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.
The fifth one was 65 million years ago, when the dinosaurs vanished. Today we're losing biodiversity at a similar rate. And this is, of course, an anthropogenic mass extinction. The primary cause is human communities. But what we're trying to do in extinction studies is to think about scale in different ways.