Fossils provide information about prehistoric life. They form when organisms are quickly buried and replaced with minerals over time. Fossils include hardened remains, like bones and shells, and traces of organisms, such as footprints. Scientists can use fossils to learn about ancient environments, climates, and the timeline of life on Earth.

2. Chapter: Clues to Earth’s Past Table of Contents Section 3: Absolute Ages of Rocks Section 1: Fossils Section 2: Relative Ages of Rocks

23. Section Check 1 Question 1 What are fossils? NC: 5.01

24. Section Check 1 Answer Fossils are the remains, imprints or traces of prehistoric organisms. NC: 5.01

25. Section Check 1 Question 2 What type of fossils represents organisms that existed in abundance on Earth for short periods of time? A. index B. original C. relative D. trace NC: 5.01

26. 1 Section Check Answer The answer is A. Geologists can estimate the ages of rock layers based on the particular index fossils they contain. NC: 5.01

27. Section Check 1 Question 3 How do permineralized remains differ from casts? NC: 5.01

28. 1 Section Check Answer Permineralized remains are fossils in which the spaces within organisms’ hard structures are filled with minerals from groundwater. Some original material from the fossil organisms’ bodies might be preserved. A cast is a fossil that forms when the mold of a completely decayed organism fills with sediment or minerals. NC: 5.01