Genetic mutations are the random changes in DNA, altering the order of nucleotides in the genome of an individual.
The genetic material within the cells is constantly replicating and repairing itself. In general, this process is performed without any errors. However, a mutation may occasionally happen when a single base is substituted for another, or there is a deletion or insertion of a base. Even the duplication or inversion of a DNA segment may occur.
If the mutation is harmless to the individual, and it happens in the gametes, it will be inherited by the descendants
Genetic mutations are one of the leading causes of diversity in the gene pool of a population. They create distinct versions of the same genes, called alleles.
How it works:
Evolutionary change is mostly an adaption to leave more offspring; it is something impossible to obtain by chance. A random mutation worsens the individual in most cases, and only very few of them improve it.
Mutations are necessary for evolution to happen, but they are not sufficient. The problem is that if the only driving force of evolution is mutations, which occur at random, how can the mutation “know” what will make the individual better adapted to its environment and what will make it worse?
One example of a mutation can be a small random change in the gene of a tiger, such that it causes its teeth to become sharper. If this represents a reproductive advantage over the other members of the population, the descendants of this tiger, the ones that inherit this gene, will also have a reproductive advantage over the rest of the individuals of the species. Over time, there will be only tigers with sharp teeth.