- Reptiles are cold blooded animals that have dry scaly skin. The scientific name for reptiles, "reptilia," means "creeping animals." Perhaps the most important thing that sets these vertebrates apart from other classes of animals is that they lay eggs on dry land. Their eggs contain enough nutrition for the babies to hatch fully formed.
- Amphibians, on the other hand, lay their eggs in water. Every kind of amphibian matures through a stage that involves breathing through gills. The life cycle of all amphibians includes some stages lived in water and other stages lived on land. Mature amphibians can also breathe through their skin, which is kept constantly moist by means of mucus glands.
- There are three groups of amphibians: frogs, salamanders and caecilians. Frogs are native to Europe, Asia, Africa, North America, South America and Australia. Whatever their size, mature frogs do not have tails. Most of them have long hind legs that make jumping easy. In addition, almost every kind of frog has bulging eyes.
- Male frogs attract their mates by their calls. Then they mount the females when they are ready to deposit their eggs in water, an amphibian characteristic. The males fertilize the whole clump of eggs right after they leave the females' bodies. The clump of fertilized eggs is attached to a water plant. When the tadpoles hatch, they breathe through gills (another amphibian characteristic) and have tails but no legs, like a fish.
- As the tadpole matures, its gills become unnecessary and disappear. Then the frog, like other amphibians, breathes through its skin. Four legs emerge and the tail drops off. The frog has the potential to live on land as well as in the water, making it clearly amphibious.
