Earth history; Cambrian
Early in the Cambrian, animals developed hard parts for protection and support for their soft bodies. The outer shell of a brachiopod formed a feeding chamber, while the shield of a trilobite gave fixture points for muscles and legs. Animals with a skeleton could grow larger and colonise new areas of the sea floor. The arthropods could swim, move fast and develop into predators. The animals used different materials to form a skeleton. The first animals were small and used phosphate, sponges used silica, and within 10 million years the larger animals used calcium carbonate. By the end of the Cambrian, the ancestors of most major animal groups had developed in the ocean.
Publisert 18. mai 2011 16:00