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?

Answer: (b) Ecological niche

A niche is the physical space AND the role: what the species eats, when it is active, what it does in the community.

The idea

Habitat = address. Niche = profession. Two species can share a habitat, but no two can hold the same niche for long (competitive exclusion, Gause).

Where it lives → habitat → What it eats, when it is active, who eats it → role → Habitat + role → niche

Why the others are wrong

(a) An ecotone is the transition zone between two ecosystems (forest–grassland edge).

(c) Habitat is only the physical place — the “address”.

(d) Home range is the area an animal moves around in regularly — space only.

The trap

“Habitat” is the familiar word, but the question adds “functional role” — only niche covers both.

Also know

Two more terms from the options. An ecotone is the border strip between two ecosystems, such as a mangrove between land and sea; it often holds more species than either side, called the edge effect. A home range is the area one animal covers in its daily life.