A population is all the members of a specific species that life in a particular area. For example, the population of rabbits in a forest.
Community is used to describe all the populations of different species that live together in that area. I.e. all the living things in an area. For example, a community would include all the rabbits, finches, and trees that live in a forest.
The ecosystem refers to all the living and non-living things in an area. For example, it considers the community of rabbits, finches, and trees that live in a forest, as well as the sunlight, the gases in the air, and the water in the lakes.
