![]() About a hundred million years ago, the reptiles that we call dinosaurs ruled the world. And mammals nurtured their young inside themselves. ![]() ![]() Reptiles laid eggs that could hatch on land. Amphibia could live on land, but they had to reproduce in water. But from about 400 to 500 million years ago, some plants and animals began to live on land. Now, at first, like most bacteria, these lived in the oceans. At the Cambrian Explosion 540 million years ago, cells began to combine in millions, or billions, to form large organisms. But we're gonna begin it by going back 540 million years to the Cambrian Explosion so we can see the appearance of our species as part of the larger story of the evolution of life on Earth. This segment is about threshold six, and threshold six is when our own species appears. And eventually, within the last million years, our own species would evolve. Not until the last 600 million years did large organisms evolve. Organisms so small that they cannot be seen with the naked eye. ![]() The big question for this segment is, what is threshold six, and why is it so important? So, once life was created, how did it evolve and change over 4 billion years and create more and more complex organisms? Well, for almost 3 billion years, life on Earth consisted of single cells. ![]()
0 Comments
Leave a Reply. |