Food Chains and Food Webs Energy Flow in Nature Energy Roles • An organism’s energy role in an ecosystem may be that of a producer, consumer, or decomposer. Producers • An organism that can make its own food is a producer. • Autotroph • Source of all food in an ecosystem. • Capture energy from sunlight and stores it as food energy. Consumers • Consumers are heterotrophs, or living things that cannot make food for themselves. • A food chain contains several kinds of consumers, each of which occupies a different trophic level. • Herbivore, carnivores, omnivores Consumer Tropic Levels • Primary consumers eat producers (herbivores) • Secondary consumers eat primary consumers (carnivores) • Tertiary consumers eat secondary consumers (carnivores) • Scavengers are carnivores that feed on the bodies of dead organisms. Decomposers • Help break down wastes and dead organisms and return the raw materials to the environment • Bacteria and fungi Food Chains • Series of events where one organism eats another and obtains energy. • First organism in chain is the producer. • The second organism is the consumer that eats the producer. Plankton—Crab—Seal—Orca This is only one possible chain in a marine ecosystem. Come up with an example to fill in the blocks of a food chain in two different ecosytems. Food Webs • Consists of many overlapping food chains in an ecosystem. • Some organisms may play more than one role by changing consumer levels. What happens in a food web if one or more of the organisms disappear? Which animals are carnivores and herbivores? Energy Pyramids • A diagram that shows the amount of energy that moves from one feeding level to another in a food web. • Represented in a triangle with the most energy at the producer level. Energy Loss and Use • 10% of energy transferred to next higher level. • 90% of energy is used by organisms’ life processes. • Due to energy loss, ecosystem cannot support many feeding levels.
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