Chapter 57

Chapter 57 - Chapter 57 Community Ecology 57.1 What are...

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Chapter 57 – Community Ecology 57.1 – What are ecological communities? o An ecological community is an assemblage of different species interacting in the same place (interactions can be varied and complicated) (e.g. brood parasitism) o Species richness is the number of species a community contains o Organisms within a community rely on each other for energy o Primary producers are photosynthetic autotrophs that convert solar energy into organic energy that is utilized by the biological organisms in the community o Primary productivity is an essential factor in determining the community it determines how much energy flows in, and therefore how much biomass can be supported o Gross primary productivity is the rate of photosynthesis o Net primary productivity is the amount of energy that is converted to usable organic forms (net primary production) o Net primary production is the amount of primary producer biomass that is available o Primary productivity varies by region o Energy always enters an ecosystem from an external source, like the sun o It flows through various trophic levels in a chain of organisms eating each other Called a food chain o An organisms trophic level is the distance an organism is from the ultimate energy source o Major trophic levels include Photosynthesizers – solar energy – plants and bacteria Herbivores – tissues of primary producers – termites, grasshoppers Primary carnivores – herbivores – spiders, wolves Secondary carnivores – primary carnivores – tuna, falcons Omnivores – several trophic levels – humans, crabs Detritivores – dead bodies and waste – fungi, bacteria, vultures
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o All organisms at the same level are the same number of steps away o Fewer individuals and less biomass can be supported at higher trophic levels o Food chains do not reflect the dietary diversity of organisms o Trophic relationships are more accurately depicted by food webs o Trophic levels change for a number of reasons
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Chapter 57 - Chapter 57 Community Ecology 57.1 What are...

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