Valence shell
The number of electrons in the outermost shell of a particular atom determines its reactivity, or tendency to form chemical bonds with other atoms. This outermost shell is known as the valence shell, and the electrons found in it are called valence electrons.
This has happened before in Yellow Stone National Park in CA. Removing a species form the Pyramid causes the ecosystem to collapse, as species become over hunted and others are starved. One type of organism could become overpopulated, therefor lack of natural variation.
That process is called homeostasis
Secondary succession has soil when primary doesn't
I don't know if this helps Sorry if it doesn't I tried
The answer is population I think
