Coevolution is the method by which two or extra kinds emerge in tandem by exercising selection forces on each other. Coevolution happens when two or more species reciprocally influence each other's development.
Coevolution is basically a change in one species, that is some way triggers ore "commands" the changes that will happen in other species (these two are normally related in some way, like a predator and pray for example).
Remember that a cell that is surrounded by an environment with a higher osmotic pressure, will produce that the cell get some water outside to make some dilution to the salt concentration that surrounds the protozoan.
Autotrophs are organisms that are able to use a source of energy such as sunlight, to produce their own food. Heterotrophs cannot produce their own food and must rely on the foods they ingest for energy.
