How do biological communities get to be the way they are?

Biological communities evolve through ecological succession. Ecological succession is the change in the structure and composition of species in a specific ecological community over time that can be observed. Ecological succession can occur as a natural process of time, or it can be instigated by a sudden event, a wild fire, for example. There are natural changes that occur that effect the species type and variation that exists and thrive in the communities.