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Vertebrates in the Sea & on Land. Section 32.1. 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
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Vertebrates in the Sea & on Land Section 32.1
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
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
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)
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
Three Groups of Modern Amphibians • Frogs & toads – largest group • Salamanders & newts • Caecilians – less than 1%
