Population ecology
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Population Ecology. Population Demographics. Demographics are the various characteristics of a population including, Population Size, Age Structure, Density, and Distribution Demographics allow one to determine the ecological and evolutionary relationships between various species populations.

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Population Ecology

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Population ecology

Population Ecology


Population demographics

Population Demographics

  • Demographics are the various characteristics of a population including, Population Size, Age Structure, Density, and Distribution

  • Demographics allow one to determine the ecological and evolutionary relationships between various species populations


Population size

Population Size

  • Population size is represented by the variable N

  • Peterson Population Estimating is a common method for determining Population Size (N)

  • Population Growth can be represented as either ‘exponential’ or ‘logistic’


Peterson population estimate

Peterson Population Estimate

  • The Peterson Estimate is a mark and recapture method divided into two sample periods (Precensus and Census)


Peterson estimate calculation

Peterson Estimate Calculation

  • During the Precensus, individuals are captured and marked (M)

  • During the Census, individuals are captured, some of which have marks (R) and some which do not. The total captured on the Census equals (n).

  • Peterson Estimate = (n x M) / R


Peterson estimate assumptions

Peterson Estimate Assumptions

  • Assumes that no births, death, immigration, or emigration occur during the census period

  • Assumes that mark are permanent and do not adversely effect the organism


Population growth

Population Growth

  • Factors that increase population size include ‘births’ an ‘immigration’

  • Factors that decrease population size include ‘deaths’ and ‘emigration’

  • The Net Reproductive Rate (r)

    r = [(births + immigration) – (deaths + emigration)]


Exponential growth

Exponential Growth

  • Population Growth (G)

    G = r x N

  • New Population Value (Nx)

    N1 = (r x N) + N

    N2 = (r x N1) + N1


Logistic growth

Logistic Growth

  • Population Growth (G)

    G = r x N [(K-N) / K)]

  • New Population Value (Nx)

    N1 = (r x N [(K-N) / K)]) + N

    N2 = (r x N1 [(K-N1) / K)]) + N1


Age structure

Age Structure

  • Age structure is the number of individuals in each of several to many age categories


Population density

Population Density

  • Population Density is the number of individuals in a specified area of a habitat


Population distribution

Population Distribution

  • Population Distribution is the general pattern in which individuals or a population are dispersed through a specified area

  • Clumped, Uniform, or Random


Survivorship curves

Survivorship Curves

  • Type I

  • High Survivorship until fairly late in life, then a large increase in death


Population ecology

  • Type II

  • Fairly constant death rate at all ages


Population ecology

  • Type III

  • Low survivorship early in life due to high death rate but if they reach adulthood they survive long


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