Answer/Explanation:
Gene mutations are changes to the DNA sequence that arise by chance. These changes can cause the gene to have different functions. Usually, these functions are not beneficial - i.e. the mutation makes the gene work less efficiently or not at all.
However, on rare occasions, the altered gene function is advantageous, meaning it gives the organism a benefit for survival.
Mutations in the germ line are always passed on to the next generation, i.e. they are inherited. But if a mutation gives a selective advantage by helping survival, then that organism is more likely to survive to reproductive age and pass the mutation on.
The inheritance of this mutation and the selective pressures acting upon it are the driving forces of evolution.
The accumulation of mutations and the pressures of natural selection can affect different populations of the same species differently. For example, if one small population of birds migrates to an island with a different food source, then the selective pressures will be different than for their relatives on the mainland.
Over time, speciation will occur, and two new species will form. While they have a common ancestor, they are no longer the same species as evolution has caused them to diversify.
