Explain the importance of fossils in deciding evolutionary relationships.

Fossils are defined as the remnants or traces of dead plants and animals that died more than 10,000 years ago. It helps in the comparison of primitive organisms with their present descendants and is the connecting link between two groups. 

Fossils are mainly formed when plants and animals die in watery environments or are buried in mud and silt. Soft tissues decompose quickly, leaving the hard bones or shells behind afterward. 

Paleontology studies fossilized past life. Paleontology provides evidence for evolution by providing fossil records of living organisms and how they evolved. Fossils can be dated using relative dating, absolute dating, etc. Fossil ages influence evolutionary connections.

Fossils form when deceased sea, lake, and river creatures sink and are buried in sedimentary rocks because animals don't degrade without oxygen. Fossils are creatures preserved in rocks. Animal bones are preserved in sedimentary rocks layer by layer. The deeper layers had older fossils while the top layers had newer fossils. As time passes, sediment accumulates over it and hardens to form rock. 

For example, archeopteryx.