Understanding Population Growth: Multiplication and Exponential Rates, Slides of Ecology and Environment

Download Understanding Population Growth: Multiplication and Exponential Rates and more Slides Ecology and Environment in PDF only on Docsity! Lecture 9: Population Growth and Regulation Docsity.com Concepts • 9.1 Population grow by multiplication rather than addition • 9.2 Age structure influences population rate • 9.3 A life table summaries age-specific schedules of survival and fecundity • 9.4 The intrinsic rate of increase can be estimated from the life table • 9.5 Population size is regulated by density- dependent factors Docsity.com Geometric growth curve: N(0)=100, λ=1.5 (a): y on a arithmetic scale; (b) y on a logarithmic scale. Docsity.com Exponential growth • Nt=N0exp(rt) • Where r is the exponential growth rate • Compare to N(t)=N(0) λt • λ=exp(r) or r=ln(λ) • These models are used to describe dynamics of populations. Geometric growth is used for population generations not overlap (discrete time interval), exponential growth model is for continuous population. Docsity.com Population size change and model parameter Increasing population, λ>1, r>0 Constant pop. Size, λ=1, r=0 Decreasing population, 0<λ<1, r<0 Docsity.com r determines the shape of the growth. r=0, no change in population size r<0, decrease in population size; r>0, increase in population size. Properties of exponential growth Widely used in biology Docsity.com Nt=N0Exp(rt) Give a time t, we can predict the population size. An Example: Deer population: N0=300, r=0.5, after 5 years, what’s the population size? N5=N0 Exp(rt)=300*exp(0.5*5)=3655 (495, 815, 1344, 2216, 3655) t=10, ? Prediction of population growth 44,524 Docsity.com