APES chapter 6 Friedland and Relyea

population

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

community

3rd level of complexity. All populations of organisms in a given area

population ecology

study of factors that cause populations to increase or decrease

population size

total number of individuals within a defined area at a given time

population density

# of individuals per unit area @ a given time

population distribution

how many individuals are distributed w/ respect to one another

sex ratio

ratio of males to females

age structure

how many individuals fit into particular age categories

density dependent factors

limiting factor that depends on population size

limiting resource

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

carrying capacity

the number of individuals that can be sustained in an area

density independent factors

Limiting factor that affects all populations in similiar ways, regardless of population size.

growth rate

# of offspring an idividual can produce in a given time period, minus the deaths

intrinsic growth rate

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

exponential growth model

model which estimates a population's future size

j-shaped

starts slowly but then accelerates as the population increases because the base size of the population is increasing.

logistic growth model

a description of idealized population growth that is slowed by limiting factors as the population size increases

s-shaped

a plot of the number of individuals against time, also known as a logistic growth: involves rapid exponential population growth followed by a steady decrease in population growth with time until the population size levels off.

overshoot

The extent to which a population exceeds the carrying capacity of its environment

die-off

A rapid decline in a population due to death.

k-selected species

Species that produce a few, often fairly large offspring but invest a great deal of time and energy to ensure that most of those offspring reach reproductive age.

r-selected species

Species that reproduce early in their life span and produce large numbers of usually small and short-lived offspring in a short period.

survivorship curves

They show the likelihood of survival at different ages throughout the lifetime of the organism.

corridors

A strip of natural habitat that connects two adjacent nature preserves to allow migration of organisms from one place to another

metapopulation

A collection of populations that have regular or intermittent gene flow between geographically separate units

community ecology

the study of how interactions between species affect community structure and organization

competition

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

competitive exclusion principle

ecological rule that states that no two species can occupy the same exact niche in the same habitat at the same time

resource partitioning

in a biological community, various populations sharing environmental resources through specialization, thereby reducing direct competition

predatation

an interaction in which one organism kills and eats another

pathogens

Microbes that cause disease

mutualism

the relation between two different species of organisms that are interdependent

commensalism

the relation between two different kinds of organisms when one receives benefits from the other without damaging it

symbiotic

mutually beneficial; supporting one another's life

keystone species

a species whose impact on its community or ecosystem are much larger and more influential than would be expected from mere abundance

predator mediated competition

Competition in which a predator is instrumental in reducing the abundance of a superior competitor, allowing inferior competitors to persist.

ecosystem engineers

species that dramatically alter their environment

ecological succession

series of changes in the species in a community, often following a disturbance

primary succession

the series of changes that occur in an area where no soil or organisms exist

secondary succession

succession on a site where an existing community has been disrupted

pioneer species

first species to populate an area during primary succession

theory of island biogeography

The number of species found on an island is determined by a balance between two factors: the immigration rate (of species new to the island) from other inhabited areas and the extinction rate (of species established on the island). The model predicts that at some point the rates of immigration and extinction will reach an equilibrium point that determines the island's average number of different species (species diversity).