Zoology in NEET is memory heavy but not memory only, because the diagram based and assertion reason questions need understanding. This set runs through human physiology, animal kingdom and classification, structural organisation, genetics and evolution, biotechnology, and ecology. Explanations point to the NCERT line the question came from, so revision stays anchored to the source text.
A population of beetles shows industrial melanism. Dark beetles increased from 5% to 95% in 50 years in polluted areas. What type of selection is most likely operating?
Answer: B
Industrial melanism is a classic example of directional selection where environmental change (pollution) favors one phenotype (dark color) over another.
Q.42Medium
Which statement about mutations is correct?
Answer: C
Mutations are random, non-directed changes in DNA that provide genetic variation for natural selection to act upon. They're not inherently harmful or beneficial.
Q.43Medium
In a population, the allele frequency of 'a' is 0.4 and 'A' is 0.6. If the population is in Hardy-Weinberg equilibrium, what is the expected frequency of heterozygotes?
Answer: C
Frequency of heterozygotes = 2pq = 2(0.6)(0.4) = 0.48 in Hardy-Weinberg equilibrium.
Q.44Medium
A frameshift mutation occurs in the middle of a gene. What is the most likely consequence?
Answer: C
Frameshift mutations shift the reading frame for all downstream codons, typically resulting in nonfunctional proteins or premature termination.
Q.45Medium
A silent mutation in the third codon position of a gene coding for protein synthesis most likely occurs due to:
Answer: A
The wobble hypothesis explains how changes in the third codon position often don't change the amino acid due to the degeneracy of the genetic code, resulting in silent mutations.
Q.46Medium
In a testcross of a dihybrid (AaBb) with a homozygous recessive (aabb), if the offspring ratio deviates from 1:1:1:1, it indicates:
Answer: B
A 1:1:1:1 ratio indicates independent assortment. Deviation suggests the genes are linked on the same chromosome, with recombination occurring at a frequency less than 50%.
Q.47Medium
Peppered moths in industrial England showed rapid evolution from predominantly light-colored to dark-colored populations. This is an example of:
Answer: A
Industrial pollution darkened tree bark, favoring dark moths through directional selection. This is a classic example of evolution in response to environmental change.
Q.48Medium
A mutation converts an amino acid codon (GUU for valine) to a stop codon (UAA). This type of mutation would most severely affect the protein by:
Answer: B
A nonsense mutation (codon to stop codon) causes premature termination of translation, resulting in a truncated, usually nonfunctional protein. This is more severe than missense mutations.
Q.49Medium
In a cross between two heterozygous individuals (Aa × Aa), if the homozygous dominant genotype (AA) is lethal and dies in utero, the surviving offspring ratio would be:
Answer: B
Aa × Aa normally produces 1 AA : 2 Aa : 1 aa. If AA is lethal, only Aa and aa survive in a 2:1 ratio.
