The correct option is THE ELECTRON IN THE OUTERMOST ELECTRON SHELL.
Different levels of energy exist in the atom of an element and these levels are filled with electrons. The electrons in the innermost shell has the lowest energy level while the electrons in the outermost shell has the highest energy level. For an electron to increase its energy level, it has to move to an higher shell; and to decrease its energy level it has to move to a lower shell.
They compete for food, water and space
Speciation is the
process by which new and distinct species are formed. One of the most important
factors necessary for speciation to occur is the genetic isolation of two
populations. This genetic isolation can, over long periods of time, cause these
two groups to become genetically incompatible. Factors that can lead to this
genetic isolation include geographic separation and hostility among population
groups.
