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## Population Ecology

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**The branches of ecology**Population statics Density Distribution Population dynamics Natality Mortality Survivorship curves Life history strategy Age structures Population models Exponential growth Logistic growth The human population Population Ecology**Almost every population distribution in nature is clumped.**Life history strategies are a series of tradeoffs that maximize the net reproductive rate. Exponential growth is growth at a constant rate, and therefore is rare. Human populations increase as they move through the demographic transition. Human total fertility is falling. Good or bad news? Major Ideas**Exponential Growth**Growth rate (r), or rate of change of a population on a per capita basis, is the birth rate minus the death rate: r = b − d The instantaneous growth rate, dN/dt, can be expressed as: dN/dt = rN**From Exponential to Logistic**dN/dt = rN The logistic equation takes into account the carrying capacity of the environment: dN/dt = rN [(K − N)/K] The element [(K − N)/K] reflects decline in growth as population size approaches its carrying capacity**Logistic Growth Curve**Carrying capacity of the environment (K) Number of individuals (N) Time