Ancient Life Preserved in the Rock


A fossil is any sort of evidence of past life on Earth. First proposed by Charles Darwin, evolution is the changing pattern of life forms through the ages. Unfortunately, one of the side effects of evolution is extinction. Extinction is the disappearance of a species forever.

The Earth was formed about 4.6 billion years ago. About a billion years after it formed, the first evidence of life is observed on the planet. From about 3.5 billion years ago to about 0.5 billion years ago, life on the planet was very simple. It consisted of micro-organisms, bacteria, worms and jellyfish. There were no hard parts to preserve in the rock, so fossils during this time are very rare. Then, about 544 million years ago, there was suddenly an explosion of life and diversification in the oceans. Fossils became abundant; hard parts, such as shells, and teeth are preserved in the rock. Eventually, a worldwide pattern of life-forms became evident. From these observations of a sequence of fossil groups from oldest to youngest, scientists established a relative time sequence known as the Geologic Time Scale.

Homework # 12: Due Monday, May 11, 2009

In review book, read pages 124 - 133. Do questions 52-54, on page 134 and the Chapter review questions, 1-8 on pages 134 and 135.

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