What can a paleontologist learn from fossils? why have so few organisms become fossilized?

Paleontologists learn about the existence of life on Earth over a thousand of years by digging up buried fossils in the ground and studying them. Paleontologists can also identify organisms that are ancient of those that are living today. It has been studied that few organisms become fossilized because of the circumstances that an organism has specific rare conditions that are required for fossilization.