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SAI International School
Subject- Biology
Chapter- Heredity And Evolution

Subtopic- Fossils, Evolution by Stages, Artificial Selection
Module-28
Lesson Notes

FOSSILS
 Fossils are the preserved traces of living-organisms from the past.
 The term fossil is usually applied to bones, teeth or shells of animals that doesn’t
exist anymore.
 Other impressions like footprints are also part of fossilised remains of once lived
life.
 Large parts of animal bones, dried dead skin and hair, have also been
discovered with their bones.
 Around ninety-nine percent of the animal, fossils consist of preserved parts and
these provide us valuable information about life in the past.

Process of Fossil Formation
 Fossils may vary from microscopic organisms (single bacterial cell) to dinosaurs.
 Layers of fossils are formed one after another over years. For e.g., Some
invertebrates on the sea-bed die 100 million years ago, and are buried in the
sand.
 More sand accumulates, and sandstone forms under pressure. Millions of years
later, dinosaurs living in the area die, and their bodies, too, are buried in mud.
 This mud is also compressed into rock, above the rock containing the earlier
invertebrate fossils.
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