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Ecology 4 Dec 10 2007 - Ecosystems Global climate change I...

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    Ecosystems &  Global climate change I Trophic levels, food chains & food webs II Intro to ecosystem cycles III Global C cycle and rising CO 2   IV Greenhouse effect and increases in GE V Evidence for global climate change VI Consequences of climate change  VII Who/what is causing this? VII What can be done?
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    Ecosystem  (definition):  All of the organisms in an area, together with  their physical environment Emphasis in ecosystem ecology is on the  exchange of energy and materials  between  the living and nonliving components  Ecosystem concept: biological and physical  components of the environment are a single  interactive system
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    Trophic (feeding) levels form a food chain–   defined by where organisms obtain their energy Primary producers  (autotrophs) obtain  energy from sunlight by photosynthesis Herbivores  (eat primary producers) Carnivores   (eat herbivores or other  carnivores) Decomposers  (energy comes from from  chemical bonds, released by breaking down  organic matter)
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    Sometimes a food web is more accurate A boreal forest food web (Canada)
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    Food chains represent a pyramid of energy,  biomass and numbers: top carnivores are  always rare
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    Decomposition is a critical part of  ecosystem function • Decomposers break down— mineralize —  organic matter, making nutrients available to  plants for uptake (some nutrients remain  unavailable—are  immobilized – by being  taken up by the decomposers) • Some of the nutrients are  leached , or lost,  from the system into the groundwater, or in  runoff • Without decomposers, we’d all be in deep  doo-doo (literally) 
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    Decomposers also have food webs • Terrestrial and aquatic systems have  complex decomposer food webs • Involve a wide diversity of different kinds  of organisms  • These include microscopic organisms,  including bacteria and animals, small but  visible animals and fungi, and larger  organisms
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    Some common organisms in decomposer  food webs • Largest—scavenger animals (hyenas, vultures; also  insects like maggots (Dipteran larvae) • Dung beetles hold a unique place of honor • Intermediate scale—earthworms, termites:  consume and alter OM, decompose wood etc. • Smallest multicellular animals—nematodes,  insects and arachnids 
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    Springtails (Collembola, an insect) are important decomposers in many soils
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    and let’s not forget….. The  most  critical and important soil  decomposers: Fungi  (break down non-living plant organic  matter for energy and carbon) Bacteria  (break down living and dead cells  of plant, animals, fungi and other bacteria;  responsible for major nutrient cycling in  soils)
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