In concise terms, an organism’s niche is “the ecological role and space that an organism fills in an ecosystem.” The term is a vital bit of modern biological terminology, however, and merits a robust exploration.
A niche comprises many dimensions, but can be roughly divided into two components: the ecological ‘space’ it fills, as well as the physical space it literally fills. Let’s use a beaver as an example. These largest of North American rodents have a complex, important niche in their ecosystem. Beavers serve as food for several predators (wolves, coyotes, etc.), and they themselves use a variety of trees and other vegetation as food and building materials. Their niche extends to the way their behavior impacts physical environment however — the ‘role’ they play as pond-builders.
Beavers are unique among animals for the scale at which they alter their physical environment. By felling trees and building dams, they both thin out forests and create ponds. The thinning of the forest canopy allows plants in the understory to get more sun; their pond-creating behavior provides valuable habitat for all sorts of aquatic and semi-aquatic wildlife. Frogs, fish, waterfowl, insects and their larvae, water plants, salamanders — all make use of the wetlands created by beavers. All of the above dimensions qualify as part of the ecological space this species fills. There is also the physical space: the temperatures they tolerate, the topography they prefer, the amount of water they need to be able to construct their dams in the first place.
Even the way beavers consume oxygen and release carbon dioxide via respiration is part of their niche. A complete description of their niche would include all of the aforementioned factors and dozens more — it would completely map out, across dozens of dimensions, the way beavers relate to every other biotic (living) and abiotic (nonliving) component of their ecosystem.
Biologists make a distinction between fundamental niche and realized niche. A fundamental niche describes the biological and physical constraints (water requirements, temperature levels, etc.) on where an organism can live; the space an organism could fill were it not from pressure from other organisms (competitors, predators, etc.). A realized niche is the space an organism actually occupies, usually a smaller portion of the fundamental niche for which it is best adapted. For example, red squirrels may be able to survive wherever there are enough conifers to provide them with food. However, competition from larger gray squirrels may keep them from living in every coniferous forest they would otherwise be able to occupy.
According to the competitive exclusion principle, no two species can occupy the same exact niche. At least not in the long term. When species find themselves vying for the same niche, one or the other (or both) must change. One may simply be driven to extinction, or perhaps one or both of the species will evolve to use a slightly different niche. If two finch species compete for the same medium-sized seed-eating niche, perhaps one will evolve to take advantage of larger seeds, reducing the overlap of their niches (and thus the competitive pressure).
Truthfully, it gets even more complex than this. There are competing definitions of niche, with subtle variations — some focus only on the role the organism fills, and exclude physical habitat requirements; some describe only the available spaces in an ecosystem, regardless of whether they are filled or not. Not to mention, there are more dimensions to measuring a niche than most of us are capable of imagining all at once. The important thing to realize is that niches have become essential to the way we think of organisms in relation to each other and their environment. Niches help shape organisms (and vice versa), and they provide a powerful way to think about evolutionary pressures. It’s almost as though organisms are puzzle pieces, and niches show us the shapes of the spaces they fit into.
Wikipedia: Ecological Niche
Biology Online Definition: Ecological Niche
ScienceDaily: Ecological Niche
An Ecological niche is the “space” a plant or animal occupies in the environment. Some animals occupy a very specialized niche (such as earthworms, which eat dead matter and create dirt) while others occupy a very broad niche, like most trees, which filter CO2, create habitats, create food, etc.
I hope this helped!
An ecological niche of any organism depends upon not only its location but also what it does. In simplier terms, you are determining where the organism lives and what it does.
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