Evolutionary Biology MCQs
🌱 Evolutionary Biology MCQs – Part 1 (Q1–Q25)
Q1. The concept of natural selection was proposed by:
A) Jean-Baptiste Lamarck
B) Charles Darwin
C) Gregor Mendel
D) Alfred Wallace
✅ Answer: B) Charles Darwin
Explanation: Darwin proposed natural selection as the mechanism of evolution. Wallace independently suggested similar ideas.
Q2. Lamarck’s theory of evolution is based on:
A) Natural selection
B) Inheritance of acquired characters
C) Genetic drift
D) Mutation
✅ Answer: B) Inheritance of acquired characters
Explanation: Lamarck suggested traits acquired during life (e.g., giraffe’s neck) are inherited, though later disproved.
Q3. “Survival of the fittest” was a phrase popularized by:
A) Charles Darwin
B) Herbert Spencer
C) Gregor Mendel
D) August Weismann
✅ Answer: B) Herbert Spencer
Explanation: Darwin used “natural selection”; Herbert Spencer coined the phrase.
Q4. The industrial melanism in peppered moths (Biston betularia) is an example of:
A) Genetic drift
B) Natural selection
C) Mutation pressure
D) Speciation
✅ Answer: B) Natural selection
Explanation: Dark-colored moths had an advantage in polluted areas → directional selection.
Q5. Hardy–Weinberg principle states that:
A) Allele frequencies remain constant in absence of evolutionary forces
B) Evolution is always occurring
C) Mutations drive constant change
D) Natural selection stops evolution
✅ Answer: A)
Explanation: In a stable population (no selection, drift, migration, mutation, random mating), allele frequencies remain constant.
Q6. Which of the following is NOT an agent of evolutionary change?
A) Mutation
B) Natural selection
C) Random mating
D) Genetic drift
✅ Answer: C) Random mating
Explanation: Random mating preserves allele frequencies, others cause evolutionary change.
Q7. Founder effect is associated with:
A) Natural selection
B) Large populations
C) Small populations isolated from larger gene pool
D) Mutation only
✅ Answer: C)
Explanation: Founder effect = loss of variation when a small group forms a new population.
Q8. Adaptive radiation is best illustrated by:
A) Darwin’s finches in Galápagos
B) Peppered moths in England
C) Industrial melanism
D) Convergent evolution
✅ Answer: A)
Explanation: Finches evolved into many species with different beaks = adaptive radiation.
Q9. Convergent evolution results in:
A) Different ancestors, similar traits
B) Same ancestors, similar traits
C) Genetic drift
D) Artificial selection
✅ Answer: A)
Explanation: Unrelated organisms evolve similar adaptations (e.g., wings of bat and bird).
Q10. Homologous structures indicate:
A) Convergent evolution
B) Divergent evolution from common ancestor
C) Random evolution
D) Mutation
✅ Answer: B)
Explanation: Homologous organs (whale flipper, bat wing, human arm) show divergent evolution.
Q11. Which of the following is a vestigial organ in humans?
A) Appendix
B) Heart
C) Liver
D) Kidney
✅ Answer: A) Appendix
Explanation: Appendix is a vestige of cecum used for cellulose digestion in ancestors.
Q12. The earliest evidence of life on Earth comes from:
A) Stromatolites (fossilized cyanobacteria)
B) Dinosaurs
C) Trilobites
D) Homo habilis
✅ Answer: A) Stromatolites
Explanation: Oldest fossils (~3.5 billion years) are stromatolites formed by cyanobacteria.
Q13. The “primordial soup” theory of life’s origin was proposed by:
A) Darwin and Wallace
B) Oparin and Haldane
C) Miller and Urey
D) Watson and Crick
✅ Answer: B) Oparin and Haldane
Explanation: Proposed life originated from organic molecules in primitive oceans.
Q14. Miller–Urey experiment demonstrated:
A) DNA synthesis from nucleotides
B) Formation of amino acids from inorganic molecules under primitive Earth conditions
C) Artificial cell synthesis
D) RNA world hypothesis
✅ Answer: B)
Explanation: Electric spark in gases (CH₄, NH₃, H₂, H₂O) produced amino acids.
Q15. “RNA world” hypothesis suggests that early life used RNA for:
A) Information storage only
B) Enzymatic functions only
C) Both information storage and catalysis
D) Photosynthesis
✅ Answer: C)
Explanation: RNA can act as genetic material and ribozyme.
Q16. Stabilizing selection favors:
A) Both extremes of a trait
B) Intermediate phenotypes
C) Random alleles
D) Migration
✅ Answer: B)
Explanation: Stabilizing selection reduces extremes, favors average traits (e.g., human birth weight).
Q17. Directional selection results in:
A) Maintenance of average
B) Shift towards one extreme
C) Random variation
D) Loss of selection pressure
✅ Answer: B)
Explanation: Trait distribution shifts in one direction (e.g., antibiotic resistance).
Q18. Disruptive selection results in:
A) Elimination of extremes
B) Favoring both extremes over average
C) No selection
D) Gene flow
✅ Answer: B)
Explanation: Leads to two extreme phenotypes being selected.
Q19. Which scientist proposed the theory of punctuated equilibrium?
A) Darwin and Wallace
B) Eldredge and Gould
C) Lamarck
D) Hugo de Vries
✅ Answer: B) Eldredge and Gould
Explanation: Evolution occurs in rapid bursts, separated by long stasis.
Q20. Which type of speciation occurs without geographic isolation?
A) Allopatric
B) Sympatric
C) Peripatric
D) Parapatric
✅ Answer: B) Sympatric
Explanation: Sympatric speciation occurs within same area (often via polyploidy in plants).
Q21. Genetic drift is strongest in:
A) Large populations
B) Small populations
C) Populations under stabilizing selection
D) Hardy–Weinberg equilibrium
✅ Answer: B) Small populations
Explanation: Drift = random allele frequency changes, greatest in small populations.
Q22. The “selfish gene” theory was proposed by:
A) Richard Dawkins
B) Charles Darwin
C) Thomas Malthus
D) Hugo de Vries
✅ Answer: A) Richard Dawkins
Explanation: Genes act to maximize their own survival through organisms.
Q23. Which evolutionary force introduces new alleles into a population?
A) Migration (gene flow)
B) Genetic drift
C) Selection
D) Mutation
✅ Answer: D) Mutation
Explanation: Only mutation creates new alleles; others alter existing allele frequencies.
Q24. Which is an example of artificial selection?
A) Industrial melanism
B) Antibiotic resistance in bacteria
C) Breeding of dogs from wolves
D) Convergent evolution
✅ Answer: C) Dog breeding
Explanation: Artificial selection = human-directed breeding.
Q25. Which is considered the “unit of evolution”?
A) Individual
B) Population
C) Species
D) Gene
✅ Answer: B) Population
Explanation: Evolution occurs via allele frequency changes in populations, not individuals.
🌱 Evolutionary Biology MCQs – Part 2 (Q26–Q50)
Q26. Which of the following provides the strongest evidence for evolution?
A) Fossil record
B) Similar behavior
C) Analogous organs
D) Learned habits
✅ Answer: A) Fossil record
Explanation: Fossils provide direct chronological evidence of evolutionary change.
Q27. The wings of a bird and the wings of an insect are examples of:
A) Homologous organs
B) Analogous organs
C) Vestigial organs
D) Divergent traits
✅ Answer: B) Analogous organs
Explanation: Same function (flying), but different origin and structure → convergent evolution.
Q28. The flipper of a whale and the human arm are examples of:
A) Analogous organs
B) Vestigial organs
C) Homologous organs
D) Convergent organs
✅ Answer: C) Homologous organs
Explanation: Same evolutionary origin, different functions → divergent evolution.
Q29. Which fossil is regarded as a connecting link between reptiles and birds?
A) Seymouria
B) Archaeopteryx
C) Ichthyostega
D) Australopithecus
✅ Answer: B) Archaeopteryx
Explanation: Archaeopteryx had feathers like birds but teeth and tail like reptiles.
Q30. The study of distribution of organisms across the globe is called:
A) Taxonomy
B) Biogeography
C) Phylogeny
D) Ecology
✅ Answer: B) Biogeography
Explanation: Biogeography gives evidence for evolution through species distribution.
Q31. The sudden appearance of new species in fossil record is explained by:
A) Gradualism
B) Punctuated equilibrium
C) Lamarckism
D) Stabilizing selection
✅ Answer: B) Punctuated equilibrium
Explanation: Species remain stable, then rapid bursts of change occur.
Q32. Darwin’s finches are a classic example of:
A) Convergent evolution
B) Adaptive radiation
C) Stabilizing selection
D) Artificial selection
✅ Answer: B) Adaptive radiation
Explanation: Finches evolved into different species with distinct beaks.
Q33. Which is NOT a prezygotic reproductive isolating mechanism?
A) Temporal isolation
B) Mechanical isolation
C) Hybrid sterility
D) Behavioral isolation
✅ Answer: C) Hybrid sterility
Explanation: Hybrid sterility occurs after fertilization (postzygotic).
Q34. Polyploidy is a common mechanism of speciation in:
A) Mammals
B) Birds
C) Plants
D) Reptiles
✅ Answer: C) Plants
Explanation: Polyploidy (extra sets of chromosomes) is frequent in plant speciation.
Q35. The Hardy–Weinberg equilibrium equation is:
A) p² + 2pq + q² = 1
B) p + q = 0
C) p² + q² = 1
D) 2pq = 0
✅ Answer: A)
Explanation: For a population at equilibrium: p² (AA) + 2pq (Aa) + q² (aa) = 1.
Q36. In Hardy–Weinberg equilibrium, p represents:
A) Frequency of heterozygotes
B) Frequency of dominant allele
C) Frequency of recessive allele
D) Phenotypic ratio
✅ Answer: B)
Explanation: p = dominant allele frequency, q = recessive allele frequency.
Q37. A change in allele frequency due to chance events is called:
A) Gene flow
B) Genetic drift
C) Natural selection
D) Mutation
✅ Answer: B) Genetic drift
Explanation: Random changes in allele frequency, especially in small populations.
Q38. Which is an example of genetic drift?
A) Industrial melanism
B) Bottleneck effect
C) Antibiotic resistance
D) Convergent evolution
✅ Answer: B) Bottleneck effect
Explanation: Population crash → reduced genetic diversity (bottleneck or founder effect).
Q39. Which of the following is NOT part of Darwin’s theory?
A) Variation exists in populations
B) Survival of the fittest
C) Inheritance of acquired characters
D) Overproduction of offspring
✅ Answer: C) Inheritance of acquired characters
Explanation: That was Lamarck’s idea, not Darwin’s.
Q40. The modern concept of evolution integrating genetics with Darwinism is called:
A) Neo-Darwinism
B) Punctuated equilibrium
C) Lamarckism
D) Synthetic theory
✅ Answer: A) Neo-Darwinism (Synthetic theory)
Explanation: Combines Darwin’s natural selection with Mendelian genetics.
Q41. Which scientist is associated with the mutation theory of evolution?
A) Darwin
B) Lamarck
C) Hugo de Vries
D) Wallace
✅ Answer: C) Hugo de Vries
Explanation: Proposed evolution occurs via sudden mutations.
Q42. Which evolutionary force counters natural selection by introducing new alleles?
A) Genetic drift
B) Mutation
C) Stabilizing selection
D) Non-random mating
✅ Answer: B) Mutation
Explanation: Mutation is the ultimate source of variation.
Q43. The term “gene pool” refers to:
A) Total number of chromosomes
B) Total genetic information in a population
C) Collection of proteins in a cell
D) Group of related species
✅ Answer: B) Total genetic information in a population
Explanation: Gene pool = all alleles of all individuals in a population.
Q44. Which is the best example of coevolution?
A) Bees and flowering plants
B) Humans and appendix
C) Dog breeds
D) Bacteria in soil
✅ Answer: A) Bees and flowering plants
Explanation: Mutual adaptation of pollinators and plants.
Q45. Which evidence supports common ancestry of life?
A) Different genetic codes
B) Universal genetic code and ATP usage
C) Only fossils
D) Different enzymes
✅ Answer: B)
Explanation: All life shares universal genetic code, ATP, and ribosomes.
Q46. Which organ is vestigial in snakes?
A) Eyes
B) Hind limb bones
C) Tongue
D) Brain
✅ Answer: B) Hind limb bones
Explanation: Snakes have rudimentary pelvic bones, evidence of ancestry.
Q47. Which of the following is an example of adaptive convergence?
A) Streamlined body in fish, dolphin, and ichthyosaur
B) Darwin’s finches
C) Different breeds of dogs
D) Galápagos tortoises
✅ Answer: A)
Explanation: Streamlined bodies evolved independently in unrelated groups.
Q48. The first vertebrates to colonize land were:
A) Amphibians
B) Reptiles
C) Fish
D) Mammals
✅ Answer: A) Amphibians
Explanation: Amphibians evolved from lobe-finned fish.
Q49. Which group of mammals is most closely related to humans evolutionarily?
A) Rodents
B) Primates
C) Marsupials
D) Monotremes
✅ Answer: B) Primates
Explanation: Humans belong to order Primates (with apes, monkeys).
Q50. Which is the closest living relative of humans?
A) Gorilla
B) Chimpanzee
C) Orangutan
D) Gibbon
✅ Answer: B) Chimpanzee
Explanation: Molecular studies show chimpanzees share ~98–99% DNA with humans.
🌱 Evolutionary Biology MCQs – Part 3 (Q51–Q75)
Q51. The idea that “ontogeny recapitulates phylogeny” was proposed by:
A) Lamarck
B) Haeckel
C) Darwin
D) Wallace
✅ Answer: B) Haeckel
Explanation: Haeckel suggested embryonic development (ontogeny) repeats evolutionary history (phylogeny), though not literally true today.
Q52. Which of the following is a transitional fossil between fish and amphibians?
A) Seymouria
B) Archaeopteryx
C) Ichthyostega
D) Australopithecus
✅ Answer: C) Ichthyostega
Explanation: Ichthyostega shows features of both fish and amphibians.
Q53. Which of the following is NOT a mechanism of evolution?
A) Mutation
B) Genetic drift
C) Natural selection
D) Cell division
✅ Answer: D) Cell division
Explanation: Cell division is life’s process, not an evolutionary force.
Q54. Which type of selection maintains multiple phenotypes in a population?
A) Stabilizing selection
B) Directional selection
C) Balancing selection
D) Disruptive selection
✅ Answer: C) Balancing selection
Explanation: Maintains genetic diversity (e.g., heterozygote advantage in sickle-cell anemia).
Q55. Which concept explains the sudden increase of diversity during the Cambrian period?
A) Punctuated equilibrium
B) Cambrian explosion
C) Gradualism
D) Genetic drift
✅ Answer: B) Cambrian explosion
Explanation: ~540 mya, rapid diversification of animal phyla occurred.
Q56. The earliest eukaryotic cells are believed to have evolved through:
A) Lamarckian inheritance
B) Endosymbiosis
C) Genetic drift
D) Mutation only
✅ Answer: B) Endosymbiosis
Explanation: Mitochondria/chloroplasts originated from symbiotic bacteria.
Q57. Which evolutionary evidence is provided by comparative embryology?
A) Similarity of adult forms
B) Similar embryonic stages among vertebrates
C) Fossil intermediates
D) Homologous structures
✅ Answer: B)
Explanation: Vertebrate embryos show pharyngeal slits, tails, suggesting common ancestry.
Q58. Who wrote On the Origin of Species?
A) Alfred Wallace
B) Charles Darwin
C) Jean Lamarck
D) Hugo de Vries
✅ Answer: B) Charles Darwin
Explanation: Published in 1859, it explained natural selection.
Q59. Which is an example of coevolution?
A) Predator–prey arms race
B) Appendix in humans
C) Vestigial wings in ostrich
D) Founder effect
✅ Answer: A) Predator–prey arms race
Explanation: Reciprocal adaptations between interacting species (e.g., snakes vs. newts).
Q60. Which phenomenon explains similarity in structures due to common ancestry?
A) Convergent evolution
B) Homology
C) Analogy
D) Mutation
✅ Answer: B) Homology
Explanation: Homologous organs arise from a common ancestor.
Q61. Which concept describes the splitting of one species into two or more?
A) Extinction
B) Speciation
C) Adaptation
D) Mutation
✅ Answer: B) Speciation
Explanation: Speciation creates new species through reproductive isolation.
Q62. Which is an example of postzygotic isolation?
A) Temporal isolation
B) Hybrid sterility (e.g., mule)
C) Behavioral isolation
D) Mechanical isolation
✅ Answer: B) Hybrid sterility
Explanation: Hybrids form but are sterile → postzygotic barrier.
Q63. Which type of evolution leads to unrelated organisms developing similar traits?
A) Divergent evolution
B) Convergent evolution
C) Parallel evolution
D) Coevolution
✅ Answer: B) Convergent evolution
Explanation: Similar adaptations in unrelated groups (e.g., shark vs. dolphin).
Q64. Which is the best molecular evidence for evolution?
A) Fossils
B) DNA and protein sequence similarities
C) Vestigial organs
D) Biogeography
✅ Answer: B)
Explanation: Greater DNA similarity → closer evolutionary relationship.
Q65. Which scientist emphasized the role of population growth and competition in evolution?
A) Thomas Malthus
B) Charles Darwin
C) Jean Lamarck
D) Alfred Wallace
✅ Answer: A) Thomas Malthus
Explanation: Malthus’ essay on population growth influenced Darwin’s thinking.
Q66. Which type of evolution is represented by marsupial mammals of Australia resembling placental mammals elsewhere?
A) Divergent
B) Convergent
C) Adaptive radiation
D) Parallel
✅ Answer: B) Convergent
Explanation: Similar niches → marsupials & placentals evolved alike independently.
Q67. Which process allows exchange of genes between populations?
A) Mutation
B) Genetic drift
C) Gene flow
D) Selection
✅ Answer: C) Gene flow
Explanation: Migration (gene flow) introduces alleles between populations.
Q68. The modern human (Homo sapiens) first appeared approximately:
A) 10,000 years ago
B) 2 million years ago
C) 200,000 years ago
D) 5 million years ago
✅ Answer: C) 200,000 years ago
Explanation: Fossil and genetic evidence: humans emerged in Africa ~200,000 years ago.
Q69. Which is the correct sequence in human evolution?
A) Australopithecus → Homo habilis → Homo erectus → Homo sapiens
B) Homo habilis → Australopithecus → Homo erectus → Homo sapiens
C) Homo erectus → Homo habilis → Australopithecus → Homo sapiens
D) Australopithecus → Homo erectus → Homo habilis → Homo sapiens
✅ Answer: A)
Explanation: Fossil record supports this progression of human evolution.
Q70. Which feature distinguishes modern humans from earlier hominids?
A) Bipedalism
B) Large brain size (~1400 cc)
C) Use of tools
D) Opposable thumb
✅ Answer: B) Large brain size
Explanation: Humans have much larger brains compared to earlier hominids.
Q71. Which was the first hominid to use fire?
A) Australopithecus
B) Homo habilis
C) Homo erectus
D) Neanderthal
✅ Answer: C) Homo erectus
Explanation: Homo erectus controlled fire for cooking and protection.
Q72. Which hominid buried their dead and showed symbolic thought?
A) Australopithecus
B) Homo habilis
C) Neanderthal
D) Homo erectus
✅ Answer: C) Neanderthal
Explanation: Neanderthals practiced burial rituals and had symbolic culture.
Q73. Which discovery supported the idea that DNA is a molecular clock of evolution?
A) Fossil record
B) Protein sequence analysis
C) DNA sequence homology
D) Vestigial structures
✅ Answer: C) DNA sequence homology
Explanation: Rate of DNA mutations can estimate evolutionary divergence.
Q74. The earliest primates lived approximately:
A) 65 million years ago
B) 200,000 years ago
C) 5 million years ago
D) 1 million years ago
✅ Answer: A) 65 million years ago
Explanation: Primates first appeared after dinosaur extinction (~65 mya).
Q75. Which theory proposes that mitochondria and chloroplasts originated from symbiotic bacteria?
A) Cell theory
B) Endosymbiotic theory
C) RNA world hypothesis
D) Mutation theory
✅ Answer: B) Endosymbiotic theory
Explanation: Evidence: circular DNA, 70S ribosomes, double membranes.
🌱 Evolutionary Biology MCQs – Part 4 (Q76–Q100)
Q76. The oldest hominid fossil “Lucy” belongs to:
A) Homo erectus
B) Australopithecus afarensis
C) Homo habilis
D) Neanderthal
✅ Answer: B) Australopithecus afarensis
Explanation: Discovered in Ethiopia (~3.2 mya), Lucy is a famous early bipedal hominid.
Q77. Which group of animals evolved first?
A) Reptiles
B) Amphibians
C) Fish
D) Mammals
✅ Answer: C) Fish
Explanation: Fish were the earliest vertebrates (~500 mya). Amphibians, reptiles, mammals appeared later.
Q78. The term “living fossil” refers to:
A) Extinct species
B) Species unchanged for millions of years
C) Transitional fossils
D) Artificially preserved fossils
✅ Answer: B) Species unchanged
Explanation: Examples: Coelacanth, Limulus (horseshoe crab), Ginkgo biloba.
Q79. Which factor most strongly drives adaptive radiation?
A) Mutation
B) Availability of new ecological niches
C) Random drift
D) Inbreeding
✅ Answer: B)
Explanation: New environments/niches promote adaptive radiation (e.g., Darwin’s finches).
Q80. Which is the best example of parallel evolution?
A) Wings of bats and insects
B) Placental and marsupial mammals evolving similarly
C) Streamlined bodies of fish and dolphins
D) Human and chimpanzee skulls
✅ Answer: B) Placental and marsupial mammals
Explanation: Related groups evolve similar adaptations independently in different regions.
Q81. Which phenomenon decreases variation within populations but increases differences between populations?
A) Mutation
B) Gene flow
C) Genetic drift
D) Natural selection
✅ Answer: C) Genetic drift
Explanation: Drift reduces variation and may cause population divergence.
Q82. Which event allowed mammals to diversify extensively?
A) Evolution of photosynthesis
B) Extinction of dinosaurs
C) Origin of life
D) Rise of amphibians
✅ Answer: B) Extinction of dinosaurs
Explanation: After dinosaur extinction (~65 mya), mammals radiated into new niches.
Q83. Which law states that “ontogeny recapitulates phylogeny”?
A) Darwin’s law
B) Haeckel’s law
C) Lamarck’s law
D) Mendel’s law
✅ Answer: B) Haeckel’s law
Explanation: Although oversimplified, Haeckel proposed embryonic development reflects evolutionary history.
Q84. Which organ in whales is considered vestigial?
A) Flippers
B) Hind limb bones
C) Blowhole
D) Heart
✅ Answer: B) Hind limb bones
Explanation: Whales have tiny pelvic bones, remnants of land-dwelling ancestors.
Q85. The main driving force of evolution, according to Darwin, is:
A) Genetic drift
B) Mutation
C) Natural selection
D) Random mating
✅ Answer: C) Natural selection
Explanation: Darwin emphasized variation + struggle + survival of the fittest.
Q86. The “biogenetic law” is related to:
A) Embryology
B) Paleontology
C) Biogeography
D) Genetics
✅ Answer: A) Embryology
Explanation: Biogenetic law → “ontogeny recapitulates phylogeny.”
Q87. Which evolutionary concept did August Weismann strongly support?
A) Use and disuse
B) Inheritance of acquired characters
C) Germplasm theory (germline–somatic separation)
D) Mutation theory
✅ Answer: C) Germplasm theory
Explanation: Weismann: hereditary information is in germ cells, not somatic cells.
Q88. Which fossil hominid is known as “handy man”?
A) Australopithecus
B) Homo habilis
C) Homo erectus
D) Neanderthal
✅ Answer: B) Homo habilis
Explanation: Named for tool use, lived ~2.5 mya.
Q89. Which evolutionary mechanism can produce adaptation?
A) Mutation alone
B) Natural selection
C) Genetic drift
D) Inbreeding
✅ Answer: B) Natural selection
Explanation: Only selection reliably produces adaptive traits.
Q90. Which is the correct chronological order of evolution of life forms?
A) Prokaryotes → Eukaryotes → Fish → Amphibians → Reptiles → Mammals → Humans
B) Eukaryotes → Prokaryotes → Fish → Amphibians → Mammals
C) Amphibians → Fish → Reptiles → Humans
D) Reptiles → Amphibians → Fish → Humans
✅ Answer: A)
Explanation: Fossil record confirms this sequence.
Q91. The genetic material of the earliest organisms was probably:
A) DNA
B) RNA
C) Protein
D) Lipid
✅ Answer: B) RNA
Explanation: RNA world hypothesis → RNA acted as both genetic material and enzyme.
Q92. Which factor can maintain polymorphism in a population?
A) Inbreeding
B) Balancing selection
C) Founder effect
D) Bottleneck effect
✅ Answer: B) Balancing selection
Explanation: Maintains multiple alleles (e.g., heterozygote advantage).
Q93. Which of the following is an example of disruptive selection?
A) Medium-sized birds favored
B) Both small and large beak sizes favored
C) Average height favored
D) One extreme trait favored
✅ Answer: B)
Explanation: Disruptive selection favors two extremes, reduces intermediates.
Q94. Which principle explains that species evolve slowly with accumulation of small changes?
A) Punctuated equilibrium
B) Gradualism
C) Mutation theory
D) Catastrophism
✅ Answer: B) Gradualism
Explanation: Darwin emphasized slow, continuous evolution (gradualism).
Q95. The bottleneck effect occurs when:
A) A small group migrates to a new habitat
B) A population undergoes drastic reduction in size
C) Mutation rate increases
D) Random mating occurs
✅ Answer: B)
Explanation: Population crash reduces genetic diversity.
Q96. Which phenomenon explains that mitochondria and chloroplasts were once free-living bacteria?
A) Punctuated equilibrium
B) Endosymbiosis
C) Gradualism
D) Mutation theory
✅ Answer: B) Endosymbiosis
Explanation: Supported by their circular DNA, 70S ribosomes, double membranes.
Q97. Which scientist performed the “meat and maggot” experiment disproving spontaneous generation?
A) Francesco Redi
B) Louis Pasteur
C) Miller and Urey
D) Darwin
✅ Answer: A) Francesco Redi
Explanation: Showed maggots came from flies, not meat itself.
Q98. Who finally disproved spontaneous generation using the swan-neck flask experiment?
A) Darwin
B) Pasteur
C) Redi
D) Koch
✅ Answer: B) Louis Pasteur
Explanation: Demonstrated microbes come from existing life, not spontaneous origin.
Q99. Which event marked the origin of oxygen in Earth’s atmosphere?
A) Origin of RNA world
B) Photosynthesis by cyanobacteria
C) Formation of ozone layer
D) Cambrian explosion
✅ Answer: B) Cyanobacteria photosynthesis
Explanation: Great Oxidation Event (~2.4 bya) → O₂ buildup due to cyanobacteria.
Q100. Evolutionary biology ultimately explains:
A) Variation in individuals only
B) Diversity and unity of life through descent with modification
C) Ecology alone
D) Genetics alone
✅ Answer: B)
Explanation: Evolution explains both diversity (speciation) and unity (common ancestry) of life.
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