BIOL120 Study Guide - Midterm Guide: Geologic Time Scale, Relative Dating
25 Oct 2017
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Biol 165 (diversity of life) notes for midterm 1. Fragments of rock found to be 4. 3 billion years old indicate that the earth is approximately 4. 5 billion years old. Cellular life dates back to being 4 billion years old. Prokaryotes evolved by 3. 5 billion years ago while the eukaryotic fossils are only about. Large multicellular organisms appeared about 0. 57 billion years ago and plants came on land about 0. 45 billion years ago. Humans appeared about 150 000 yrs ago (0. 00015 billion years ago) Time periods were determined by historic relative dating of rocks. Boundaries between the eras and periods symbolise major extinctions that occurred on earth. P-t boundary (permian-triassic most severe extinction on earth) occurred around 252. The k-pg boundary (cretaceous-paleogene dinosaur extinction (non avian or bird)) occurred around 66 mya. Hypothesis on the origin of life on earth:
