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As opposed to a food chain, which shows the direct link between an organism and its food source, a food web shows the multiple sources of food for living things. Food webs are separated into trophic levels, with the larger predators making up the high trophic levels, according to an article by Robert Leo Smith for Microsoft Encarta Encyclopedia.
Producers
Producers are organisms, such as plants, that are able to make their own food. These organisms occupy the first, and lowest, trophic level because a number of other organisms use them as a source of food.
Primary Consumers
Primary consumers are animals that use plants as their primary source of energy. These animals are often weaker or smaller than others and are prey for larger animals, according to Associated Labs. These animals are often found in the second trophic level.
Secondary Consumers
Secondary consumers are organisms that get energy from eating other animals. These predators are often the largest and strongest animals in an ecosystem. They are found in the third or fourth trophic levels, depending on whether they eat herbivores or omnivores.
Herbivores
Primary consumers are often herbivores, meaning that they only eat plants. Rabbits, horses and deer fit into this category.
Omnivores
Omnivores are animals, such as humans, bears, blue jays and wood peckers, that eat animals and plants. These organisms are usually found in the third trophic level.
Carnivores
Carnivores are animals, such as wolves, lions, tigers, hawks and seals, that only eat other animals. These animals often occupy the third and fourth trophic levels, depending on whether they have predators.
Source:
"Microsoft Encarta Encyclopedia;" Food Web; Robert Leo Smith; 2006.
Associated Labs: Producers, Consumers and Decomposers
More Information:
Encyclopedia Britannica: Trophic Level
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