1. FOSSILS & EVOLUTIONARY RATE Dr. Jagdish kaur P. G. G. C
FOSSILS & EVOLUTIONARY RATE Dr. Jagdish kaur P.G.G.C.,Sector 11, Chandigarh

2. EVOLUTION
SIMPLY THE CHANGES OVER TIME

3. Human Evolution

4. Evolutionary Timeline
The evolutionary timeline is divided into sections of time called eras – which are then divided into smaller units of time called periods.

5. EVOLUTIONARY HISTORY

6. Fossils most fossils are found in sedimentary rock
Fossil – evidence of an organism which lived long ago
paleontologist – scientist who studies ancient life
most fossils are found in sedimentary rock

7. TYPE OF FOSSILS
BODY FOSSILS : Whole bodies or pieces of body of past organism.
Tells shape,stucture,size etc.
TRACE FOSSILS : features left behind of past life.
Tells the behaviour

8. BODY FOSSILS

9. TRACE FOSSILS

10. Types of Fossils:
casts– mineralization of a space left by a decayed organism
molds– empty space in rock from a decayed organism
These are formed when an organism such as snail is burried in mud, under water for ages; as the organism undergoes decomposition, its shape is replaced by minerals, living a cast of the original animal in the surrounding sedementary rock.

11. Types of Fossils:
imprints – made typically by thin objects that have been pressed into an area
Imprints such as footprints or leafprints ,are preserved deepressions formed in soft mud or sand that subsequently dry and change into sedimentary rock.

12. Types of Fossils:
carbonized – high temps & pressures expel gaseous elements leaving only carbon

13. Types of Fossils:
petrified – entire organism is replaced by mineral matter.
Petrification occurs when minerals dissolved in groundwater seep in to the tissues of dead organism and replace its organic material, thus turning the animal or plant into stone. Petrified bones of dinasaurs and petrified wood of trees are formed this way.

14. Types of Fossils: ice- or amber- preserved fossils
Amber is the sticky hardened resin of evergreen trees ; responsible for trapping many prehistoric insects. As little bacterial decay occurred, the insect bodies have been preserved.

15. Types of Fossils: coprolite – fossilized faecal matter
Coprolites - fossil dung and stomach content that provides useful information about food habits of the organism.

16. How the age of fossils is determined

17. Dating of Sedimentary Rock
© 2008 Paul Billiet ODWS

18. Types of Dating of Sedimentary Rocks

19. Relative dating .
© 2008 Paul Billiet ODWS

20. Absolute dating
Accurate dating can be obtained using radiometric dating
This uses the phenomenon of radioactive decay of isotopes
© 2008 Paul Billiet ODWS

21. HALF LIFE
TIME TAKEN BY ORIGINAL AMOUNT OF ATOMS TO GET HALVED.

22. Potassium-Argon Method
Potassium-40 (40-K) decays to form Argon-40 (40-Ar), which is trapped in the .
[K-40 Half life= 1.3billion yrs ] Formula:
Formula :
© 2008 Paul Billiet ODWS

23. Carbon-14 Method Carbon-14 (14-C) decays to form nitrogen-14.
[Half life ,000 yrs.]
Formula:
© 2008 Paul Billiet ODWS

24. What is the significance of Fossil record ?

25. SIGNIFICANCE:
It is the goal of a group of scientist to determine the phylogeny [evolutionary history of organism] .
Helps scientist in classifying organisms.
In determining the changes occued in climates.
Helps to discover foems of life that existed in past.
Tells the evolutionary history of organisms.

26. THE END !