Biodiversity
Tetrapoda includes four classes: amphibians, reptiles, mammals, and birds. Overall the biodiversity of tetrapods has grown exponentially over time from a single amphibian group sometime in the Devonian to many thousands of species today. The overall composition of biodiversity was driven primarily by amphibians in the Palaeozoic, dominated by reptiles in the Mesozoic and expanded by the explosive growth of birds and mammals in the Cenozoic. As biodiversity has grown so has the number of niches tetrapods occupied. The first tetrapods lived in waterside habitats and fed primarily on fish, today the Earth supports a great diversity of tetrapods that live in many habitats and subsist on a variety of diets.
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