Ch. 56: Community Ecology - Biological Communities o Species occur at any particular locality o Characterized by… Species richness: number present Primary productivity: amount of energy produced o Interactions among members govern many ecological and evolutionary processes o 2 views individualistic concept: an aggregation of species that happen to occur at one place holistic concept: integrated unit/superorganism-more than the sum of its parts o community composition changes gradually across landscapes o sometimes species abundance changes in a synchronous patterno ecotones: places where environment changes abruptly -Ecological Nicheo All the ways an organism uses environmental resources Food, shelter, relationships, storage, space utilization, temperature range, mating conditions, moisture requirements -Competition o Interspecific: when 2 species attempt to use same resource and there’s not enough o Interference: physical interactions over access to resources o Exploitative: individuals consuming the same resources -Types of Niches o Fundamental: entire area species is capable of using based on physiological tolerance limits and resource needs o Realized: actual set of environmental conditions in which species establishes stable population o Niche restriction Other species presentPredator absence or presence Absence of pollinatorsPresence of herbivores o 3 monkey species spider monkeys eat 85% fruit capuchins eat 18% animals and 75% fruits howlers each 80% leavesall occupy the same niche and split up resources so they don’t compete as much o JH Connell’s study of barnacles -Competitive Exclusion o If two species are competing for a limited resource, the species that uses the resource more efficiently will eventually eliminate the other one locally o G.F. Gause’s classic experiments using 3 paremecium species Predicted on would outcompete the other -Gold out competed red -Red and green both survived by dividing resources o Realized nich overlapped less o 2 warbler populations at different elevations Population density drops to 0 as the species meet o Resource partitioning among sympatric lizard species Subdivided niche to avoid direct
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