Question

Vestigial organs are
A. Primitive organs
B. Primordial organs
C. Organs reduced due to disuse
D. Organs marked only in the embryonic stage

Answer 1

Hint: Evolution has been a remarkable concept to know about humans. Vestigial organs are one of the evolutionary concepts that were their ancestral form of the trait. These structures can arise due to gene mutation that causes changes in proteins, resulting in vestigial structure.

Complete answer:
Evolution is not a perfect process. As new structures are developed in response to environmental changes, the old ones are sometimes detained. The organs which occur in reduced form and are useless to the possessor, but correspond to the fully developed functional organ of related animals are called vestigial or rudimentary organs.

The existence of useless or vestigial organs is not explained by the theory of special creation, according to which all the organs of the animal have been specially designed to meet its need. The doctrine of organic evolution, on the other hand, offers a very satisfactory explanation for the presence of useless organs in animals. These organs were fully developed, functional and necessary in the ancestral forms, but are gradually disappearing in the living form due to changes in their mode of life. Darwin compares vestigial organs to letters in a word that are not pronounced but provides clues to the word's organ. Vestigial organs are found in humans as well as in other organs.

Mutation for the decrease in size and functioning of an organ appear frequently in nature. If the organ is essential for survival, such mutations prove lethal, that is, kill the organism. If the organ is no longer required for survival, such mutation accumulates and makes the organ vestigial.

So, the correct answer is option C, organ reduced due to disuse.

Note: Mendelian factor or gene is a unit of inheritance that passes from one generation to the next through the gamete and controls the expression of a character in the organisms usually along with another factor of the allelic type. It is now known that Mendelian gators, determinants are present in a linear sequence on the chromosomes.