Biology B, Ch 14-Interactions in Ecosystems

density dependent limiting factors

Limiting factors (such as competition, predation, parasitism, and disease) that are affected by the number of individuals in a given area

symbiosis

a close ecological relationship between two or more organisms of different species that live in direct contact with one another

population crash

a dramatic decline in the size of a population over a very short period of time

survivorship curve

a generalized diagram showing the number of surviving members of a population over time from a measured set of births

population density

a measurement of the number of individuals living in a defined space

logistic growth

a population begins with a period of slow growth followed by a brief period of exponential growth before leveling off at a stable size; appears as an S-shaped curve

parasitism

a symbiotic relationship similar to predation--one organism benefits while the other is harmed--but a parasite keeps its host alive and a predator quickly kills and eats its prey

commensalism

a type of symbiosis in which one organism benefits while the other neither benefits nor is harmed

ecological niche

all of the abiotic and biotic factors that a species needs to survive, stay healthy, and reproduce; the role of an organism in its environment

habitat

all of the biotic and abiotic factors in the area where an organism lives

mutualism

an interspecies interaction in which both organisms benefit from the relationship

density independent limiting factors

aspects of the environment that limit a population's growth regardless of the density of the population; ex. drought, flood, unuusually hot or cold temperatures, natural disasters such as volcanoes, tornadoes, or hurricanes, or human activities that cause habitat destruction

random dispersion

individuals are spread randomly within an area or volume

uniform dispersion

individuals live at specific distances from each other because of territoriality and intraspecies competition for limited resources

clumped dispersion

individuals may live close together in groups in order to facilitate mating, gain protection, or access food resources

exponential growth

occurs when a population size increases dramatically over a period of time; appears as a J-shaped curve

ecological equivalents

species that occupy similar niches but live in different geographical regions

primary succession

the establishment and development of an ecosystem in an area that was previously uninhabited; ex. on a newly formed volcanic island or rock newly exposed by a retreating glacier

limiting factor

the factor that has the greatest effect in keeping down the size of a population; there are density-dependent and density-independent limiting factors

pioneer species

the first organisms that live in a previously uninhabited area; typical examples are lichens and some mosses, which can break down solid rock into smaller pieces

carrying capacity

the maximum number of individuals of a particular species that the environment can normally and consistently support

immigration

the movement of individuals into a population from another population

emigration

the movement of individuals out of a population and into another population

predation

the process by which one organism captures and feeds upon another organism

secondary succession

the reestablishment of a damaged ecosystem in an area where the soil was left intact; ex. after a forest fire or after a farmer has cleared land, then quit farming it

succession

the sequence of biotic changes that regenerate a damaged community or create a community in a previously uninhabited area; includes primary succession and secondary succession

competition

the struggle between organisms to survive in a habitat with limited resources

population dispersion

the way in which individuals of a population are spread in an area or volume; the three types of dispersion are clumped, uniform, and random

competitive exclusion

when two species are competing for the same resources, one species will be better suited to the niche, and the other species will be pushed into another niche or become extinct