Index fossils & living fossils
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This document discusses index fossils and living fossils. It defines index fossils as fossils that can identify and show the relative age of the rocks they are found in, as they were widespread but existed for only a brief period. Living fossils are organisms that have existed for extremely long periods without changing much from their ancient fossil forms. Examples given are brachiopods called Lingulata that have remained virtually unchanged for over 500 million years from the Cambrian period to present.
Index fossils & living fossils
- 1. INDEX FOSSILS AND LIVING FOSSILS DR. MUHAMMAD TARIQ DEPARTMENT OF ZOOLOGY GOVT. COLLEGE OF SCIENCE, WAHDAT ROAD, LAHORE
- 2. INDEX FOSSILS • A fossil that identifies & shows the relative age of the rocks in which it is found.
- 3. INDEX FOSSILS…contd… • Index fossils come from species that were widespread • But existed for a relatively brief period of time.
- 4. INDEX FOSSILS…contd… • The fossil record shows clearly that over time, life on Earth has changed.
- 5. INDEX FOSSILS • Fossils in relatively young rocks tend to resemble animals & plants that are living today. • (Index Fossil: A fossil known to
- 6. INDEX FOSSILS…Contd… • In older rocks, fossils are less similar to modern organisms. • As scientists collected fossils from different rock layers & formations,
- 7. INDEX FOSSILS…Contd… • The fossil record shows clearly that over time, life on Earth has changed. • Fossils in relatively young rocks tend to resemble animals & plants that are living today.
- 8. INDEX FOSSILS…Contd… • They discovered that they could often recognize the rock layer by the assemblage of fossils it contained.
- 9. INDEX FOSSILS…Contd… • Some fossils proved particularly useful in matching up rock layers from different regions.
- 10. INDEX FOSSILS…Contd… • These fossils, called index fossils, • are widespread • but only existed for a relatively brief period of time.
- 11. INDEX FOSSILS…Contd… • When a particular index fossil is found, • the relative age of the bed is immediately known.
- 12. LIVING FOSSILS • Fossils which range from ancient time up to the present day • without any change in primitive characters are referred to as Living Fossils.
- 13. LIVING FOSSILS…contd… • In contrast to index fossils, living fossils are organisms • that have existed for a tremendously long period of time • without changing very much at all.
- 14. LIVING FOSSILS…contd… • E.g., The Lingulata brachiopods have existed from the Cambrian period to the present, • A time span of over 500 MYs!
- 15. LIVING FOSSILS • Modern specimens of Lingulata are almost indistinguishable from their fossil counterparts (Fig.8).
- 16. Fig.8: Fossil Lingula (left) & Modern Lingula (right).