What is your question? I can help!
In any ecosystem, there are factors to control populations.
In a stream, the predators of a certain organism will help keep populations checked. Moreover, the limited resources, such as space and food, will keep the population from growing out of control.
Polymerization would be the answer you're looking for.
Just like how mitosis sorta sounds like toe, I guess you can say "My Toe ill" to remember that mitosis is the repairing of cells.