I do not dispute whales came from land animals, I dispute that the changes were gradual AND that they were driven by "survival of the fittest'.
Look, I am not a biologist, nor am I ecology expert, but even I can see that you don't understand Evolution and what it mean by "survival of the fittest".
No, not by “survival of the fittest”, it is driven by changed environment, eg climate change in the regions, the scarcity of resources or food supply (which would increase competition between organisms), the increase or decrease in certain atmospheric gases, changes in terrains, etc, or it could be combination of any of the above
It is the changes in the environment itself that drive (Natural) “Selection”, which is where populations need to adapt to changes or else it cannot sustain the populations, thereby risking possible extinction.
So, the changes in environments are the driving forces for the needs to force selected changes in populations of organisms. Natural Selection (not “survival of the fittest”) is the mechanism for the ability of organisms to changes, passing these changes through genetic information (eg DNA, RNA).
And Valjean is right, physical changes in organisms are seriously limited by the organisms’ own anatomy:
Evolution has to work with what it has, and how something can adapt/evolve is severely constrained by the anatomy and physiology you have to work with.
TagliatelliMonster is also right:
1. "survival of the fittest" is not actually a thing in evolution, but a sensational / popular media catch phrase
The term is often misunderstood, but worse, it is often misused.
And I think you are doing both, because you have already intended to use this phrase to justify your argument (mistaken opinion) that Evolution is about “marching towards perfection”.
Evolution isn’t about striving for perfection, but about adapting enough so that populations can continue to reproduce offspring with better physical traits than previous or current populations.
Survival don’t mean organisms needs to be biggest or strongest or smartest.
For instance, in the Cretaceous-Paleogene extinction occurred the larger land animals, particularly larger dinosaurs died off, while smaller dinosaurs - birds - and smaller reptiles and mammals survive, and without the competition from the larger dinosaurs, these mammals, reptiles and birds were able to radiate in diversity.
Being the largest and strongest don’t guarantee survival during extinction-level events.