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Ch 53 - population ecology (1 slide per page)

# 7 campbell 9th ed 25 logistic growth exponential

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Unformatted text preview: If N is = in 2 populations, the one with the greater r will grow faster Figure 53.7 (Campbell 9th ed) 25 Logistic Growth Exponential growth is unrealistic since resources are not unlimited! • More individuals means less resources per individual • At some N there is not enough resources for individuals to live. • The max pop size that the environment can support = carrying capacity (K) Carrying capacity (K) is a specific population size!!! As N approaches K, pop growth rate slows down • Fewer resources/ ind = < healthy thus: > deaths < births When N reaches K, pop growth stops (dN/dt = 0) Figure 53.9 (Campbell 9th ed) 26 Logistic vs Exponential Growth Exponential: The larger N, the faster the population grows (i.e. dN/dt increases) Logistic - At low N, like exponential, population growth rate increases as N increases; - BUT as N approaches carrying capacity (K) the growth rate slows down; - Once N reaches K, the population stops growing (i.e. growth rate (dN/dt = 0) Logistic growth can be modeled mathematically Logistic growth = Exponential growth + an extra term (K N) dN rN dt K Figure 53.9 (Campbell 9th ed) 31 The Logistic Model is Density Dependent density-dependent - birth & death rates change with density due to variety of biotic / abiotic factors Competition for food, water, space, light, mates etc can increase with increasing N 32 The Logistic Model is Density Dependent density-dependent - birth & death rates change with density due to variety of biotic / abiotic factors Disease prevalence can increase with increasing N 33 • Density-independent factors can alsoenvironment alter birth and death ratesgrowth affect population (& thus λ or r) Changes in the w/o regard to – population alter density-independenttheFactors thatsize birth & death rates regardless of N (e.g. high/low temp, heavy rain, drought, fire, wind, toxin) (usually abiotic but…) 43 SKIP • Logistic growth: Know what logistic growth is and how it differs from exponential growth but do not need to know the model. • Table 53.3 • Section 53.4 (1179-1181) • Figure 53.15 (1182) • Population Dynamics and Figures 53.18 – 53.21 (1185-1187) • The Global Human Population and Figure 53.23 (1187-1188) • Infant mortality and Figure 53.25 (1189) • Global carrying Capacity and Figure 53.26 (1190-1191) 45 NEXT Chapter 54: Community Ecology...
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