Chapter 6

Front 1

Population

Back 1

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

Front 2

Exponential growth model

Back 2

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 numbers of reproducing individuals currently in the population (N0). The formula is:

rt

Nt=N0e

e is 2.72

Front 3

Resource partitioning

Back 3

When two species divide a resource based on differences in their behavior or morphology. Competition for a limiting resource can lead to this. In evolutionary terms, when competition reduces the ability of individuals to survive and reproduce, natural selection will favor individuals that overlap less with other species in the resources they use.

Front 4

Community

Back 4

All of the populations of organisms with area.

Front 5

Predation

Back 5

An interaction in which one animal typically kills and consumes another animal.

Front 6

Population ecology

Back 6

The study of factors that cause populations to increase or decrease.

Front 7

Logistic growth model

Back 7

A growth model that describes a population whose growth is initially exponential, but slows as the population approaches carrying capacity of the environment. Ecologists have modified the exponential growth model to incorporate environmental limits on population growth, including limiting resources.

Front 8

Population size

Back 8

The total number of individuals that belong within a defined area at a given time.

Front 9

Mutualism

Back 9

An interaction between two species that increases the chances of survival or reproduction for both species. Each species in a mutualistic interaction is ultimately assisting the other species in order to benefit itself. If the benefit is too small, the interaction will no longer be worth the cost of helping the other species.

Front 10

Population density

Back 10

The number of individuals per unit area at a given time.

Front 11

Overshoot

Back 11

When a population becomes larger than the environment's carrying capacity.

Front 12

Commensalism

Back 12

A relationship between species in which one species benefits and the other species is neither harmed nor helped. This is very common in nature. In contrast to other species interactions, commensalism has a positive effect on one species and no effect on the other species.

Front 13

Population distribution

Back 13

A description of how individuals are distributed with respect to one another.

Front 14

Die-off

Back 14

A rapid decline in a population due to death.

Front 15

Symbiotic relationship

Back 15

The relationship between two species that live in close association with each other. These kinds of relationships are all throughout the world in negative, positive, and neutral interactions.

Front 16

Sex ratio

Back 16

The ratio of males to females in a population.

Front 17

K- selected species

Back 17

A species with a low intrinsic growth rate that causes the population to increase slowly until it reaches carrying capacity.

Front 18

Keystone species

Back 18

A species that plays a far more important role in its community than its relative abundance might suggest.

Front 19

Age structure

Back 19

A description of how many individuals fit into particular age categories in a population.

Front 20

r-selected species

Back 20

A species that has a high intrinsic growth rate, which often leads to population overshoots and die-offs.

Front 21

Predator-mediated competition

Back 21

Organism who reduce abundance of a superior competitor and therefore allows inferior competitors to exist.

Front 22

Density-dependent factors

Back 22

A factor that influences an individual's probability of survival and reproduction in a manner that depends on the size of the population.

Front 23

Survivorship curves

Back 23

A graph that represents the distinct patterns of species survival as a function of age.

Front 24

Ecosystem engineers

Back 24

A keystone species that creates of maintains habitat for other species.

Front 25

Limiting resource

Back 25

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

Front 26

Ecological succession

Back 26

The predictable replacement of one group of species by another group of species over time.

Front 27

Carrying capacity ( K )

Back 27

The limit of how many individuals in a population the environment can sustain.

Front 28

Metapopulation

Back 28

A group of spatially distinct populations that are connected by occasional movements of individuals between them.

Front 29

Primary succession

Back 29

Ecological succession occurring on surfaces that are initially devoid of soil.

Front 30

Density-independent factors

Back 30

A factor that has the same effect on a individual's probability of survival and the amount of reproduction at any population size.

Front 31

Community ecology

Back 31

The study of interactions between species.

Front 32

Secondary succession

Back 32

The succession of plant life that occurs in areas that have been disturbed but have not lost their soil. It follows an event, such as a forest fire or hurricane, that removes vegetation but leaves the soil intact. It also occurs in abandoned agricultural fields.

Front 33

Growth rate

Back 33

The number of offspring an individual can produce in a given time period, minus the deaths of the individual or its offspring during the same period.

Front 34

Competition

Back 34

The struggle of individuals to obtain a shared limiting resource.

Front 35

Pioneer species

Back 35

A species that can colonize new areas rapidly and grow well in full sunshine.

Front 36

Intrinsic growth rate ( r )

Back 36

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

Front 37

Competitive exclusion principle

Back 37

The principle stating that two species competing for the same limiting resource cannot coexist. Under a given set of environmental conditions, when two species have the same realized niche, one species will perform better and will drive the other species to extinction.

Front 38

Theory of island biogeography

Back 38

A theory that demonstrates the dual importance of habitat size and distance in determining species richness.

Front 39

Biotic potential

Back 39

The ability of a population of living species to increase under ideal environmental conditions – sufficient food supply, no predators, and a lack of disease. An organism's rate of reproduction and the size of each litter are the primary determining factors for biotic potential.

Front 40

Bottom up control

Back 40

It refers to ecosystems in which the nutrient supply and productivity and type of primary producers control the ecosystem structure.

Front 41

Doubling time

Back 41

The number of years it takes a population to double.

Front 42

Environmental resistance

Back 42

The sum of the environmental factors (such as drought, mineral deficiencies, and competition) that tend to restrict the biotic potential of an organism or kind of organism and impose a limit on numerical increase.

Front 43

Top down control

Back 43

It refers to when a top predator controls the structure or population dynamics of the ecosystem.

Front 44

Climax community

Back 44

The final stage of succession, remaining relatively unchanged until destroyed by an event such as fire or human interference.