What is darwin theory

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Darwinian theory of evolution....................... is based on his observations during the sea voyage around the world in ship HMS Beagle................... the two key concepts of darwinian theory are .................branch decent............... which is also called............... adaptive radiation................ and ..............natural selection ...............what is natural selection is ....,...................... the organisms which survive better in natural conditions are the fittest...................... Darwin theory support survival of the fittest ..................adaptability is inherited ................and the fitness is the end result of the ability to adapt and get selected by the nature and...................... in our NCERT book examples of natural selection are given............ industrial melanism.......... and ............chemical resistant .........and read them........????????