1. They are ectothermic,
aquatic
vertebrates.
2. Their skin is generally covered with scales.
3. Their limbs are modified into fins for swimming.
1. They are
ectothermic
vertebrates.
2. Their skin is usually smooth and lacks scales, hair, and feathers.
They are dependent upon moisture and subject to
desiccation; their skin must remain moist to aid in breathing.
3. They have three-chambered hearts.
4. They lack claws on their toes.
1. They are
ectothermic
vertebrates.
2. Their skin has scales, but no hair or feathers.
3. They have three-chambered hearts (except for alligators and
crocodiles, which have four-chambered hearts).
4. They have claws on their toes (except those which do not have legs,
such as legless lizards).
5. They are the first animals, in evolution, to develop the
amniotic egg. This allows reptiles to lay eggs on land.
1. They are
endothermic
vertebrates.
2. Their skin is covered with feathers.
3. They have four-chambered hearts.
4. Their bones are lightweight and usually hollow.
5. Their forelimbs are modified as wings.
6. They lay eggs.