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Lecture 17

BIOL 215 Lecture 17: BIOL 210 LEC 17


Department
Biology
Course Code
BIOL 215
Professor
Ehab Abouheif
Lecture
17

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Lecture 17
Tuesday, November 8, 2016
10:09 AM
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Graph 1:
Higher survival at low density, and less survival at high density.
Limited resources in the winter is driving it.
The more individuals - the harder it is to get through winter.
Survivorship increases with density in summer.
Probably a predator effect - if increasing with number of
individuals its not resource mediated its probably resource neutral.
Slope - measures how strong the density dependence.
Steeper - stronger density dependence
Flat Line - no density dependence.
The Classic Constant Quota Model (inspired at carrying capacity)
o If you fish at maximum sustained yield - everything works out.
o Constant Quota: proposes a fixed catch that does not change with stock size
o Escapement: number of fishes allowed to escape fishery.
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o
o What's the problem with the model?
Depending on number of fish you get a different density after fishing.
When stock is relatively low - fewer fish escape.
Doesn't acknowledge populations are very density dependent in terms
of predation and resource limitation.
COMMUNITY DYNAMICS
1. Food chains and trophic levels (405-409)
2. Key stone and dominant species (396-397, 412-417)
3. Disturbance (417-419 and 426-434)
4. The special case of islands (440-445)
PREDATION AND COMPETITION
Two Major forces structuring communities.
Predator can enable coexistence when it prefers better competitor.
LINEAR RELATIONSHIPS OF FEEDING:
Food chains
A lot of community ecology - understanding these trophic relationships.
Can change through time.
i.e. top predator becomes more abundant, modifies entire chain (orca)
Proposed as
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