Mutations can affect the coding of "base pairs" in the chromosome of an individual by various means like:
1) by Deletion
2) by Duplication
3) by Translocation
4) by Inversion
After all that changes, codes deviates from normal information & can affect individual in negative way. In that manner, Mutations affect individual traits.
Hope this helps!
<u>Answer:</u>
<em>It is not true to say that common ancestors occurs only within a single species rather two species with similar traits might have a common ancestor. </em>
<u>Explanation:</u>
If the ancestor is same for both the species then it is said that both the species are closely related and share common ancestor with similar evolutionary relationship.
Phylogenetic tree are drawn and studies are done to understand the ancestor of a species. The evolution has occurred from the ancestor to the new species formed.