Life, Part 2 (The Ocean)

While there were no signs of life on land, it was just beginning to take shape in the deepest reaches of the ocean. Single-celled life-forms, prokaryotes, moved around on the ocean floor. Over the course of thousands of years, a split between prokaryotes known as archaea and bacteria occured. The bacteria used a primitive form of photosynthesis, and some even evolved into cyanobacteria, which, like the bacteria of the time, used photosynthesis and produced oxygen as a waste product. The first forms of life on land likely could have been seen during this time. Over the course of years, eukaryotic cells, cells with a nucleus and organelles, evolved on the ocean floor. They joined together to make the first multi-cellular organisms. Our ancient ancestors. Even though it seemed as if life was beginning to take shape, a perilous event seemed to have stopped it from continuing any further. And it was just the beginning too. This event was the first ice age. Glaciers sprung up on every corner of the young planet, which might have killed all life. But, there is also the possibility that it increased the growth of it. After this ice age, the gathering of oxygen in the atmosphere also allowed the formation of an ozone layer around the Earth, protecting it from the sun's radiation. And, surprisingly, the first complex multi-cellular organisms appeared after this ice age, in a sudden explosion of many, many new forms of life. Creatures such as trilobites, early molluscs, anomalocarids, and even early fish evolved during this time. (Anomalocaris) This period of time was also when the earliest forms of fungi evolved on land, and even some forms of plant life in the sea, such as sponges and corals. Life seemed to be greatly recovering after the first ice age. The cambrian era marked a major explosion of life in the oceans. Though what was most remarkable about this period of time was how fish evolved. The first jawless fishes and fishes with spines started to appear. These fish were our early ancestors, creatures that would make way for many forms of life in the future. The first ray finned fish evolved to swim around the vast oceans, and were hunted by early arthopods. Arthropods, speaking of which, could possibly have been the first creatures to ever set foot on land and inhabit it, even before the first amphibians. (Eurypterid scorpion climbing onto land) Meanwhile, the first plants were also moving onto land, which evolved from green algae living on lake edges, and joined the fungi. Fish were getting bigger and stronger. And the Devonian period was the heyday for the fish. They dominated the oceans, and came in many different shapes and forms. Some of them even evolved sets of teeth or armor, such as the infamous Dunkleosteus. (Dunkleosteus' teeth were actually just tooth-like bones that were a part of it's armor.) But the big changing point in history for the fish were when a certain type evolved a peculiar set of bones and rays on it's fins reminiscent of fingers. It also had a strange, slightly frog-like head, and looked like a sort of crossbreed between an early amphibian and a fish. It had evolved a peculiar set of adaptations to the shallow waters of it's time, and would be known as the missing link between water and land animals. It swam up to the surface of the ocean, ready to finally move out of the water and on to the rocky, green land above. It swam over, and stepped onto the rocks with it's peculiar fins, which would change evolutionary history for years to come. It's name was Tiktaalik, the first fish on land.