They form when an ice field is broken up by strong waves and wind. It ended with the largest mass extinction in history and was followed by the Mesozoic Era. It existed during the Permian and Jurassic period . It began breaking up during the Jurassic period, forming continents Gondwanaland and Laurasia , separated by the Tethys Sea. Lice are an example of a parasite that affects many animals.
Parasitism is a type of symbiosis .
The period is the basic unit of geological time in which a single type of rock system is formed, lasting tens of millions of years. It ended with the largest mass extinction and was followed by the Mesozoic Era. Ancient sharks swam the seas during the Permian period. In classification, a phylum is a group of related or similar organisms. A phylum contains one or more classes.