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 60 of 103
Question #1181
The hormone that stimulates the secretion of gastric acid is:
A. Secretin
B. Gastrin
C. GIP
D. CCK
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Correct Answer: Option B

Explanation:
Gastrin, released by G cells in the stomach antrum, stimulates parietal cells to secrete HCl. Secretin stimulates bicarbonate, CCK stimulates enzyme secretion and gallbladder contraction, GIP inhibits gastric secretion.
This question belongs to: Science Biology
Question #1182
The blood vessel with the highest blood pressure is the:
A. Aorta
B. Pulmonary artery
C. Vena cava
D. Capillary
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Correct Answer: Option A

Explanation:
The aorta receives blood directly from the left ventricle under high pressure (systolic ~120 mmHg). Pressure decreases as blood moves through arteries, capillaries, and veins. Vena cava pressure is near zero.
This question belongs to: Science Biology
Question #1183
The condition where the pleural cavity fills with air, causing lung collapse, is:
A. Pneumonia
B. Pleurisy
C. Emphysema
D. Pneumothorax
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Correct Answer: Option D

Explanation:
Pneumothorax is the accumulation of air in the pleural space, causing lung collapse. Pneumonia is lung infection, emphysema is alveolar damage, pleurisy is inflammation of pleura. It can be spontaneous or traumatic.
This question belongs to: Science Biology
Question #1184
The vitamin that is required for the synthesis of rhodopsin is:
A. Vitamin A
B. Vitamin D
C. Vitamin C
D. Vitamin E
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Correct Answer: Option A

Explanation:
Vitamin A (retinal) combines with opsin to form rhodopsin, the visual pigment in rod cells for dim-light vision. Deficiency causes night blindness.
This question belongs to: Science Biology
Question #1185
The hormone that stimulates the thyroid gland to release T₃ and T₄ is:
A. TSH
B. LH
C. ACTH
D. FSH
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Correct Answer: Option A

Explanation:
Thyroid-stimulating hormone (TSH) from the anterior pituitary binds to receptors on thyroid follicular cells, stimulating synthesis and release of thyroid hormones (T₃ and T₄). ACTH targets adrenal cortex.
This question belongs to: Science Biology
Question #1186
The scientist who discovered the antibiotic streptomycin from soil bacteria was:
A. Alexander Fleming
B. Selman Waksman
C. Louis Pasteur
D. Robert Koch
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Correct Answer: Option B

Explanation:
Selman Waksman and colleagues isolated streptomycin from Streptomyces griseus in 1943, the first effective treatment for tuberculosis. Fleming discovered penicillin, Pasteur developed vaccines, Koch identified TB bacterium.
This question belongs to: Science Biology
Question #1187
The process of converting atmospheric nitrogen into ammonia by microorganisms is called:
A. Nitrification
B. Denitrification
C. Nitrogen fixation
D. Ammonification
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Correct Answer: Option C

Explanation:
Biological nitrogen fixation, performed by bacteria (Rhizobium, Azotobacter) and cyanobacteria, reduces N₂ to NH₃. Nitrification oxidizes ammonia to nitrates, denitrification returns N₂, ammonification releases ammonia from organic matter.
This question belongs to: Science Biology
Question #1188
Which organelle is the site of the Calvin cycle?
A. Chloroplast stroma
B. Mitochondrial matrix
C. Thylakoid membrane
D. Cytoplasm
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Correct Answer: Option A

Explanation:
The Calvin cycle (C3 cycle) occurs in the stroma of chloroplasts, where CO₂ is fixed into sugars using ATP and NADPH from light reactions. Thylakoid membrane is the site of light reactions.
This question belongs to: Science Biology
Question #1189
The cell type responsible for producing myelin in the peripheral nervous system is:
A. Astrocyte
B. Microglia
C. Oligodendrocyte
D. Schwann cell
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Correct Answer: Option D

Explanation:
Schwann cells wrap around axons in the PNS to form myelin sheaths. Oligodendrocytes myelinate axons in the CNS. Astrocytes support neurons, microglia are immune cells.
This question belongs to: Science Biology
Question #1190
The disease caused by the human papillomavirus (HPV) is:
A. Tuberculosis
B. Cervical cancer
C. Cholera
D. Malaria
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Correct Answer: Option B

Explanation:
Certain high-risk strains of HPV are a major cause of cervical cancer. Vaccines are available. TB is bacterial, malaria protozoan, cholera bacterial.
This question belongs to: Science Biology
Question #1191
The fluid that fills the anterior chamber of the eye is:
A. Synovial fluid
B. Vitreous humor
C. Cerebrospinal fluid
D. Aqueous humor
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Correct Answer: Option D

Explanation:
Aqueous humor is a clear fluid in the anterior and posterior chambers of the eye, providing nutrients and maintaining intraocular pressure. Vitreous humor is the gel in the posterior segment.
This question belongs to: Science Biology
Question #1192
The enzyme that breaks down starch into maltose in the small intestine is:
A. Salivary amylase
B. Maltase
C. Sucrase
D. Pancreatic amylase
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Correct Answer: Option D

Explanation:
Pancreatic amylase, secreted into the duodenum, continues starch digestion initiated by salivary amylase, producing maltose and dextrins. Maltase then breaks maltose to glucose. Sucrase acts on sucrose.
This question belongs to: Science Biology
Question #1193
The process by which plants produce food using light energy is called:
A. Fermentation
B. Chemosynthesis
C. Cellular respiration
D. Photosynthesis
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Correct Answer: Option D

Explanation:
Photosynthesis converts light energy into chemical energy (glucose) using CO₂ and H₂O, releasing O₂. It occurs in chloroplasts. Respiration breaks down glucose, fermentation is anaerobic, chemosynthesis uses chemical energy.
This question belongs to: Science Biology
Question #1194
The vitamin that functions as an antioxidant and is also known as tocopherol is:
A. Vitamin D
B. Vitamin C
C. Vitamin E
D. Vitamin A
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Correct Answer: Option C

Explanation:
Vitamin E (tocopherol) is a fat-soluble antioxidant that protects cell membranes from lipid peroxidation. Vitamin C is water-soluble antioxidant, A is for vision, D for calcium.
This question belongs to: Science Biology
Question #1195
The disease caused by the protozoan Plasmodium falciparum is:
A. Amoebic dysentery
B. Giardiasis
C. Sleeping sickness
D. Malaria
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Correct Answer: Option D

Explanation:
Malaria is transmitted by Anopheles mosquito; P. falciparum causes severe, often fatal malaria. Amoebic dysentery is Entamoeba, sleeping sickness Trypanosoma, giardiasis Giardia.
This question belongs to: Science Biology
Question #1196
The scientist who discovered the vaccine for smallpox was:
A. Louis Pasteur
B. Robert Koch
C. Edward Jenner
D. Jonas Salk
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Correct Answer: Option C

Explanation:
Edward Jenner developed the first successful vaccine using cowpox to protect against smallpox in 1796. Pasteur developed rabies vaccine, Salk polio, Koch identified TB bacterium.
This question belongs to: Science Biology
Question #1197
The technique used to measure the concentration of a solution based on light absorption is:
A. Electrophoresis
B. Chromatography
C. Centrifugation
D. Spectrophotometry
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Correct Answer: Option D

Explanation:
Spectrophotometry measures the absorbance of light by a solution at a specific wavelength, which is proportional to the concentration of the absorbing substance (Beer-Lambert law).
This question belongs to: Science Biology
Question #1198
The process of sperm formation in the testes is called:
A. Gametogenesis
B. Spermatogenesis
C. Oogenesis
D. Fertilization
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Correct Answer: Option B

Explanation:
Spermatogenesis is the production of haploid spermatozoa from spermatogonia in the seminiferous tubules. Oogenesis is egg production, gametogenesis is the general term.
This question belongs to: Science Biology
Question #1199
The hormone that increases blood calcium levels is:
A. Thyroxine
B. Parathyroid hormone
C. Insulin
D. Calcitonin
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Correct Answer: Option B

Explanation:
Parathyroid hormone (PTH) raises blood calcium by increasing bone resorption, kidney reabsorption, and activating vitamin D. Calcitonin lowers calcium. Thyroxine regulates metabolism, insulin glucose.
This question belongs to: Science Biology
Question #1200
The compound that is the primary energy currency of the cell is:
A. NADH
B. ATP
C. FADH₂
D. Glucose
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Correct Answer: Option B

Explanation:
Adenosine triphosphate (ATP) stores energy in its high-energy phosphate bonds and releases it for cellular work. Glucose and NADH are fuel molecules, not direct energy carriers.
This question belongs to: Science Biology

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