Midterm_II_StudyGuide_ENVST100

Midterm_II_StudyGuide_ENVST100 - Midterm II Study Guide...

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Midterm II Study Guide Environmental Studies 100: Environmental Ecology Lecture #10 1. Predator: Any organism that consumes all or part of another living organism thereby benefiting itself and reducing the growth, fecundity or survivorship of its prey a. Predation includes parasitism or partial consumption 2. Predation can have a dramatic impact on community structure and composition a. Can increase diversity by preventing competitive exclusion i. Case Study: Determining Lower Limit of Mussel Bed 1. Starfish eats mussels, which is a dominant competitor on rocky intertidal communities 2. By removing starfish, only mussels exist after five years, while with the inclusion of starfish, same species diversity before experiment 3. Conclusion: a predator can promote diversity by removing dominant competitor, allowing coexistence of competitors 3. Keystone Predator a. A predator having a major influence on community structure and diversity i. An influence that is disproportionate to its abundance ii. Its removal or addition leads to major changes in abundance of many other species b. Case Study: Is Pisaster (starfish) always a keystone species? i. No effect of Pisaster as a keystone depends on wave exposure and mussel productivity 1. High wave exposure on rocky shores—classic keystone predation 2. Protected rocky—not strong keystone, but still important for reducing mussels 3. Rocky shores with periodic sand Burial—Pisaster still abundant but impacts not strong or clear ii. Regulation of Keystone predation by small changes in ocean temperature 1. Starfish is very sensitive to temperature 2. Slight decreases in temperature slow it down and prevent it from being keystone predator 3. Thus, with El Nino upwelling in parts of NW, communities could change drastically 4. Summary a. What is a predator : Any organism that consumes all or part of another living organism thereby benefiting itself and reducing the growth, fecundity or survivorship of its prey b. What is a Keystone Predator : A predator having a major influence on community structure and diversity whose influence is disproportionate to its abundance and its removal/addition leads to major changes in abundance of other species
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c. A keystone species is defined by the circumstance , not the species i. Pisaster was not a keystone everywhere it lived—the natural environment controlled this Lecture #11 1. Predator Mediated Coexistence—Predator ‘mediates’ or facilitates coexistence by reducing dominant competitor a. In order for this to work, must have a situation where the environment facilitates a dominant competitor i. For example, in the case of Pisaster, wave exposed shores provide and environment where mussels can recruit and be the dominant species, however, sandy conditions prevent one species from dominating b. Keystone Predation is a subset of this category 2. Predator Mediated Existence on Land a. Darwin states “If turf which long has been mown…be let to grown, the more vigorous plants gradually kill the less grown plants”
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This note was uploaded on 12/25/2009 for the course ENV S 100 taught by Professor Staff during the Fall '08 term at UCSB.

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Midterm_II_StudyGuide_ENVST100 - Midterm II Study Guide...

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