Part 4: Mechanism of Evolution – Natural Selection & Types (25 MCQs)
Part 4: Mechanism of Evolution – Natural Selection & Types (25 MCQs)
Q76. Natural selection operates on:
a) Individuals
b) Populations
c) Communities
d) Ecosystems
Answer: a
- a) Correct: Natural selection acts on individuals, but its effect is seen in populations over generations.
Q77. The unit of evolution is:
a) Individual
b) Gene
c) Population
d) Chromosome
Answer: c
- c) Correct: Population = unit of evolution (allele frequency changes).
Q78. Which of the following is the driving force of evolution?
a) Natural selection
b) Mutation
c) Gene flow
d) All of these
Answer: d
- d) Correct: All contribute, but natural selection is the main force.
Q79. Industrial melanism is an example of:
a) Disruptive selection
b) Directional selection
c) Stabilizing selection
d) Genetic drift
Answer: b
- b) Correct: Peppered moths → directional selection (dark forms favored).
Q80. Stabilizing selection favors:
a) Average phenotypes
b) Extreme phenotypes
c) Both extremes
d) Mutations
Answer: a
- a) Correct: Stabilizing = favors average, eliminates extremes.
Q81. Birth weight in humans is an example of:
a) Directional selection
b) Stabilizing selection
c) Disruptive selection
d) Genetic drift
Answer: b
- b) Correct: Average birth weight is favored → stabilizing selection.
Q82. Directional selection results in:
a) No change in population mean
b) Shift in mean towards one extreme
c) Increase in both extremes
d) Genetic equilibrium
Answer: b
- b) Correct: Directional = shifts population mean.
Q83. Disruptive selection favors:
a) Intermediate phenotype
b) Both extremes
c) Only average
d) None
Answer: b
- b) Correct: Disruptive = favors extremes, eliminates average.
Q84. Sickle cell heterozygotes have an advantage in malaria areas due to:
a) Stabilizing selection
b) Directional selection
c) Balancing selection (heterozygote advantage)
d) Genetic drift
Answer: c
- c) Correct: Heterozygote advantage → balancing selection maintains both alleles.
Q85. Which type of selection maintains polymorphism?
a) Stabilizing
b) Directional
c) Disruptive
d) Balancing
Answer: d
- d) Correct: Balancing selection preserves genetic variation.
Q86. Natural selection acts on:
a) Genotypes directly
b) Phenotypes
c) Allele frequencies
d) Gametes
Answer: b
- b) Correct: Selection acts on phenotypes, which indirectly affects allele frequencies.
Q87. Natural selection increases:
a) Harmful mutations
b) Adaptations in a population
c) Random drift
d) Gene flow
Answer: b
- b) Correct: Natural selection = adaptive evolution.
Q88. Which of the following is NOT an agent of evolution?
a) Mutation
b) Genetic drift
c) Random mating
d) Natural selection
Answer: c
- c) Correct: Random mating maintains equilibrium, doesn’t cause evolution.
Q89. The sickle-cell allele persists in Africa due to:
a) Genetic drift
b) Mutation pressure
c) Natural selection (malaria resistance)
d) Gene flow
Answer: c
- c) Correct: Selection maintains heterozygotes (AS) → malaria resistance.
Q90. Directional selection leads to:
a) No evolutionary change
b) New adaptations by shifting traits
c) Extinction always
d) Polymorphism only
Answer: b
- b) Correct: Directional selection shifts population traits towards advantage.
Q91. Stabilizing selection reduces:
a) Genetic variability
b) Extreme phenotypes
c) Both a and b
d) Neither
Answer: c
- c) Correct: Stabilizing reduces extremes → less variability.
Q92. When two different extreme phenotypes are favored, it is called:
a) Stabilizing selection
b) Directional selection
c) Disruptive selection
d) Genetic drift
Answer: c
- c) Correct: Disruptive = favors both extremes.
Q93. Finches of Galapagos islands show:
a) Directional selection
b) Stabilizing selection
c) Adaptive radiation
d) Genetic drift
Answer: c
- c) Correct: Finches evolved into many forms → adaptive radiation, influenced by selection.
Q94. Which evolutionary force produces non-adaptive changes?
a) Mutation
b) Genetic drift
c) Natural selection
d) Gene flow
Answer: b
- b) Correct: Genetic drift = random, non-adaptive changes in small populations.
Q95. In case of antibiotic resistance in bacteria, which selection is operating?
a) Directional selection
b) Stabilizing selection
c) Disruptive selection
d) Balancing selection
Answer: a
- a) Correct: Resistant bacteria favored → directional selection.
Q96. When average phenotype is eliminated, it is:
a) Stabilizing selection
b) Disruptive selection
c) Directional selection
d) Balancing selection
Answer: b
- b) Correct: Disruptive removes intermediates.
Q97. Natural selection operates through:
a) Variations
b) Differential survival
c) Differential reproduction
d) All of the above
Answer: d
- d) Correct: All are components of natural selection.
Q98. Which of the following is an example of directional selection in humans?
a) Birth weight
b) Skin color
c) Height increase in certain populations
d) Blood groups
Answer: c
- c) Correct: Directional selection → taller height favored in some populations.
Q99. Which selection type reduces extremes but maintains status quo?
a) Stabilizing
b) Directional
c) Disruptive
d) Artificial
Answer: a
- a) Correct: Stabilizing = reduces extremes.
Q100. Which of the following explains why sickle-cell trait is common in Africa?
a) Mutations occur frequently
b) Drift is strong in large populations
c) Selection favors heterozygotes against malaria
d) Balanced lethal system
Answer: c
- c) Correct: Heterozygotes resist malaria → balanced polymorphism.
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