Biology 1002B Lecture Notes - Uracil, Homochirality, Lightning
24 Aug 2013
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2: the origins of life & the primordial soup. The estimated age of the earth is known to be around 4. 6 billion years. Although the first evidence of life (prokaryotic cells) is known to have existed 3. 8 billion years ago, life may have actually originated around 4 billion years ago. Oxygen (o2) does not start to extensively accumulate in the atmosphere until 2. 7 billion years ago. Eukaryotic cells make their first appearance on earth around 2. 2 billion years ago. Multi-cellular eukaryotes are introduced to earth at around 1. 4 billion years ago. It is around 600 million years ago that animals begin to take shape and some 150,000 years ago that. The three major domains on earth under which all organisms can be classified consist of: prokarya (prokaryotes), archaea (prokaryotes), and eukarya (eukaryotes). It is hypothesized that everything living on the earth today can be categorized as a descendent of a.
