How does fitness relate to natural selection

Fitness relates to natural selection because of you are not physically fit then you are more likely to live shorter and get eaten by other things.

fitness relates to natural selection because if you aren't "fit" then you most likely won't survive as long as other, having you die or get eaten and killed before others.

small, big, or no change could occur in the phenotype. it could cause something as simple as a cats ears to curl backwards or something as frighting as death. it could also occur in the protien-coding area and have an effect on that but no effect on the amino acids. what has to occur is a changing in the hox gene or the control gene.

thats not even an aswer choice