Population Ecology

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Population Ecology
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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 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

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Peterson Population Estimate

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

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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

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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

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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)

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Exponential Growth

• Population Growth (G)
• G r x N
• New Population Value (Nx)
• N1 (r x N) N
• N2 (r x N1) N1

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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

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Age Structure

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

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Population Density

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

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Population Distribution

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

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Survivorship Curves

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

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• Type II
• Fairly constant death rate at all ages

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