Evolution is referred to as the changes acquired by a species or a certain population of a species gradually over a long period of time. These changes should be heritable.

Contribution of Lanark

According to the Theory of inheritance of acquired characters or Lamarckism, put forward by Lanark, the use and disuse of an organ leads to acquiring change in the features of that organ. These changes are also inherited by the offspring’s. The favorable variations caused due to use and disuse after a considerably long period of time, results in evolution of a new species.