BIO407H5 Lecture Notes - Detritivore, Species Richness, Directional Selection

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55. 1 what are ecological communities: the species that live and interact in an area constitute an ecological community. Communities are loose assemblages of species: ecological communities are not assemblages of organism that move together as units when environmental conditions change. Rather, each species has unique interactions with its biotic and abiotic environment. The organisms in a community use diverse sources of energy: a trophic level consists of the organisms whose energy source has passed through the same number of steps to reach them. Plants and other photosynthetic organisms constitute a trophic level called photosynthesizers or primary producers. Many species are omnivores; trophic levels are often not clearly distinct: biomass: the weight of living matter, distributions of energy and biomass for a particular ecosystem usually have similar shapes. Variations in their dimensions depend on the nature of the dominant organism at each trophic level and how they allocate their energy.