Scientific Creation Story Part 3 Natural Selection

About the scientific story of creation, explanation of science for the origins of the universe and the world.

SCIENTIFIC

The process of natural selection had begun. As variations arose by chance, some tended toward the preservation of the individual, others toward its destruction. Those variations, however slight, which were in any degree profitable to the individual cell in its complex relations to other cells and to the external environment tended toward its preservation, and only those cells which happened to possess the most profitable variations survived. In this way, nature improved upon her products; simple living cells became more sophisticated and their characteristics became more diverse.

Plant and animal cells of a similar type began to unite into colonies. Reproduction continued. Offspring tended to inherit the advantages that their parents had exhibited, and in the billions of young colonies produced, the number of offspring was increasing geometrically.

Competition arose among the increasing numbers of living things. Food, space, water, and air were in demand. The slightest advantages helped to determine which animals and which plants would survive to pass on new characteristics to their offspring and which would simply perish.

The time was about 2,000 million years ago, and the earth was in its Archeozoic, or "primitive life," stages. All life was concentrated in the salt seas, in the forms of simple one-celled animals and plants. Extensive volcanic activity and mountain-building was going on, and there was no life outside the warm oceans.

Eight hundred million years passed, and the earth entered the Proterozoic, or "1st life," era. Invertebrate phyla evolved, becoming more and more varied from one another. After another 650 million years, the earth entered the Paleozoic era, the era of "ancient life," in which extremely diverse products of evolutionary development were abundant.

At the beginning of the Paleozoic era, around 550 million years ago, the earth's climate was uniformly mild and the continents were submerged beneath wide, shallow, salt seas. There was no life except in the salt water, but there it was teeming. On the ocean floor, corals fastened themselves and found food in the water which they had learned to filter. There were nautiloids, like squids on conch shells, and crinoids, which look like flowers but are really animals. Most numerous were the trilobites, looking like scarabs with shieldshaped heads and many legs, and the brachiopods, somewhat like clams. The largest animals at this time were the 6' eurypterids, or sea scorpions, with their powerful crunching claws.

The 1st period of the Paleozoic era, the Cambrian period, lasted for 105 million years. In the next period, the Ordovician, which lasted another 70 million years, the invertebrates reached the peak of their dominance, the brachiopods were abundant, and the trilobites and nautiloids had reached their climax. It was then, in the Ordovician period, that a new creature emerged, different from the rest in one important aspect: It had bones.

These boned animals were the ostracoderms--primitive, jawless fishes. Not only did the jawless fishes have an outer covering of bone, but they had developed something new--a living, growing skeleton, giving inner support. The vertebrates had arrived.

The jawless fishes had small, simple brains connected to the spinal column. Some of them had eyes, other had eyes and nostrils for smelling. They were good swimmers and as time went on the more advanced jawless fishes left the ocean to become the early colonists of freshwater streams.

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