Evolution of reptiles

Evolution of reptiles

1. Seminar topic: EVOLUTION OF REPTILES THROUGH AGES

2. Seminar Content Introduction - EVOLUTION Representing vertebrate evolution Labyrinthodonts Amniotic egg Classification of reptiles Skull Vertebral Column Limbs and Skin Mass extinction Conclusion References

3. INTRODUCTION Evolution is the change in the inherited characteristics of biological populations over successive generations. Evolutionary processes give rise to diversity at every level of biological organization, including species, individual organisms and molecules such as DNA and proteins A Reptile is any amniote (tetra pod that can lay eggs on land) that is neither a mammal nor a bird.  Unlike mammals, birds, and certain extinct reptiles, living reptiles have Scales or scutes (rather than fur or feathers) and are cold blooded .

4. BODY FINS FINS BODY BODY BODY EVOLVED VERTEBRATES- Terapods to Bipods body lifted from the ground with two legs REPTILES- TETRAPOD –Body lifted from the ground AMPHIBIANS- TETRAPOD –Both Limbs (Fore & Hind) and body touches the ground (Parallel to ground) PISCES – Body adopted to live in water with fins E V O L U T I O N O F V E R T E B R A T E S REPRESENTING VERTEBRATE EVOLUTION

5. LABYRINTHODONTS The reptiles were derived from the amphibians, specifically from certain Labyrinthodonts Transition from amphibian to reptile took place during the Carboniferous period of the earth history Of course the final crossing from the amphibians to the reptiles occurred with the perfection of Amniote Egg The oldest known fossil amniote egg is from Lower Permian sediments in North America The appearance of the lower jaw or the migration of the backboned animals from the water on to the land paved a way for the success of reptiles on the earth

6. Amniote Egg The egg mainly consists of : Amnion : consists of amniotic liquid and embryo Yolk : provides nutrients to the embryo Allantois: receives the waste products produced by the fetus Chorion : encloses Amnion, Allantois, yolk and yolk sac Shell : It is both tough and porous to protect and exchange O 2 and CO 2 respectively.

7. CLASSIFICATION OF REPTILES : Subclasses: Anapsida- Proto reptiles which include turtle Diapsida- majority of the reptiles, progenitor of birds Euryapsida- Plesiosaurs, Placodonts and Ichthyosaurs Synapsida- mammal like reptiles, progenitors of mammals

8. CLASSIFICATION OF REPTILES

9. PICTURE SHOWING PTEROSAURS WHICH HAD GLIDER WINGS

10. Pineal foramen , characteristic of labyrinthodonts persists in the early reptiles but disappears with the advancement Pterygoid bone of the palate are prominent in reptiles and in primitive forms, these bones carry well developed teeth Skull in reptiles is rather deep , in contrast to the flattened skull of the Labyrinthodonts Primitive otic notch is suppressed SKULL The occipital condyle is single in most of the reptiles, a character that is fore shadowed in the Anthracosaurs

11. VERTEBRAL COLUMN OF A TYPICAL REPTILE The clavicle(collar bone) and the inter clavical bone is present in the reptilian shoulder girdle which is much reduced as compared with these elements in the Labyrinthodonts Among the primitive reptiles, the ribs form a continuous and generally similar series from the skull to the pelvis Primitive reptiles have two sacral vertebrae wherein amphibians have only one Ilium will be attached to the sacrum Clavicle Sacrum

12. LIMBS AND SKIN OF REPTILES Limb bones are generally slender than these bones in the labyrinthodonts In the wrist there are never more than 2 central bones but labyrinthodonts have 4 central bones 2 proximal bones in the ankle as contrasted with the 3 in the amphibians The phalangeal formula of reptiles (seymouria) is 2-3-4-5-3(4) Skin : It has horny epidermis folded overlapping scales and scutes

13. MASS EXTINCTION: Evolution of reptiles has been marked by three mass extinction as shown in the right. MESOZOIC ERA is known as the age of reptiles.

14. EARTH DURING MESOZOIC ERA

15. C O N C L U S I O N Evolution is the fundamental property of life. Evolution of life through ages throw a light on palaeobiosphere of the past. Evolution in all groups of life help in the reconstruction of the historical geology. In particular the history of the earth. Reptiles will bridge the connection between aquatic and terrestrial vertebrates. This is the stage where we can see all the modification. Some evolutionary aspects will remain unchanged even today. Reptile evolution can be seen in all the forms of nature i.e., air, water and on land.

16. REFERENCES Edwin H Colbert (1969) Evolution of Vertebrates- Publ. V.R. Damodaran for Wiley Eastern limited- Second edition- Pp- 110 – 126. www.google.com/images en.wikipedia.org/wiki/ Evolution_of_reptiles

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