(a) How does the study of fossils help to understand evolution.

Explanation

Fossils are remains of hard parts of life-forms found in rocks. Rocks form sediments and a cross-section of earth's crust indicates the arrangement of sediments are over the other during the long history of earth. Different aged rock sediments contain fossils of different life-forms which died during the formation of the particular sediment.Some of these fossils appear similar to modern organisms. They represent extinct organism (example : dinosaurs). The study of fossils in different sedimentary layers indicates the geological period in which they existed and that life forms varied over time. The study of fossils also tells us that certain life forms are restricted to certain geological time spans. This points to the fact that new life forms have arisen at different times in the history of earth. This called paleontological evidence.