Lec13_2011BILD3

Lec13_2011BILD3 - Lecture 14 Population Ecology I I Density...

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Lecture 14: Population Ecology I I. Density & dispersion II. Demography - life tables III. Life histories
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Population - group of individuals of the same species that live in the same area and have a chance to mate Population is a fundamental biological unit: - biological species concept is rooted in interbreeding individuals within a population - population genetics considers how allelic variation changes as a function of different evolutionary forces - population biology considers how the size and demography of populations influence their rate of growth and persistence
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I. Density & dispersion What defines a population? density = the number of individuals per unit area How do ecologists measure density?
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How to measure density? A. Count - standardized census methods (plots, transects) B. Count sample and extrapolate C. Proxy - nests, feeding damage, tracks D. Mark - recapture
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Mark-recapture capture 1st sample of animals mark those animals, release capture 2nd sample of animals how many are marked (recaptured) paint insects bird bands fish tag
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Mark - recapture statistics N = n 1 n 2 m Say you capture and mark 10 turtles in a lake On a 2nd visit, you capture 15 turtles 5 turtles are marked N = 10*15 5 = 30 N = population size n 1 = # captured & marked n 2 - # captured in 2nd sample m - # re captured
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Patterns of dispersion random , uniform , or clumped spatial distributions What factors influence the spacing of individuals in a population? random : position of each individual is independent of other individuals
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clumped: individuals aggregate in patches - influenced by resource availability or social interactions social interactions resources resources
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uniform dispersion : individuals are evenly distributed - influenced by negative interactions such as territoriality or resource competition - aka overdispersion
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Dispersion patterns can vary, depending on the scale of observation - distribution of Clematis fremontii
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II. Demography
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