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Organisms That Metabolize Organic Molecules Produced by Other Organisms

When ecologists look at an environment, they categorize different organisms based on their eating habits. Organisms such as plants and algae can make their own food from sunlight and inorganic molecules like minerals. Autotrophs differ from heterotrophs, which are organisms which consume organic matter that comes from other organisms. Heterotrophs can be anything from animals to insects, fungi and bacteria. Heterotrophs can be further sub-classified into decomposers, which consume the organic molecules of dead organisms.

Ecosystems
- Ecosystems are physical environments plus the organisms that live in them. An ecologist considers a physical environment to be minerals like nitrogen and carbon, rocks, mountains, soil, and waterways. The organisms that inhabit an environment either consumer the inorganic elements of the environment or consume eat other. This differentiates organisms into autotrophs and heterotrophs. The boundaries of an ecosystem are often imposed by an observer's frame of reference. One example of this is a pond found within a forest. You could look specifically at the pond as an ecosystem, or you could look at the entire forest as an ecosystem and include the pond as one small part of it.
Autotrophs
- Autotrophs are classified as "primary producers" in ecology because they are able to take in elements from an environment such as carbon dioxide, hydrogen and nitrogen, and make their own food from these. They influence their environment by changing the composition of the atmosphere, soil or water. For example, trees absorb carbon dioxide and release oxygen. This is an important function that influences other kinds of life forms which are unable to perform this activity. Examples of autotrophs are trees, seaweed and grass.
Heterotrophs
- The term heterotroph means "nourished by others.". Also known as "consumers," they rely on other organisms for food because they are not able to make their own. Heterotrophs may consume autotrophs or even other heterotrophs. For this reason, heterotrophs are further subdivided based on what they eat. They can be carnivores, herbivores, omnivores or saprobes. Herbivores only eat plants, omnivores eat both plants and animals. Carnivores only eat other animals. Saprobes break down and consume the remains of dead plants and animals, and are also known as decomposers. Heterotrophs can be be animals, insects, fish, bacteria, coral or fungi.
Decomposers
- Saprobes, or decomposers, metabolize the organic molecules of deceased organisms. This is an important aspect for an ecosystem, because the saprobe returns elements back to the environment. These returned elements, like nitrogen or water, are released into the air, water or soil, which makes them available to be consumed by autotrophs. Some examples of saprobes are bacteria, mushrooms, mildew, ants and earthworms.

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