The main difference between mammals and reptiles is the way they regulate body heat. Mammals can produce body heat while reptiles need external heat source such as the sun. That is why most reptiles will bask in the sun to get warm. Mammals give birth to live young while reptiles lay eggs. The mammal youngling is very dependent to its parents for protection and nourishment while a reptile hatchling doesn’t need any parent in order to live as they can fend for themselves the moment they hatch. Moreover, mammals have hairs and furs while reptiles have scales.