chordates part 3. fins are thin membranes supported by bone

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