Answer the following:

Explain Lamarck’s theory of use and disuse of organs with suitable examples.

Lamarck had given the theory of inheritance of acquired characters based on the new needs and use and disuse of organs. This theory is also known as Lamarckism.

Lamarck’s theory was based on certain assumptions which are as follows:

● According to him, environment is continuously changing and in order to get adapt to the changing environment, each organism has some new needs because if the organism won’t change with the environment there will be no survival.

● So, according to him in order to fulfill the new needs, the organism makes certain changes in the use of the organs. It happens that in order to fulfill the need they start using one organ at a very higher rate and avoids the use of some organ. From here the concept of use and disuse of organs was aroused.

● According to the concept of use and disuse of organ Lamarck concluded that the organ that we use more frequently becomes stronger and the one which is rarely used starts disappearing.

● Also, he thought that the characters that the organism acquires due to change in environment are inherited by the coming generations.

● For understanding the concept of Lamarck we can use Giraffe as an example.

According to Lamarck, the ancestors of the Giraffe were not as long as that we see today. They were small as grass; small plants were available to them as food. Later on, when there was no availability of food they started stretching trees using their neck and forelimbs. So, due to this change in environment and fulfilling his need giraffe has acquired the structure as we see today and due to this, he had such long neck and forelimbs.

Following picture depicts Lamarckism in giraffe: