Something I did in science

Certain traits are more common in a population because the traits increase an individual's chance of surviving to reproductive maturity and or/having the opportunity to reproduce and pass on individual genes to the next generation.

One piece of evidence is that gobies live in a long river with a short waterfall they are more likely to have a long body. This is because they have to be faster because there is a lot of predators in the water because it is shallow water, and they need a short waterfall because they can not climb that well. So this means you are more likely to find a long goby in the long river, with a short waterfall. Another piece of evidence is that the short fat goby are more likely to live in a short river tall waterfall environment. This is because the short fat gobies are slow and can't avoid the predators as easily

Another piece of evidence is that there were more black mice then the white mice at 160 white mice to 82 black mice. This started to change since the white mice died but the black mice population survived. And at late 2008 they had equal populations with both at 130 of each. Then the black mice population kept growing and the white mice population kept decreasing ending with 140 black mice to 120 white mice. This was because the black mice did not die as easily because they blended in with the environment, and the white mice did not so they were caught easier than the black mice.