Okay I need help with something, and it needs to be sorted as soon as possible. I'm just really confused right now and I don't know what to do. I've got a science fair project due in a few days, and I'm doing it on a basic overview of evolution, but I've run into a roadblock. I don't quite understand the differences between natural selection and sexual selection. Natural selection is the process by which a mutation that gives an organism an advantage that makes it more likely to pass on its genetic code is made mainstream in a population. This means that the adaptation give it a better chance of survival and a better chance at being chosen to pass on its genes. Sexual selection is best demonstrated by a peacock's tail. It doesn't supply any survival benefit, yet it just so happens that peahens have sexual preference for peacocks who have bigger and better groomed tails. That probably started out as a health issue, but natural selection made the tails bigger and bigger, to the point where the tails are now of a ridiculous size. This is where I get confused. Have I got it wrong? Is natural selection only the increased chance of survival, while sexual selection is how the females choose their mate? If not, how do I draw a defining line between the two? Help please, I don't understand.
You've pretty much got it right; natural selection is more of a necessity, but at the same time there isn't much control of that in the animal kingdom (a bit different with humans, but only a bit). Sexual selection is where one sex chooses a mate, mainly.
Sexual selection is a part of natural selection. Natural selection isn't about survival of the individual per se; it's about what genes get passed on to the next generation. So if, by means of sexual selection, a partner chooses to mate with you, then your genes get passed on to the next generation. It may not help the individual in its own lifetime though. On the other hand, advantages in regards to survival also help the individual to help reach the age of sexual maturity so he can mate etc. Life's all about sex. Evolution says so.
