Literally just the ones who survive long enough to have offspring, which survive to have offspring of their own, and so on. Occasionally there are mutations, and while this can be a bad thing, it can also be a good thing if it proves beneficial to the environment this animal happens to be in. Like the bird with the shorter, stouter beak has an easier time cracking seeds open, so its offspring are better able to feed, and eventually the other birds die out because they starve. Or the moth that blends in with the bark of a tree is able to avoid being eaten by birds and thus is able to reproduce and make more like itself, only to then end up getting eaten because the industrial revolution leaves all the trees coated in soot, so it stands out rather than being blended in, and now the dark-colored moths that blend in with the soot are able to survive and reproduce.
Christians look at plants and animals that are adapted to their environment and think that God made them that way, whereas the scientist looks at what evidence there is and is able to deduce that this is but the latest iteration in a long line. I have no idea how many times I've seen some creationist claim that there are no "transitional fossils" and yet they are all over the place. There is also now DNA analysis which helps to point to this as well. This is why it really bothers me when I see the terms "micro evolution" and "macro evolution" tossed around, because to me it just illustrates a fundamental misunderstanding of what evolution is, and how it works on all levels. It's honestly just a cope because anyone with more than two brain cells to rub together can see how viruses and other micro-scale organisms will literally evolve right before your eyes because of how short their generations are, but they don't want to admit to themselves that the same would apply to all other organisms.
Personally, when I was still a Christian, I had no problem with evolution because I saw that as simply part of God's work, and I saw Genesis as allegorical rather than literal. How better to create all living creatures on the same day than to create a common ancestor for all of them, after all. There really need not be any conflict between religion and evolution, since evolution is just about changes over time, but a lot of Christians seem see it as an attack on their religion, and also seem to confuse it as an alternate to creation when it explicitly defines itself as needing an already existing organism to work. Now, there is a secular, scientific theory on the origin of life, but it isn't evolution, it has its own name, abiogenesis (ironic, no?).
In any case, what does any of this have to do with the whole "tradwives" topic anyway?