Evidences of Evolution (NCERT) - Free MCQ Practice Test with solutions,

Biogenetic law or Recapitulation theory was given by Ernst Haeckel in 1866. It states that 'ontogeny repeats phylogeny'. Ontogeny is the life history of an organism while phylogeny is the evolutionary history of the race of that organism. This means that an organism repeats its ancestral history during its development.

Homologous organs have a common origin and are built on the same basic pattern but perform different functions and are modified accordingly.

The correct answer is:

d) Flipper of seal and wings of birds are homologous organs.

Explanation:

• Homologous organs have a similar anatomical structure and evolutionary origin but may perform different functions.

  • Example: Seal flippers, bird wings, bat wings, and human hands all share the same basic bone structure (humerus, radius, ulna, etc.), indicating common ancestry, despite their different functions.

• Analogous organs perform similar functions but have different anatomical structures and evolutionary origins.

  • Example: Bird wings and insect wings both enable flight but evolved independently (insect wings lack bones).

Why Not the Other Options?

• a) Incorrect. Bird and insect wings are analogous (same function, different structure/origin).

• b) Incorrect. Human hands and bird wings are homologous (same structure, different functions).

• c) Incorrect. Human hands and bat wings are homologous (same bone structure).

Key Concept:

Homology reflects shared ancestry, while analogy reflects convergent evolution.

Final Answer:

d) Flipper of seal and wings of birds are homologous organs.​

Molecular evolution is a change in the sequence composition of cellular molecules to explain biological changes at the molecular and cellular level using principle of evolutionary biology and population genetics.

A thorn of Bougainvillea and a tendrill of Curcurbita, both are stem modifications and thus represent homologous structures. The modifications indicate the evolution of the organ to suit different functions which is also known as divergent evolution.

Analogous organs are the organs which have similar function but are different in their structural details and origin. The analogous structures are the result of convergent evolution. The wings of an insect are analogous to wings of a bird because the basic structure of the wings of the insects is different from the wings of bird. However, their function is similar.

The theory of Hardy- Weinberg equilibrium states that in the absence of disturbance on the level of genetic structure, a population’s existance will not continue. Thus mating should be in a random way.

Organs which have a common fundamental anatomical plan and similar embryonic origin whatever varied functions they may perform are regarded as homologous organs. For examples the flippers of a whale, a bats wing, fore-limb of a horse, a bird’s wing and forelimbs of human are structurally as well as functionally different.

Given figures represent the forelimbs of different vertebrates, which possess the same basic structural plan, i.e., in each case, the forelimb consists of humerus, radio-ulna, carpals, metacarpals and digits. Thus, the skeletal parts of these forelimbs are similar in structure and arrangement, but have different shapes and functions. It depicts the example of homologous structures.

Natural selection is the most widely accepted theory concerning the principal causal mechanism of evolutionary change profounded by Charles Darwin and Alfred Russel Wallace. It results from the differential reproduction (some members of a population produce abundant offspring, some only a few and still others none), one phenotype as compared with other phenotypes in the same population. This determines the relative share of different genotypes which individuals possess and propagate in a population. Industrial melanism supports evolution by natural selection. It is an adaptation where the moths living in the industrial areas developed melanin pigments to match their bodies to the tree trunks.