PDF Lect05 Logistic growth

PDF Lect05 Logistic growth - INSECT ECOLOGY -...

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Lecture 5, page 1 INSECT ECOLOGY -- ENTOMOLOGY/BIOLOGY 127 LECTURE 5 -- LOGISTIC GROWTH I. Population growth when resource abundance changes The two models that we discussed during the previous lecture, geometric population growth and exponential population growth , assumed that resources were unlimited. Population growth was unregulated. The models that we will consider today assume that resource abundance affects birth and death rates and consequently population growth rate changes as a function of population size => regulated population growth. II. Logistic Growth The logistic equation (Verhulst 1838, Pearl and Reed 1920) incorporates both the intrinsic capacity of a population to grow and the limitations imposed by the environment. dN N (K - N) ––– = r N(1 - –– ) = r N –––––– dt K K K carrying capacity => maximum population size that can be supported in the environment K N T i m e Population stops growing when r = 0, N = 0, N = K. K represents a stable equilibrium. However, there can be multiple equilibria; some equilibria may be unstable!
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PDF Lect05 Logistic growth - INSECT ECOLOGY -...

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