The third video in a walkthrough requested by XanderMisfit. An age ends, leaving place to a new world filled with oxygen (actually, fishes "breathe" oxygen too, they just get it from H2O). The thing that happens when the fish instantly becomes an amphibian, that's not an accurate representation of evolution at all (but once again, it's a game). A fish can't give birth to a frog for example. This would occur through progressive mutation through many generations. Imagine a fish that can, through mutation, survive outside water 1 more second than other fishes. Imagine this 1 second is required for survival in this environment, then only fishes with this mutated ability (or better) would survive and reproduce. Among their babies, some would get the ability (with potential mutation in their genes, for better, or worse, in which case they would probably not survive). Now imagine that this goes on for millions of years; progressively that older race of fishes gets wiped out and you get a species that can potentially live outside water as the survivor. Maybe they didn't get completely wiped out; some fishes might've developed another way to survive in the environment without needing to breathe longer outside of water so they could stay fishes (through different mutations) or some other fishes developed in another environment that was suited to them as they were, continuing their lives as normal. So at the same time, you get amphibians and new types of fishes that continue to evolve independently. So you get many different species after a while, a long while, because of different requirements and mutations. Note that I don't claim to know what were the conditions in which they evolved or what would be the cause of having to live outside water. I'm referring to a potential situation. I'm not a biologist and I don't claim to be particularly knowledgeable about evolution apart from the basics I learned. There might be mistakes in my explanations, but not as far as I know.