ecological community.doc

3 Pages

Biomedical Engineering
Course Code
BMEN 515
William Huddleston

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• Species that live and interact in an area constitute an ecological community • Ecological communities are not assemblages of organisms that move together as units when environmental conditions change, rather each species has unique interactions with its biotic and abiotic environments • Organisms in a community can be divided into trophic levels based on their source of energy • Trophic level: consists of the organisms whose energy source has passed through the same # of steps to reach them • Photosynthesizers=primary producers • All nonphotosynthetic organisms (heterotrophs) consumer either directly or indirectly the energy-rich organic molecules produced by primary producers • Primary consumers: eat plants constitute a trophic level called herbivores • Secondary consumers: eat herbivores • Decomposers: detrivores eat dead bodies • Organisms that obtain food from more than one trophic level are omnivores • Sequence of interactions in which a plant is eaten by an herbivore, which is in turn eaten by a secondary consumer-food chain; food web • Most communities have 3-5 trophic levels; biomass: weight of living matter • in most terrestrial ecosystems photosynthetic plants dominate, both in terms of the energy they represent and the biomass they contain • mammals may consume 30-40 percent of the annual aboveground grassland plant biomass; insects may consume an additional 5=15 percent; soil organisms 6-40 percent of the belowground biomass in grasslands • in aquatic ecosystems, dominant photosynthesizers are bacteria and protists ; high rates of cell division • predators restrict habitat and geographic distribution of their prey • austrialian biogeographic region is home to a birds- megapodes (mound- builders) that don’t incubate eggs; lay eggs in a mound of decomposing vegetable material; warmed by decomposition; parent visits regularly to add or remove decaying material for temperature • prey species have evolved a rich variety of adaptations that make them difficult to capture, subdue and eat; toxic hairs, bristles, tough spines, noxious chemicals, camouflage and mimicry of inedible objects or of larger dangerous animals • Batesian mimicry: palatable species may mimic an unpalatable or noxious one-process; works because a predator that captures an individual of an unpalatable or noxious species learns to avoid other prey individuals of similar appearance • Mullerian mimicry: two or more unpalatable or noxious species may converge to resemble one another • for a microparasite to persist in a host population, atleast one new host must become infected with the microparasite before each infected host dies • 3 distinct clases: susceptible, infected and r
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