individuals, while their age, often as a proportion of maximum life span, is plotted on the x-axis. Life history strategies occur along a continuum characterized as r- and K-selection Where individual species fall on the r-K continuum is largely determined by the environment in which they live and the environment they live in is influenced by their presence and life styles McArthur & Wilson developed an elegant system for describing the stability and age distribution of natural populations known as “r/K selection” The variables r and k in r-and k-selection come from the logistic equation for population growth I = rN (K-N / K) calculates the annual growth of a population I = the annual increase for the population, r = the annual growth rate: (birth rate + immigration rate) – (death rate + emigration rate) N = the population size K = the carrying capacity: (max density at which population can exist in given environment) r-Strategist K- Strategist Habitat unstable, variable, long term stability ephemeral, unpredictable Succession early “weedy” colonists, climax community, reduced Stage good dispersal abilities dispersal abilities Population maximized, exponential; low, at equilibrium; Growth less vulnerable to extinction vulnerable to extinction Potential vs. Extinction Potential Competition variable, reduced; continual and intense, Among resources exceed demand; resources in short supply; Individuals weak competitors good competitors Life History precocial young, early altricial young, late maturity
individuals, while their age, often as a proportion of maximum life span, is plotted on the x-axis. Life history strategies occur along a continuum characterized as r- and K-selection Where individual species fall on the r-K continuum is largely determined by the environment in which they live and the environment they live in is influenced by their presence and life styles McArthur & Wilson developed an elegant system for describing the stability and age distribution of natural populations known as “r/K selection” The variables r and k in r-and k-selection come from the logistic equation for population growth I = rN (K-N / K) calculates the annual growth of a population I = the annual increase for the population, r = the annual growth rate: (birth rate + immigration rate) – (death rate + emigration rate) N = the population size K = the carrying capacity: (max density at which population can exist in given environment) r-Strategist K- Strategist Habitat unstable, variable, ephemeral, unpredictable long term stability Succession Stage early “weedy” colonists, good dispersal abilities climax community, reduced dispersal abilities Population Growth Potential vs. Extinction Potential maximized, exponential; less vulnerable to extinction low, at equilibrium; vulnerable to extinction Competition Among Individuals variable, reduced; resources exceed demand; weak competitors continual and intense, resources in short supply; good competitors Life History precocial young, early altricial young, late maturity
3330_Exam_2_Student_Review_2011.docx