Lec15_2011BILD3

Lec15_2011BILD3 - BILD 3 Lecture 15 Community Ecology I...

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BILD 3 Lecture 15 - Community Ecology I. Ecological niche II. Interspecific competition III. Consumption IV. Mutualism V. Trophic structure
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I. Ecological niche A niche is a summary of an organism’s tolerances and requirements. Niche : n-dimensional hypervolume defined by axes that represent the different environmental tolerances and resource requirements of a species. Fundamental niche : the full range of conditions under which a species can survive and reproduce Realized niche : portion of fundamental niche that a species can actually occupy as a result of its interactions with other species
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The niche concept originated from insights Joseph Grinnell published about the distribution of the California Thrasher in 1917. Grinnell considered a niche to be a subdivision of a particular habitat. Within the California Floristic Province the species is restricted to dense vegetation (mostly chaparral and sage scrub) in California. Ground-foraging and requires a closed canopy but an open under story for running.
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(a) different plant species (b) sand shrimp (c) hypothetical aquatic organism
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Types of biotic interactions Species A, benefits Species B, harmed Predator-prey Host-parasite A benefits B unaffected Commensalism A benefits B benefits Mutualism, symbiosis A harmed by B B harmed by A Competition + / - + / 0 + / + - / -
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I. Interspecific Competition - different species compete for a particular resource that limits growth or survival - limiting resources include light, space, and nutrients - note that intraspecific competition involves the same process - competition can decrease population growth rates
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Interspecific competition between individuals of different species causes a mutually depressing effect on the populations of both. If strong enough, interspecific competition can lead to the exclusion of species from a local site.
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GF Gause pioneered experimental studies of competition in the lab.
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