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SNC1D: BIOLOGY UNIT Sustaining Ecosystems Exam Review Biodiversity • the variety of organisms in an ecosystem Biodiversity Ecosystems with high biodiversity are more sustainable because of redundancy in the food web. If the number of rabbits decreases, the foxes can still eat squirrels. Biodiversity Biodiversity will be higher in natural ecosystems than in artificial ecosystems (e.g., a park). Abiotic factor • A non-living component of an ecosystem Ex: sunlight, wind Biotic factor • A living component of an ecosystem Ex: decomposers, predators Limiting factor • any factor (abiotic or biotic) that restricts the size of a population Ex. pH (acidity) in an aquatic ecosystem Community • all living things in an ecosystem Population • all individuals of the same species in the same ecosystem Carrying Capacity • the maximum population size (of a particular species) that an ecosystem can sustain Ecological Niche • the function of a species in its ecosystem (what it eats, what eats it, how it behaves) Trophic Level • the position an organism occupies in a food chain (the first or lowest trophic level is Producers) Producer • an organism that makes its own food Consumer • an organism that feeds off other organisms Decomposer • an organism (e.g., bacteria, fungi) that breaks down dead and decaying organisms (often not shown in food webs) Food Web The greatest biomass/energy is found at the lowest trophic level: the producers (here, the phytoplankton). Energy Only about 10% of the energy is passed on to the next level of the food chain; the remainder is used by the organism for metabolism and growth. Food Web: Effects If the population of leopard seals declined, the populations of its prey (e.g. fish) would increase and the populations of its predators (e.g. smaller toothed whales). Cycling of Matter in Ecosystems Carbon Cycle: the movement of carbon between the lithosphere, atmosphere, hydrosphere, & biosphere Cycling of Matter in Ecosystems atmospheric pool of carbon dioxide Cycling of Matter in Ecosystems plants take up carbon dioxide for photosynthesis Cycling of Matter in Ecosystems animals eat plants Cycling of Matter in Ecosystems carbon dioxide released by respiration Cycling of Matter in Ecosystems fossil fuels Cycling of Matter in Ecosystems carbon dioxide released by combustion Cycling of Matter in Ecosystems death of organisms & decay by bacteria 2. Photosynthesis • the chemical reaction that stores energy in nutrients (in plants) carbon dioxide + water → glucose + oxygen 4. Cell Respiration • the chemical reaction that extracts energy from nutrients (in plants and animals) glucose + oxygen → carbon dioxide + water Sustainable Farming Soil-sustaining farming practices include no-tillage (to reduce erosion) and drip irrigation (to reduce erosion and leaching). Habitat Fragmentation • when wildlife areas are chopped up into disconnected parts Habitat Fragmentation This is a bad thing because you need a large area for large, stable populations. To Improve Sustainability One large block is better than an equal area of smaller blocks. To Improve Sustainability The closer areas are to each other, the greater the chance populations will be able to interact. Wildlife corridors connect areas and further increase the chance of interaction.