chapt56 - Community Ecology Chapter 56 1 Biological...

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1 Community Ecology Chapter 56
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2 Biological Communities Community: all the organisms that live together in a specific place Evolve together Forage together Compete Cooperate
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3 Communities can be characterized either by their constituent species or by their properties Species richness: the number of species present Primary productivity: the amount of energy produced Interactions among members govern many ecological and evolutionary processes Biological Communities
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4 Interactions in a community Predation Mutualism Assemblage: the species included are only a portion of those present in the community Biological Communities
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5 Two views of structure and functioning of communities Individualistic concept: H.A. Gleason; a community is nothing more than an aggregation of species that happen to occur together at one place Holistic concept: F.E. Clements: a community is an integrated unit; superorganism-more than the sum of its parts Biological Communities
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6 Biological Communities Most ecologists today favor the individualistic concept In communities, species respond independently to changing environmental conditions Community composition changes gradually across landscapes
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7 Biological Communities Abundance of tree species along a moisture gradient in the Santa Catalina Mountains of Southeastern Arizona Each line represents the abundance of a different tree species Community composition changes continually along the gradient
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8 Biological Communities Sometimes the abundance of species in a community does change geographically in a synchronous pattern Ecotones: places where the environment changes abruptly
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9 Ecological Niche Niche: the total of all the ways an organism uses the resources of its environment Space utilization Food consumption Temperature range Appropriate conditions for mating Requirements for moisture and more Billock
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10 Ecological Niche Interspecific competition: occurs when two species attempt to use the same resource and there is not enough resource to satisfy both Interference competition: physical interactions over access to resources Fighting Defending a territory Competitive exclusion: displacing an individual from its range
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11 Ecological Niche Fundamental niche: the entire niche that a species is capable of using, based on physiological tolerance limits and resource needs Realized niche: actual set of environmental conditions, presence or absence of other species, in which the species can establish a stable population
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12 Ecological Niche J.H. Connell’s classical study of barnacles
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13 Ecological Niche Other causes of niche restriction Predator absence or presence Plant species Absence of pollinators Presence of herbivores Billock Billock
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14 Ecological Niche G.F. Gause’s classic experiment on competitive exclusion using three Paramecium species shows this principle in action
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This note was uploaded on 09/16/2008 for the course BIOL 1722 taught by Professor Jagdeeswaran during the Spring '08 term at North Texas.

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chapt56 - Community Ecology Chapter 56 1 Biological...

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