These notes are provided to help direct your study from the textbook . If you were to study only these notes, you would not learn enough to do well in the course. It is important that you know these periods because as we progress through the evolution of the vertebrates, times of occurrence will typically be given in terms of these periods. When examining the fossil record, some things to keep in mind. Organisms fossilized better in some environments grasslands, forests are very poor at producing fossils.
Older fossils are less common than recent fossils.
During some periods, the rate of change was so fast there was little chance of producing a fossil of the intermediate life forms. At other times, there would be little to no change for a very long time, with a much greater chance of producing a fossil. When attempting to describe the nature of some ancient habitat or the habits of a fossil animal, we use the principle of uniformitarianism , which says that processes that occurred in the past are the same processes that occur today. For example, the movement of glaciers causes striation in the rock as the glacier passes over the rock. Similar striations found in an ancient rock would be assumed to be caused by an ancient glacier.