Enough protective ozone was built about how many years ago?
Correct answer: C. 420 billion
- A. 320 million
- B. 429 million
- C. 420 billion
- D. 320 billion
Explanation
About 420 million years ago, enough protective ozone had built up to make life on land possible. Ironically, the change from a reducing atmosphere to an oxidizing atmosphere also meant that life could no longer arise abiotically.
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Evolution describes heritable change in populations over generations through variation, natural selection and adaptation. Lamarckism explains inheritance of acquired characteristics, while Darwinism explains selection of favourable inherited variations; these historical explanations must not be confused with the modern genetic account of evolutionary change.
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