Chapter 37: Populations

Ecology

study of the relationships among organisms and the environment.

population

consists of interbreeding organisms of one species occupying the same area at the same time.

community

includes all populations, representing multiple species, in the same region.

ecosystem

is the biotic, or living, community plus the abiotic, or nonliving, environment

biosphere

all parts of the planet where life exists

habitat

the physical location where the members of a population live.

Population density

number of individuals of a species per unit area or unit volume of a habitat.

Population distribution

describes how individuals are scattered through the habitat.
•Uniform
•Clumped
•Random

Subpopulations

separate a population, If separated for a long period of time, subpopulations may become new species.

Birth rate

number of individuals produced per unit of time.

Immigration

movement of individuals into a population

Death rate

the number of deaths per unit of time

Emigration

movement of individuals out of a population.

Survivorship curves

show the proportion of surviving individuals at each age.

Life tables

group of individuals within a population from birth to death. In the accompanying survivorship curve

type I survivorship curve

representative of species that invest much energy caring for young and have low death rates early in life. Most individuals survive to reproduce.

Type II survivorship curve

have an approximately equal probability of dying at any age.

Type III survivorship curve

representative of species that invest little energy raising their young and have high death rates among offspring. Few individuals survive to reproductive age.

population growth formula

G=rN
- G is the growth rate
- r is the per capita rate of increase
- N is the initial size of the population

Exponential growth

when its growing / death rate increases over a given time period ( J-shaped curve)

Environmental resistance

combination of factors that keeps a population from reaching its maximum growth rate. (ase as population size increases due to competition, predation)

carrying capacity

which is the maximum number of individuals that the ecosystem can support indefinitely

logistic

population size approaches the carrying capacity, the growth rate slows (s curve)

logistic growth equation

G=rN⁡((K-N)/K)
- G is the growth rate
- r is the per capita rate of increase
- N is the initial population size
- K is the carrying capacity

Density-dependent factors

result from interactions between organisms

Density-independent factors

effects that are unrelated to population density.

Life history

all of the events of an organism's life from conception through death.

opportunistic life history

short-lived, reproduce at an early age, and have many offspring that receive little care.

equilibrium life history

tend to be long-lived, mature late, and receive extended parental care.