What are fossils? How are they formed? Described in brief two methods of determining the age of fossils. State any one role of fossils in the study of the process of evolution.

Fossils are defined as the dead remains of plants and animals that lived in remote past.

Dead plants and animals are decomposed by the microorganisms in presence of oxygen and moisture. The complex substances are broken into simpler substances but sometimes in absence of oxygen and moisture, the dead bodies are not decomposed completely and gets preserved in form of fossils in the rocks.

The methods through which the age of fossils can be determined as follows:

1. Relative method:

Those fossils which are present in more closer layer to the surface of Earth are found to be more recent and those which are present in deep layers are found to be more old.

2. Carbon dating: Since the animals and plants contains carbon-14 atoms which are radio-active in nature. After becoming the fossils, the radioactivity of carbon-14 starts decreasing. So, the fossil age can be found by finding the radioactivity present in the fossil and in living objects and then comparing them.

The presence of fossils proves the evolution. The example of Fossil is: A bird Archaeopteryx has many characteristics of reptiles and seems to be evolved from reptiles.