A scientist is studying about the food chain and biomagnifications in a grassland. This study would be at the level of a (n):
Community
A population is a summation of all the organisms of the same group or species, which live in a particular geographical area, and have the capability of interbreeding.
Community is an interacting group of various species in a common location. For example, a forest of trees and undergrowth plants, inhabited by animals and rooted in soil containing bacteria and fungi.
Ecosystem is a biological community of interacting organisms and their physical environment.
The biosphere is the global sum of all ecosystems. It can also be termed as the zone of life on Earth