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Energy Flow in Ecosystems Food Chains & Food Webs Energy • Energy flows in a one-way stream from primary producers to various consumers through the food chain Food Chains • Food chains are series of steps in which organisms transfer energy by eating and being eaten • Producer Herbivore Carnivore Food Webs • Feeding relationships are usually more complex than just a simple chain • Many animals eat more than one kind of food • Complex networks of feeding relationships are called food webs. Everglades food web - Describe three food chains that are part of this web? - What role do decomposers play in a food web? - Why is a food web a more accurate representation of feeding relationships than a food chain? Trophic Levels • Each step in a food chain or food web is called a trophic level • “nourishment level” Carnivores/ omnivores herbivores autotrophs Carnivores/omnivores Food Webs & Disturbances • Keystone species: a species that has an unusually large effect on its ecosystem • Ex: sea otters Ecological Pyramid Models • Pyramids model the distribution of energy and matter in an ecosystem. • Three types you need to know: • Energy Pyramid • Biomass Pyramid • Pyramid of Numbers Energy Pyramid • Shows the amount of energy available at each trophic level of a food chain or food web. • Only a small portion of energy in each trophic level makes it to the next level • 10% rule Between each trophic level 90% of energy is lost to the atmosphere as heat. Only 10% of energy is transferred from one level to the next. Ecological Pyramids Pyramid of Numbers Shows the individual number of organisms at each trophic level. Biomass Pyramid Measures the total dry mass of organisms at each trophic level.