Food Chains & Food Webs
Where do living things get energy from? The sun provides the primary source of energy for life on earth. Organisms also get energy from other plants and animals. Animals that eat plants for food may in turn become food for other animals. This sequence is called a food chain.
Most animals are part of more than one food chain and eat more than one kind of food in order to meet their food and energy requirements. These interconnected food chains form a food web. The types of organisms involved in a food chain are producers, consumers (including herbivores, carnivores, omnivores, parasites, and scavengers), and decomposers. |
CarnivoresAnimals that only eat OTHER ANIMALS are called carnivores. ***Think of them as meat eaters!
Carnivores that eat herbivores are called secondary consumers. (i.e. Wolves are carnivores that eat rabbits which eat plants.) Carnivores that eat other carnivores are called tertiary consumers. (i.e. Killer whales eat seals which eat smaller fish which eat plankton.) |
Example of a Food Web |
Example of a Food Chain |
Transfer of Energy Through the Food Chain
As energy is transferred from one organism to another, the amount of energy available at the next level becomes less and less. For example, when a herbivore eats, only a fraction of the energy (that it gets from plant food) becomes new body mass; the rest of the energy is lost as waste or used up by the herbivore to carry out its life processes (i.e., movement, digestion, reproduction). Therefore, when the herbivore is eaten by a carnivore, it passes only a small amount of total energy (that it has received) to the carnivore. Of the energy transferred from the herbivore to the carnivore, some energy will be "wasted" or "used up" by the carnivore. The carnivore then has to eat many herbivores to get enough energy to grow. The further along the food chain you go, the less food (and hence energy) remains available. The food chain is an inefficient system.
Energy Pyramid
This energy pyramid shows many plants providing food and energy to giraffes. As you go up, there are fewer giraffes than plants and even fewer lions than giraffes. As you continue along the food chain, fewer consumers exist. A large mass of living things at the base is needed to support a few at the top. Many herbivores are needed to support a few carnivores.
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