Ecology 4

# Ecology 4 - Population Growth Species Interactions To...

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1 Population Growth & Species Interactions To calculate age -specific population growth specific population growth …. # expected female offspring left by a female = sum (over all ages x) of ( offspring at a given age x ) times ( probability of survival to age x ) R 0 = Σ l x m x R 0 = Σ l x m x xl x m x 0 1.0 0 5 .64 0 15 .54 0 25 .49 0.6 35 .46 0.9 45 .42 0.1 55 .35 0 R 0 = .29 +.41 +.04 = 0.74 Is this population growing?

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2 R 0 > 1 population increasing R 0 < 1 population decreasing R 0 = 1 stable (ZPG) --- IF stable age distribution Suppose R 0 = 1: # males # females X 4 3 2 1 t=0 t=1 # males # females R 0 > 1 population increasing R 0 < 1 population decreasing R 0 = 1 stable (ZPG) --- IF IF stable age distribution Suppose R 0 = 1: ? age distributions
3 Where we ’ve been ve been …. 1. Exponential population growth • no controls 2. Logistic population growth • add finite world 3. Age-specific population growth • add generation structure Logistic growth: * result of competition among members of a population What happens if competition occurs among species? if competition occurs among species? I. Mechanisms of Competition • Hutchinsonian niche… temperature fitness sunlight temperature sunlight

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4 I. Mechanisms of Competition Fundamental niche : all the hypervolume that describes space in which the organism has positive fitness fitness or resource use Niche variable : E.g, temperature, foraging height Species 1 Species 2 Niche overlap I. Mechanisms of Competition
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Ecology 4 - Population Growth Species Interactions To...

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