Eras

... explosion. This "explosion" occurred over a period of 40-50 million years. It's called an explosion because relative to other geological eras, a lot of new forms did indeed appear. If you look at the fossils from one site, e.g. the Burgess shales, you do see forms appearing "suddenly" ...

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... in the near past and will likely exist in the near future? For the sake of argument, I will assume that past, current, and future environment are eras of indeterminable length marked by distinctly different environmental conditions. Perhaps the person who created the question intended a meaning ...

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I have always wondered. We have all these eras and ages in which a particular group of animals was dominant but we do not have a time when birds dominated the earth and by dominated I mean lived in very large numbers and were the major animals. ...

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