger than the carrying capacity.
A population Crash; as a result of an overshoot.
Reproductive Strategies and Survivorship Curves
Species that fall under the carrying capacity denoted as "K"; these species have certain traits in common: large organisms, reproduce later in life, produce few offspring and care for them.
Species that fall under intrinsic growth rate which is denoted to "R" species. Contrast "K" species: don't remain near their carrying capacity, small organisms, reproduce early and frequently with many offspring and no care.
Patterns plotted on a graph where there are three basic curves: labeled type I, type II, and type III
Strips of habitat that connect separated populations, provide some connectedness among the populations.
A group of spatially distinct populations that are connected by occasional movements of individuals between them.
The study of competition, predation, mutualism, and commensalism, which determine the survival of a species in a habitat.
The struggle of individuals to obtain a limiting resource
Competitive Exclusion Principle
Two species competing for the same limiting resource cannot coexist
Two species divide a resource based on differences in the species; behavior or morphology
The use of one species as a resource by another species.
Typically kill their prey and consume most of their kill.
Consume plants as prey. Typically eat only a small fraction of a plant without killing it.
Live in or on the organisms they consume, "host." Consume only small fractions of their host- rarely causes death of host.
Parasites that cause disease in their host.
Organisms that lay eggs inside other organisms. Larvae slowly consume host inside out leading to host's death.
Benefits two interacting species by increasing both species' chances of survival or reproduction.
A type of relationship in which one species benefits but the other is neither harmed nor helped
The relationship of two species that live in close association with each other.
A species that plays a role in its community that is far more important than its relative abundance might suggest
An outbreak of a species that reduces a population which are superior competitors and increases the abundance of the inferior competitors.
When a keystone species creates or maintains a habitat for other species.
Composition of a Community
The predictable replacement of one group of species by another group of species over time.
Occurs on surfaces that are initially devoid of soil.
Occurs in areas that have been disturbed but have not lost their soil.
A species ability to colonize new areas rapidly a grow well in full sunshine.
Species Richness; Habitat Size and Distance
Theory of Island Biogeography
Demonstrates the dual importance of habitat size and distance in determining species richness.
By Aleah Disney