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The Lederberg replica plating experiment showed that
A) Mutation are actually pre-adaptive and evolution is not directed process in fact, evolution is based on chance events in nature and chance mutation in the organism
B) Mutation appear in organisms in response to change in the environment, conscious reaction, desire or use and disuse of organs
C) Mutations are random and continuous variations that form the raw material for gradual changes of evolution
D) All of these

Last updated date: 18th Jun 2024
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Hint: Esther and Joshua Lederberg studied evolution on the basis of natural selection. They performed an experiment due to which bacteria can be grown and maintained. The bacteria grew as isolated colonies on the culture plates.

Complete answer:
To answer this question, we must know about the Lederberg replica plating experiment.
Lederberg experiment-
-The experiment consisted of an original plate in which the bacteria were spread.
-The bacteria grew into several colonies.
-Then these colonies were transferred from the original plate to a new plate which contained penicillin.
-The colonies X and Y survived which shows that they already had mutation genes for penicillin resistance.
-Then the original plate was washed with penicillin. The colonies X and Y live.

So he concluded that the penicillin- resistant bacteria were already present in the population. They only evolved when they were exposed to the antibiotic.

Through this experiment he concluded that
-The mutation is not a directed process. It happens by chance in response to the events.
-The mutation occurs due to the change in the environment. This is in accordance with Darwinism.
-These mutations are not sudden but gradual and are inheritable.

Thus the correct answer is option (D)

Note: Through this experiment, he proved that the mutant strains are better adapted to the changes in the environment. The mutation is already present in the population but remains unexpressed until the change occurs. These mutations are carried over to new generations.