Niche

The term niche refers to the particular job, or function, that a living thing plays in the particular place it lives. Also called an ecological niche, this concept refers to the precise way in which an organism fits into its environment. A niche includes all the factors that are important to the organism's existence. No two species can occupy the same niche.

In order to study a niche, life scientists must understand all of the factors that are important to a living thing's existence. These factors include: an organism's: diet; energy, light, and moisture requirements, ideal temperature; ideal habitat; and ideal reproduction conditions. Therefore, the word function is key to understanding the idea of an ecological niche.

The idea of niche as a function has also been described as the job a living thing has—and as with any job—it can be very specialized or very general. Some organisms have very broad niches, meaning that they are fairly flexible in terms of the type of things they eat and temperature they tolerate. In other words, their overall living needs can be met in a less specialized environment. The opossum and the raccoon are examples of animals with very broad niches since they eat a wide variety of plants and animals and adjust well to different climates. However, many species play a narrow or specialized role and therefore have a narrow niche. Two examples are the giant panda of central China and the koala of Australia. The panda lives in the bamboo forests and eats only one type of bamboo, while the koala can only live where certain species of eucalyptus trees grow and survives by eating the leaves. Other factors influence a niche, and in the case of the koala, its existence becomes more fragile since it must live in a warm climate and it does not produce its young in great numbers. Not surprisingly, animals with the broader niche survive fairly easily and thrive in certain areas, while those animals with the more specialized niche, like the koala and the giant panda, are more likely to become endangered species as their habitats are destroyed.

Some life scientists say that a niche can be understood primarily in terms of competition, while others say it has more to do with one species being best fitted for a certain role. As early as the 1930s, life scientists developed the principle called competitive exclusion. One of the pioneers arguing for the primary importance of competition was the Russian microbiologist Georgil F. Gauze (1910– ), who conducted tests on different species of protozoa (one-celled organisms). Gauze successfully raised different species of protozoa, each in its own environment. He then put them together and discovered that one died out completely while the other thrived. In another test, he found that although the two species survived, neither did so in great numbers, and each occupied a different territory (or a separate part of the test tube). From this work came Gauze's nowaccepted principle that although two species may occupy the same habitat, they never share the same niche. A common example of such a phenomenon is that of the woodpecker and nuthatch. Both are birds that eat grubs (insects) that they find under tree bark. However, despite the fact that they are both after the same meal, neither occupies the niche of the other since woodpeckers start at the bottom of a tree and work their way up, while nuthatches begin at the top and work down.

Beyond an organism's feeding habits, there are scores of other factors that go into describing an organism's niche. For example, the simple earthworm plays a key role in its habitat as a consumer of dead organic matter and as food for other animals (such as birds). It is a host for certain parasites, and its burrowing has a beneficial plowing effect on the soil, loosening it up and allowing air to circulate. As the example of the earthworm shows, understanding an organism's niche also allows scientists to better understand both the organism and the environment it lives in.