According to Lamarck, the evolution of life forms had occurred by the use and disuse of organs. Organs that are used more, develop more, while those that are not used become vestigial in the long run. The character developed by an organism during its life time is passes on to the progeny. He gave the long neck of giraffe as an example; according to him, it is an outcome of the attempt to stretch their neck continuously to eat leaves from tall trees. As they passed this acquired character of long neck to succeeding generations, giraffes came to acquire long neck over a long period of time.\xa0\xa0The gradual unfolding of organisms from pre-existing organisms through changes since the beginning of life is called evolution. The theory proposed by J.B. Lamarck is known as the theory of inheritance of acquired characters. According to this theory, the use and disuse of an organ leads to acquiring of change in that organ. These changes or variations can be passed on from one generation to the next but this idea of inheritance of acquired characters was soon discarded.The gradual unfolding of organisms from pre-existing organisms through changes since the beginning of life is called evolution. The theory proposed by J.B. Lamarck is known as the theory of inheritance of acquired characters. According to this theory, the use and disuse of an organ leads to acquiring of change in that organ. These changes or variations can be passed on from one generation to the next but this idea of inheritance of acquired characters was soon discarded.