Question

Ecology is the study of the differences between plants and animals in their environment

Answer 1

Are you asking whether this is true or false?

I don't really like it as a definition, so I would go with "false".

The thing it, its not really the study of differences (although it might include studying some differences) as much as it's a study of the interactions of the organisms and their environment: it does not have to include any differences at all!