Explanation

Darwin. Based on observation made during a sea voyage in a sail ship called HMS Beagle round the world. Charles Darwin conclude that the existing living forms share similarities to varying degrees not only among themselves but also with the life forms that existed millions of years ago The fitness, according to Darwin, refers ultimately and only to reproductive fitness. Hence, those who are better fit in an environment, leave more progeny than other. These, therefore will survive more and, hence are selected by nature. He called it natural selectional and implied it as a mechanism of evolutions