There are around 6,000 amphibian species worldwide, with about 300 of them found in the United States. Amphibians are a group of animals that include frogs, toads, and salamanders. They are characterized by their limbs which are attached to the body through skin instead of bone, and by their ability to breathe using lungs instead of gills. Although they share several features, each group has its own unique characteristics. Amphibians have been important in revealing information about evolution because they show how different organisms can arise from the same genetic material. A new species can evolve from a previous one by becoming geographically separated or by changing certain traits. This happens when individuals with similar traits (genes) come into contact and some of their offspring survive to reproduce themselves. Over time, they develop differences due to natural selection - the ones with the best adaptations (characters) survive to pass on their genes to the next generation. Amphibians are also important to humans because they provide food and other resources, such as medicine. In addition, some people collect amphibians for entertainment or as pets. There are even organizations that specialize in protecting amphibians! Amphibians are prone to extinction due to human activity.