Food Chain/Web

Within food webs there are three main categories of organisms: producers, consumers, and decomposers. Producers are organisms that synthesize their own organic compounds or food using diffuse energy and inorganic compounds. Producers sometimes are called autotrophs (self-feeders) because of this unique ability. For example, green plants are autotrophs because they manufacture the compounds they need through photosynthesis. The process of photosynthesis is summarized below:

Photosynthesis uses radiant energy from the sun to transform gaseous carbon dioxide (released as organisms respire) and water into glucose and other simple sugars which plants use as a food to survive and grow. Gaseous oxygen is released as a waste product of photosynthesis and is used by other organisms during their respiratory metabolism. Photosynthetic organisms are called primary producers and they are the first trophic level of the food web. Their rate of productivity determines how much fixed energy in the form of potential energy of plant biomass is available to higher trophic levels.

Above the primary producers are all of the consumers heterotrophs (other feeders). Heterotrophs feed on other organisms to obtain their energy and are classified according to the types of food they eat. Consumers that eat plants are called herbivores. Herbivores comprise the second trophic level of the food web and are called primary consumers because they are the first consumer group. Grass-eating deer and cows are primary consumers.

Above the primary consumers, the food web fans out to include consumers that eat other animals, carnivores, and consumers that eat both plants and animals, omnivores. Within the food web carnivores and omnivores can be on any higher trophic levels. Some are secondary consumers meaning they eat primary consumers. Wolves that eat deer (primary consumers) are secondary consumers. Other higher-level consumers are tertiary and eat further up on the food web or perhaps on many levels.

In addition to this grazing food web there is another trophic section known as the decomposer food web. There are two main types of consumers of dead biomass: detritus feeders and decomposers. Both are called detritivores since they utilize dead plants and animals, or detritus. Detritus feeders, such as earthworms, ingest organic waste and fragment it into smaller pieces which the decomposers such as bacteria and fungi can digest. Unlike organisms in the grazing part of the food web decomposers are extremely efficient feeders. Species can rework detritus, progressively extracting more fixed energy. Eventually the waste is broken down into simple inorganic chemicals such as H₂0 and CO₂ structures and nutrients. The nutrients then may be re-used by the primary producers in the grazing part of the food web. The decomposer food web is very active inside of compost piles and turns kitchen wastes into a soil conditioner. Decomposers are active in all natural ecosystems.