They say that it shows gradual evolution and transition etc. What are they basing this on?..
The fact that, for a number of species, there's a very clear record of descendancy through many transitional forms.
There's just not such a clear record for
every species, and why would there be? Fossilization is rare. For instance, at one point, there were over one billion passenger pidgeons. How many passenger pidgeon fossils are there? Zero.