exam 2 review - Keystone species a species that is not...

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Keystone species: a species that is not necessarily abundant but exerts strong control over community structure. Indirect effects Trophic cascade: alternating positive and negative effects caused by the consumption of a species at a different trophic level. For example, the consumption of a species at next level will reduce pressure caused by that species on the next lower species. Killer whale predation on sea otters has decreased populations 5 fold. Over harvesting of sharks has increased its prey and decreased the prey’s prey. How communities of many species interact. How is species diversity maintained…how are dominant players restrained from forming monocultures (keystone predators)? Disturbance: something that occurs that destroys individuals or biomass from a community usually by altering resource availability. Patterns determined by projecting long term patterns from short term analysis and by looking at the history of a particular site Disturbance regime: type, frequency, and severity of disturbance Fire opens up the pine cones that are shut with resin and that contain the seeds. Primary succession: succession that occurs in a lifeless area where no organisms had existed and where soil had not yet formed. (example, glacier slides and leaves moraines which are sites for primary succession) Secondary succession: the removal of all of the organisms but leaving the soil intact through a disturbance. The sequence of species that follow is a successional pathway Pioneering species: organisms to first arrive in a disturbed site, have good dispersal ability Facilitation: existing species make conditions more favorable for subsequent species Tolerance: existing species do not affect establishment of subsequent species Inhibition: one species affects establishment of another Gleason: argued that the development of a community after a disturbance is random, a matter of chance whether or not the new community is similar to the old Species area theory: under equal circumstances, the larger the geographic area, the more species. As latitude increases, species diversity increases. Communities in tropics (equator) have more species than in temperate/subarctic High productivity hypothesis…high productivity=high diversity Energy hypothesis…temperature affects productivity and ability of organisms Tropical regions have had more time for speciation than in other regions Intermediate disturbance hypothesis: moderate type, frequency, and severity of disturbance=high species richness and diversity Trophic levels in food web important: Earth’s energy can support more herbivores than carnivores. Biomagnification: when an artificial/synthetic chemical is passed on between tophic levels and it is stored and concentrated rather than excreted. More levels in food chain increases potential for concentration Clostridium botulinum: a decomposer, anaerobic bacterium that is very toxic to humans Dead algae promote growth of C. botulinum, mussels filter out algae, clarifying water and
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exam 2 review - Keystone species a species that is not...

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