Discover Relative Ages of Rock Layers with Index Fossils and Living Fossils that Evolved Little
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Index fossils & living fossils
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Discover Relative Ages of Rock Layers with Index Fossils and Living Fossils that Evolved Little
- 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).