In this article we will discuss about the role of habitat, microhabitat and niche in ecology.
Habitat refers to a specific place where a species normally lives. For example, habitat of a tiger is the forest, of a shark is the sea, and of Plasmodium are the red blood cells. More than one animal or plant may live in the same habitat. For example, tiger, deer, wolf, fox, lion, etc. may be found in the same forest.
Animals exhibit habitat specificity and require specific environmental conditions to live. For example, a fish lives in an aquatic habitat, but a river fish can live only in freshwater, while a sea fish can live only in a marine habitat. Some organisms are more tolerant than the other.
A habitat can be subdivided into regions with different environmental conditions. These subdivisions are called microhabitat. For example, in a pond, some organisms are surface dwellers while some others are bottom dwellers.
For a species to maintain its population, its individuals must survive and reproduce. Certain combinations of environmental conditions are necessary for individuals of each species to tolerate the physical environment, obtain energy and nutrients and avoid predators.
The total requirements of a species, i.e. resources and physical conditions determine where it can live and how abundant it can be at any one place within its range. These requirements are termed abstractly as the ecological niche. In other words, niche is a term used to indicate not only the habitat but also the role played by the organisms in the environment.
G.E. Hutchinson (1958) suggested that the niche could be modelled as an imaginary space with many dimensions, in which each dimension or axis represents the range of specific environmental condition or resource that is required by the species. Thus, the niche of a plant might include the range of temperatures that it can tolerate, the intensity of light required for photosynthesis, specific humidity regimes and minimum quantities of essential soil nutrients for uptake.
A useful extension of the niche concept is the distinction between fundamental and realised niches (Fig. 2). The fundamental niche of a species includes the total range of environmental conditions that are suitable for existence without the influence of interspecific competition or predation from other species. The realised niche describes that part of the fundamental niche was actually occupied by the species.
A habitat possesses many niches and supports many species. An organism changes its niches as they develop. For example, the common toad, Bufo bufo occupies the aquatic environment when it is a tadpole and feeds on algae and detritus. But after it metamorphosis’s into an adult it becomes terrestrial and becomes insectivorous.
According to Odum, while the habitat is the organism’s ‘address’, its ecological niche is its ‘profession’. Two organisms may be found in the same habitat, but do not occupy the same ecological niche. Each plays a different role in its habitat. Different animals that occupy similar ecological niche in different geographical regions are called ‘ecological equivalents’.