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CBSE Class 12th Biology Notes for Chapter 7 Evolution

        Chapter 7 Evolution

  • The origin of life can be understood only against the background of origin of earth.


  • Most scientist believe in chemical evolution I.e. formation of biomolecules preceded the appearance of the first cellular forms of life.


  • The subsequent events as to what happened to the first form of life are a conjectured story based on Darwinian ideas of organic evolution by natural selection.


  • Diversity of life forms on earth has been changing over millions of years.


  • It is generally believed that variations in a population result in variable fitness. Other phenomena like habitat fragmentation and genetic drift may accentuate these variations leading o appearance of new species and hence evolution.


  • Homology is accounted for by the idea of branching descent. Study of comparative anatomy, fossils ad comparative biochemistry provides evidence for evolution

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