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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Question #1961
The hormone that increases water reabsorption in the collecting duct is:
A. Aldosterone
B. Natriuretic peptide
C. Renin
D. Antidiuretic hormone (ADH)
Discuss
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Correct Answer: Option D

Explanation:
ADH (vasopressin) from the posterior pituitary increases water permeability of collecting duct cells by inserting aquaporins, reducing urine volume.
This question belongs to: Science Biology
Question #1962
The functional unit of the nervous system is:
A. Alveolus
B. Osteon
C. Nephron
D. Neuron
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Correct Answer: Option D

Explanation:
The neuron is the basic structural and functional unit of the nervous system, consisting of a cell body, dendrites, and an axon. It transmits electrical impulses.
This question belongs to: Science Biology
Question #1963
The central nervous system consists of:
A. Brain and sense organs
B. Brain and spinal cord
C. Brain and cranial nerves
D. Spinal cord and sympathetic nerves
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Correct Answer: Option B

Explanation:
CNS = brain + spinal cord. The peripheral nervous system (PNS) includes cranial and spinal nerves. The autonomic nervous system controls involuntary functions.
This question belongs to: Science Biology
Question #1964
Which part of the brain controls body temperature, hunger, and thirst?
A. Medulla oblongata
B. Hypothalamus
C. Cerebrum
D. Cerebellum
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Correct Answer: Option B

Explanation:
The hypothalamus is the body's thermostat and regulates hunger, thirst, sleep, and emotions. It also controls the pituitary gland.
This question belongs to: Science Biology
Question #1965
The myelin sheath around axons in the CNS is formed by:
A. Astrocytes
B. Schwann cells
C. Oligodendrocytes
D. Microglia
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Correct Answer: Option C

Explanation:
In the central nervous system, oligodendrocytes wrap axons forming the myelin sheath. In the peripheral nervous system, Schwann cells perform this function.
This question belongs to: Science Biology
Question #1966
The gap between two neurons where nerve impulse transmission occurs is called:
A. Node of Ranvier
B. Axon terminal
C. Dendrite
D. Synapse
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Correct Answer: Option D

Explanation:
A synapse is a junction between two neurons (or neuron and effector) where neurotransmitters are released to propagate the signal.
This question belongs to: Science Biology
Question #1967
The largest part of the human brain is the:
A. Cerebrum
B. Cerebellum
C. Thalamus
D. Medulla oblongata
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Correct Answer: Option A

Explanation:
The cerebrum is the largest and most developed part, responsible for thought, memory, sensory processing, and voluntary movement.
This question belongs to: Science Biology
Question #1968
The enzyme pepsin is secreted by which cells of the stomach?
A. G cells
B. Parietal cells
C. Goblet cells
D. Chief cells
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Correct Answer: Option D

Explanation:
Chief (peptic) cells secrete pepsinogen, which is activated to pepsin by HCl. Parietal cells secrete HCl and intrinsic factor. Goblet cells secrete mucus.
This question belongs to: Science Biology
Question #1969
The enzyme trypsin is involved in the digestion of:
A. Proteins
B. Nucleic acids
C. Carbohydrates
D. Fats
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Correct Answer: Option A

Explanation:
Trypsin, a pancreatic protease, hydrolyzes proteins into peptides in the small intestine. It is secreted as inactive trypsinogen and activated by enterokinase.
This question belongs to: Science Biology
Question #1970
Which part of the small intestine is the main site of nutrient absorption?
A. Duodenum
B. Colon
C. Ileum
D. Jejunum
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Correct Answer: Option D

Explanation:
The jejunum, with its long villi and microvilli, is the primary site for absorption of digested nutrients. The ileum also absorbs vitamin B₁₂ and bile salts.
This question belongs to: Science Biology
Question #1971
The enzyme that breaks down lactose is:
A. Amylase
B. Maltase
C. Sucrase
D. Lactase
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Correct Answer: Option D

Explanation:
Lactase hydrolyzes lactose (milk sugar) into glucose and galactose. Lactose intolerance is due to lactase deficiency. Sucrase acts on sucrose, maltase on maltose.
This question belongs to: Science Biology
Question #1972
The salivary gland located below the tongue is the:
A. Lacrimal gland
B. Sublingual gland
C. Submandibular gland
D. Parotid gland
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Correct Answer: Option B

Explanation:
The sublingual glands are the smallest of the three paired salivary glands, located under the tongue. The parotid is near the ear, submandibular under the jaw.
This question belongs to: Science Biology
Question #1973
The vector for dengue virus is:
A. Aedes aegypti mosquito
B. Anopheles mosquito
C. Culex mosquito
D. Tsetse fly
Discuss
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Correct Answer: Option A

Explanation:
Dengue is transmitted by Aedes aegypti, which also spreads chikungunya, Zika, and yellow fever. Anopheles transmits malaria, Culex filariasis, tsetse sleeping sickness.
This question belongs to: Science Biology
Question #1974
Which disease is caused by the bacterium Salmonella typhi?
A. Typhoid
B. Cholera
C. Tetanus
D. Diphtheria
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Correct Answer: Option A

Explanation:
Typhoid fever is caused by Salmonella typhi, transmitted through contaminated food and water. Widal test is used for diagnosis. Cholera is Vibrio cholerae.
This question belongs to: Science Biology
Question #1975
HIV attacks which type of immune cells?
A. Neutrophils
B. Macrophages
C. B lymphocytes
D. Helper T lymphocytes (CD4+)
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Correct Answer: Option D

Explanation:
HIV specifically infects and destroys CD4+ T cells, leading to immunodeficiency and AIDS. Without treatment, opportunistic infections occur.
This question belongs to: Science Biology
Question #1976
Which of the following is a fungal disease?
A. Cholera
B. Polio
C. Tetanus
D. Ringworm
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Correct Answer: Option D

Explanation:
Ringworm (tinea) is caused by dermatophyte fungi (Trichophyton, Microsporum). Tetanus is bacterial, polio viral, cholera bacterial.
This question belongs to: Science Biology
Question #1977
BCG vaccine is used to prevent:
A. Polio
B. Measles
C. Hepatitis B
D. Tuberculosis
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Correct Answer: Option D

Explanation:
Bacille Calmette-Guérin (BCG) is a live attenuated vaccine against tuberculosis. It is given at birth in many countries. Oral polio vaccine (OPV) for polio.
This question belongs to: Science Biology
Question #1978
Which scientist is associated with the discovery of the smallpox vaccine?
A. Louis Pasteur
B. Jonas Salk
C. Robert Koch
D. Edward Jenner
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Correct Answer: Option D

Explanation:
Edward Jenner developed the first successful vaccine against smallpox in 1796 using cowpox virus. Pasteur developed rabies vaccine, Koch TB bacterium, Salk polio.
This question belongs to: Science Biology
Question #1979
The disease 'rabies' is caused by:
A. Bacteria
B. Virus
C. Fungus
D. Protozoa
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Correct Answer: Option B

Explanation:
Rabies is a fatal viral disease affecting the nervous system, transmitted by the bite of infected animals (dogs, bats). Louis Pasteur developed the rabies vaccine.
This question belongs to: Science Biology
Question #1980
The deficiency of vitamin C causes:
A. Night blindness
B. Rickets
C. Scurvy
D. Beriberi
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Correct Answer: Option C

Explanation:
Scurvy results from vitamin C deficiency, leading to bleeding gums, poor wound healing, and anemia. Vitamin A deficiency causes night blindness, D rickets, B₁ beriberi.
This question belongs to: Science Biology

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