Which substance accounts for nearly 80 percent of Earth's atmosphere?

Oxygen

Amphibians live near water sources because they need an area where they can lay and protect their eggs. The early stages of an amphibian's life is spent mostly underwater. This is where they mature and slowly develop into land organisms. In the early stage of their life, they breathe through their gills and they do not have limbs yet. As they grow gradual changes in their body structures are prominent, this process if called metamorphosis.