Answer:
the great number of different species of organisms that have existed on Earth
Step-by-step explanation:
The great number of different species of organisms that have existed on Earth.
Mutations occur in an alleatory way. According to Darwin (father of Theory of Natural Selection), mutations will make individuals be better adapted or less adapted to their environment. When individuals are better adapted, populations tend to be more likely to survive, reproduce and adapt better.
Due to the large amount of mutations which occur on individuals, Natural Selection generates pressure over species, many tend to adapt and so, millions of species exist.