Question

How does comparing the DNA of different species helps in evolutionary studies???

Answer 1

The different species have evolved over a period of time and this is because of minor changes in their DNAs
Since the DNA contains information in the simplest form, so we get vital ideas as to what kind of changes in the DNA have imposed corresponding changes in the bodies of the organisms, and hence lead us to think that if we impose further changes in the DNA externally, then what external changes will be there in the organisms.
The changes over time that happen in certain kind of organisms over time is Evolution and the DNA (DeoxyriboNucliec Acid) helps us study these changes, and hence Evolution.