1 (h) Food Chains, Webs, & Pyramids
Notes #2:Food Webs, Energy Pyramids, and Symbiosis
All organisms use energy. Energy enters most ecosystems as sunlight and is converted into food by producers. This energy is transferred to each organism that eats a producer, and then to other organisms that feed on these consumers. The movement of energy through an ecosystem can be shown in diagrams called food chains and food webs.
A food chain shows only one possible path along which energy can move through an ecosystem. But just as you do not eat the same thing every day, neither do most other organisms. Most producers and consumers are part of many food chains. A more realistic way to show the flow of energy through an ecosystem is a food web.
When an organism in an ecosystem eats, it obtains energy. The organism uses some of this energy to move, grow, reproduce, and carry out other life activities. This means that only some of the energy it obtains will be available to the next organism in the food web. The most energy is available at the producer level of the pyramid.
A food chain shows only one possible path along which energy can move through an ecosystem. But just as you do not eat the same thing every day, neither do most other organisms. Most producers and consumers are part of many food chains. A more realistic way to show the flow of energy through an ecosystem is a food web.
When an organism in an ecosystem eats, it obtains energy. The organism uses some of this energy to move, grow, reproduce, and carry out other life activities. This means that only some of the energy it obtains will be available to the next organism in the food web. The most energy is available at the producer level of the pyramid.
Decomposers are organisms that break down large chemicals in dead organisms into small chemicals. Decomposers are “nature’s recyclers.” They return basic chemicals to the environment for other living things to reuse. For example, the leaves of many trees die in autumn and drop to the ground. Decomposing bacteria spend the next months breaking down the chemicals in the dead leaves. The broken-down chemicals mix with the soil and can then be absorbed by the roots of nearby plants.
Symbiosis (sim bee oh sis) is a close relationship between two species that benefits at least one of the species. The three types of symbiotic relationships are mutualism, commensalism, and parasitism. A relationship in which both species benefit is called mutualism (myoo choo uh liz um). A relationship in which one species benefits and the other species is neither helped nor harmed is called commensalism (kuh men suh liz um). Parasitism (pa ruh sit iz um) involves one organism living on or inside another organism and harming it. The organism that benefits is called a parasite, and the organism it lives on or in is called a host
Symbiosis (sim bee oh sis) is a close relationship between two species that benefits at least one of the species. The three types of symbiotic relationships are mutualism, commensalism, and parasitism. A relationship in which both species benefit is called mutualism (myoo choo uh liz um). A relationship in which one species benefits and the other species is neither helped nor harmed is called commensalism (kuh men suh liz um). Parasitism (pa ruh sit iz um) involves one organism living on or inside another organism and harming it. The organism that benefits is called a parasite, and the organism it lives on or in is called a host
