What are the four basic levels of ecological study, and what is the focus of inquiry at each of these levels?

I don't know what it's asking to start with and can't find anything relevant online, in my textbook or in my study guide! Since it says levels, I think it might be 1) individual 2) population 3) community 4)ecosystem.. but frankly I don't know.. please help!

Please refer to your later post, which I saw first.

Sra