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23 Cards in this Set
- Front
- Back
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Closed population
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- No movement of individuals between population sites
- DeltaN= B-D |
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Population Growth Rate
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dN/dt=(b-d)N
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Continuous Growth
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- Time step that is infinitely small
- represented by a smooth curve |
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Birth Rate
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- # of births or deaths per unit time over a vary short time interval
- controlled by pop size |
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Death Rate
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Instantaneous birth rate
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- (b)
- births per individual per unit time - measured per capita - B=bN |
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Instantaneous Death Rate
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- (d)
- deaths per individual per unit time - D=dN |
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Instantaneous rate of increase
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r=b-d
- per capita rate of pop growth over short period of time |
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Exponential growth model (growth rate)
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- dN/dt=rN
- proportional to r: if pos pop grows - larger the pop, faster the growth |
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Instantaneous Geowth Model (population size)
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Doubling-time
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- No matter how large or small the population it will always double in size after a fixed time interval
- if pop is growing t=ln(2)/r - larger the r, shorter the doubling time |
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Non-overlapping generations
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- Seasonal reproductive events
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Discrete growth
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- Time is not continuous variable
- r*d= discrete growth factor |
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Finite rate of increase
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Lambda=1+r*d
- measured proportional change in pop from one year to the next |
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Recursion Equation
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N*t=(lambda)^t(No)
- measures discrete pop size |
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Deterministic Model
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- Outcome is determined solely by inputs, nothing is left to chance
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Environmental stochastisity
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- Good and bad years for population growth.
- extinction will result if variance=2(avg of r) |
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Demographic stochasticity
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- especially important at small pop sizes
Probability= b/(b+d) |
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Continuous Growth Model Equations
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dN/dt= B-D
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Assumptions of Exponential Growth Model
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- Population is closed
- Constant b and d - No genetic structure (no variation cause of constant b and d) - any genetic variation must be constant - No age or size structure - Continuous growth with no time lags |
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Discrete Exponential Growth Model Equations
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Continuous vs. Discrete Exponential Growth Models
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Population Size
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N=No(e^rt)
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