Population Ecology

53.4-53.5Population EcologyLife HistoryNatural selection produces some traits that favor a populations ability to survive and reproduceVariables include:When reproduction begins (age at first reproduction or age at maturity)How often an organism reproducesHow many offspring are produced per reproductive episodeOrganisms do not consciously choose when or how many offspring to haveExcept humans more on that in 53.6

Life History K-selectionDensity-dependentFavored at high density areas where populations are at or near carrying capacity (K) and face a lot of competitionHave late reproduction, few offspring, parents invest in raising offspringEx: primates, elephants

Life HistoryR-selectionDensity-independentFavored in low density areasMaximizes r (per capita rate of increase) in areas well below carrying capacity with little competitionHave early reproduction, many offspring, little parental careEx: insects, many plants

Limiting FactorsEnvironmental factors prevent exponential growth

Population LimitationsDensity Dependent FactorsLimitations due to the size of populationDeath rate rises as population density risesDensity Independent FactorsLimitations with no relationship to population sizeBirth or death rate does not change with population density

Density DependentCompetitionTerritorialityPredationDiseaseToxic wasteIntrinsic factors

Density IndependentNatural DisastersTornado, Hurricane, Fire, Volcano, etc.

Population Dynamics

Populations of different species tend to cycle with each otherExample: hare and lynx