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 #1781
Consider statements about human diseases: 1. Influenza is caused by a virus. 2. Leprosy is caused by a fungus. 3. Malaria is transmitted by Anopheles mosquito. 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 D

Explanation:
Influenza (flu) is a respiratory illness caused by the influenza virus. Malaria is a parasitic disease caused by Plasmodium and transmitted exclusively by the bite of an infected female Anopheles mosquito. Leprosy (Hansen's disease) is a chronic infectious disease caused by the bacterium Mycobacterium leprae, not a fungus. Thus, statements 1 and 3 are correct.
This question belongs to: Science Biology
Question #1782
Consider statements about human immunity: 1. Colostrum provides passive immunity to infants. 2. Allergies are exaggerated immune responses. 3. Autoimmune diseases occur when the immune system attacks self-cells. 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 B

Explanation:
Colostrum, the first milk produced by the mother, is rich in IgA antibodies, providing natural passive immunity to the newborn. Allergies (hypersensitivities) occur when the immune system overreacts to harmless environmental antigens (allergens). Autoimmune diseases arise when the immune system loses tolerance and mistakenly attacks the body's own healthy cells and tissues. All statements are correct.
This question belongs to: Science Biology
Question #1783
Consider statements about human nutrition: 1. Calcium is essential for blood clotting. 2. Iron is a component of hemoglobin. 3. Iodine is required for thyroid hormone synthesis. 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:
Calcium ions (Ca2+) are essential cofactors in the blood coagulation cascade, required for converting prothrombin to thrombin. Iron is the central atom in the heme group of hemoglobin, enabling oxygen transport in red blood cells. Iodine is an indispensable component of the thyroid hormones thyroxine (T4) and triiodothyronine (T3). All three statements are biologically accurate.
This question belongs to: Science Biology
Question #1784
Consider statements about vitamins: 1. Vitamin E acts as an antioxidant. 2. Vitamin K is synthesized by gut bacteria. 3. Vitamin C is essential for collagen synthesis. 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 B

Explanation:
Vitamin E (tocopherol) is a fat-soluble antioxidant that protects cell membranes from oxidative damage by free radicals. Vitamin K is partially synthesized by the symbiotic bacteria residing in the human intestine, contributing to the body's supply. Vitamin C (ascorbic acid) is a crucial cofactor for the enzymes prolyl and lysyl hydroxylase, essential for the synthesis and stabilization of collagen. All statements are correct.
This question belongs to: Science Biology
Question #1785
Consider statements about genetics: 1. Aneuploidy is caused by the failure of chromatids to separate. 2. Down syndrome is caused by trisomy 21. 3. Turner syndrome has the karyotype 47, XXY. Which are correct?
A. 2 and 3 only
B. 1, 2 and 3
C. 1 and 3 only
D. 1 and 2 only
Discuss
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Correct Answer: Option D

Explanation:
Aneuploidy is a chromosomal abnormality resulting from nondisjunction, the failure of homologous chromosomes or sister chromatids to separate properly during cell division. Down syndrome is a genetic disorder caused by the presence of an extra copy of chromosome 21 (trisomy 21). Turner syndrome is a sex chromosome anomaly in females characterized by the karyotype 45, X0, not 47, XXY (which is Klinefelter syndrome). Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1786
Consider statements about evolution: 1. The beak of Darwin's finches is an example of adaptive radiation. 2. Industrial melanism is an example of natural selection. 3. Homologous organs indicate convergent evolution. Which are correct?
A. 1, 2 and 3
B. 2 and 3 only
C. 1 and 3 only
D. 1 and 2 only
Discuss
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Correct Answer: Option D

Explanation:
Darwin's finches on the Galapagos Islands evolved diverse beak shapes from a common ancestor to adapt to different food sources, a classic example of adaptive radiation. Industrial melanism in the peppered moth demonstrates natural selection, where darker moths survived better in soot-covered environments. Homologous organs indicate divergent evolution from a common ancestor, whereas analogous organs indicate convergent evolution. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1787
Consider statements about ecology: 1. Nitrogen fixation is performed by cyanobacteria. 2. Denitrification releases nitrogen gas into the atmosphere. 3. Ammonification converts ammonia to nitrate. 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:
Nitrogen fixation, the conversion of atmospheric N2 to ammonia, is performed by certain bacteria and cyanobacteria (blue-green algae). Denitrification is the process where denitrifying bacteria convert nitrates in the soil back into nitrogen gas (N2), returning it to the atmosphere. Ammonification is the decomposition of organic nitrogen into ammonia by microbes; nitrification converts ammonia to nitrate. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1788
Consider statements about environment: 1. The Chipko movement was for forest conservation. 2. Joint Forest Management involves local communities. 3. Biodiversity hotspots have low species richness. 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:
The Chipko movement was a grassroots environmental movement in India where villagers hugged trees to prevent them from being cut down, highlighting forest conservation. Joint Forest Management (JFM) is a government initiative involving local communities in the protection and management of degraded forest lands. Biodiversity hotspots are regions with exceptionally high levels of species richness and endemism, not low. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1789
Consider statements about microorganisms: 1. Penicillin is extracted from a fungus. 2. Streptomycin is extracted from a bacterium. 3. Viruses can be cultured in synthetic media. Which are correct?
A. 2 and 3 only
B. 1 and 2 only
C. 1 and 3 only
D. 1, 2 and 3
Discuss
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Correct Answer: Option B

Explanation:
Penicillin, the first antibiotic, is extracted from the fungus Penicillium notatum. Streptomycin is an antibiotic derived from the actinomycete bacterium Streptomyces griseus. Viruses are obligate intracellular parasites and cannot be grown or cultured on artificial synthetic media; they require living host cells (like embryonated eggs or cell cultures) to replicate. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1790
Consider statements about biotechnology: 1. Gene therapy aims to correct genetic defects. 2. Transgenic animals have foreign DNA in their genome. 3. Biopesticides are highly toxic to humans. Which are correct?
A. 2 and 3 only
B. 1, 2 and 3
C. 1 and 3 only
D. 1 and 2 only
Discuss
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Correct Answer: Option D

Explanation:
Gene therapy is an experimental technique that involves introducing genes into a patient's cells to correct or compensate for genetic defects causing disease. Transgenic animals have had their genome deliberately altered by the insertion of foreign DNA from another species. Biopesticides, derived from natural materials like bacteria, plants, or minerals, are generally target-specific and non-toxic to humans and the environment, unlike synthetic chemical pesticides. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1791
Consider statements about animal husbandry: 1. The Murrah breed is famous for high milk yield in buffaloes. 2. The Leghorn breed is famous for egg production in poultry. 3. Apiculture refers to fish farming. Which are correct?
A. 1, 2 and 3
B. 2 and 3 only
C. 1 and 3 only
D. 1 and 2 only
Discuss
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Correct Answer: Option D

Explanation:
The Murrah is a premier indigenous breed of water buffalo in India, renowned for its high milk yield and fat content. The White Leghorn is an exotic breed of chicken highly valued in the poultry industry for its excellent egg-laying capacity. Apiculture is the rearing and management of honeybees for honey and wax; fish farming is called pisciculture or aquaculture. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1792
Consider statements about scientists: 1. Carolus Linnaeus developed binomial nomenclature. 2. Louis Pasteur developed the rabies vaccine. 3. Gregor Mendel discovered the structure of DNA. 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:
Carolus Linnaeus, a Swedish botanist, formalized the system of binomial nomenclature for naming organisms. Louis Pasteur made immense contributions to microbiology, including the development of the first effective vaccine against rabies. Gregor Mendel is the father of genetics, known for his laws of inheritance; the structure of DNA was discovered by Watson and Crick. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1793
Consider statements about cell biology: 1. The cell membrane is made of a phospholipid bilayer. 2. Ribosomes are the site of lipid synthesis. 3. The cytoskeleton provides structural support. 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:
The cell membrane (plasma membrane) is primarily composed of a phospholipid bilayer with embedded proteins, following the fluid mosaic model. The cytoskeleton is a network of protein filaments (microtubules, microfilaments, intermediate filaments) that provides structural support, shape, and facilitates intracellular transport. Ribosomes are the site of protein synthesis, not lipid synthesis (which occurs in the smooth ER). Thus, statements 1 and 3 are correct.
This question belongs to: Science Biology
Question #1794
Consider statements about plant biology: 1. Phototropism is growth towards light. 2. Geotropism is growth in response to gravity. 3. Thigmotropism is growth in response to water. Which are correct?
A. 1 and 2 only
B. 1 and 3 only
C. 1, 2 and 3
D. 2 and 3 only
Discuss
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Correct Answer: Option A

Explanation:
Phototropism is the directional growth of a plant organ in response to light, typically positive in shoots. Geotropism (gravitropism) is the growth response to gravity, with roots showing positive geotropism (growing down) and shoots negative geotropism (growing up). Thigmotropism is the growth response to touch or physical contact, seen in climbing plants like vines, not water (which is hydrotropism). Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1795
Consider statements about human anatomy: 1. The humerus is the bone of the upper arm. 2. The radius and ulna are bones of the lower arm. 3. The patella is a bone in the skull. Which 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:
The humerus is the single, long bone of the upper arm, connecting the shoulder to the elbow. The radius and ulna are the two parallel bones of the forearm (lower arm), connecting the elbow to the wrist. The patella, commonly known as the kneecap, is a small, flat, triangular bone located at the front of the knee joint, not in the skull. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1796
Consider statements about human physiology: 1. The liver stores glycogen. 2. The spleen filters blood and removes old RBCs. 3. The appendix is essential for digestion. 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 C

Explanation:
The liver plays a crucial role in carbohydrate metabolism, storing excess glucose as glycogen and releasing it when blood sugar drops. The spleen acts as a blood filter, removing old, damaged, or abnormal red blood cells and storing platelets. The appendix is a small, blind-ended tube attached to the cecum; it has no significant role in human digestion and is considered a vestigial organ. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1797
Consider statements about human diseases: 1. Dengue is caused by a protozoan. 2. Filariasis is caused by a nematode worm. 3. Pneumonia affects the respiratory system. Which are correct?
A. 1 and 3 only
B. 2 and 3 only
C. 1 and 2 only
D. 1, 2 and 3
Discuss
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Correct Answer: Option B

Explanation:
Dengue is a viral disease caused by the Dengue virus, not a protozoan (malaria is caused by a protozoan). Filariasis (elephantiasis) is caused by parasitic nematode worms like Wuchereria bancrofti, which block lymphatic vessels. Pneumonia is an infection that inflames the air sacs in one or both lungs, affecting the respiratory system. Thus, statements 2 and 3 are correct.
This question belongs to: Science Biology
Question #1798
Consider statements about human immunity: 1. B-lymphocytes produce antibodies. 2. T-lymphocytes are involved in cell-mediated immunity. 3. Vaccines cure active viral infections. Which are correct?
A. 1, 2 and 3
B. 1 and 3 only
C. 2 and 3 only
D. 1 and 2 only
Discuss
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Correct Answer: Option D

Explanation:
B-lymphocytes (B cells) differentiate into plasma cells that secrete antibodies, providing humoral immunity. T-lymphocytes (T cells) are responsible for cell-mediated immunity, directly attacking infected or cancerous cells. Vaccines are prophylactic; they stimulate the immune system to develop memory and prevent future infections, but they do not cure active, ongoing viral infections. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1799
Consider statements about human nutrition: 1. Scurvy is caused by Vitamin D deficiency. 2. Anemia is often caused by iron deficiency. 3. Goiter is caused by iodine 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 B

Explanation:
Scurvy is caused by a deficiency of Vitamin C (ascorbic acid), leading to bleeding gums; rickets is caused by Vitamin D deficiency. Iron is essential for hemoglobin synthesis, and its deficiency leads to iron-deficiency anemia, causing fatigue and weakness. Iodine is required for thyroid hormone production, and its deficiency causes the enlargement of the thyroid gland, known as goiter. Thus, statements 2 and 3 are correct.
This question belongs to: Science Biology
Question #1800
Consider statements about vitamins: 1. Vitamin A deficiency causes night blindness. 2. Vitamin B1 deficiency causes beriberi. 3. Vitamin C is essential for blood clotting. 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:
Vitamin A is essential for the formation of rhodopsin in the retina; its deficiency causes night blindness. Vitamin B1 (thiamine) deficiency leads to beriberi, characterized by nerve and heart issues. Vitamin K, not Vitamin C, is essential for the synthesis of blood clotting factors like prothrombin. Vitamin C is essential for collagen synthesis and immunity. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology

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