NEET Biology Evolution MCQs Set 04

Answer: (d) A, B and C

Explanation:
1. Darwin observed that resources are limited, that population size is stable, and that members of a population vary.
2. Mutation as the source of variation was not known to Darwin, so D is not among his observations.

Teacher's Note:
1. Darwin did not know about mutations.
2. The idea of mutation came from Hugo de Vries.

Answer: (b) homologous organs

Explanation:
1. These forelimbs have the same basic structure but are modified for different functions.
2. Such organs are homologous and show divergent evolution.

Teacher's Note:
1. Homologous organs show common ancestry.
2. Analogous organs have a similar function but different structure.

Answer: (c) light emitted by these stars took thousands or millions of years to reach our eyes

Explanation:
1. Stars are extremely far away.
2. Their light takes thousands or millions of years to reach us, so we see them as they were in the past.

Teacher's Note:
1. Distances in space are measured in light years.
2. The light we see left the star long ago.

Answer: (c) Diversity was the same since creation and will be the same in future also

Explanation:
1. Fossil records show that life forms changed and that new forms arose at different times.
2. They also show that some forms existed only in certain periods, so the claim that diversity never changes is incorrect.

Teacher's Note:
1. Fossils in rock layers show change over time.
2. Species have appeared and become extinct throughout earth history.

Answer: (d) Homo habilis probably ate meat

Explanation:
1. Statements (a), (b) and (c) agree with the textbook account of human evolution.
2. Homo habilis had a brain capacity of 650-800 cc and probably did not eat meat, so (d) is incorrect.

Teacher's Note:
1. Homo erectus (900 cc) probably ate meat.
2. Homo habilis was the first human-like being.

Answer: (c) natural selection due to anthropogenic action

Explanation:
1. Human activity (use of chemicals and drugs) creates the selection pressure.
2. Resistant individuals survive and reproduce by natural selection, so this is natural selection due to anthropogenic action.

Teacher's Note:
1. Resistant bacteria and pests are produced by the selection of existing variants.
2. The human influence does not make the selection artificial.

Answer: (d) convergent evolution

Explanation:
1. Unrelated organisms with different ancestry developed similar structures for similar needs.
2. This is convergent evolution, and the structures are analogous.

Teacher's Note:
1. Convergent evolution gives analogous organs.
2. Divergent evolution gives homologous organs.

Answer: (c) random mating

Explanation:
1. Gene flow, genetic recombination, mutation, genetic drift and natural selection change allele frequencies.
2. Random mating helps maintain Hardy-Weinberg equilibrium, so it does not cause evolution.

Teacher's Note:
1. Five factors affect the Hardy-Weinberg equilibrium.
2. They are gene flow, genetic drift, mutation, recombination and natural selection.

Answer: (c) convergent evolution

Explanation:
1. In Australia many marsupials evolved from a common ancestor in different directions, and placental mammals also evolved there in their own way.
2. Their similar forms in the same type of habitats are an example of convergent evolution.

Teacher's Note:
1. Australian marsupials and placental mammals show convergent evolution.
2. For example the marsupial mole and the placental mole.

Answer: (c) 2 billion years ago

Explanation:
1. The earth is about 4.6 billion years old.
2. The first cellular form of life probably originated about 2000 million (2 billion) years ago.

Teacher's Note:
1. First non-cellular life is dated about 3 billion years ago.
2. Cellular life came about a billion years later.

Answer: (a) 49%, 42%

Explanation:
1. q squared = 0.09, so q = 0.3 and p = 1 - 0.3 = 0.7.
2. Homozygous dominant = p squared = 0.49 (49%) and heterozygous = 2pq = 2 x 0.7 x 0.3 = 0.42 (42%).

Teacher's Note:
1. Use p + q = 1 and p squared + 2pq + q squared = 1.
2. Start from the homozygous recessive frequency.

Answer: (d) These capsules had molecules with no ability of self replication

Explanation:
1. The first non-cellular forms of life were giant molecules (probably RNA) in capsules.
2. They were capable of self replication, so the statement that they could not replicate is incorrect.

Teacher's Note:
1. RNA could act as both genetic material and catalyst.
2. This supports the RNA world idea.

Answer: (b) White winged moths were more in number

Explanation:
1. After industrialisation the tree trunks were covered with soot and turned dark.
2. Black moths were camouflaged and survived, so they were more in number in 1920. White winged moths were more in 1850, so statement (b) is incorrect for 1920.

Teacher's Note:
1. Predation by birds acted as the selection pressure.
2. Where the air was clean, the white moths remained common.

Answer: (b) reproductive fitness

Explanation:
1. Darwin used fitness to mean the ability to survive and reproduce.
2. Those with more offspring in the next generation are fitter, so fitness is reproductive fitness.

Teacher's Note:
1. Fitness is not physical strength.
2. Survival of the fittest means survival of the best reproducers.

Answer: (a) founder effect

Explanation:
1. When a few individuals start a new population, the allele frequency of the new population may differ greatly from the original one.
2. This is the founder effect, a type of genetic drift.

Teacher's Note:
1. Founder effect and bottleneck effect are two types of genetic drift.
2. Founder effect is due to a small group migrating to a new area.

Answer: (b) more individuals acquire the mean character value

Explanation:
1. A narrower and taller peak means that the variation about the mean has decreased.
2. More individuals now have the mean value, which is stabilising selection.

Teacher's Note:
1. Stabilising selection favours the mean value.
2. Directional selection shifts the peak and disruptive selection forms two peaks.

Answer: (d) ontogeny repeats phylogeny

Explanation:
1. The biogenetic law says that the embryonic development (ontogeny) of an organism repeats its evolutionary history (phylogeny).
2. So option (d) is correct.

Teacher's Note:
1. Haeckel's idea was later rejected by von Baer.
2. Remember it as ontogeny recapitulates phylogeny.

Answer: (c) When bacteria are transferred to a new medium they develop an adaptive mutation

Explanation:
1. Mutations occur at random and are not caused by the environment, so bacteria do not develop adaptive mutations on transfer to a new medium.
2. Existing variants that suit the new medium are selected. Statements (a), (b) and (d) are correct.

Teacher's Note:
1. Mutations are random and the environment only selects.
2. Short lived organisms evolve new forms faster.