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 variation in shell color. After a pesticide treatment, dark-colored beetles survive better. This is an example of:
Answer: B
Directional selection occurs when one extreme phenotype has higher fitness. Dark beetles have selective advantage, shifting population toward darker phenotype.
Q.2Hard
In a gene pool of 500 individuals with allele frequencies p = 0.7 and q = 0.3, how many heterozygous individuals are expected according to Hardy-Weinberg principle?
Which of the following mutations would most likely be lethal?
Answer: C
Loss of an entire chromosome causes imbalance in gene dosage affecting multiple essential genes, making it almost always lethal.
Q.4Hard
Which of the following best explains why antibiotic-resistant bacteria increase in a population after antibiotic exposure?
Answer: C
Pre-existing resistant bacteria survive antibiotic exposure while susceptible ones die, increasing resistant population frequency—natural selection.
Q.5Hard
If a woman with normal vision (but carrier for color blindness) has children with a color-blind man, what percentage of their daughters are expected to have normal vision?
Answer: B
Carrier mother (XBXb) × Color-blind father (XbY) produces: XBXb (carrier daughter), XbXb (color-blind daughter), XBY (normal son), XbY (color-blind son). 50% of daughters (1 out of 2) have normal vision.
Q.6Hard
Gene flow between two populations can prevent genetic drift from causing fixation of alleles because:
Answer: A
Gene flow (migration) introduces alleles from one population to another, counteracting genetic drift and maintaining genetic variation.
Q.7Hard
A three-point testcross in Drosophila yields recombinant classes with lower frequencies than parental classes. This demonstrates:
Answer: B
Lower recombinant frequencies indicate genes are linked but can undergo crossing over, producing recombinants at lower frequencies than parentals.
Q.8Hard
A lethal allele that causes embryonic death in homozygous condition would alter the expected dihybrid ratio from 9:3:3:1 to:
Answer: A
If one dominant homozygous class (AABB, AABb, or AAbb) is lethal, the 9:3:3:1 ratio adjusts accordingly. Common outcome is 9:3:4 when one class is removed.
Q.9Hard
In humans, if both parents are heterozygous carriers of sickle cell anemia (HbAS), what is the probability of their child being completely unaffected?
Answer: C
Cross: AS × AS produces AA (unaffected, 41), AS (carrier, 21), SS (affected, 41). Probability of unaffected = 41 + 21 = 43 = 0.75
Q.10Hard
The concept of 'adaptive radiation' is best exemplified by:
Answer: A
Darwin's finches underwent adaptive radiation, diverging from a common ancestor into multiple species with different beak morphologies adapted to different food sources.
Q.11Hard
A population experiences a bottleneck reducing its size from 10,000 to 100 individuals. Which evolutionary consequence is MOST likely?
Answer: C
Bottlenecks drastically reduce population size, increasing genetic drift. Random allele loss occurs, reducing genetic variation and increasing chance of fixation.
Q.12Hard
In a X-linked trait, if the allele frequency of the recessive allele in males is 0.1, what is the allele frequency of the recessive allele in females at Hardy-Weinberg equilibrium?
Answer: B
For X-linked traits in males (hemizygous), allele frequency equals phenotype frequency. In females at equilibrium, the allele frequency is the same as in males: 0.1
Q.13Hard
A mutation changes a GC base pair to AT in a non-coding region of DNA. This mutation's evolutionary significance depends primarily on:
Answer: A
Mutations in non-coding regions vary in importance. Those in regulatory elements (promoters, enhancers) can be significant; most others are neutral.
Q.14Hard
A new allele arises in a small island population of 100 individuals. The allele frequency is 0.02. Over the next 10 generations without selection, what is most likely to happen?
Answer: A
In small populations, genetic drift can cause alleles to be randomly lost. With frequency only 0.02 in a population of 100, the allele is vulnerable to random loss.
Q.15Hard
In a three-point testcross involving genes A, B, and C with map distances A-B = 10 map units and B-C = 20 map units, if coefficient of coincidence is 0.8, what is the interference value?
Answer: A
Interference = 1 - Coefficient of Coincidence = 1 - 0.8 = 0.2. This measures how much one crossover interferes with adjacent crossovers.
Q.16Hard
A researcher observes that in a population of snails, shell color is controlled by a single gene with two alleles (B and b). Yellow shells (BB) = 100, Brown shells (Bb) = 300, White shells (bb) = 600. Is this population in Hardy-Weinberg equilibrium?
Answer: B
Total individuals = 1000. p = (200+300)/2000 = 0.25, q = 0.75. Expected: BB = 62.5, Bb = 375, bb = 562.5. Observed shows excess homozygotes, indicating inbreeding or population substructure.
Q.17Hard
Which of the following would NOT cause a change in allele frequencies in a population?
Answer: B
Random assortment of chromosomes during meiosis doesn't change allele frequencies; it only creates different combinations. Selection, drift, and gene flow all change frequencies.
Q.18Hard
A species shows 5 pairs of chromosomes. During meiosis in an individual heterozygous for all 5 genes (AaBbCcDdEe), what is the maximum number of different gamete types that can be produced?
Answer: C
Without crossing over, the number of different gamete types = 2^n, where n = number of heterozygous gene pairs = 2^5 = 32.
Q.19Hard
In a population affected by a recent bottleneck event, which is most likely to occur?
Answer: C
A bottleneck reduces population size dramatically, causing random loss of alleles and making genetic drift the dominant evolutionary force, reducing genetic variation.
Q.20Hard
A researcher studying gene expression notices that identical twins show different phenotypes for a trait despite having identical genotypes. This is most likely due to:
Answer: A
Epigenetic changes (DNA methylation, histone modifications) and differential environmental exposure can cause phenotypic differences in genetically identical individuals.
