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Ecosystems Study Guide (page 2)

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Updated on Feb 22, 2013

Requirements of Organisms

Every organism needs food, water, and shelter, which must come from the area in which it lives. This area is called an organism's habitat. Within its habitat, an organism has a function or role to play to help maintain the community. The role of some organisms is to capture sunlight and produce food compounds. We call these organisms plants or autotrophs, a word that roughly translates as one who feeds oneself. We also call plants producers because they produce their own food. Other organisms eat plants and some eat each other. These organisms are called heterotrophs, which means eater of others. We also call heterotrophs consumers, and most animals are in this group because they must consume food (they cannot make their own). Still other organisms, such as pillbugs, eat the leftover remains or droppings of other organisms. These organisms are referred to as detritivores, which means eater of detritus (leaf litter).

An Organism's Niche

The roles an organism plays in a community and how it affects and is affected by its habitat are the factors that determine an organism's niche. An easy way to understand the concept of a niche is to think of it as being an organism's "location" and "occupation" within a community. For example, birds and squirrels both live in a tree habitat, but they do not occupy the same niche because they eat different foods. Their "locations" are the same, but they have different food-gathering abilities and requirements as their "occupations."

In Short

The study of living organisms and the ways in which they interact with their physical environment and each other is called ecology. All these relationships form an ecosystem. In all cases, ecosystems exhibit two primary features:

  1. a single direction to the flow of energy, in the form of chemical bonds, from photosynthetic organisms, such as green plants or algae, to animals that eat the plants or other animals.
  2. the cycling of inorganic minerals, such as nitrogen, calcium, and phosphorous, through living organisms and then back to the environment. The return of these inorganic materials to the environment happens largely by the action of organisms known as decomposers (such as bacteria and fungi) and others called detritivores (such as pillbugs, sowbugs, millipedes, and earthworms).

A complete definition of an ecosystem could be stated as a combination of biotic and abiotic components through which energy flows and inorganic material recycles.

Practice problems of this concept can be found at: Ecosystems Practice Questions

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