The sudden, large-scale changes that result in the immediate creation of new species, a concept termed 'saltation', was hypothesized by which early geneticist?
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.
Question 192 of 519
📘 CLASS XII
The term for structural similarities between different species that arose from a common ancestor (e.g., forelimbs of a human, bat, and whale) is:
Homology refers to similarity in structure due to common ancestry, even if the structures now have different functions.
Question 193 of 519
📘 CLASS XII
Which evolutionary force is characterized by random changes in allele frequencies, particularly pronounced in small populations?
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).
Question 194 of 519
📘 CLASS XII
The process of an entire population shifting towards one extreme phenotype is known as:
Directional selection favors individuals at one end of the phenotypic range, causing the average phenotype of the population to shift over generations.
Question 195 of 519
📘 CLASS XII
What is the ultimate source of genetic variation in a population?
Mutation is the only process that introduces new alleles and new genetic material into a population. Other mechanisms redistribute existing variation.
Question 196 of 519
📘 CLASS XII
Which term describes the movement of alleles from one population to another, often by migration and subsequent breeding?
Gene flow (or migration) is the transfer of genetic variation from one population to another, which tends to reduce genetic differences between populations.
Question 197 of 519
📘 CLASS XII
The phenomenon where organisms with similar ecological niches and selective pressures evolve similar structures, despite not sharing a recent common ancestor, is called:
Convergent evolution occurs when unrelated species independently evolve similar traits due to similar environmental challenges (e.g., wings in birds and insects).
Question 198 of 519
📘 CLASS XII
What is the primary significance of fossils in the study of evolution?
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.
Question 199 of 519
📘 CLASS XII
Genetic variation is essential for evolution to occur because it provides the:
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.
Question 200 of 519
📘 CLASS XII
Which of the following is an example of an Analogous organ?
Analogous organs have different structural origins but perform similar functions (e.g., the complex eyes of cephalopods and vertebrates evolved independently—convergent evolution).
