BSCI 106
Outline #4
Fall 2009
Dr. Via
Population Growth
A.
Levels in Ecology
1. Individual organisms:
_____________ ecology
2. Populations of interacting individuals: ______________ ecology
Q:
where does behavioral
3. Communities of interacting species:
______________ ecology
ecology belong?
4. Systems of communities:
______________ ecology
B.
Ecological interactions
Natural selection (differential survival or reproduction of individuals w/
different phenotypes)
1. Interactions with environment lead to differential survival or reproduction.
2. Individuals that interact more successfully will contribute more offspring
= natural selection
3.
If “successful traits” are genetically variable in population, then they
are passed on to offspring and the population comes to look
= evolution
more and more like the successful phenotype
C.
Population Growth
1.
Many interactions depend on population size and density– need to know
How many individuals in the population NOW?
How many will there be at some time in the future?
How fast is the population growing?
2.
Exponential growth:
N
t
= R
t
N
0
population grows without bound
s
implest model:
parent dies before
offspring mature = _____________________
then,
R = #offspring/female
3.
Simple example: nonoverlapping generations
Each individual has 2 offspring (i.e., R=2), then dies
What will the population size be after t generations (Nt)?
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 Fall '08
 Porter
 Demography, Population Ecology, rmax

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