Evolution — Class 12 MCQs with Answers

Evolution — important questions & MCQs with answers (Class 12 Biology)

6 solved questions from this chapter's difficulty levels, each with its answer and explanation. Tap an option to check yourself.

0 of 6 answered

1. Q1 of 6Easy

   Theory of natural selection by:

   AMendelBLamarckCCharles DarwinDPasteur
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   Answer: Charles Darwin

   Explanation: Charles Darwin proposed natural selection in On the Origin of Species (1859): heritable variation plus differential survival and reproduction drives evolutionary change, distinct from Lamarck's use-and-disuse idea.

2. Q2 of 6Easy

   Direct evidence of evolution:

   AEmbryological similaritiesBHomologous organsCBiochemical similaritiesDFossils
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   Answer: Fossils

   Explanation: Fossils are time-stamped remains preserved in rock strata, giving direct palaeontological evidence of extinct organisms and evolutionary change, unlike embryological or molecular evidence which is only indirect.

3. Q3 of 6Medium

   Lamarck's theory: inheritance of:

   AAcquired characters (now disproved)BGenetic mutations onlyCRandom selectionDNone
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   Answer: Acquired characters (now disproved)

   Explanation: Lamarck's use-and-disuse hypothesis claimed traits gained during an organism's life, like a stretched neck, pass to offspring; this inheritance of acquired characters is now disproved, unlike Darwin's natural selection.

4. Q4 of 6Medium

   Homologous organs (e.g., human arm, whale flipper, bat wing):

   ARandom similarityBSame function onlyCIndicate common ancestryDNo relation
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   Answer: Indicate common ancestry

   Explanation: Homologous organs like the human arm, whale flipper and bat wing share the same bony plan and embryonic origin from a common ancestor, then diverged in function — divergent evolution, not the convergence behind analogous organs.

5. Q5 of 6Hard

   Hardy-Weinberg principle holds when:

   AInbreedingBStrong selectionCBottleneckDNo mutation, migration, selection, drift; random mating
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   Answer: No mutation, migration, selection, drift; random mating

   Explanation: Hardy-Weinberg equilibrium needs a large population with random mating and no mutation, migration, natural selection or genetic drift; any one of these five forces shifts allele frequencies away from p squared + 2pq + q squared = 1.

6. Q6 of 6Hard

   Wings of bird and butterfly are:

   AAnalogous (convergent evolution)BHomologousCIdenticalDVestigial
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   Answer: Analogous (convergent evolution)

   Explanation: Bird and butterfly wings serve the same flight function but evolved independently from unrelated ancestral structures — convergent evolution producing analogous organs, unlike the shared-ancestry homology of vertebrate forelimbs.

Evolution notes: key concepts (Class 12 Biology)

Evolution: theories of Lamarck, Darwin's natural selection and de Vries' mutations; the chemical origin of life (Oparin-Haldane, Miller-Urey); evidences from homology, analogy, fossils, embryology and molecules; the Hardy-Weinberg principle and the factors disturbing it; adaptive radiation; and human evolution.

Natural selection

Darwin's mechanism: heritable variations that improve survival and reproduction (fitness) are favoured and spread over generations. Wallace co-proposed it.

Lamarckism

Inheritance of acquired characters via use and disuse (giraffe's long neck). Now discarded, as characters acquired in a lifetime are not inherited.

Mutation theory

de Vries proposed evolution by large, sudden, discontinuous mutations (saltation) in Oenothera, unlike Darwin's small continuous variations.

Chemical evolution

Oparin-Haldane: life arose from non-living molecules in a reducing atmosphere; Miller-Urey made amino acids from CH₄, NH₃, H₂ and water vapour with sparks.

Homologous organs

Same fundamental structure and origin but different functions (vertebrate forelimbs); evidence of divergent evolution from a common ancestor.

Analogous organs

Different structure and origin but the same function (butterfly and bird wings); evidence of convergent evolution driven by similar environments.

Fossils

Remains or impressions of past life in rocks — direct evidence, dated by radioactive decay. Archaeopteryx is a connecting link between reptiles and birds.

Hardy-Weinberg principle

Allele frequencies stay constant across generations in a large, random-mating population with no mutation, migration, drift or selection (genetic equilibrium).

Genetic drift

Random change in allele frequencies in small populations; the founder effect and bottleneck effect are examples that disturb equilibrium.

Adaptive radiation

Evolution of many species from one ancestor into different habitats/niches; e.g., Darwin's finches and Australian marsupials.

Industrial melanism

In Biston betularia, dark moths increased on soot-blackened trees after industrialisation — a demonstration of natural selection in action.

Types of natural selection

Stabilising (favours the average), directional (favours one extreme, e.g., melanism) and disruptive (favours both extremes against the mean).

Speciation

Formation of new species, usually requiring reproductive isolation; allopatric speciation follows geographic separation of populations.

Human evolution

Australopithecus → Homo habilis (tool user) → Homo erectus → Homo sapiens; a trend of rising cranial capacity and erect posture.