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 55 of 103
Question #1081
The type of cell division that creates genetic variation through crossing over is:
A. Binary fission
B. Mitosis
C. Meiosis
D. Fragmentation
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Correct Answer: Option C

Explanation:
Meiosis I features crossing over (prophase I) and independent assortment of homologous chromosomes, creating genetic diversity in gametes. Mitosis produces identical cells, binary fission is asexual, fragmentation is a form of asexual reproduction.
This question belongs to: Science Biology
Question #1082
The condition in which the blood does not clot properly due to deficiency of clotting factor VIII is:
A. Anemia
B. Hemophilia A
C. Thalassemia
D. Leukemia
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Correct Answer: Option B

Explanation:
Hemophilia A is an X-linked recessive bleeding disorder caused by deficiency of factor VIII. Hemophilia B is factor IX deficiency. Anemia is low RBCs, thalassemia abnormal hemoglobin, leukemia cancer of WBCs.
This question belongs to: Science Biology
Question #1083
The organ that stores urine before excretion is the:
A. Ureter
B. Kidney
C. Urinary bladder
D. Urethra
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Correct Answer: Option C

Explanation:
The urinary bladder is a muscular sac that temporarily stores urine received from the kidneys via the ureters, until micturition. The urethra drains urine to the exterior.
This question belongs to: Science Biology
Question #1084
The vitamin that is a coenzyme in the decarboxylation of pyruvate to acetyl-CoA is:
A. Riboflavin (B₂)
B. Thiamine (B₁)
C. Pyridoxine (B₆)
D. Niacin (B₃)
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Correct Answer: Option B

Explanation:
Thiamine pyrophosphate (TPP), derived from vitamin B₁, is a cofactor for pyruvate dehydrogenase, which catalyzes the oxidative decarboxylation of pyruvate to acetyl-CoA. Riboflavin is FAD, niacin is NAD, pyridoxine PLP for transamination.
This question belongs to: Science Biology
Question #1085
The scientist who first observed chloroplasts was:
A. Robert Hooke
B. Andreas Schimper
C. Julius von Sachs
D. Antonie van Leeuwenhoek
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Correct Answer: Option B

Explanation:
Andreas Schimper first described chloroplasts and coined the term in 1883. Hooke discovered cells, Leeuwenhoek observed live cells, Sachs showed starch is produced by photosynthesis.
This question belongs to: Science Biology
Question #1086
The technique used to measure the rate of photosynthesis by counting oxygen bubbles is:
A. Manometry
B. Spectrophotometry
C. Bubble counting
D. Respirometry
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Correct Answer: Option C

Explanation:
In aquatic plants like Hydrilla, the rate of photosynthesis can be estimated by counting the number of oxygen bubbles released per minute under light. Manometry measures pressure changes, respirometry respiration, spectrophotometry light absorbance.
This question belongs to: Science Biology
Question #1087
The hormone that stimulates the reabsorption of water in the collecting duct is:
A. Aldosterone
B. Antidiuretic hormone (ADH)
C. Renin
D. Atrial natriuretic peptide
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Correct Answer: Option B

Explanation:
ADH (vasopressin) increases water permeability of the collecting duct cells by inserting aquaporins, reducing urine volume. Aldosterone increases sodium reabsorption, renin is an enzyme, ANP promotes sodium excretion.
This question belongs to: Science Biology
Question #1088
The structure that carries oxygenated blood from the lungs to the heart is the:
A. Aorta
B. Pulmonary vein
C. Pulmonary artery
D. Superior vena cava
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Correct Answer: Option B

Explanation:
The four pulmonary veins drain oxygen-rich blood from the lungs into the left atrium. The pulmonary artery carries deoxygenated blood from right ventricle to lungs. Vena cava brings deoxygenated blood to right atrium.
This question belongs to: Science Biology
Question #1089
The process of taking in oxygen and releasing carbon dioxide is called:
A. Excretion
B. Digestion
C. Respiration
D. Circulation
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Correct Answer: Option C

Explanation:
Respiration includes external respiration (breathing, gas exchange) and internal respiration (cellular metabolism). Digestion is food breakdown, circulation is transport, excretion is waste removal.
This question belongs to: Science Biology
Question #1090
The disease caused by deficiency of vitamin D in children is:
A. Osteomalacia
B. Rickets
C. Pellagra
D. Scurvy
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Correct Answer: Option B

Explanation:
Rickets is characterized by weak, soft bones, bowed legs, and growth retardation due to impaired calcium deposition. In adults, equivalent is osteomalacia. Scurvy is vitamin C, pellagra niacin.
This question belongs to: Science Biology
Question #1091
The hormone that stimulates the Leydig cells to produce testosterone is:
A. GnRH
B. Inhibin
C. FSH
D. LH
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Correct Answer: Option D

Explanation:
Luteinizing hormone (LH) binds to Leydig cells in the testes, stimulating them to produce and secrete testosterone. FSH stimulates Sertoli cells for spermatogenesis. GnRH from hypothalamus stimulates release of LH and FSH.
This question belongs to: Science Biology
Question #1092
The connective tissue that transports oxygen and nutrients is:
A. Bone
B. Cartilage
C. Blood
D. Adipose
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Correct Answer: Option C

Explanation:
Blood is a fluid connective tissue that circulates through vessels, transporting oxygen (bound to hemoglobin), nutrients, hormones, and waste products. Bone provides support, cartilage cushions, adipose stores fat.
This question belongs to: Science Biology
Question #1093
The type of reproduction that involves only one parent and no gamete fusion is:
A. Fertilization
B. Asexual reproduction
C. Sexual reproduction
D. Cross-pollination
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Correct Answer: Option B

Explanation:
Asexual reproduction (binary fission, budding, fragmentation, vegetative propagation) produces genetically identical offspring from a single parent. Sexual reproduction involves gamete fusion. Fertilization is gamete union.
This question belongs to: Science Biology
Question #1094
The scientist who isolated the first antibiotic, penicillin, from Penicillium notatum was:
A. Alexander Fleming
B. Howard Florey
C. Selman Waksman
D. Ernst Chain
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Correct Answer: Option A

Explanation:
Alexander Fleming discovered penicillin in 1928. Florey and Chain later purified it and demonstrated its therapeutic potential. Waksman discovered streptomycin. The discovery of penicillin revolutionized medicine.
This question belongs to: Science Biology
Question #1095
The organ that produces the hormone erythropoietin is the:
A. Spleen
B. Kidney
C. Liver
D. Bone marrow
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Correct Answer: Option B

Explanation:
The kidneys sense low oxygen levels and secrete erythropoietin (EPO), which stimulates red blood cell production in the bone marrow. The liver also produces some EPO in fetal life. Bone marrow is the target, not producer.
This question belongs to: Science Biology
Question #1096
The vitamin that acts as an antioxidant and is important for immune function is:
A. Vitamin A
B. Vitamin B₁₂
C. Vitamin C
D. Vitamin K
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Correct Answer: Option C

Explanation:
Vitamin C is a potent water-soluble antioxidant, enhances iron absorption, and supports immune cells. Vitamin A also supports immunity but is not primarily an antioxidant; vitamin E is fat-soluble antioxidant.
This question belongs to: Science Biology
Question #1097
The genetic disease caused by the absence of an enzyme that breaks down phenylalanine is:
A. Sickle cell anemia
B. Albinism
C. Phenylketonuria
D. Cystic fibrosis
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Correct Answer: Option C

Explanation:
Phenylketonuria (PKU) is an autosomal recessive disorder due to deficiency of phenylalanine hydroxylase, leading to accumulation of phenylalanine, causing mental retardation if untreated. Albinism is tyrosinase deficiency, sickle cell HbS mutation, cystic fibrosis CFTR defect.
This question belongs to: Science Biology
Question #1098
The process by which solid waste is eliminated from the body is:
A. Secretion
B. Defecation
C. Urination
D. Exhalation
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Correct Answer: Option B

Explanation:
Defecation is the elimination of undigested solid waste (feces) from the rectum. Urination removes liquid nitrogenous waste, exhalation removes CO₂ and water vapor, secretion is release of useful substances.
This question belongs to: Science Biology
Question #1099
The hormone that promotes the breakdown of glycogen to glucose in the liver is:
A. Cortisol
B. Insulin
C. Glucagon
D. Thyroxine
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Correct Answer: Option C

Explanation:
Glucagon, released by pancreatic alpha cells when blood glucose is low, activates glycogen phosphorylase, leading to glycogenolysis and release of glucose from the liver. Insulin promotes glycogenesis. Cortisol and thyroxine have permissive effects.
This question belongs to: Science Biology
Question #1100
The structure that absorbs water and forms feces is the:
A. Large intestine
B. Stomach
C. Small intestine
D. Esophagus
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Correct Answer: Option A

Explanation:
The colon (large intestine) reabsorbs water, electrolytes, and vitamins produced by gut bacteria, compacting the indigestible residue into feces. The small intestine absorbs nutrients, stomach digests, esophagus transports.
This question belongs to: Science Biology

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