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 78 of 103
Question #1541
Identify the INCORRECT statement about the human nervous system:
A. The cerebellum maintains body balance.
B. The medulla oblongata regulates heartbeat and respiration.
C. The cerebrum controls voluntary actions.
D. The hypothalamus controls reflex actions of the spinal cord.
Discuss
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Correct Answer: Option D

Explanation:
The hypothalamus regulates body temperature, hunger, and thirst, and controls the pituitary. Reflex actions are primarily coordinated by the spinal cord, not the hypothalamus. Hence, D is incorrect.
This question belongs to: Science Biology
Question #1542
Consider the following statements about vitamins:
1. Vitamin A is fat-soluble.
2. Vitamin C is water-soluble.
3. Vitamin D can be synthesized in the skin by sunlight.
Which of the above is/are correct?
A. 1 and 2 only
B. 2 and 3 only
C. 1 and 3 only
D. 1, 2, and 3
Discuss
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Correct Answer: Option D

Explanation:
All three are correct: A is fat-soluble, C is water-soluble, D is synthesized in skin from cholesterol derivatives upon UV exposure.
This question belongs to: Science Biology
Question #1543
Assertion (A): Diabetes mellitus is characterized by hyperglycemia.
Reason (R): It is caused by deficiency or resistance to insulin.
A. A false, R true.
B. A true, R false.
C. Both A and R are true, and R is the correct explanation.
D. Both A and R are true, but R is not the correct explanation.
Discuss
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Correct Answer: Option C

Explanation:
Diabetes mellitus results in high blood glucose due to insulin deficiency (Type 1) or resistance (Type 2). The reason correctly explains the assertion.
This question belongs to: Science Biology
Question #1544
Which of the following statements about plant tissues is correct?
A. Sclerenchyma cells have thick lignified walls and are often dead.
B. Collenchyma provides mechanical support and is dead at maturity.
C. Phloem transports water and minerals.
D. Xylem transports organic nutrients.
Discuss
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Correct Answer: Option A

Explanation:
Sclerenchyma provides strength, with thick lignified walls; cells are usually dead at maturity. Xylem transports water, phloem transports food, collenchyma is living with uneven thickening.
This question belongs to: Science Biology
Question #1545
Identify the correct statement about evolution:
A. Lamarck proposed the theory of natural selection.
B. Fossils provide direct evidence of evolution.
C. Analogous organs indicate common ancestry.
D. The human appendix is a homologous organ.
Discuss
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Correct Answer: Option B

Explanation:
Fossils are direct evidence showing transitional forms. Lamarck proposed use and disuse, not natural selection. Analogous organs do not indicate common ancestry; homologous do. Appendix is vestigial.
This question belongs to: Science Biology
Question #1546
Consider the following statements about the circulatory system:
1. Arteries carry blood away from the heart.
2. Veins have valves to prevent backflow.
3. Capillaries are thick-walled vessels.
Which of the above is/are correct?
A. 1, 2, and 3
B. 1 and 3 only
C. 1 and 2 only
D. 2 and 3 only
Discuss
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Correct Answer: Option C

Explanation:
Arteries carry blood from the heart; veins have valves; capillaries are thin-walled for exchange. Statement 3 is false. So 1 and 2 are correct.
This question belongs to: Science Biology
Question #1547
Assertion (A): Cuscuta is a parasitic plant.
Reason (R): It has chlorophyll and can photosynthesize its own food.
A. A is false, but R is true.
B. A is true, but R is false.
C. Both A and R are true, but R is not the correct explanation.
D. Both A and R are true, and R is the correct explanation.
Discuss
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Correct Answer: Option B

Explanation:
Cuscuta (dodder) is a holoparasite, lacking chlorophyll, and derives nutrients from the host plant via haustoria. Therefore, A is true but R is false.
This question belongs to: Science Biology
Question #1548
Which of the following statements about chromosomes is correct?
A. A karyotype shows the sequence of nucleotides.
B. Chromosomes are made of DNA and proteins.
C. Gametes contain two sets of chromosomes.
D. Human somatic cells have 23 chromosomes.
Discuss
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Correct Answer: Option B

Explanation:
Chromosomes consist of DNA wrapped around histone proteins. Somatic cells have 46 chromosomes (23 pairs), gametes 23. A karyotype is a picture of chromosomes, not sequence.
This question belongs to: Science Biology
Question #1549
Identify the INCORRECT statement about the digestive system:
A. Villi increase the surface area for absorption in the small intestine.
B. Bile is produced in the gall bladder.
C. Trypsin is secreted by the pancreas.
D. Pepsin is active in the acidic environment of the stomach.
Discuss
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Correct Answer: Option B

Explanation:
Bile is produced by the liver and stored in the gall bladder. The gall bladder does not produce bile. All other statements are correct.
This question belongs to: Science Biology
Question #1550
Consider the following statements about the nitrogen cycle:
1. Nitrogen fixation converts N₂ to ammonia.
2. Nitrification converts ammonia to nitrates.
3. Denitrification returns nitrogen to the atmosphere.
Which of the above is/are correct?
A. 1 and 3 only
B. 1, 2, and 3
C. 2 and 3 only
D. 1 and 2 only
Discuss
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Correct Answer: Option B

Explanation:
All three processes are part of the nitrogen cycle: fixation (N₂ → NH₃), nitrification (NH₃ → NO₂⁻ → NO₃⁻), and denitrification (NO₃⁻ → N₂).
This question belongs to: Science Biology
Question #1551
Assertion (A): Frogs have a three-chambered heart.
Reason (R): This allows complete separation of oxygenated and deoxygenated blood.
A. A is false, but R is true.
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 true, but R is false.
Discuss
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Correct Answer: Option D

Explanation:
Amphibians have two atria and one ventricle; mixing of blood occurs because of the single ventricle. Complete separation is achieved only in four-chambered hearts. So A true, R false.
This question belongs to: Science Biology
Question #1552
Which of the following statements about pollination is correct?
A. Self-pollination always requires external agents.
B. Cross-pollination increases genetic variation.
C. Hydrophily is pollination by insects.
D. Entomophily is pollination by wind.
Discuss
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Correct Answer: Option B

Explanation:
Cross-pollination between different plants promotes genetic diversity. Self-pollination does not need external agents; entomophily is by insects, hydrophily by water, anemophily by wind.
This question belongs to: Science Biology
Question #1553
Identify the correct statement about the human excretory system:
A. The loop of Henle helps in concentrating urine.
B. Urine is formed in the urinary bladder.
C. The urethra connects the kidney to the bladder.
D. The functional unit of the kidney is the neuron.
Discuss
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Correct Answer: Option A

Explanation:
The loop of Henle creates a concentration gradient in the medulla, enabling water reabsorption and concentrated urine. Urine is formed in kidneys, the unit is nephron, ureter connects kidney to bladder.
This question belongs to: Science Biology
Question #1554
Consider the following statements about proteins:
1. They are made of amino acids.
2. Peptide bonds link amino acids.
3. Hemoglobin is a transport protein.
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 C

Explanation:
All are correct: proteins are polymers of amino acids joined by peptide bonds; hemoglobin is a protein that transports oxygen in blood.
This question belongs to: Science Biology
Question #1555
Assertion (A): AIDS is caused by a retrovirus.
Reason (R): HIV contains RNA and the enzyme reverse transcriptase.
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:
HIV is a retrovirus with RNA genome and reverse transcriptase, which converts viral RNA into DNA. This defines retroviruses, and the reason correctly explains the assertion.
This question belongs to: Science Biology
Question #1556
Which of the following statements about the ozone layer is correct?
A. It is located in the troposphere.
B. It is depleted by increased CO₂ levels.
C. Ozone is composed of three oxygen atoms and is harmless at ground level.
D. It absorbs harmful UV radiation.
Discuss
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Correct Answer: Option D

Explanation:
The ozone layer in the stratosphere absorbs most of the Sun's harmful UV radiation. CFCs, not CO₂, cause its depletion. Ozone at ground level is a pollutant. So B is correct.
This question belongs to: Science Biology
Question #1557
Identify the INCORRECT statement about cell division:
A. Meiosis results in four haploid cells.
B. Cytokinesis follows nuclear division.
C. Mitosis produces two identical daughter cells.
D. Crossing over occurs in mitosis.
Discuss
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Correct Answer: Option D

Explanation:
Crossing over occurs during prophase I of meiosis, not in mitosis. Mitosis produces identical diploid cells, meiosis reduces chromosome number by half, and cytokinesis divides the cytoplasm.
This question belongs to: Science Biology
Question #1558
Consider the following statements about vitamins:
1. Vitamin C deficiency causes scurvy.
2. Vitamin D deficiency causes beriberi.
3. Vitamin A deficiency causes night blindness.
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:
Scurvy is vitamin C deficiency; night blindness is vitamin A deficiency. Beriberi is due to vitamin B₁ deficiency, not D. So 1 and 3 are correct.
This question belongs to: Science Biology
Question #1559
Assertion (A): Green plants are called autotrophs.
Reason (R): They can synthesize their own food by photosynthesis.
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 false, R true.
D. A true, R false.
Discuss
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Correct Answer: Option A

Explanation:
Autotrophs produce organic compounds from inorganic CO₂ and water using light energy (photosynthesis). This exactly defines green plants. So both are true, and R explains A.
This question belongs to: Science Biology
Question #1560
Which of the following statements about the brain is correct?
A. The hypothalamus is responsible for intelligence.
B. The cerebellum controls speech and memory.
C. The medulla oblongata regulates heart rate.
D. The cerebrum controls body temperature and hunger.
Discuss
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Correct Answer: Option C

Explanation:
The medulla oblongata contains centers for heart rate, breathing, and blood pressure. Hypothalamus controls temperature and hunger, cerebrum intelligence and memory, cerebellum coordination.
This question belongs to: Science Biology

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