The statement that is NOT part of the classical Darwinian theory of evolution by natural selection is (A) A trait which is constantly used will get inherited by next generation. This idea is Lamarckian, not Darwinian.​

Introduction: Darwinian Theory of Natural Selection MCQ

Darwinian theory of natural selection explains how evolutionary change occurs through heritable variation, struggle for existence, and differential survival and reproduction of better‑adapted individuals. In exam MCQs, it is crucial to distinguish true Darwinian ideas from Lamarckian concepts such as inheritance of acquired characters.​

Correct Answer and Core Concept

• Correct option: (A) A trait which is constantly used will get inherited by next generation.

• This statement reflects Lamarck’s theory of inheritance of acquired characters and use and disuse, not Darwin’s natural selection.​

Darwin’s classical theory rests on:

• Heritable variations already present in populations.​

• Struggle for existence because more offspring are produced than can survive.​

• Survival and reproduction of the fittest, i.e., individuals best adapted to the environment leave more offspring.​

Option (A): Lamarckian, Not Darwinian (Incorrect Statement)

(A) A trait which is constantly used will get inherited by next generation.

• This describes Lamarck’s law of use and disuse and inheritance of acquired characters, where organs used more become stronger and are then inherited; organs not used degenerate.​

• Classical examples include the idea that giraffes stretched their necks to reach leaves and then passed longer necks to offspring, or that blacksmiths develop strong arm muscles and their children inherit this acquired strength.​

Why this is NOT Darwinian:

• Darwin did not base natural selection on systematic inheritance of use‑induced modifications; he emphasized pre‑existing heritable variation in populations and differential reproduction.​

• Modern evolutionary biology and genetics show that most environmentally acquired bodily changes (like muscle size) are not inherited in the classical Lamarckian sense.​

Therefore, option (A) is not part of classical Darwinian theory and is the correct choice for this MCQ.

Option (B): Variations in a Population (Darwinian, True Statement)

(B) Phenotypic variations exist among the individuals of a population of a species

• Darwin emphasized that natural variation occurs among individuals of any population; they differ in size, color, speed, behavior, etc.​

• These phenotypic variations often have a heritable genetic basis, providing the raw material on which natural selection acts.​

Why this fits Darwinism:

• One of the core principles of Darwinian natural selection is that variation must exist among individuals for selection to operate.​

• Without variation, every individual would have equal fitness, and no differential survival or reproduction would occur.​

Thus, option (B) is a correct statement of Darwinian theory, so it is not the answer to the MCQ.

Option (C): Best-Fitted Individuals Survive (Darwinian, True Statement)

(C) Individuals that best fit into a given environment are more likely to survive

• Darwin summarized natural selection as “survival of the fittest”, where “fittest” means best adapted to the current environment, not necessarily strongest or largest.​

• Individuals with advantageous heritable traits are more likely to survive and reproduce, passing those traits to more offspring.​

Why this fits Darwinism:

• This directly reflects the principle of differential survival and reproduction, a central pillar of Darwin’s theory.​

• Over generations, such differential reproduction leads to populations becoming better adapted to their environments, which Darwin described as the essence of natural selection.​

Hence, option (C) is a correct Darwinian statement, not the odd one out.

Option (D): Random Variations in Populations (Darwinian, True Statement as Worded)

(D) Each population can randomly acquire a distinct and separate suite of variations.

• Darwinian variations are typically described as random and directionless with respect to the needs of the organism; natural selection then filters these variations.​

• Different populations, especially if geographically isolated, can independently accumulate different sets of variations, eventually leading to divergence and possibly speciation.​

Why this is compatible with Darwinism:

• Darwin recognized that species become adapted to their environment through natural selection acting on heritable variation, with different environments favoring different variants.​

• The idea that each population can have its own distinct suite of variations aligns with population-based thinking that underlies Darwinian evolution and later population genetics.​

Therefore, option (D) is also consistent with Darwinian thought, so it cannot be the “NOT part” statement.

Quick Comparison Table for All Options

In summary, the only option that does not belong to the classical Darwinian theory of evolution by natural selection is option (A), which is a Lamarckian concept of inheritance of acquired characters through use and disuse.