APES Chapter 6 (Unit 1)

individual

individual

a single organism

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.

ecosystem

all biotic and abiotic factors in an area

biosphere

Consists of all life on Earth and all parts of the Earth in which life exists, including land, water, and the atmosphere.

density dependent factors

A limiting factor of a population wherein large, dense populations are more strongly affected than small, less crowded ones.

density-independent factors

limiting factor that affects all populations in similar ways, regardless of population size

overshoot

when a population becomes larger than the environment's carrying capacity

dieoff/dieback

a rapid decline in a population due to death

negative feedback loop

dampens or buffers changes; this tends to bring the system to its equilibrium state, making it more stable.

positive feedback loop

enhances or amplifies changes; this tends to move a system away from its equilibrium state making it more unstable.

LD50

the point at which 50 percent of the test organisms die from a toxin.

exponetial population growth

when the size of each generations offspring is larger than the generation before it

logistic population growth

population growth that levels off as population size approaches carrying capacity

metapopulations

a group of spatially distinct populations that are connected by the occasional movements of individuals between them

population size

the number of individuals in a population

corridors

a strip of natural habitat that connects separated populations

population density

Number of individuals per unit area

population dispersion

the way in which individuals of a population are spread out over an area or volume

population distribution

a description of how individuals are distributed with respect to one another

population sex ratio

the ratio of males to females in a population

population age structure

Determines future growth potential (via individuals of reproductive age)

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.

K-selected species characteristics

large, long lives, few offspring, slow reproductive speed, type I, and parental care

r-selected species characteristics

small, short lives, many offspring, fast reproductive speed, type III, land little parental care

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 suvivorship curve

a pattern of low survivorship throughout the individuals life, few reach adulthood

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

The division of environmental resources by coexisting species such that the niche of each species differs by one or more significant factors from the niches of all coexisting species

predators

animals that kill and eat other animals; eating most of what they kill

Herbivores

Consumers that eat only plants

Parasites

An organism that lives in or on another organism, deriving nourishment at the expense of its host

predation

the use of one species as a resource by another species

keystone species

a species on which other species in an ecosystem largely depend, such that if it were removed, the ecosystem would change drastically.

ecological succession

series of gradual changes that occur in a community following a disturbance

calculating exponential growth

N(0)e^(rt)

Mutualism

A relationship between two species in which both species benefit

Commensalism

A relationship between two organisms in which one organism benefits and the other is unaffected

symbiotic relationship

the relationship of two species that live in close association with each other

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

a keystone species that creates or maintains habitat for other species

primary succession

An ecological succession that begins in an area where no biotic community previously existed. Areas devoid of soil (rocks), break up over time forming soil.

secondary succession

Succession follows a disturbance that destroys a community without destroying the soil. (climax community)

pioneer species

First species to populate an area during primary succession

island biogeography

The study of rates of colonization and extinction of species on islands or other isolated areas based on size, shape, and distance from other inhabited regions

Climax community

An ecological community in which populations of plants or animals remain stable and exist in balance with each other and their environment.

carrying capacity

The largest number of individuals in a population that an environment can support with its available resources