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Evolution of Amphibians to Mammals

 

            
            
             In the beginning, all life evolved from the oceans. It started very small, then evolved to produce creatures, which were larger than life. First, there were plants and insects. Next which evolved were reptiles and fish. From those reptiles and fish came the amphibians. The amphibians were the predecessors to the first mammals. Evolution is the reason behind all of the changes witnessed by our planet.
             All animal life on this planet started in the sea. Around three hundred and fifty million years ago the land on Earth was overran by plants and insects. All of the plants and insects on land were enticing to some adventurous fish. Some of these fish slowly evolved legs instead of their fins and lungs instead of gills so they could breath the air. The first types of species to make this migration to the land were amphibians. Amphibians are animals, which can live both on land as well as in the water. They are comfortable in both environments. .
             Eventually reptiles began to evolve from the amphibians. This occurred around ten million years after the first amphibians. The first reptiles consisted of ancestors to the crocodile, dinosaurs, birds, and mammal like reptiles first started coming into existence. One of the major differences between the amphibians and the new reptiles is the development of the amniotic egg as well as stronger legs, and jaw muscles. The first reptiles split into two very distinct groups. The first group developed an aorta on the right side of the head. The second group developed an aorta on the left side of the head. The early reptiles also had no diaphragm, as well as their brain case was loosely attached. They had a continuous supply of replacement teeth, also their teeth were held in place by a single root.
             The first mammals are believed to have evolved from the group of reptiles whose aorta developed on the left side of their head. The changes that went through for this new species of animal were pretty elaborate.


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