Ecology - Food Chains and Food Webs

• Due No due date
• Points 15
• Questions 15
• Time Limit None

Instructions

Food Chains and Food Webs

Chemical energy is necessary for survival. AUTOTROPHS (plants) are able to make their own chemical energy through the process of PHOTOSYNTHESIS. This chemical energy can be passed up to the food chain to support the CONSUMERS (animals) in an ecosystem.

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Without producers, there could be no consumers! Therefore, energy always flows from producers to consumers. Energy is first transferred from producers to HERBIVORES (plant eaters), and then from herbivores to CARNIVORES (meat eaters). Once energy is passed forward, it can never flow back.

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A food chain is used to show the flow of energy from one organism to another.

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grass --> grasshopper --> mouse --> snake --> hawk

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If BIODIVERSITY is lost in an ecosystem, this means less available food for all others. As connections are lost in food webs, ecosystems become less stable. If you remove the mouse from the food chain above the snake will not have food and will die.

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Also, if you remove the mouse, the grasshopper population will increase FOOD WEBS consist of many predator-prey relationships because many consumers have several alternate sources of chemical energy. A food web shows multiple food sources for different organisms.

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DECOMPOSERS are a special type of consumer that can feed on any organism aft it dies. Decomposers are extremely important in a food chain or food web because they help to limit the amount of waste in an ecosystem.

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An ecological pyramid is used to show different "levels" in an ecosystem. Sometimes the levels are called "TROPHIC LEVELS."

The base (bottom level) of the ecosystem are the producers/autotrophs (plants). All other levels represent consumers/heterotrophs (animals). There must be more producers than consumers for an ecosystem to be stable. Each level of the pyramid directly supports the level above it.

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The second level of the pyramid represents HERBIVORES, who directly rely on the producers for food. The third, fourth, and maybe even fifth level consumers represent PREDATORS called CARNIVORES. The top level represents the top predators of the ecosystem which are the "top of the food chain."

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The pyramid also represents the amount of available energy in an ecosystem. As you move up the pyramid, the amount of available energy DECREASES. This is because at each level, there are less and less organisms. At each level, energy does not "build up." At each level, most of the energy obtained is lost to the environment as heat. This is because organisms don't "save" all of the energy that they obtain- they spend most of it. When organisms spend energy, it is lost to the environment as heat.

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REMEMBER:

• A food chan and food web show the flow of energy in an ecosystem.
• The arrows represent the direction the energy moves.
• Food chains/webs ALWAYS start with a plant (producer).