(August 2004) Biological Diversity For approximately 4.5 billion years, the Earth has been evolving from a barren volcanic landscape into the vibrant globe full of life that it is today. The first forms of life, small microorganisms, have been found in fossils from 3.5 billion years ago. Around 1.5 billion years ago, motile microorganisms emerged allowing life to migrate to different environments with different environmental conditions like increased exposure to ultraviolet radiation or higher temperatures. Microorganisms began to evolve with the changing environmental conditions of the planet. These new environmental conditions, acting as selective pressures, drove the evolutionary process. They…