Creationism anti-science propaganda claims that all the major forms of life suddenly appeared during the Cambrian age. The fact is that only primitive life forms existed at that time. Fossils of life forms dating to pre-Cambrian times are rare simply because they did not have hard parts, which developed during the Cambrian period.
Here are the facts, which are based on solid geological evidence, evidence which creationists have not, and can not, refute:
During the Cambrian, no plants, with the exception of algae, existed. Land plants did not come into existence until 200 million years later.
Swimming fishes did not appear until 100 million years after the close of the Cambrian. Reptiles and birds did not exist until 130 million years after the end of the Cambrian. Mammals did not appear until 440 million years after the close of the Cambrian.