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By around 500 million years ago, bacteria in the oceans had evolved into the earliest fish. These strange creatures had no jaws; they had funnel-like Sucking mouths. |
The first animals – including the common ancestor of all animals today – evolved in the sea over half a billion years ago. We have no direct evidence of what they were like.
But by studying animals today, we can work out features they must have shared – small size, soft bodies, and a tendency to stay very still or creep slowly across the ocean floor.
The creatures had bodies built from multiple cells with specialised roles, like organisms before them. Now, those cells could also form sheets called epithelia, allowing structures to develop. Along with increased genetic complexity, this set the scene for big changes.
Earth’s environment was in flux during the Cambrian period, and the Ediacaran period that came before it. Sea levels rose, and chemicals washed into the ocean. In the underwater world, evolution got to work. New creatures emerged that could move further than ever before – and change their environment by burrowing and building. Soon, the new species were living in every habitat across the length and breadth of the ocean.
Credit: Natural History
Picture credit: Google
