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Population Ecology

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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  1. Population Ecology

  2. 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

  3. 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’

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

  5. 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

  6. 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

  7. 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)]

  8. Exponential Growth • Population Growth (G) G = r x N • New Population Value (Nx) N1 = (r x N) + N N2 = (r x N1) + N1

  9. 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

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

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

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

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

  14. Type II • Fairly constant death rate at all ages

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

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