Circumstances

What other factors, if any, besides natural selection contribute to the survival of a species?

I would say that chance, or rather, the circumstance for one species at any given time, contributes heavily to the survival of a species. We said yesterday, I think, that dinosaurs were incredibly "fit"; that is, they survived for a very long time. I do think it is only slightly unfair to call the dinosaurs unfit due to the unfortunate circumstance of the impact of the Chicxulub asteroid. Granted, a prime example of fitness if the ability to adapt to change of circumstance or to have already adapted to survive most anything (i.e the cockroach), though we can hardly blame dinosaurs for not adapting to such a sudden and drastic change. Similarly, I think it would be unfair to, after a nuclear fallout, call most animals unfit for survival. The deep-sea life would likely remain unaffected by the fallout almost purely because of their distance away from the surface. Is this because they are the most fit? I am uncertain about this.