Evolution – Hardy-Weinberg Principle and A Brief Account of Evolution: NEET MCQs with Answers

15 free questions on Evolution – Hardy-Weinberg Principle and A Brief Account of Evolution for NEET (UG), starting with previous-year NEET and AIPMT questions. Try each one, then tap Show answer for the answer and a short explanation.

Syllabus covered: Hardy-Weinberg Principle and A Brief Account of Evolution: Gene flow and genetic drift; Hardy-Weinberg’s principle;

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Question 1

Previous-year question
At a gene locus with two alleles A and a, if the frequency of the dominant allele A is 0.4, what will be the frequencies of homozygous dominant, heterozygous and homozygous recessive individuals in the population? [NEET 2019]
  1. 0.36 (AA); 0.48 (Aa); 0.16 (aa)
  2. 0.16 (AA); 0.24 (Aa); 0.36 (aa)
  3. 0.16 (AA); 0.48 (Aa); 0.36 (aa)
  4. 0.16 (AA); 0.36 (Aa); 0.48 (aa)
Show answer
Answer: (C) 0.16 (AA); 0.48 (Aa); 0.36 (aa)
Explanation: With p = 0.4 and q = 0.6, p2 = 0.16, 2pq = 2 × 0.4 × 0.6 = 0.48 and q2 = 0.36. These are the frequencies of AA, Aa and aa respectively, and they sum to 1.

Question 2

Previous-year question
A population will NOT exist in Hardy-Weinberg equilibrium if [AIPMT 2015]
  1. There are no mutations
  2. There is no migration
  3. The population is large
  4. Individuals mate selectively
Show answer
Answer: (D) Individuals mate selectively
Explanation: Hardy-Weinberg equilibrium requires random mating along with a large population, no mutation, no migration and no selection. Selective (non-random) mating alters genotype frequencies and therefore destroys the equilibrium.

Question 3

Previous-year question
In a population of 1000 individuals, 360 belong to genotype AA, 480 to Aa and the remaining 160 to aa. Based on this data, the frequency of allele A in the population is [AIPMT 2014]
  1. 0.4
  2. 0.5
  3. 0.6
  4. 0.7
Show answer
Answer: (C) 0.6
Explanation: The total number of alleles is 2000. The A alleles number (2 × 360) + 480 = 1200, so the frequency of A is 1200/2000 = 0.6.

Question 4

Previous-year question
The correct chronological order of geological eras is [AIPMT 1991]
  1. Palaeozoic → Archaeozoic → Coenozoic
  2. Archaeozoic → Palaeozoic → Proterozoic
  3. Palaeozoic → Mesozoic → Coenozoic
  4. Mesozoic → Archaeozoic → Proterozoic
Show answer
Answer: (C) Palaeozoic → Mesozoic → Coenozoic
Explanation: An era is a division of geological time containing one or more periods. The sequence runs Palaeozoic → Mesozoic → Coenozoic. The Palaeozoic and Mesozoic are subdivided into periods, while the Coenozoic is divided into periods and epochs; the Mesozoic is the age of reptiles and the Coenozoic the age of mammals and birds.

Question 5

Previous-year question
Genetic drift is a change in [AIPMT 1993]
  1. gene frequency within the same generation
  2. appearance of recessive genes
  3. gene frequency from one generation to the next
  4. none of the above
Show answer
Answer: (C) gene frequency from one generation to the next
Explanation: Genetic drift is defined as any random change, directed or undirected, in the gene frequency of a population as it passes from one generation to the next.

Question 6

Previous-year question
Two geographical regions separated by high mountains are [AIPMT 1994]
  1. Oriental and Australian
  2. Palaearctic and Oriental
  3. Nearctic and Palaearctic
  4. Neotropical and Ethiopian
Show answer
Answer: (B) Palaearctic and Oriental
Explanation: P. L. Sclater (1858) and later A. R. Wallace (1876) divided the world into six biogeographic realms — Palaearctic, Ethiopian, Oriental, Australian, Nearctic and Neotropical. The Palaearctic and Oriental realms are separated by the high Himalayan mountain range.

Question 7

Previous-year question
The earliest fossil form in the phylogeny of the horse is [AIPMT 1994]
  1. Merychippus
  2. Mesohippus
  3. Eohippus
  4. Equus
Show answer
Answer: (C) Eohippus
Explanation: Hoofed animals such as the horse originated in the Eocene epoch in North America. The first horse-like animal from which the modern Equus evolved was Eohippus (Hyracotherium). Mesohippus and Merychippus are later extinct genera of the line.
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Question 8

Previous-year question
The ‘golden age of dinosaurs’ or the age of reptiles was the [AIPMT 1994]
  1. Mesozoic
  2. Coenozoic
  3. Palaeozoic
  4. Psychozoic
Show answer
Answer: (A) Mesozoic
Explanation: During the Mesozoic era dinosaurs attained enormous size and were most abundant, which is why this era is called both the age of reptiles and the golden age of dinosaurs.

Question 9

Previous-year question
The occurrence of endemic species in South America and Australia is due to [AIPMT 2001]
  1. these species having become extinct in other regions
  2. continental separation
  3. there being no terrestrial route to these places
  4. retrogressive evolution
Show answer
Answer: (B) continental separation
Explanation: Seas formed by continental drift acted as barriers to free intercontinental movement. Organisms on these separated land masses evolved independently, producing endemic species that are restricted to a particular region of the world.

Question 10

Previous-year question
Reptiles were dominant during which era? [AIPMT 2002]
  1. Cenozoic era
  2. Mesozoic era
  3. Palaeozoic era
  4. Archaeozoic era
Show answer
Answer: (B) Mesozoic era
Explanation: The Mesozoic era began about 253 million years ago and lasted roughly 186 million years. Reptiles dominated the land, sea and air during this time, so it is called the ‘Age of Reptiles’.

Question 11

Previous-year question
Under which condition does the gene ratio remain constant for any species? [AIPMT 2002]
  1. Sexual selection
  2. Random mating
  3. Mutation
  4. Gene flow
Show answer
Answer: (B) Random mating
Explanation: When mating is random, the mixing of alleles at meiosis and their subsequent recombination do not alter allele frequencies in future generations. Sexual selection, mutation and gene flow all disturb the Hardy-Weinberg equilibrium.

Question 12

Previous-year question
Random genetic drift in a population probably results from [AIPMT 2003]
  1. large population size
  2. highly genetically variable individuals
  3. interbreeding within the population
  4. a constant low mutation rate
Show answer
Answer: (C) interbreeding within the population
Explanation: Genetic drift (Sewall Wright effect) is a statistically significant change in population gene frequency arising by chance and not from selection, emigration or immigration. It is most likely to result from interbreeding within a small isolated population.

Question 13

Previous-year question
In a randomly mating population at equilibrium, which of the following brings about a change in gene frequency in a non-directional manner? [AIPMT 2003]
  1. Migration
  2. Mutation
  3. Random drift
  4. Selection
Show answer
Answer: (C) Random drift
Explanation: Random genetic drift is the loss or increase of alleles purely by chance and therefore alters gene frequencies without any particular direction. Mutation, selection and migration all shift frequencies in a directional manner.

Question 14

Previous-year question
At a particular locus the frequency of allele A is 0.6 and that of allele a is 0.4. What will be the frequency of heterozygotes in a randomly mating population at equilibrium? [AIPMT 2005]
  1. 0.36
  2. 0.16
  3. 0.24
  4. 0.48
Show answer
Answer: (D) 0.48
Explanation: From p² + 2pq + q² = 1, the heterozygote frequency is 2pq = 2 × 0.6 × 0.4 = 0.48.

Question 15

Previous-year question
The Jurassic period of the Mesozoic era is characterised by [AIPMT 2006]
  1. radiation of reptiles and origin of mammal-like reptiles
  2. extinction of dinosaurs and appearance of angiosperms
  3. appearance of flowering plants and first dinosaurs
  4. dominance of gymnosperms and appearance of the first birds
Show answer
Answer: (D) dominance of gymnosperms and appearance of the first birds
Explanation: The Jurassic is the second period of the Mesozoic. Gymnosperms continued to dominate the vegetation along with ferns and cycads, dinosaurs ruled the land, and the first flying reptiles (pterosaurs) and the first birds appeared.

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