Here's a breakdown:

* Population: A group of individuals of the same species living in the same area at the same time. For example, the population of deer in a forest.

* Species: A group of organisms that can interbreed and produce fertile offspring.

* Ecosystem: A community of living organisms (biotic factors) and their non-living environment (abiotic factors) interacting as a system.

Let me know if you have any other questions!