Ch 53 - population ecology (1 slide per page)

G some rodents and lizards iii low survival

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Unformatted text preview: es e.g. some rodents and lizards III = Low survival probability early in life, high probability for remainder of life e.g. many fish, oysters, or plants have many offspring at a time but provide no care. Figure 53.6 (Campbell 9th ed) Changes in population size can be modeled mathematically 17 B = births D = deaths I = immigration E = emigration N = population size N=B–D+I–E t = time ∆ = change in… ∆N =B–D+I–E ∆t Change in Population size over time interval t Figure 53.3 (Campbell 9th ed) 18 Can we compare B and D among populations? If 2 populations each add 2 individuals over a year did they grow at the same rate? It depends on how big the starting populations were! Pop 1: N=4 N=4+2=6 % change = 2/4 = 0.5 x 100 = +50% Pop 2: N = 20 N = 20 + 2 = 22 % change = 2/20 = 0.1 x 100 = +10% • Even though both grew by 2 over one year, their growth rate differed a lot. • So how do we compare B and D in populations of different size? • Instead of total number of births (B) and deaths (D) in the entire population, calculate the average # of births and deaths per individual (per capita) Per capita birth and death rates 19 Let: B = births D = deaths N = population size t = time b = avg # of births/ individual/ time interval = probability an individual will give birth over a time interval = aka “per capita birth rate” e.g. d = probability an individual will die over a time interval (e.g. 1 year) = ak...
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