What is the cell nucleus?

The concept of keystone species is controversial among ecologists because most organisms are highly interdependent. if each of the trophic levels is dependant on all others how can we say one is most important

Scientists discover two populations of mice on either side of a major river. the two populations have almost identical genes but the mice from one side cannot breed with mice from the other. this is most likely because

In the ocean why are the greatest amount of primary producers found in the epipelagic zone and how does that affect biodiversity