What are fossils? What do they tell us about the process of evolution?

Explanation

A fossil is evidence of an organism that lived long ago. These are remnants or impressions of the extinct organisms Which existed on earth millions of years ago. Fossils can be of following types:
a. Trace Fossils- These are indirect evidence of the dead organism. E.g footprint, trail etc.
b. Cast-: In rocks, the spaces are filled with dead organism making its replica or cast.
c. Moulds- organism buried in sediment and decayed leaving an impression.
d. Petrified Fossils minerals replacing the hard part of the organism
e. Frozen Fossils- Organism trapped in. ice or in tree sap which hardened later.
Fossils help us understand the process of evolution in following ways:
These are the clues to the past, trace the path of evolution
a. Help in building evolutionary relationships among the present organisms E.g. fossil evidence like Archaeopteryx and some characteristics of present-day birds like this hoatzin suggest that dinos·acrs might have been the ancestors of today.s birds
b. Fossils help us in learning diversity of life and animal behaviour in the past. This helps in understanding ancient environment ang climate and categorizing geological time scale.