Metabolism (pronounced: meh-TAB-uh-liz-um) is the chemical reactions in the body's cells that change food into energy. Our bodies need this energy to do everything from moving to thinking to growing. Specific proteins in the body control the chemical reactions of metabolism.
Animal cell does not have cell wall because they do not need them.
The question on this specific query is rather confusing however, in trying to explain human population has grown into a massive populace which can be called overpopulation which in sense causes a specie to be invasive in an ecosystems and more biosystems.
