Question

In a famous experiment, A.Weismann cut off tails of new-born mice generation after generation. At the end of the experiment, tails of mice neither disappeared nor shortened. This experiment
a. Supports Darwin’s theory of natural selection
b. Proves that tail is an essential organ of vertebrates.
c. Disproves de Vries mutation theory
d. Shows that Lamarck was wrong in his theory of inheritance of acquired characters.

Answer 1

Hint: Evolution describes changes or variations which accumulate at the generation level. These lead to changes at the micro-level or macro level. So, evolution can be divided into two types- microevolution and macroevolution. Several scientists performed different experiments and provided evidence for evolution.

Complete answer:
There are some important reasons for changes in organisms over time:
- Recombination
- Arrangement of chromosomes at the metaphase plate
- Independent assortment
- Genetic drift
- Mutations
- Natural selection

Jean-Baptiste Pierre Antoine de Monet (Lamarck) was a French naturalist and gave certain postulates regarding evolution of organisms.
His theory was based on Anagenesis (evolution without branching patterns) and followed transformation (a species converts completely into another generation).

Postulates:
- Internal force is present in every organism.
- The body size increases over the course of time.
- Any organism develops a new character according to the environment.
- Inheritance of acquired characters (most important)- It states that the offspring acquires the same character from a parent if the parent acquired that character in their lifetime.

In contradiction of this point(inheritance of acquired characters), A.Weismann proposed an experiment in which he cut off the tails of 68 white mice in hope that all offspring would be tailless but all the mice had tails even after the consecutive crossing of tailless parents. So, Lamarck’s postulate was disregarded.

Hence, the correct answer is option (D).

Additional information:
Darwin’s theory of natural selection was based on the origin of species and survival of the fittest and they included a study on finches. De Vries mutation theory was based on the genomic level.

Note: Some important points:
When an organism acquires modification in function or structure during its life due to environmental factors is referred to as acquired characters. such changes do not transmit genetically. But according to Lamarck’s theory of inheritance of acquired characters, if the changes acquired by an individual during its lifetime, these changes are inherited by their offspring as well.
- August Weismann disproved Lamarck’s theory.
- Inheritance of acquired character is also called soft inheritance.
- The modified version of the theory is called neo Lamarckism.