I am currently finishing my second year as an undergraduate at UW.

My program is Math and the course load is heavy. However, I have been interested in Natural Science since I was a child. I really really want to spend some extra time taking courses from one of the subjects mentioned in the title. However, I intend to know about them further before deciding which to take (work load, future job prospects, etc.). What kind of jobs can I expect for each of these majors? Another important question to me is: which of them is comparatively easier to get into graduate studies (What I mean is, many graduate studies programs only admit students with a related undergraduate major while my major is apparently not nature sci)?

I know I can Google these majors and I already did, but I would like to hear your opinions if you have much knowledge about these or are in one of these programs now. Thank you so much in advance and I would really appreciate your ideas! :)