W09_L6_Population+Dynamics

W09_L6_Population+Dynamics - Alyssa Andersen I have a...

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Alyssa Andersen I have a problem • What fraction of you log in with a Clicker? – How many clickers? • Easy. PRS reports this. – How many people in the room? • hmmmmmm How many people are in the room? 1. ______ 2. ______ 3. ______ 4. ______ 5. ______ • What we know: – Marked Individuals (n1): – Recaptured individuals (n2): – Number of recapture individuals who were previously ‘marked’ (m2): • What we want to know: – How many in the room (N): Mark / Recapture Assumptions • ____________ • ____________ • ____________ • ____________ What about estimating abundance here? Would mark—recapture methods be useful?
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Population Growth and Demography MATH AHEAD Some population concepts Ramets – genetically identical individuals (clones) Genets genetically distinct individuals, produced by sexual reproduction. Population – individuals of the same species occupying a defined location at a defined time Population density – number of individuals per unit area. Metapopulation – a population of populations – a collection of spatially separated populations that interact with each other. Metapopulation A SIMPLE model of population growth •Open population - numbers change due to immigration and emigration from outside the population in addition to births and deaths •Closed population - numbers change only due to births and deaths N t + B B = # births N t+1 = N = population size t = time –D D = # deaths + I I = # immigrants –E E = # emigrants In one location, i.e., a local but open population N t+1 = N t + B - D Two types of population growth Exponential or geometric: the per-capita growth rate is constant or density independent Logistic (asymptotic or sigmoidal): the per-capita growth rate varies with population density or is density dependent Exponential Logistic Time Population Size
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Density-independent population growth in a closed population N (t+1) = N (t) + b . N (t) -d . N (t) B = bN (t) ; D = dN (t) N/ t = (b-d)N Let b = birth rate per individual (# births per individual per unit time) Let d = death rate per individual (# dying per individual per unit time) N (t+1) -N t = (b-d)N t dN/dt = (b-d)N (as time --> 0) N t+1 = N t + B – D + I – E This is a continuous time expression: works if organisms reproduce continuously (overlapping generations) dN/dt = rN b-d = (birth rate - death rate) = the instantaneous rate of increase**** Note that rate implies a time step .
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This note was uploaded on 10/08/2009 for the course BIS 2 taught by Professor Schwartzandkeen during the Spring '09 term at UC Davis.

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W09_L6_Population+Dynamics - Alyssa Andersen I have a...

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