Q. Which one of the following terms describes not only the physical space occupied by an organism, but also its functional role in the community of organisms? (UPSC Prelims 2013)
Answer:
Ecological niche
Notes: The correct answer is
[B] Ecological niche. In ecology, the concept of a niche is much broader than just a physical location; it encompasses the totality of an organism's existence and its interactions within an ecosystem.
- Ecological Niche (Statement B is Correct): Coined by Joseph Grinnell and later refined by Charles Elton and G.E. Hutchinson, an ecological niche represents the functional role and position of a species in its environment. It includes how it meets its needs for food and shelter, how it survives, and how it reproduces. It covers the range of physical, chemical, and biological conditions it can tolerate. Crucially, no two species can occupy the exact same niche in the same habitat for long (Gause’s Principle).
- Habitat (Statement C is Incorrect): A habitat is simply the physical place where an organism lives (its "address"). While a habitat might support many different species, each of those species will have a unique niche within that habitat. For example, a forest is a habitat, but a woodpecker and an owl living in that forest have very different niches.
- Ecotone (Statement A is Incorrect): An ecotone is a transition area between two biological communities or ecosystems, such as the area between a forest and a grassland (a marshland is an ecotone between river and land). It is a zone of junction and often has higher species richness (the "edge effect").
- Home Range (Statement D is Incorrect): A home range is the geographic area over which an animal habitually travels in search of food or mates. It is a spatial concept used in animal behavior and is not concerned with the "functional role" or the biological interactions defined by a niche.