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Mon. Tues. Wed. Thurs. Fri.Week ofOct. 20
Week ofOct. 27
Independent project set-up
Week ofNov. 3
Forest ecology lab – dress for weather
Exam 2T lab switch?
Week ofNov. 10
Independent project analysis
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What do we measure?
Total population size = number of indivduals
How they are arranged in space
How many are in each age or size class
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Figure 13.5
There is a simple statistical test to test for distribution
Mechanisms?
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What do we measure?
Total population size = number of indivduals
How they are arranged in space
How many are in each age or size class
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Outline
Introduction
How are populations defined and measured?
How do populations grow?
How does population size change through time and space?
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Growth = births – deaths + immigration – emigration
When calculating growth rate, usually just seeing change in numbers over time
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Populations grow by multiplication ratherthan by addition
Just like interest in the bank
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Figure 14.3
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Exponential growth
-new individuals are added (born) to population continuously
r = per capita growth rate = contribution of each individual in population
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dN/dt = rN
Rate at which individuals are added = growth
rate on a per individual basis x population size
= derivative of exponential equation
= slope of line
Exponential growth
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Figure 14.4
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Exponential vs. Geometric Growth
Exponential – continuous reproduction- growth is smooth curve
Geometric – discrete breeding seasons- calculate growth at discrete
intervals
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Geometric growth
Growth rate = = population size at one time point/ size
at previous time point
N (t+1) = N(t)
N(t) = N(0) t
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Geometric growth: N(t) = N(0) t
Exponential growth: N(t) = N(0) ert
= er
Ln = r
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Figure 14.5
Exponential
Per capita growth rate = constantRate of increase= dN/dt, increases with N
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Figure 14.6
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Age structure (# of individuals in each age class) of a population affects
population growth
Why??
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Figure 14.8
Stable Fast growth
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Age structure of a population affects population growth
Life table = a summary by age of the survivorship and fecundity of individuals in a population
Shows differences in birth and death rate for different parts of population
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Table 14.3
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Figure 14.7
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Stable age distribution – the proportion of individuals in various age classes in a population that has been growing at a constant rate
- only happens if age-specific birth and death rates are constant over time
- each age class grows at same rate
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What parameters affect growth rate?
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More common to see this patternWhat’s going on?
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Some metric of population sizeSo
me
fact
or
that
aff
ects
gro
wth
rat
eDensity dependence
Lots of examples in bookCommon in nature
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Figure 14.19
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Some metric of population sizeSo
me
fact
or
that
aff
ects
gro
wth
rat
eDensity independence
Very few examples in bookCommon in nature
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Figure 14.27
Population Size
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r = ro(1-N/K)
r = intrinsic growth rate at small N x the
reduction in growth rate due to crowding
K = carrying capacity of population
Logistic growth
R changes as N changes such that
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dN/dt = roN (1-N/K)
Change in N with time = intrinsic growth rate at
small N x population size x the reduction in
growth rate due to crowding
Logistic growth
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Figure 14.17
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Figure 14.16
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If I give you an equation and a value for K and/orr or , I expect that you can sketch the graph.
I expect that you will understand what the terms in the equations mean.
I expect that you understand the assumptions of each model and the differences between them.
I expect that you know what is in a life table and what parameters affect growth rate and what a life table can be used for.
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