Changes in internal fertilization and the composition of the eggshell further protected the developing embryo from drying out. Limited by their need to re-hydrate, amphibians developed a rib cage that allowed for expansion and contraction while increasing the volume of air that could be processed by the lungs. Within 20 million years these new animals had colonized the land.Īdapting to a terrestrial lifestyle demanded more evolutionary changes, propelled by the need to survive more efficiently. Gills would evolve into nostrils and internal lungs, ventilated by a throat-pump. One hundred seventy million years after the first vertebrates hatched in the sea, a lobe-finned fish crawled out of the Panthalassa onto shore … and gasped a breath of air. Necessity is the mother of invention, adaptation the means to survival. The planet’s first true hunters evolved, and with them the wolves of the sea-the sharks.įor many species of fish, the Panthalassic Ocean quickly became a dangerous place to live. It would be an innovation that would lead to mass diversification, separating predator from prey, instantly reshuffling the ocean’s food chain. And then, some 80 million years after the first fish appeared, a revolutionary feature came into being-a set of biting jaws. Others developed senses that allowed them to see, taste, smell, hear, and feel within their watery environment. Because their internal skeletons were composed of cartilage, many species grew a thick armor-like, bony shield that covered their heads as a means of protection. The first of these vertebrates were filter feeders, possessing no jaws in which to seize prey.
The age of fish-the Devonian Era-had arrived. Amid this Cambrian explosion arose one other creature-a unique animal, tiny in size, that possessed a backbone, which separated its brain and nervous system from the rest of its organs. From multi-cellular organisms sprang trilobites and corals, jellyfish and mollusks, sea scorpions and squids.
And then, 540 million years ago, life suddenly took off. Life first began in these waters 3.5 billion years ago as a single-celled organism and remained that way with very little change over the next 3 billion years. The Pacific is all that remains of the Panthalassa, an ancient ocean that was once so vast it covered everything on our planet but the super-continent of Pangaea. Encompassing 60 million square miles, the Pacific Ocean is the largest and oldest body of water on our planet, and with an average depth of fourteen thousand feet, it is also the deepest, possessing some of the most biologically diverse creatures ever to inhabit the Earth.
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