15 extra multiple-choice questions for Evolution (12th Standard Zoology, Samacheer Kalvi), beyond the ones printed in the textbook — each with the correct option highlighted and a clear, worked explanation. Free to read in English and Tamil.
Q1
What is the estimated age of the solar system and Earth according to radiometric dating of meteorites?
- A. 3.5 to 3.6 billion years
- B. 4.5 to 4.6 billion yearsCorrect
- C. 1.5 to 2.0 billion years
- D. 5.5 to 5.6 billion years
Explanation. Radiometric dating of meteorites indicates that the solar system and Earth are approximately 4.5 to 4.6 billion years old. The newborn Earth remained inhospitable for several hundred million years due to extreme heat.
Q2
During which period of the Mesozoic era did the first egg-laying mammals originate?
- A. Jurassic
- B. Cretaceous
- C. TriassicCorrect
- D. Permian
Explanation. The Mesozoic era, known as the golden age of reptiles, is divided into the Triassic, Jurassic, and Cretaceous periods. Egg-laying mammals originated during the Triassic period.
Q3
Which abiotically produced lipid spheres can spontaneously self-assemble into a bilayer in a solution and maintain a distinct internal chemical environment?
- A. Coacervates
- B. Microspheres
- C. LiposomesCorrect
- D. Protoviruses
Explanation. Liposomes are abiotically produced lipids in a solution that spontaneously self-assemble into a lipid bilayer. Some proteins inside them acquired enzymatic properties, aiding the fast multiplication of molecules.
Q4
Which method of fossil dating is utilized to determine the precise age of a fossil by measuring the decay of radioactive isotopes?
- A. Relative dating
- B. Absolute datingCorrect
- C. Strata dating
- D. Morphological dating
Explanation. Absolute dating uses radiometric techniques to measure the decay of isotopes, allowing scientists to find the precise age of a fossil. Relative dating only compares fossils to rocks of known ages.
Q5
Which organism serves as a transitional stage or connecting link between the phyla Annelida and Arthropoda?
- A. Archaeopteryx
- B. PeripatusCorrect
- C. Platypus
- D. Ichthyostega
Explanation. Peripatus is a classical connecting link showing characteristics of both Annelida and Arthropoda. Archaeopteryx serves as a connecting link between reptiles and birds.
Q6
What term is used to describe the sudden, unexpected appearance of ancestral vestigial organs in a highly evolved organism, such as a human baby born with a tail?
- A. Analogous structures
- B. Atavistic organsCorrect
- C. Homologous structures
- D. Rudimentary organs
Explanation. Atavistic organs represent the sudden reappearance of ancestral traits in highly evolved species. A classic example is a human baby born with a short, functional tail.
Q7
Who propounded the biogenetic law, summarizing that ontogeny briefly repeats or recapitulates phylogeny?
- A. Charles Darwin
- B. Jean Baptiste de Lamarck
- C. Ernst Von HaeckelCorrect
- D. Hugo de Vries
Explanation. Ernst Von Haeckel propounded the biogenetic law, or theory of recapitulation. It states that the embryonic development of an individual (ontogeny) repeats the evolutionary history of its ancestral race (phylogeny).
Q8
Jean Baptiste de Lamarck published his evolutionary views and principles in which famous book in 1809?
- A. The Origin of Species
- B. Philosophie ZoologiqueCorrect
- C. Systema Naturae
- D. The Descent of Man
Explanation. Jean Baptiste de Lamarck published his theory of inheritance of acquired characters and the use-disuse theory in his famous book titled Philosophie Zoologique in 1809.
Q9
What was the main reason dark-winged peppered moths (Biston betularia) became dominant in England after industrialization?
- A. They developed resistance to industrial soot and chemical pollutants.
- B. Lichens grew densely on dark trunks, providing them food.
- C. Soot-darkened tree trunks and the decline of light lichens allowed them to camouflage.Correct
- D. High temperatures induced melanic mutations in the moth population.
Explanation. Post-industrial pollution killed tree lichens and darkened tree trunks with soot. This allowed the dark-winged moths to camouflage and escape avian predators, while white-winged moths were easily spotted.
Q10
Which type of natural selection operates when an environment undergoes gradual changes, shifting the phenotypic peak of a population toward one extreme?
- A. Stabilizing selection
- B. Disruptive selection
- C. Directional selectionCorrect
- D. Centrifugal selection
Explanation. Directional selection occurs in a gradually changing environment, removing individuals from one end of the phenotypic distribution and shifting the average phenotype toward the favored extreme over generations.
Q11
Which of the following conditions would prevent a natural population from maintaining Hardy-Weinberg genetic equilibrium?
- A. Absence of mutations
- B. Selective mating among individualsCorrect
- C. Large population size
- D. Absence of gene migration
Explanation. For a population to remain in Hardy-Weinberg equilibrium, mating must be entirely random. Non-random or selective mating alters genotype frequencies and drives evolutionary change.
Q12
Which fossil ancestor of modern Europeans is famous for its cave paintings, as well as drawing figures on floors and walls?
- A. Neanderthal man
- B. Homo erectus
- C. Cro-Magnon manCorrect
- D. Australopithecus
Explanation. Cro-Magnon man, found in France, was highly adapted and famous for creative cave paintings and carvings on walls and floors. They are considered ancestral to modern Europeans.
Q13
Which of the following is categorized as a post-zygotic isolating mechanism that prevents gene flow between two different species?
- A. Seasonal isolation
- B. Ecological isolation
- C. Hybrid inviabilityCorrect
- D. Behavioural isolation
Explanation. Pre-zygotic mechanisms (seasonal, ecological, behavioral) prevent mating or fertilization. Post-zygotic mechanisms, like hybrid inviability, act after fertilization, leading to embryonic death before reaching reproductive maturity.
Q14
What type of speciation occurs when biological populations of the same species become geographically isolated from one another by physical barriers like mountains or land separation?
- A. Sympatric speciation
- B. Allopatric speciationCorrect
- C. Parapatric speciation
- D. Quantum speciation
Explanation. Allopatric (geographical) speciation occurs when biological populations are separated by physical barriers. This separation blocks gene flow, leading to independent genetic changes and the evolution of new species.
Q15
Why did the extinction of the Dodo bird of Mauritius Island place the Calvaria tree in imminent danger of coextinction?
- A. The Dodo bird was the exclusive pollinator of the Calvaria tree flowers.
- B. Calvaria tree seeds require the action of stones and digestive juices in the Dodo's gizzard to make their tough endocarp permeable for germination.Correct
- C. Calvaria trees required the nest debris of Dodos as organic nutrients for seedling growth.
- D. The Dodo bird protected young Calvaria seedlings from herbivorous insect pests.
Explanation. Calvaria tree seeds have a very tough endocarp. Historically, Dodos ingested the seeds, and the stones and juices in their gizzards worn down the seed coat, rendering it permeable and facilitating germination.
