Introduction: Amphibians are those animals that live on land but reproduce in the water. The reason they do this is because, evolutionarily, they have not developed the hard-shelled egg that is present in reptiles and birds that keeps the developing young moist. Therefore, their eggs would dry out very quickly if they were laid on land.

Examples of amphibians include frogs, newts, and salamanders.

Amphibians usually start their lives looking very differently than they do as adults. Frogs start out as tadpoles, having gills and a long tail used for swimming. As they age, they undergo a process called metamorphosis, where different genes activate. When this occurs, the gills transform into lungs and the tail starts to shrink. While they are different body forms, if one were to take a blood sample from a tadpole and the frog into which it turns, it would be found that they have the same DNA.

Directions for this Lesson: Answer the practice questions, watch the video, and then check the resources for more information about amphibians.