Population Ecology

A group of organisms of the same species living in the same general area

• Population density & distribution • Life histories • Reproductive strategies • Population size • Population growth rate

The number of individuals per unit are or volume

• Count numbers in a subset & extrapolate total size • Mark & recapture

The distribution of individuals in different age-groups

• The history of a population's survival • Reproductive success • How the population relates to environment factors

Track survivorship in a population at each stage and help to determine the most vulnerable stages of the life cycle

Basically take the information from a life table to construct a graph showing average survivorship for the species throughout its life

(K-selected) low death rates during early & middle life, then increase death rates when old (humans)

Death rate is constant throughout the organisms life span (squirrels, corals)

(R-selected) high death rates for the young, few survive to adulthood, slower death rate for survivors (oysters, dandelions)

• Take immediate advantage of favorable conditions • Typically exhibit Type 3 survivorship curve • These species often produce large numbers of offspring & provide little parental care • Often weedy or pest species • r-selected

• Develop & reach sexual maturity slowly • Produce few, well-cared for offspring • Typically larger bodied and longer lived • Exhibit type 1 survivorship curve • k-selected

• exponential growth • logistic population growth

• (J curve) most often seen with r-selected species • usually occurs in an environment with unlimited resources • does not add a constant number of individuals for each time period • population reproducing at its maximum rate

• (s curve) • occurs when the growth rate decreases as the population size approaches carrying capacity • k-selected

The maximum population size that a particular environment can sustain

Usually biotic factors, these factors exert more pressure as the population becomes larger in size • caused by interactions/competition with living organisms • also risk of spreading disease

Usually abiotic factors, these factors exert the same pressure regardless of the population size • caused by environment; effects are the same whether the population is large or small

• increase populations of organisms we wish to harvest • decrease populations of pests • save populations of organisms threatened with extinction