Biology MCQs

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Biology MCQs

Practice complete Biology MCQs covering Introduction to Biology, Cell Biology, Cell Structure, Cell Division, Biomolecules, Plant Physiology, Human Physiology, Genetics, Evolution, Biotechnology, Ecology, Classification of Living Organisms, Plant Kingdom, Animal Kingdom, Microbiology, Human Diseases, Nutrition, Reproduction, Environmental Biology, and all other important topics. Includes chapter-wise and exam-oriented multiple-choice questions with detailed answers and explanations for JKSSB, SSC, Banking, Railway, UPSC, CUET, NEET, State PSCs, and other competitive exams.

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Page 79 of 103
Question #1561
Consider the following statements about DNA replication:
1. It is semiconservative.
2. It requires DNA polymerase.
3. It occurs in the cytoplasm of eukaryotic cells.
Which of the above is/are correct?
A. 1, 2, and 3
B. 1 and 2 only
C. 1 and 3 only
D. 2 and 3 only
Discuss
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Correct Answer: Option B

Explanation:
DNA replication is semiconservative and uses DNA polymerase. In eukaryotes, it occurs in the nucleus, not cytoplasm. So statement 3 is incorrect.
This question belongs to: Science Biology
Question #1562
Assertion (A): Insectivorous plants capture insects.
Reason (R): They grow in nitrogen-rich soil.
A. A is true, but R is false.
B. Both A and R are true, and R is the correct explanation.
C. Both A and R are true, but R is not the correct explanation.
D. A is false, but R is true.
Discuss
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Correct Answer: Option A

Explanation:
Insectivorous plants (e.g., Venus flytrap) capture insects to obtain nitrogen because they grow in nitrogen-poor soils. So A is true, but R is false (nitrogen-poor, not rich).
This question belongs to: Science Biology
Question #1563
Identify the correct statement about blood groups:
A. Rh factor is unrelated to pregnancy complications.
B. Group O has both A and B antigens.
C. Group A has anti-B antibodies.
D. Group AB is the universal donor.
Discuss
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Correct Answer: Option C

Explanation:
Blood group A has A antigens and anti-B antibodies. Group O has no antigens, AB is universal recipient, Rh incompatibility can cause erythroblastosis fetalis.
This question belongs to: Science Biology
Question #1564
Consider the following statements about biotechnology:
1. Restriction enzymes cut DNA at specific sequences.
2. Ligase joins DNA fragments.
3. PCR amplifies DNA.
Which of the above is/are correct?
A. 1 and 3 only
B. 1 and 2 only
C. 2 and 3 only
D. 1, 2, and 3
Discuss
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Correct Answer: Option D

Explanation:
Restriction enzymes cut DNA at recognition sites, DNA ligase seals fragments, and PCR amplifies specific DNA sequences. All three are fundamental tools in biotechnology.
This question belongs to: Science Biology
Question #1565
Assertion (A): Epithelial tissues form protective layers.
Reason (R): They are highly vascularized to transport nutrients.
A. Both A and R are true, and R is the correct explanation.
B. Both A and R are true, but R is not the correct explanation.
C. A is false, but R is true.
D. A is true, but R is false.
Discuss
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Correct Answer: Option D

Explanation:
Epithelial tissues cover body surfaces and line cavities, providing protection. However, they are avascular (lack blood vessels) and receive nutrients by diffusion from underlying connective tissue. So R is false.
This question belongs to: Science Biology
Question #1566
Which of the following statements about the human reproductive system is correct?
A. Sperm production occurs in the vas deferens.
B. Fertilization usually occurs in the uterus.
C. Testosterone is produced by the seminal vesicles.
D. The placenta provides nutrients and oxygen to the fetus.
Discuss
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Correct Answer: Option D

Explanation:
The placenta exchanges nutrients, gases, and wastes between mother and fetus. Sperm are produced in testes, fertilization is in the fallopian tube, testosterone by Leydig cells.
This question belongs to: Science Biology
Question #1567
Identify the INCORRECT statement about bacteria:
A. They reproduce by binary fission.
B. All bacteria are pathogenic.
C. They are prokaryotic.
D. They have a cell wall made of peptidoglycan.
Discuss
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Correct Answer: Option B

Explanation:
Not all bacteria cause disease; many are beneficial (e.g., nitrogen fixers, gut flora). The other statements are true.
This question belongs to: Science Biology
Question #1568
Consider the following statements about the heart:
1. The SA node is the natural pacemaker.
2. The AV node delays the impulse before it passes to ventricles.
3. The Purkinje fibers conduct impulses through the ventricular walls.
Which of the above is/are correct?
A. 1 and 2 only
B. 1 and 3 only
C. 2 and 3 only
D. 1, 2, and 3
Discuss
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Correct Answer: Option D

Explanation:
All three are correct: SA node initiates impulse, AV node delays it to allow atrial emptying, Purkinje fibers spread impulse through ventricles.
This question belongs to: Science Biology
Question #1569
Assertion (A): Water is essential for photosynthesis.
Reason (R): Water is split to release oxygen, and its hydrogen is used to reduce CO₂.
A. Both A and R are true, but R is not the correct explanation.
B. A false, R true.
C. A true, R false.
D. Both A and R are true, and R is the correct explanation.
Discuss
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Correct Answer: Option D

Explanation:
Photolysis of water provides electrons and protons for the light reactions, releasing O₂; NADPH formed carries hydrogen to reduce CO₂ in the Calvin cycle. R correctly explains A.
This question belongs to: Science Biology
Question #1570
Which of the following statements about animal tissues is correct?
A. Smooth muscle is voluntary and non-striated.
B. Neurons are the only cells that produce myelin.
C. Skeletal muscle is involuntary and striated.
D. Cardiac muscle is striated and involuntary.
Discuss
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Correct Answer: Option D

Explanation:
Cardiac muscle has striations and contracts involuntarily. Skeletal muscle is voluntary, smooth involuntary; myelin is produced by Schwann cells (PNS) and oligodendrocytes (CNS), not neurons.
This question belongs to: Science Biology
Question #1571
Identify the correct statement about vitamins and minerals:
A. Iodine deficiency causes anemia.
B. Iron is required for blood clotting.
C. Calcium is essential for bone formation.
D. Vitamin C is a fat-soluble vitamin.
Discuss
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Correct Answer: Option C

Explanation:
Calcium is a major component of bones. Vitamin C is water-soluble, iron is for hemoglobin (oxygen transport), iodine deficiency causes goiter, anemia is from iron/B₁₂/folate deficiency.
This question belongs to: Science Biology
Question #1572
Consider the following statements about photosynthesis:
1. C3 plants fix CO₂ directly in the Calvin cycle.
2. C4 plants have Kranz anatomy.
3. Photorespiration is higher in C4 plants.
Which of the above is/are correct?
A. 2 and 3 only
B. 1 and 2 only
C. 1 and 3 only
D. 1, 2, and 3
Discuss
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Correct Answer: Option B

Explanation:
C3 plants use Calvin cycle directly; C4 plants have Kranz anatomy and a CO₂-concentrating mechanism. Photorespiration is negligible in C4 plants, higher in C3. Thus, 3 is incorrect.
This question belongs to: Science Biology
Question #1573
Assertion (A): The cell wall of fungi is made of cellulose.
Reason (R): Chitin is a characteristic component of fungal cell walls.
A. Both A and R are true, but R is not the correct explanation.
B. A is false, but R is true.
C. A is true, but R is false.
D. Both A and R are true, and R is the correct explanation.
Discuss
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Correct Answer: Option B

Explanation:
Fungal cell walls contain chitin, not cellulose. Cellulose is found in plant cell walls. Thus, A is false and R is true.
This question belongs to: Science Biology
Question #1574
Which of the following statements about the food chain is correct?
A. Energy increases at each trophic level.
B. Decomposers are at the top of the food chain.
C. A grazing food chain starts with living plants.
D. Producers are always animals.
Discuss
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Correct Answer: Option C

Explanation:
Grazing food chain begins with producers (plants). Decomposers break down dead matter at all levels; energy decreases at higher levels; producers are plants/algae.
This question belongs to: Science Biology
Question #1575
Identify the INCORRECT statement about the human eye:
A. Rods are responsible for color vision.
B. The optic nerve transmits impulses to the brain.
C. The iris controls the amount of light entering the eye.
D. The cornea and lens focus light onto the retina.
Discuss
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Correct Answer: Option A

Explanation:
Cones are responsible for color vision; rods detect light intensity, important in dim light. All other statements are correct.
This question belongs to: Science Biology
Question #1576
Consider the following statements about hormones:
1. Insulin is a peptide hormone.
2. Thyroxine is an amino acid derivative.
3. Cortisol is a steroid hormone.
Which of the above is/are correct?
A. 1 and 3 only
B. 2 and 3 only
C. 1 and 2 only
D. 1, 2, and 3
Discuss
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Correct Answer: Option D

Explanation:
Insulin is a peptide, thyroxine derived from tyrosine, cortisol a steroid. All three classifications are correct.
This question belongs to: Science Biology
Question #1577
Assertion (A): Bacteria can be killed by antibiotics like penicillin.
Reason (R): Penicillin inhibits the synthesis of bacterial cell wall.
A. A false, R true.
B. Both A and R are true, but R is not the correct explanation.
C. A true, R false.
D. Both A and R are true, and R is the correct explanation.
Discuss
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Correct Answer: Option D

Explanation:
Penicillin targets the transpeptidase enzyme, blocking peptidoglycan cross-linking, leading to cell lysis. This is the mechanism, so R correctly explains A.
This question belongs to: Science Biology
Question #1578
Which of the following statements about plant reproduction is correct?
A. Pollination is the transfer of pollen from anther to stigma.
B. The ovary develops into the seed.
C. Double fertilization produces a diploid endosperm.
D. The pollen tube enters the ovule through the chalaza.
Discuss
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Correct Answer: Option A

Explanation:
Pollination is indeed pollen transfer. Double fertilization produces triploid endosperm; pollen tube enters via micropyle; ovary becomes fruit, ovule becomes seed.
This question belongs to: Science Biology
Question #1579
Identify the correct statement about glycolysis:
A. It occurs in the mitochondrial matrix.
B. It produces 36 ATP per glucose.
C. It requires oxygen.
D. It converts glucose into two pyruvate molecules.
Discuss
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Correct Answer: Option D

Explanation:
Glycolysis breaks one glucose into two pyruvate, yielding 2 ATP and 2 NADH. It occurs in cytoplasm and is anaerobic.
This question belongs to: Science Biology
Question #1580
Consider the following statements about the cell membrane:
1. It is composed of a phospholipid bilayer.
2. It is fully permeable.
3. Proteins are embedded in the membrane.
Which of the above is/are correct?
A. 1 and 2 only
B. 1 and 3 only
C. 1, 2, and 3
D. 2 and 3 only
Discuss
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Correct Answer: Option B

Explanation:
The cell membrane has a phospholipid bilayer with embedded proteins and is selectively permeable, not fully permeable. So 2 is incorrect.
This question belongs to: Science Biology

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