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 84 of 103
Question #1661
Which of the following statements about the plant stem is correct?
A. It is the main site of photosynthesis in most plants.
B. It is usually positively phototropic.
C. It bears leaves, flowers, and fruits.
D. It grows downward into the soil.
Discuss
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Correct Answer: Option C

Explanation:
Stem bears leaves and reproductive structures. It is positively phototropic (grows towards light). Leaves are the main photosynthetic organs. Roots grow downward.
This question belongs to: Science Biology
Question #1662
Identify the INCORRECT statement about the human reproductive system:
A. The scrotum maintains testes temperature lower than body temperature.
B. Spermatogenesis occurs in the epididymis.
C. The Cowper’s glands secrete mucus for lubrication.
D. The seminal vesicles secrete a fructose-rich fluid.
Discuss
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Correct Answer: Option B

Explanation:
Spermatogenesis occurs in the seminiferous tubules of the testes. The epididymis stores and matures sperm. So D is incorrect.
This question belongs to: Science Biology
Question #1663
Consider the following statements about vitamins:
1. Vitamin K is essential for bone health.
2. Vitamin D deficiency can cause rickets.
3. Vitamin A is also known as tocopherol.
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 B

Explanation:
Vitamin K supports bone protein osteocalcin; D deficiency causes rickets. Vitamin A is retinol; vitamin E is tocopherol. So 3 is incorrect.
This question belongs to: Science Biology
Question #1664
Assertion (A): Genetic variation is essential for evolution.
Reason (R): Without variation, natural selection cannot occur because there are no differences to select from.
A. Both A and R are true, but R is not the correct explanation.
B. A true, R false.
C. A false, R true.
D. Both A and R are true, and R is the correct explanation.
Discuss
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Correct Answer: Option D

Explanation:
Genetic variation provides the raw material for natural selection. If all individuals were identical, selection could not favor any. R correctly explains A.
This question belongs to: Science Biology
Question #1665
Which of the following statements about lipids is correct?
A. They are soluble in water.
B. Triglycerides are composed of glycerol and three fatty acids.
C. Cholesterol is a protein.
D. Phospholipids are the main energy storage molecules.
Discuss
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Correct Answer: Option B

Explanation:
Triglycerides are glycerol + 3 fatty acids; they are hydrophobic. Phospholipids are membrane components; triglycerides are main energy storage. Cholesterol is a steroid lipid, not protein.
This question belongs to: Science Biology
Question #1666
Identify the correct statement about the blood vessels:
A. Arteries have valves.
B. Veins have thinner walls and larger lumen than arteries.
C. Venules are smaller than capillaries.
D. Capillaries have thick muscular walls.
Discuss
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Correct Answer: Option B

Explanation:
Veins have thinner walls and larger lumens; arteries are thick and elastic; capillaries are thin for exchange; venules are larger than capillaries. Valves are in veins.
This question belongs to: Science Biology
Question #1667
Consider the following statements about the human nervous system:
1. The sympathetic nervous system prepares the body for fight-or-flight.
2. The parasympathetic nervous system has a calming effect.
3. Both are part of the somatic nervous system.
Which of the above is/are correct?
A. 1 and 3 only
B. 1, 2, and 3
C. 1 and 2 only
D. 2 and 3 only
Discuss
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Correct Answer: Option C

Explanation:
Sympathetic (fight or flight) and parasympathetic (rest and digest) are divisions of the autonomic nervous system, not somatic. Thus, 3 is incorrect.
This question belongs to: Science Biology
Question #1668
Assertion (A): DNA replication is semiconservative.
Reason (R): Each new DNA molecule consists of one old and one new strand.
A. A true, R false.
B. A false, R true.
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 D

Explanation:
Meselson and Stahl proved that after replication, each daughter DNA contains one parental and one newly synthesized strand. R exactly explains semiconservative.
This question belongs to: Science Biology
Question #1669
Which of the following statements about tissues is correct?
A. Xylem and phloem are examples of simple tissues.
B. Meristematic tissues are permanent tissues with thick walls.
C. Epidermis is a vascular tissue.
D. Simple permanent tissues are made of one type of cell.
Discuss
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Correct Answer: Option D

Explanation:
Simple permanent tissues (parenchyma, collenchyma, sclerenchyma) consist of a single cell type. Meristematic tissues are dividing and have thin walls; xylem/phloem are complex; epidermis is dermal.
This question belongs to: Science Biology
Question #1670
Identify the INCORRECT statement about the respiratory system:
A. The trachea is lined with ciliated epithelium.
B. Surfactant reduces surface tension in alveoli.
C. The right lung has two lobes.
D. The diaphragm is the primary muscle of inspiration.
Discuss
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Correct Answer: Option C

Explanation:
The right lung has three lobes, the left has two (to accommodate the heart). So C is incorrect.
This question belongs to: Science Biology
Question #1671
Consider the following statements about the circulatory system of insects:
1. It is an open circulatory system.
2. Hemolymph is the circulating fluid.
3. Blood is contained in vessels at all times.
Which of the above is/are correct?
A. 2 and 3 only
B. 1, 2, and 3
C. 1 and 2 only
D. 1 and 3 only
Discuss
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Correct Answer: Option C

Explanation:
Insects have an open circulatory system where hemolymph bathes organs directly, not always in vessels. Thus, 3 is incorrect.
This question belongs to: Science Biology
Question #1672
Assertion (A): Plants carry out photosynthesis during the day and respiration at night.
Reason (R): Photosynthesis requires light, while respiration occurs continuously.
A. Both A and R are true, but R is not the correct explanation.
B. Both A and R are true, and R is 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 C

Explanation:
Respiration occurs 24/7, while photosynthesis only in light. The statement implies they alternate, which is false. R is true: photosynthesis needs light, respiration is continuous. So A is false, R true.
This question belongs to: Science Biology
Question #1673
Identify the correct statement about plant water relations:
A. Plasmolysis occurs in hypotonic solutions.
B. Water potential is higher in concentrated solutions.
C. Osmosis is the movement of solutes.
D. Turgor pressure keeps plant cells rigid.
Discuss
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Correct Answer: Option D

Explanation:
Turgor pressure from water in the vacuole pushes the cell membrane against the wall, maintaining rigidity. Plasmolysis occurs in hypertonic solutions; osmosis is water movement; high solute concentration lowers water potential.
This question belongs to: Science Biology
Question #1674
Consider the following statements about mutations:
1. Mutations can be caused by UV radiation.
2. All mutations result in a change in the protein sequence.
3. Mutations in germ cells are heritable.
Which of the above is/are correct?
A. 2 and 3 only
B. 1 and 3 only
C. 1 and 2 only
D. 1, 2, and 3
Discuss
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Correct Answer: Option B

Explanation:
UV radiation can induce mutations; germline mutations are passed on. Not all mutations change protein sequence (silent mutations). So 2 is incorrect.
This question belongs to: Science Biology
Question #1675
Assertion (A): The process of breathing is also called pulmonary ventilation.
Reason (R): It involves the movement of air into and out of the lungs.
A. A true, R false.
B. Both A and R are true, but R is not the correct explanation.
C. A false, R true.
D. Both A and R are true, and R is the correct explanation.
Discuss
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Correct Answer: Option D

Explanation:
Pulmonary ventilation is the mechanical process of moving air in (inspiration) and out (expiration), which is breathing. R correctly defines it.
This question belongs to: Science Biology
Question #1676
Consider the following statements about the human kidneys:
1. They are located in the abdominal cavity.
2. They produce the hormone renin.
3. They filter approximately 180 liters of blood per day.
Which of the above is/are correct?
A. 1 and 2 only
B. 1, 2, and 3
C. 1 and 3 only
D. 2 and 3 only
Discuss
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Correct Answer: Option D

Explanation:
Kidneys are retroperitoneal, not in the abdominal cavity proper. They produce renin, and filter ~180 L/day (GFR ~125 mL/min). So 1 is incorrect.
This question belongs to: Science Biology
Question #1677
Assertion (A): The pituitary gland is connected to the hypothalamus by a stalk.
Reason (R): This connection allows the hypothalamus to control pituitary hormone secretion.
A. A false, R true.
B. Both A and R are true, but R is not the correct explanation.
C. Both A and R are true, and R is the correct explanation.
D. A true, R false.
Discuss
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Correct Answer: Option C

Explanation:
The infundibulum connects them, and hypothalamic releasing/inhibiting hormones travel to the anterior pituitary; posterior pituitary stores hypothalamic hormones. R correctly explains A.
This question belongs to: Science Biology
Question #1678
Which of the following statements about RNA is correct?
A. mRNA carries the genetic message from DNA to ribosomes.
B. It is usually double-stranded.
C. tRNA is the main component of ribosomes.
D. It contains the base thymine.
Discuss
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Correct Answer: Option A

Explanation:
mRNA is the template for translation. RNA is typically single-stranded, contains uracil, rRNA forms ribosome structure.
This question belongs to: Science Biology
Question #1679
Identify the correct statement about the cell wall:
A. Plant cell walls contain cellulose.
B. Animal cells have a chitinous cell wall.
C. Fungal cell walls are made of peptidoglycan.
D. Bacterial cell walls contain cellulose.
Discuss
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Correct Answer: Option A

Explanation:
Plant cell walls are primarily cellulose. Fungal walls contain chitin, bacterial peptidoglycan, animal cells lack a cell wall.
This question belongs to: Science Biology
Question #1680
Consider the following statements about mitosis:
1. It produces diploid cells.
2. It is involved in growth and repair.
3. It reduces chromosome number by half.
Which of the above is/are correct?
A. 1, 2, and 3
B. 2 and 3 only
C. 1 and 2 only
D. 1 and 3 only
Discuss
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Correct Answer: Option C

Explanation:
Mitosis yields two identical diploid cells, important for growth/repair. Meiosis halves chromosome number. So 3 is incorrect.
This question belongs to: Science Biology

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