The of a species is usually the result of predation, competition, and other types of interaction between species.

Realized Niche

Explanation:

Realized niche is also referred to as Post Competitive niche and can be defined as a thriving environmental area created by a group of organisms to survive from an exsisting Faundermental  niche where interactions (predation, competition, light, water,food) with other organisms were limited and competed for.  

For example. In a tree( Faundermental niche) which houses different species of birds, In order to survive, each specie of the birds will create a realized niche so as to survive from predation, competition, light etc which the whole tree provides.

as many times as you want

the fossil record provides evidence of a common ancestor to many species.