@scd,
Your comparison to a car is a bankrupt comparison. Car parts are not known to change, even when bombarded with heat, light or other forms of energy.
In contrast, DNA for living organisms are known to change when bombarded with various kinds of energies.
Since the only thing that constrains a life form for how big or how small it will become is DNA, plus the natural pressures of natural selection, there is no limit to how much a population can change in color, size, shape, diet and reproductive strategies…
And if you accept the idea that God guides DNA changes, then there is no limiting factor.