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 88 of 103
Question #1741
Consider statements about plant tissues: 1. Xylem transports water upwards. 2. Phloem transports food bidirectionally. 3. Cambium is a permanent tissue. Which 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 C

Explanation:
Xylem is responsible for the unidirectional upward transport of water and minerals from roots to shoots. Phloem transports organic nutrients (food) from sources to sinks, which can be bidirectional (up or down). Cambium (vascular and cork) is a lateral meristematic (dividing) tissue responsible for secondary growth, not a permanent tissue. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1742
Consider statements about human respiration: 1. Hemoglobin has a higher affinity for CO2 than O2. 2. Carbonic anhydrase is present in RBCs. 3. Most CO2 is transported as bicarbonate. Which 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 D

Explanation:
Hemoglobin has a much higher affinity for oxygen than for carbon dioxide; it binds O2 readily in the lungs. Inside RBCs, the enzyme carbonic anhydrase rapidly catalyzes the conversion of CO2 and water into carbonic acid. Approximately 70% of CO2 is transported in the blood as bicarbonate ions in the plasma. Thus, statements 2 and 3 are correct.
This question belongs to: Science Biology
Question #1743
Consider statements about human digestion: 1. Pepsin digests proteins in the stomach. 2. Trypsin is secreted by the liver. 3. Lipase emulsifies fats. Which are correct?
A. 1 only
B. 1 and 3 only
C. 2 and 3 only
D. 1, 2 and 3
Discuss
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Correct Answer: Option A

Explanation:
Pepsin is the primary proteolytic enzyme in the stomach, breaking down proteins into peptones. Trypsin is a pancreatic enzyme secreted by the pancreas, not the liver, which continues protein digestion in the small intestine. Bile, produced by the liver, emulsifies fats, but lipase (pancreatic lipase) actually digests (hydrolyzes) them into fatty acids and glycerol. Only statement 1 is correct.
This question belongs to: Science Biology
Question #1744
Consider statements about human circulation: 1. Arteries carry oxygenated blood. 2. Veins have valves to prevent backflow. 3. Capillaries have thick walls. Which are correct?
A. 2 only
B. 1 and 3 only
C. 1 and 2 only
D. 1, 2 and 3
Discuss
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Correct Answer: Option A

Explanation:
While most arteries carry oxygenated blood, the pulmonary artery carries deoxygenated blood from the heart to the lungs. Veins possess valves along their length to ensure unidirectional blood flow back to the heart against gravity. Capillaries are composed of a single layer of endothelial cells (thin walls) to facilitate the exchange of gases and nutrients. Only statement 2 is universally correct.
This question belongs to: Science Biology
Question #1745
Consider statements about human brain: 1. The cerebrum controls voluntary actions. 2. The cerebellum maintains balance. 3. The medulla controls breathing. Which are correct?
A. 2 and 3 only
B. 1 and 2 only
C. 1, 2 and 3
D. 1 and 3 only
Discuss
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Correct Answer: Option C

Explanation:
The cerebrum is the largest part of the brain, responsible for higher functions like voluntary motor actions, sensory processing, and intelligence. The cerebellum coordinates muscle movements and maintains posture and balance. The medulla oblongata contains vital centers controlling involuntary functions like heartbeat, breathing, and blood pressure. All three statements are correct.
This question belongs to: Science Biology
Question #1746
Consider statements about human hormones: 1. Insulin lowers blood sugar. 2. Adrenaline prepares the body for stress. 3. Thyroxine requires iodine for synthesis. Which 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 A

Explanation:
Insulin, secreted by the pancreas, promotes cellular glucose uptake, lowering blood sugar levels. Adrenaline (epinephrine) from the adrenal medulla triggers the fight-or-flight response, increasing heart rate and energy supply. Thyroxine, produced by the thyroid gland, requires iodine as an essential component for its synthesis; iodine deficiency causes goiter. All statements are correct.
This question belongs to: Science Biology
Question #1747
Consider statements about human reproduction: 1. Fertilization occurs in the uterus. 2. The placenta nourishes the fetus. 3. Spermatogenesis occurs in the testes. Which are correct?
A. 1 and 2 only
B. 2 and 3 only
C. 1, 2 and 3
D. 1 and 3 only
Discuss
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Correct Answer: Option B

Explanation:
Fertilization in humans typically occurs in the fallopian tube (ampullary region), not the uterus; the zygote then travels to the uterus for implantation. The placenta is the vital organ providing oxygen and nutrients to the growing fetus and removing waste. Spermatogenesis, the production of sperm, occurs in the seminiferous tubules of the testes. Thus, statements 2 and 3 are correct.
This question belongs to: Science Biology
Question #1748
Consider statements about diseases: 1. Cholera is caused by a bacterium. 2. AIDS is caused by a retrovirus. 3. Dengue is transmitted by Culex mosquito. Which 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 A

Explanation:
Cholera is a severe diarrheal disease caused by the bacterium Vibrio cholerae. AIDS is caused by the Human Immunodeficiency Virus (HIV), which is a retrovirus. Dengue fever is transmitted by the bite of an infected female Aedes aegypti mosquito, not Culex (which transmits filariasis and Japanese encephalitis). Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1749
Consider statements about nutrition: 1. Kwashiorkor is caused by protein deficiency. 2. Marasmus is caused by overall calorie deficiency. 3. Goiter is caused by iron deficiency. Which 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 A

Explanation:
Kwashiorkor is a severe form of malnutrition caused by inadequate protein intake despite sufficient calorie consumption. Marasmus results from a severe deficiency of both calories and protein, leading to extreme wasting. Goiter is the enlargement of the thyroid gland caused by iodine deficiency, not iron deficiency (which causes anemia). Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1750
Consider statements about vitamins: 1. Vitamin B12 contains cobalt. 2. Vitamin K is essential for blood clotting. 3. Beriberi is caused by Vitamin C deficiency. Which are correct?
A. 1, 2 and 3
B. 1 and 2 only
C. 2 and 3 only
D. 1 and 3 only
Discuss
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Correct Answer: Option B

Explanation:
Vitamin B12 (cyanocobalamin) is a complex vitamin that contains the trace mineral cobalt. Vitamin K is essential for the synthesis of prothrombin and other clotting factors in the liver. Beriberi is caused by a deficiency of Vitamin B1 (thiamine), whereas Vitamin C deficiency causes scurvy. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1751
Consider statements about genetics: 1. A codon consists of three nucleotides. 2. The start codon is AUG. 3. Introns are coding sequences. Which 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:
The genetic code is read in triplets of nucleotides called codons, each specifying an amino acid. AUG is the universal start codon, which also codes for methionine. In eukaryotic genes, introns are non-coding intervening sequences that are spliced out, while exons are the coding sequences that remain in the mature mRNA. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1752
Consider statements about evolution: 1. Fossils provide evidence of past life. 2. Analogous organs have different evolutionary origins. 3. Lamarck proposed natural selection. Which 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:
Fossils are the preserved remains or traces of ancient organisms, providing crucial evidence for evolution. Analogous organs (like wings of birds and insects) perform similar functions but have different structural plans and evolutionary origins, indicating convergent evolution. Jean-Baptiste Lamarck proposed the theory of inheritance of acquired characters, while Charles Darwin proposed natural selection. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1753
Consider statements about ecology: 1. A food web consists of interconnected food chains. 2. Decomposers recycle nutrients. 3. Biomass decreases at higher trophic levels. Which 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 A

Explanation:
A food web is a complex network of interconnected food chains showing multiple feeding relationships in an ecosystem. Decomposers (bacteria and fungi) break down dead organic matter, returning essential nutrients to the soil for producers. Due to energy loss at each transfer (10% law), the total biomass generally decreases at higher trophic levels, forming an upright pyramid. All statements are correct.
This question belongs to: Science Biology
Question #1754
Consider statements about environment: 1. Acid rain is caused by SO2 and NOx. 2. BOD measures water pollution. 3. Eutrophication increases aquatic biodiversity. Which 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 D

Explanation:
Acid rain is caused by emissions of sulfur dioxide (SO2) and nitrogen oxides (NOx) reacting with atmospheric water to form acids. Biological Oxygen Demand (BOD) measures the amount of oxygen required by microbes to decompose organic matter, indicating water pollution levels. Eutrophication (nutrient enrichment) causes algal blooms, depleting oxygen and killing aquatic life, thereby decreasing biodiversity. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1755
Consider statements about microorganisms: 1. Rhizobium fixes atmospheric nitrogen. 2. Yeast is used in baking. 3. All bacteria are pathogenic. Which are correct?
A. 1 and 2 only
B. 1, 2 and 3
C. 2 and 3 only
D. 1 and 3 only
Discuss
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Correct Answer: Option A

Explanation:
Rhizobium is a symbiotic bacterium found in legume root nodules that fixes atmospheric nitrogen into ammonia. Yeast (Saccharomyces cerevisiae) undergoes anaerobic respiration, producing CO2 that leavens bread dough. The vast majority of bacteria are harmless or beneficial (e.g., gut flora, decomposers); only a small fraction are pathogenic to humans. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1756
Consider statements about biotechnology: 1. Bt cotton is resistant to insects. 2. Golden rice is enriched with Vitamin A. 3. Cloning produces genetically diverse offspring. Which 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 D

Explanation:
Bt cotton is transgenic, containing genes from Bacillus thuringiensis that produce proteins toxic to specific insect pests like the bollworm. Golden rice is genetically modified to produce beta-carotene, a precursor of Vitamin A, to combat deficiency. Cloning involves creating an exact genetic copy of an organism, resulting in genetically identical offspring, not diverse ones. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1757
Consider statements about animal husbandry: 1. Artificial insemination improves cattle breeds. 2. Multiple Ovulation Embryo Transfer is used in poultry. 3. Crossbreeding combines traits of two breeds. Which 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 D

Explanation:
Artificial insemination allows the use of superior bull semen to improve cattle genetics widely. Multiple Ovulation Embryo Transfer (MOET) is a technique used in cattle and other mammals to increase herd improvement rates, not in poultry (which uses hatching eggs). Crossbreeding involves mating animals of different breeds to combine desirable traits and exploit hybrid vigor. Thus, statements 1 and 3 are correct.
This question belongs to: Science Biology
Question #1758
Consider statements about scientists: 1. Gregor Mendel is the father of genetics. 2. Edward Jenner developed the smallpox vaccine. 3. Charles Darwin proposed the cell theory. Which are correct?
A. 1 and 2 only
B. 2 and 3 only
C. 1, 2 and 3
D. 1 and 3 only
Discuss
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Correct Answer: Option A

Explanation:
Gregor Mendel, through his pea plant experiments, established the fundamental laws of inheritance, earning him the title 'father of genetics'. Edward Jenner pioneered the concept of vaccination by developing the first successful smallpox vaccine using cowpox material. Charles Darwin proposed the theory of evolution by natural selection, not the cell theory (proposed by Schleiden and Schwann). Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1759
Consider statements about cell division: 1. Cytokinesis in plant cells occurs by cell plate formation. 2. Meiosis maintains the chromosome number. 3. Mitosis occurs in somatic cells. Which are correct?
A. 1 and 3 only
B. 2 and 3 only
C. 1, 2 and 3
D. 1 and 2 only
Discuss
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Correct Answer: Option A

Explanation:
In plant cells, which have rigid cell walls, cytokinesis occurs by the formation of a new cell wall (cell plate) in the middle of the cell. Mitosis is equational division occurring in somatic cells for growth and repair, maintaining the same chromosome number. Meiosis is reductional division, halving the chromosome number to produce gametes. Thus, statements 1 and 3 are correct.
This question belongs to: Science Biology
Question #1760
Consider statements about plant anatomy: 1. Collenchyma provides flexibility. 2. Sclerenchyma cells are dead. 3. Parenchyma stores food. Which are correct?
A. 2 and 3 only
B. 1 and 3 only
C. 1, 2 and 3
D. 1 and 2 only
Discuss
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Correct Answer: Option C

Explanation:
Collenchyma cells have unevenly thickened walls, providing mechanical support and flexibility to growing plant parts like stems. Sclerenchyma consists of dead cells with heavily lignified, thick walls, providing rigid strength to plant parts. Parenchyma cells are living, thin-walled, and serve as the primary packing tissue, storing food, water, and air. All three statements are correct.
This question belongs to: Science Biology

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