As you talk in animals
nucleus/ plasma membrane / mitochondria
if you talk in plants
nucleus / the cell / plastid / mitochondria
<span>All of the populations of different species that occupy and are adapted to a given area are referred as a community.
In a community, there will be many populations of different species. Population is a group of individual in a certain area. The more species in the community, the more complex it is.</span>
Plankton is the organisms that form the base of most open ocean food webs because fish eat plankton and bigger fish like sharks eat the little fish that eats the plankton.