Question

Give the salient features of the following:

Lamarckism

Answer 1

1. Internal vital force: All organisms have a tendency to increase the size of their body or its component parts due to an internal vital force.
2. Environmental effect and new needs: Changes in environmental conditions and circumstances affect the existence of organisms. As a result, organisms make efforts to fulfil their new needs for adaptation. Sometimes, this involves a change in their habits or behaviour, including increased use of certain organs or structures and disuse of others.
3. Use or disuse of organs: The use and disuse of organs affect their structure, shape and efficiency. Increased use of an organ makes it stronger, larger and more efficient. On the other hand, disuse or reduced use gradually makes an organ weaker and smaller, and it may eventually disappear. Thus, different degrees of use of organs produce additional characteristics during an organism’s lifetime.
4. Inheritance of acquired characters: During an organism’s lifetime, new characters develop because of internal vital force, environmental factors, new needs, and the use or disuse of organs. These acquired characters are inherited from one generation to the next. Over several generations, the variations accumulate and may result in the formation of new species.