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 54 of 103
Question #1061
The structure that prevents the collapse of the trachea during breathing is:
A. Fibrous tissue
B. Ciliated epithelium
C. C-shaped cartilaginous rings
D. Smooth muscle
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Correct Answer: Option C

Explanation:
The tracheal wall contains C-shaped hyaline cartilage rings that keep the airway open, preventing collapse due to negative pressure during inspiration. Smooth muscle and fibrous tissue connect the rings, ciliated epithelium sweeps mucus upward.
This question belongs to: Science Biology
Question #1062
The process by which a plant embryo resumes growth after a period of dormancy is:
A. Pollination
B. Germination
C. Fertilization
D. Vegetative propagation
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Correct Answer: Option B

Explanation:
Germination is the resumption of metabolic activity and growth by the embryo within the seed, triggered by water, oxygen, and suitable temperature. Pollination is pollen transfer, fertilization gamete fusion, vegetative propagation asexual.
This question belongs to: Science Biology
Question #1063
The hormone that opposes the action of glucagon and lowers blood glucose is:
A. Epinephrine
B. Growth hormone
C. Cortisol
D. Insulin
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Correct Answer: Option D

Explanation:
Insulin lowers blood glucose by promoting cellular uptake and glycogen synthesis, opposing glucagon which raises glucose. Cortisol and epinephrine are counter-regulatory hormones that increase blood glucose.
This question belongs to: Science Biology
Question #1064
The pigment that protects skin from UV radiation is:
A. Keratin
B. Melanin
C. Collagen
D. Elastin
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Correct Answer: Option B

Explanation:
Melanin, produced by melanocytes, absorbs and dissipates UV radiation, protecting skin cells from DNA damage. Keratin is structural protein, collagen provides strength, elastin elasticity. Increased melanin production causes tanning.
This question belongs to: Science Biology
Question #1065
The genus of the bacterium that produces the antibiotic streptomycin is:
A. Bacillus
B. Penicillium
C. Streptomyces
D. Aspergillus
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Correct Answer: Option C

Explanation:
Streptomycin is produced by Streptomyces griseus, a soil actinobacterium. Penicillium is a mold producing penicillin, Bacillus species produce some antibiotics like bacitracin, Aspergillus produces other substances.
This question belongs to: Science Biology
Question #1066
The process of obtaining a large number of identical copies of a gene or organism is:
A. Cloning
B. Hybridization
C. Mutation
D. Transformation
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Correct Answer: Option A

Explanation:
Cloning produces genetically identical copies of a DNA fragment (molecular cloning) or an entire organism (reproductive cloning). Hybridization is crossing different varieties, mutation is change in DNA, transformation is DNA uptake.
This question belongs to: Science Biology
Question #1067
The term for the water vapor loss from plant leaves is:
A. Transpiration
B. Evaporation
C. Condensation
D. Guttation
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Correct Answer: Option A

Explanation:
Transpiration is the loss of water in the form of vapor from the aerial parts of plants, mainly through stomata. Evaporation is from any surface, guttation is liquid water loss, condensation is vapor to liquid.
This question belongs to: Science Biology
Question #1068
The scientist who discovered the oxygen cycle in nature was:
A. All of the above contributed
B. Jan Ingenhousz
C. Joseph Priestley
D. Antoine Lavoisier
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Correct Answer: Option A

Explanation:
Joseph Priestley discovered oxygen, Lavoisier named it and explained combustion and respiration, Ingenhousz showed plants produce oxygen in light. Together, their work elucidated the oxygen cycle. So all contributed.
This question belongs to: Science Biology
Question #1069
The structure that produces antibodies is:
A. Neutrophil
B. Macrophage
C. Plasma cell (B cell)
D. T lymphocyte
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Correct Answer: Option C

Explanation:
Plasma cells, differentiated from B lymphocytes, are the factories that produce and secrete large amounts of antibodies (immunoglobulins) specific to an antigen. Macrophages phagocytose, T cells regulate or directly kill, neutrophils phagocytose bacteria.
This question belongs to: Science Biology
Question #1070
The enzyme that catalyzes the conversion of pyruvate to lactic acid is:
A. Alcohol dehydrogenase
B. Lactate dehydrogenase
C. Pyruvate decarboxylase
D. Pyruvate kinase
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Correct Answer: Option B

Explanation:
Lactate dehydrogenase (LDH) reduces pyruvate to lactate using NADH, regenerating NADāŗ for glycolysis under anaerobic conditions. Pyruvate decarboxylase is in alcoholic fermentation, alcohol dehydrogenase converts acetaldehyde to ethanol, pyruvate kinase is in glycolysis.
This question belongs to: Science Biology
Question #1071
The gland that regulates sleep-wake cycles by secreting melatonin is the:
A. Thyroid
B. Pituitary
C. Pineal
D. Thymus
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Correct Answer: Option C

Explanation:
The pineal gland, a small endocrine gland in the brain, secretes melatonin in response to darkness, regulating circadian rhythms and sleep patterns. The pituitary controls other glands, thyroid metabolism, thymus immune development.
This question belongs to: Science Biology
Question #1072
The term 'genotype' refers to the:
A. Number of chromosomes
B. Genetic constitution of an organism
C. Physical appearance of an organism
D. Environmentally influenced traits
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Correct Answer: Option B

Explanation:
Genotype is the set of alleles an individual possesses for a particular gene or trait (e.g., TT, Tt, tt). Phenotype is the observable characteristic. Karyotype is the chromosome complement.
This question belongs to: Science Biology
Question #1073
The organism that is an example of a producer in a pond ecosystem is:
A. Fish
B. Frog
C. Water beetle
D. Algae
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Correct Answer: Option D

Explanation:
Algae and aquatic plants are primary producers in pond ecosystems, converting solar energy into biomass through photosynthesis. Fish and frogs are consumers, water beetles are also consumers. Producers form the base of the food web.
This question belongs to: Science Biology
Question #1074
The element that is a component of the hormone thyroxine is:
A. Iron
B. Zinc
C. Iodine
D. Cobalt
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Correct Answer: Option C

Explanation:
Iodine is incorporated into thyroxine (Tā‚„) and triiodothyronine (Tā‚ƒ) synthesized by the thyroid gland. Deficiency leads to goiter and hypothyroidism. Iron is in hemoglobin, zinc in insulin and enzymes, cobalt in Bā‚ā‚‚.
This question belongs to: Science Biology
Question #1075
The disease caused by the filarial worm Wuchereria bancrofti is:
A. Elephantiasis
B. Kala-azar
C. Sleeping sickness
D. Amoebiasis
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Correct Answer: Option A

Explanation:
Lymphatic filariasis, caused by Wuchereria bancrofti and transmitted by Culex mosquito, leads to chronic swelling of limbs (elephantiasis) due to blockage of lymphatic vessels. Amoebiasis is Entamoeba, sleeping sickness Trypanosoma, kala-azar Leishmania.
This question belongs to: Science Biology
Question #1076
The vitamin that is destroyed by excessive heat and light is:
A. Vitamin D
B. Vitamin A
C. Vitamin K
D. Vitamin C
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Correct Answer: Option D

Explanation:
Vitamin C (ascorbic acid) is water-soluble and easily destroyed by heat, light, and oxidation. Cooking reduces its content in food. Vitamin A is fat-soluble and relatively stable, D and K also fat-soluble and more stable. Vitamin C must be consumed regularly.
This question belongs to: Science Biology
Question #1077
The structure that conducts nerve impulses away from the cell body is the:
A. Synaptic terminal
B. Soma
C. Dendrite
D. Axon
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Correct Answer: Option D

Explanation:
The axon is a long process that transmits action potentials from the soma to the target cell (neuron, muscle, or gland). Dendrites receive signals, soma is the cell body, synaptic terminals release neurotransmitters.
This question belongs to: Science Biology
Question #1078
The scientist who introduced the binomial system of classification was:
A. Carolus Linnaeus
B. Aristotle
C. Theophrastus
D. Charles Darwin
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Correct Answer: Option A

Explanation:
Carolus Linnaeus, in his 10th edition of Systema Naturae (1758), systematically applied binomial nomenclature, giving each species a genus and species name. Earlier workers used polynomial names. Linnaeus is the father of taxonomy.
This question belongs to: Science Biology
Question #1079
The process of conversion of nitrates to nitrogen gas by bacteria is:
A. Ammonification
B. Nitrogen fixation
C. Denitrification
D. Nitrification
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Correct Answer: Option C

Explanation:
Denitrification, carried out by bacteria like Pseudomonas, reduces nitrates to Nā‚‚ gas, returning it to the atmosphere. Nitrification converts ammonia to nitrates, ammonification releases ammonia, nitrogen fixation converts Nā‚‚ to ammonia.
This question belongs to: Science Biology
Question #1080
The hormone that stimulates the release of pancreatic bicarbonate is:
A. Gastrin
B. Motilin
C. Cholecystokinin
D. Secretin
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Correct Answer: Option D

Explanation:
Secretin, released from the duodenum in response to acidic chyme, stimulates the pancreas to secrete bicarbonate-rich fluid to neutralize the acid. Gastrin stimulates HCl, CCK enzyme secretion, motilin GI motility.
This question belongs to: Science Biology

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