ENV 1301 Lecture 5: Environmental Studies_2-9-16
7 Apr 2016
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Document Summary
Has a strong or wide-reaching impact: far out of proportion to its abundance. Removing a keystone species has substantial ripple effects: alters the food web. Predators at high trophic levels indirectly promote populations at low trophic levels: by keeping species at intermediate trophic levels in check. Extermination of wolves led to increased deer populations: which overgrazed vegetation. Communities experience many types disturbance: removal of keystone species, natural disturbances (fires, floods, etc. , human impacts cause major community changes. Resistance: a community resists change and remains stable despite the disturbance. Resilience: a community changes in response to a disturbance, but later returns to its original state. Or, a disturbed community may never return to its original state. The predictable series of changes in a community: after a sever disturbance. Primary succession: disturbance removes all vegetation and/or soil life. Glaciers, drying lakes, volcanic lava covering the land. Pioneer species: the first species to arrive in a primary succession area.
