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Lecture

BMEN 515 Lecture Notes - Pronghorn, Secondary Succession, Primary Succession


Department
Biomedical Engineering
Course Code
BMEN 515
Professor
William Huddleston

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HOW DO SPECIES INTERACTIONS CAUSE TROPHIC CASCADES
Interactions of a single predator species in a community can cause a
progression of indirect effects across successively lower trophic levels-trophic
cascade
can be illustrated by wolf pop’n in Lamar Valley of Yellowstone National Park
wolves feed on pronghorn, mule, deer, elk, bison
share prey with coyotes, lions and bears
unrestricted hunting continued after park establishment
by 1926, wolves were extirpated from park
elk pop’n rapidly increased, when wolves were absent, elk pop’n browsed
aspen trees so intensely that no young trees were recruited after 1920
1995, wolves were reintroduced to Yellowstone and pop’n grew rapidly
Wolves preyed on elk-elk pop’n decreased
The presence or absence of a single predator influences pop’n of prey and
structure of vegetation and pop’n of other species
Organisms that create structure-ecosystem engineers
Species that exerts influence out of proportion to its abundance-keystone
species
May influence species richness of communities and the flow of energy and
materials thorugh ecosystem
HOW DO DISTURBANCES AFFECT ECOLOGICAL COMMUNTIES?
Disturbances: event that changes the survival rate of one or more species
in an ecological community-remove some species but may open up space
and resources for others
Small disturbances are much more common than large disturbances
Few large events may cause most changes (hurricanes)
Succession: change in composition of an ecological community following a
disturbance
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