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Ch 53 - population ecology (1 slide per page)

G so b bn 0034 1000 34 births in total population d

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Unformatted text preview: a “per capita death rate” e.g. So: B = bN [( 0.034) (1000) = 34 births in total population] D = dN = [(0.016) (1000) = 16 deaths in total population] ∆N = B – D+ I – E ∆t ∆N = bN - dN ∆t Per capita rate of increase 20 Let: B = births D = deaths N = population size t = time ∆N =B–D ∆t Let: r=b–d = per capita rate of increase = rate of net reproduction per individual = prob an indiv. will give birth – their prob of dying When: r = 0, population size stable (ZPG) (b=d) r > 0, population is increasing in size (b>d) r < 0, population is decreasing in size (b<d) r is the per capita rate of increase whereas dN/dt is the growth rate of the population ∆N = bN - dN ∆t ∆N = (b – d)N ∆t ∆N = rN ∆t dN = rN dt Exponential growth rate Exponential Growth 21 Population growth is unrestricted Occurs when there are infinite resources and no environmental change As population size (N) gets larger the population growth rate (dN/dt) increases (i.e. the curve gets steeper) But the population growth rate depends not only on N but also on r dN/dt = rN r = per capita rate of increase = b – d dN/dt = population growth rate N = population size Figure 53.7 (Campbell 9th ed) 22 Exponential Growth Population growth rate depends on BOTH r and N dN/dt = rN So an increase in either r or N can increase the population growth rate (i.e. the growth curve gets steeper) If r is = in 2 populations, the one with the >N will grow faster...
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