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Circulatory System – Biology and Evolution

By |2018-04-16T08:24:44+00:00May 26th, 2017|Biology|

Circulatory system: A dog heart What is the circulatory system? The circulatory system takes food and air from outside your body and brings it all over your body so that all your cells get the food and oxygen they need to stay alive. The earliest cells, about 3.8 billion years ago, didn't need [...]

What are reptiles? Biology and Evolution

By |2018-04-21T11:56:35+00:00May 26th, 2017|Biology|

Boa Constrictor snake Some kinds of amphibians evolved into reptiles about 300 million years ago. At this time, plate tectonics had moved more and more of the land on Earth into one big continent called Pangaea. All the land being together changed the weather so that it was drier and colder than before. That [...]