The sudden, large-scale changes that result in the immediate creation of new species, a concept termed 'saltation', was hypothesized by which early geneticist?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Charles Darwin
• Hugo de Vries
• Ernst Mayr
• Hardy-Weinberg
Correct Option: B  [ Hugo de Vries ]

Remark: Hugo de Vries, based on his mutation theory, coined the term 'saltation' to describe large, single-step mutations that could cause sudden evolution, contrasting with Darwin's gradualism.

The term for structural similarities between different species that arose from a common ancestor (e.g., forelimbs of a human, bat, and whale) is:

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Analogy
• Homology
• Vestigial structure
• Convergent evolution
Correct Option: B  [ Homology ]

Remark: Homology refers to similarity in structure due to common ancestry, even if the structures now have different functions.

Which evolutionary force is characterized by random changes in allele frequencies, particularly pronounced in small populations?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Gene Flow
• Natural Selection
• Mutation
• Genetic Drift
Correct Option: D  [ Genetic Drift ]

Remark: Genetic drift is the change in the frequency of an existing gene variant (allele) in a population due to random sampling of organisms, which is amplified in small populations (e.g., Bottleneck or Founder effect).

The process of an entire population shifting towards one extreme phenotype is known as:

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Stabilizing selection
• Disruptive selection
• Directional selection
• Artificial selection
Correct Option: C  [ Directional selection ]

Remark: Directional selection favors individuals at one end of the phenotypic range, causing the average phenotype of the population to shift over generations.

What is the ultimate source of genetic variation in a population?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Gene flow
• Sexual recombination
• Mutation
• Genetic drift
Correct Option: C  [ Mutation ]

Remark: Mutation is the only process that introduces new alleles and new genetic material into a population. Other mechanisms redistribute existing variation.

Which term describes the movement of alleles from one population to another, often by migration and subsequent breeding?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Genetic drift
• Gene flow
• Founder effect
• Stabilizing selection
Correct Option: B  [ Gene flow ]

Remark: Gene flow (or migration) is the transfer of genetic variation from one population to another, which tends to reduce genetic differences between populations.

The phenomenon where organisms with similar ecological niches and selective pressures evolve similar structures, despite not sharing a recent common ancestor, is called:

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Homology
• Convergent evolution
• Adaptive radiation
• Co-evolution
Correct Option: B  [ Convergent evolution ]

Remark: Convergent evolution occurs when unrelated species independently evolve similar traits due to similar environmental challenges (e.g., wings in birds and insects).

What is the primary significance of fossils in the study of evolution?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• They prove that life started in water.
• They provide direct evidence of extinct organisms and transitional forms.
• They show that all species are related.
• They explain the mechanism of mutation.
Correct Option: B  [ They provide direct evidence of extinct organisms and transitional forms. ]

Remark: Fossils provide a chronological record of life on Earth, showing the existence of organisms that are now extinct and revealing transitional forms that link different taxonomic groups.

Genetic variation is essential for evolution to occur because it provides the:

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Mechanism for genetic drift.
• Material for natural selection to act upon.
• Means of sexual reproduction.
• Basis for cell division.
Correct Option: B  [ Material for natural selection to act upon. ]

Remark: Natural selection can only lead to evolutionary change if there is existing variation in the population for the trait being selected. Mutation is the raw material, and variation is the fuel.

Which of the following is an example of an Analogous organ?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Forelimb of a bat and forelimb of a human.
• Eye of an octopus and eye of a human.
• Thorns of Bougainvillea and tendrils of Cucurbita.
• Vertebrate hearts.
Correct Option: B  [ Eye of an octopus and eye of a human. ]

Remark: Analogous organs have different structural origins but perform similar functions (e.g., the complex eyes of cephalopods and vertebrates evolved independently—convergent evolution).