1970 or 80’s?

I don’t remember much of the movie. I do know I was in grade school when I saw this so it had to of been a 1970 or 80’s movie. I know it was a sci fi movie. There was a comet that passed by close to earth and caused a change. People and animals both changed and I believe they became more violent. The only scene I really remember is the end where there was a bear, I think it was standing upright in attack mode and there was a man at the end lost all of his hair, like he slid a wig off hair loss. I only saw it once and that was eons ago. I have tried figuring it out for years and I just can’t figure it out. I do not know the actors or anything.