Completar frases 231-testVersión en línea 231-test por Farhad Key 1 for evolution evolutionary discrete which paper differ offspring In In The Origin of Species , Darwin provided abundant evidence that life on Earth has evolved over time , and he proposed natural selection as the primary mechanism for that change . He observed that individuals in their inherited traits and that selection ads on such differences , leading to change . Although Darwin realised that variation in heritable traits is a prerequisite for , he did not know precisely how organisms pass heritable traits to their . Just a few years after Darwin published The Origin of Species , Gregor Mendel wrote a groundbreaking on inheritance in pea plants . that paper , Mendel proposed a model of inheritance in which organisms transmit heritable units ( now called genes ) to their offspring . Although Darwin did not know about genes , Menders paper set the stage understanding the genetic differences on evolution is based .