Question

what characteristic does an organisms niche in an ecosystem define?
reproductive age
territory
role

Explanation:

In ecology (a subfield of Biology, which is under Natural Science), an organism's niche refers to its role in the ecosystem, including how it interacts with other organisms and its environment. Reproductive age is about the life - cycle stage of an organism, and territory is more about the physical area an organism occupies, while niche is about the functional role.

Answer:

role