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SAI International School
                                                   Subject- Biology
                                         Chapter- Heredity And Evolution
                     Subtopic- Charles Darwin, Origin of life, Organic and Chemical
                                                evolution, Speciation
                                                       Module-26
                                                     Lesson Notes
























               CHARLES DARWIN
                     Charles Darwin, an English naturalist of the 19th century made an extensive
                       study of nature for over 20 years.
                     He collected the observations on animal distribution and the relationship between
                       living and extinct animals and finally found that the present living animals share
                       similarities to some extent not only between them but also with the other species
                       that existed millions of years ago and among which some have become extinct.
                     Charles Darwin is known as the father of evolution due to his contribution to the
                       establishment of the theory of evolution.
                     Darwin’s evolutionary theory of natural selection gave a more rational
                       explanation of the formation of new species.
                     As per natural selection, various species originated from a single species as a
                       result of adaptation to the changing environment.
                     As he was a naturalist he also studied the role of earthworms in soil fertility.

               ORIGIN OF LIFE ON EARTH
                     J.B.S. Haldane, a British scientist (who became a citizen of India later),
                       suggested in1929 that life must have developed from the simple inorganic
                       molecules which were present on earth soon after it was formed.
                     He speculated that the conditions on earth at that time, which were far from the
                       conditions we see today, could have given rise to more complex organic
                       molecules that were necessary for life.

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