Chordates Part 3
• Fins are thin membranes supported by bone
•Secrete mucus, reduce drag, slimy
• Swim bladder to adjust buoyancy to compensate for heavy bone.
• Can breath while stationary
• Largest group of living vertebrates
Ichthyology: study of fish
Tetrapods (four footed): land vertebrates
• Evolved lungs- air breathing
Amphibians: (class Amphibia)
• Evolved from lobe-finned fish and lung fish 350 mya
• First vertebrates on land
•Must reproduce in water
• Amphibian means two lives, in water as larval stage and on land as an adult
• Not marine…. Why?
Reptiles: (class Reptilia)
• 300 million years old
• Snakes, turtles, saltwater crocodiles, and marine iguanas
• Skin covered with scales, water tight
• Internal fertilization
• Egg has leathery waterproof shell to reproduce on land
• Ectotherms - live in warmer climates
• Ichthyosaur (extinct)- reptiles that returned to the ocean
Sea Turtles:
• Shell fused to backbone
• Can not retract head like land based tortoises and turtles
• Legs modified into flippers
• Leave water only to lay eggs
• Examples: Green, Hawksbill, Loggerhead, Kemp’s Ridley and the Leatherback (largest)
• Migrate long distances, using wave motion and magnetic field
Birds: (class Aves)
• Evolved from a reptilian ancestor
•Reptilian remnants include: shelled egg and scales on legs
• Archaeopteryx 150 million year old reptile with feathers, teeth and tail with vertebrate
•Sea birds have evolved body shape and structure to swim, fly or feed in the ocean