Lecture28_PopBioI - r r = per capita birth rate per capita...

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Population Ecology I I. Introduction: What is population ecology? What is a population? A population is a group of individuals from the same species that live in the same area at the same time • interbreed on a • exposed to similar environment • interact via II. Basic models of population growth Question: How do biologists describe changes in population size? Answer: Use Consider whooping cranes How fast is the whooping crane population growing? • reduced to 16; now total (1/07) currently in Wood Buffalo Nat'l Park flock • breed once per year this year and last year … calculate growth rate as • like interest on a bank account, compounded • next: generalize these ideas
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II. Basic models of population growth let N 0 = pop size at start let N 1 = pop size one breeding interval later then lambda is the finite rate of increase In the whooping crane example, λ = What is λ if N 1 = 210? What is λ if N 1 = 237? Note that N 1 = N 0 λ In general, N t = How can we express population growth on a per capita (per individual) basis? Symbolize per capita growth rate as
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Unformatted text preview: r r = per capita birth rate - per capita death rate r is the instantaneous rate of increase; like interest compounded λ = e r e.g. for whooping cranes, r = N t = NOTE: λ describes discrete growth; r describes N t = N e rt Consider whooping cranes again If 16 alive in 1941 and 518 in 2007, what is r ? N t = ; N = ; t = years; r = Exponential growth Density-dependent growth Carrying capacity = maximum, sustainable population size that can be supported in a particular environment III. Case studies in population growth A. Density dependent growth What density-dependent factor constrains growth? H 1 : H 2 : H 3 : How to test these hypotheses? B. Population cycles Lynx and snowshoe hare show What drives the hare cycle? H 1 : Food shortages are responsible H 2 : Predation by lynx is responsible Test: Large study plots in similar habitat with • hare • lynx • food Several replicates each type of plot Results: Conclude: Why?...
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