Part 1 Printing the Circuit Board. 1. Choose a method to use for creating the PCB. Your choice will usually be based on the availability of materials needed by the method, the technical difficulty level of the method or the quality of PCB you desire to obtain.
Permian-Triassic Extinction. In this video segment from Evolution: Extinction!, geologist Peter Ward shows rock layers laid down during the Permian and Triassic periods. The Permian layers contain abundant animal fossils and fossilized traces of animals, while the Triassic layers are almost devoid of fossils, suggesting a mass extinction event occurred 250 million years ago, at the end of the Permian.
There was at least 1 mass extinction event during this period that covered the time between 4.6 Ga (billion years ago) to 523 Ma (million years ago), occurring near the end of the period.During this period all organisms were soft-bodied, the first hard-shelled forms didn't evolve until the the Cambrian.here was at least 1 mass extinction event during this period that covered the time between 4.6 Ga (billion years ago) to 523 Ma (million years ago), occurring near the end of the period.