EVIDENCE OF EVOLUTION

FOSSIL RECORD
Have you ever looked at a series of maps that show how a city has grown? Buildings and streets are added, changed, or destroyed as the years pass by. In the same way, fossils of animals show a pattern from early ancestors to modern descendants. Fossils offer the most direct evidence that evolution takes place. Recall that a fossil is the preserved or mineralized remains or imprint of an organism that lived long ago. Fossils, therefore, provide an actual record of Earth's past life forms. Change over time(evolution) can be seen in the fossil record. Fossilized species found in older rocks are different from those found in newer rock, as we all know, fossils of early multicellular life forms, such as the crinnoid, occur in 800-million-year-old rocks found in Indiana. Fossils of the pterodactyl, an extinct reptile, occur in 140-to 210-million-year-old rocks.

After observing such differences, Darwin predicted that intermediate form between the great groups of organisms would eventually be found. Since Darwin's time, some of these intermediates have been found, while others have not. For example, fossil intermediaries have been found between fishes and amphibians, between reptiles and mammals, adding valuable evidence about the fossil history of the vertebrates.

Today, Darwin's theory is almost universally accepted by scientists as the best available explanation for the biological diversity on Earth. Based on a large body of supporting evidence, most scientists agree on the following three major points:

1. Earth is about 4.5 billion years old.
2. Organisms have inhabited Earth for most of its history.
3. All organisms living today share common ancestry with earlier, simpler life-forms.

FORMATION OF FOSSILS
The fossil record, and Thus the record of he evolution of life, is not complete. Many species have lived in the environments where fossils do not form. Most fossils form when organisms and traces of organisms are rapidly buried in fine sediments deposited by water, wind, or volcanic eruptions. The environments that are most likely to cause fossil formation are wet lowlands, slow-moving streams, lakes, shallow seas and areas near volcanoes that spew out volcanic ash. The chances that organisms living in upland forests, mountains, grassland, or deserts will die in just the right place to be buried in sediments and fossilized are very low. Even if an organisms lives in environment where fossils can form, the chances are slim that its dead body will be buried in sediments before it decays. For example, it is very likely to be eaten and scattered by scavengers.

Furthermore, the bodies of some organisms decay faster than others do. For example, an animal with a hard exoskeleton(such as a crab) would have a better chance of becoming fossilized than would a soft-bodied organisms, such as an earthworm.
Although the fossils record will never be complete, it presents Strong evidence that evolution has taken place. When a fossils is discovered, paleontologists(scientists who study fossils) analyze the sediments around it.

By radiometric dating certain types of rocks and minerals in those sediments, paleontologists can arrange the fossils in order from oldest to youngest. When this is done, orderly patterns of evolution can been seen. Based on existing fossils, Whales are thought to have evolved from an ancestral line of four-legged mammals, which are represented by there fossils and artistic reconstruction showing what scientists think that they may have looked like. They are arranged in the order that they evolved, based on their fossil's age as determined by radiometric dating.

Source:http://www.helium.com/items/918828-fossil-record-looked-series