Vertebrates in the Sea & on Land

1. Vertebrates in the Sea & on Land Section 32.1

2. Adaptations of Vertebrates • Chordates with a backbone • Made of vertebra segments • Completely replaces the notochord • Provides a site for muscle attachment and protection of the spinal cord • Allows for a bony skull to enclose and protect the brain • Segmentation • Bilateral symmetry • Two pairs of jointed appendages • Cephalization • A true coelom • Closed circulatory system with a chambered heart

3. The First Vertebrates • First appeared about 500 million years ago • Lived in water • Agnathans – early fish without jaws or paired fins • Evolution of fish involved: • Improved swimming – flattened bodies became streamlined & paired fins for control • Development of jaws – from gill arch supports made of cartilage

4. Modern Fish • More fish species than any other vertebrate • Three groups: • Agnathans – jawless fish; hagfish & lampreys • Cartilaginous fishes – skeleton of cartilage; sharks, skates & rays • Bony fishes – skeleton of bone (95% of all fish species)

5. Agnatha – lampreys & hagfish

6. Cartilagenous fish – Sharks, skates, & rays

7. Bony Fish – most fish are in this group

8. Evolution of Amphibians • Appeared about 370 million years ago • Name means ‘double life’ – they live in water as juveniles and on land as adults • Adaptations to land include: • Legs – support body & allow movement • Lungs – do not need as much water to function • Heart – walking on land requires more energy and therefore a stronger pump

9. Three Groups of Modern Amphibians • Frogs & toads – largest group • Salamanders & newts • Caecilians – less than 1%

10. Frogs – have smoother skin than Toads

11. Salamanders & Newts

12. Caecilian