Evidences of organic evolution > Palaeontology

The preserved remains, impressions, or traces of ancient organisms found in Earth's crust that provide evidence of past life and evolution are called fossils.

Fossils are preserved remains or impressions of past organisms found mainly in sedimentary rocks, and their study is called palaeontology.

• Fossils are mainly found in sedimentary rocks.
• Sedimentary rocks form by the deposition of particles in layers called strata.
• Different-aged strata contain fossils of different life forms.
• Lower strata = older fossils (primitive forms)
• Upper strata = newer fossils (advanced forms)

Steps:

1. Organism dies.
2. Remains are covered by mud, sand, silt, resin, ice, or other sediments.
3. Soft parts decay; hard parts (bones, shells, teeth) or impressions remain.
4. Minerals gradually replace or fill the preserved remains.
5. A fossil is formed over thousands to millions of years.

Two Theories of Fossilisation:

1. Relative method: Fossils closer to the surface are more recent; fossils deeper in strata are older.
2. Absolute method (carbon dating): Based on radioactive decay of C-14; reliable for once-living material.

• Provides the most direct and convincing evidence of organic evolution.
• Helps reconstruct the phylogenetic history (evolutionary tree) of organisms.
• Reveals forms and structures of extinct organisms (e.g., dinosaurs).
• Records missing links between two groups of organisms.
• Helps reconstruct palaeoecology – the past environment and habitat of organisms.
• Confirms that life forms were different millions of years ago and that they changed over time.
• Geological time scales are based on fossil records.

• Fossils are the preserved remains or impressions of organisms buried under the 
• Palaeontology is the study of ancient life using fossils, which are preserved remains of organisms found mainly in sedimentary rocks.
• Fossils provide direct and strong evidence for evolution and help in understanding the history of life on Earth.
• During fossilisation, older and more primitive organisms are found in lower layers, while more advanced forms occur in upper layers.
• Types of fossils include actual remains (e.g. mammoth in ice), moulds (impressions), casts (filled moulds), and compressions (carbon film outlines).
• Fossilisation occurs through processes like replacement and infiltration, where organic material is replaced or filled with minerals.
• Palaeontology helps study extinct organisms, reconstruct evolutionary history (phylogeny), and identify connecting links between species.