Evolution of Terrestrial Vertebrates = tetrapods

1. anamniotes -

2. amniotes -

Amniote eggs have extraembryonic membranes:

1. yolk sac -

Amniotic eggs have 3 additional membranes

2. amnion -

3. allantois -

4. chorion -

Movement onto land - changes in morphology and physiology

1. Oxygen content - Oxygen ~ 20X more abundant on land than water

2. Density - Air ~ 1000X less dense than water.

3. Temperature regulation - Air fluctuates more in temperature than water

thermoregulation - reptiles homeothermy - birds and mammals

Two features evolved in fishes to aid them in surviving period of unpredictability:

1. Lungs -

Double circulation of tetrapods -

systemic circulation serving the body

pulmonary circulation supplying the lungs

2. Limbs -

Ichthyostega - early amphibian with strong girdles and thick bones