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Population Ecology

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Population Ecology

- 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 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’

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

- 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

- 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

- 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)]

- Population Growth (G)
G = r x N

- New Population Value (Nx)
N1 = (r x N) + N

N2 = (r x N1) + N1

- 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 is the number of individuals in each of several to many age categories

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

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

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

- Type II
- Fairly constant death rate at all ages

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