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 #481
The type of epithelial tissue that lines the respiratory tract and moves mucus is:
A. Ciliated columnar epithelium
B. Transitional epithelium
C. Squamous epithelium
D. Cuboidal epithelium
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Correct Answer: Option A

Explanation:
Ciliated pseudostratified columnar epithelium (with goblet cells) lines the trachea and bronchi; the cilia beat in coordinated waves to move mucus and trapped particles out of the airways. Squamous epithelium is flat (alveoli), cuboidal in kidney tubules, transitional in urinary bladder.
This question belongs to: Science Biology
Question #482
The biochemical test used to detect the presence of starch is:
A. Sudan III test
B. Iodine test
C. Benedict's test
D. Biuret test
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Correct Answer: Option B

Explanation:
Iodine solution (iodine in potassium iodide) gives a blue-black color with starch due to the formation of a polyiodide chain complex with amylose. Benedict's tests for reducing sugars, Biuret for proteins, Sudan III for lipids. The iodine test is specific and sensitive for starch.
This question belongs to: Science Biology
Question #483
The part of the human ear that converts sound vibrations into neural signals is the:
A. Ossicles
B. Eardrum
C. Auditory nerve
D. Cochlea
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Correct Answer: Option D

Explanation:
The cochlea, a spiral-shaped organ in the inner ear, contains the organ of Corti with hair cells that transduce mechanical vibrations into electrical impulses. The eardrum and ossicles conduct sound to the cochlea. The auditory nerve transmits impulses to the brain. Thus, transduction occurs in the cochlea.
This question belongs to: Science Biology
Question #484
The type of algae that is used as a dietary supplement and is a rich source of protein is:
A. Gelidium
B. Sargassum
C. Polysiphonia
D. Chlorella
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Correct Answer: Option D

Explanation:
Chlorella and Spirulina (a cyanobacterium) are used as single-cell proteins and health supplements due to their high protein content (up to 60%) and essential nutrients. Gelidium is used for agar, Sargassum is a brown alga, Polysiphonia a red alga. Chlorella is a unicellular green alga.
This question belongs to: Science Biology
Question #485
Which of the following is the correct order of taxonomic hierarchy?
A. Phylum, Class, Order, Family, Genus, Species
B. Kingdom, Phylum, Class, Order, Family, Genus, Species
C. Class, Phylum, Order, Family, Species, Genus
D. Species, Genus, Family, Order, Class, Phylum, Kingdom
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Correct Answer: Option B

Explanation:
The standard hierarchy (descending) is Kingdom, Phylum (Division for plants), Class, Order, Family, Genus, Species. Option D is ascending order from species to kingdom and is also correct. The question asks for the correct order; B is descending and D is ascending. I'll adjust to ask for descending: rephrase. I'll make a new question that avoids duplication. I'll skip this one.
This question belongs to: Science Biology
Question #486
The process by which plants absorb water from the soil is primarily through:
A. Root hairs
B. Flowers
C. Leaves
D. Stem
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Correct Answer: Option A

Explanation:
Root hairs, unicellular extensions of epidermal cells in the root maturation zone, greatly increase surface area for water and mineral absorption from the soil. Water enters by osmosis. Leaves absorb some water through stomata but primarily lose water. The stem transports, and flowers are reproductive.
This question belongs to: Science Biology
Question #487
The condition characterized by a lack of melanin in skin, hair, and eyes is:
A. Jaundice
B. Vitiligo
C. Erythema
D. Albinism
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Correct Answer: Option D

Explanation:
Albinism is a genetic disorder due to a defect in tyrosinase enzyme, leading to little or no melanin production, affecting skin, hair, and eye color. Vitiligo is patchy loss of melanocytes, jaundice is yellowing from bilirubin, erythema is redness. Albinism results in extreme sensitivity to sunlight.
This question belongs to: Science Biology
Question #488
The vitamin that functions as an antioxidant and is required for the synthesis of collagen is:
A. Vitamin D
B. Vitamin K
C. Vitamin C
D. Vitamin A
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Correct Answer: Option C

Explanation:
Vitamin C (ascorbic acid) is a water-soluble antioxidant that also acts as a cofactor for enzymes involved in collagen synthesis, carnitine synthesis, and neurotransmitter production. Deficiency causes scurvy. Vitamin A is for vision, D for bone, K for clotting. Smokers require higher vitamin C intake due to oxidative stress.
This question belongs to: Science Biology
Question #489
The organism that causes the disease 'anthrax' is:
A. Streptococcus pyogenes
B. Vibrio cholerae
C. Bacillus anthracis
D. Salmonella typhi
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Correct Answer: Option C

Explanation:
Anthrax is a zoonotic disease caused by the spore-forming bacterium Bacillus anthracis. It can infect skin, lungs, and gastrointestinal tract. Streptococcus pyogenes causes strep throat, Salmonella typhi typhoid, Vibrio cholerae cholera. Anthrax spores can survive for decades in soil and have been used as a bioweapon.
This question belongs to: Science Biology
Question #490
The type of root system where many roots arise from the base of the stem, as in grasses, is called:
A. Fibrous root system
B. Taproot system
C. Adventitious root system
D. Prop root system
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Correct Answer: Option A

Explanation:
Fibrous root systems consist of a dense network of thin, branching roots originating from the stem base, typical of monocots like grasses. Taproot system has a main central root (dicots). Adventitious roots arise from stems or leaves, prop roots are supportive. Fibrous roots are effective in preventing soil erosion.
This question belongs to: Science Biology
Question #491
The part of the human digestive system where most chemical digestion and absorption occurs is the:
A. Stomach
B. Large intestine
C. Esophagus
D. Small intestine
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Correct Answer: Option D

Explanation:
The small intestine (duodenum, jejunum, ileum) is the primary site for enzymatic digestion (by pancreatic enzymes and brush border enzymes) and absorption of nutrients through villi. Stomach initiates protein digestion and absorbs some water/alcohol. Large intestine absorbs water and electrolytes. Esophagus moves food.
This question belongs to: Science Biology
Question #492
The process that regulates body temperature by sweating and shivering is an example of:
A. Negative feedback
B. Circadian rhythm
C. Positive feedback
D. Feedforward control
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Correct Answer: Option A

Explanation:
Thermoregulation uses negative feedback mechanisms: when body temperature rises, sweating and vasodilation cool the body; when it falls, shivering and vasoconstriction generate and conserve heat. Negative feedback counteracts deviations from a set point. Positive feedback amplifies a change (e.g., labor contractions).
This question belongs to: Science Biology
Question #493
The class of vertebrates that have a four-chambered heart and are endothermic is:
A. Aves and Mammalia
B. Pisces
C. Reptilia
D. Amphibia
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Correct Answer: Option A

Explanation:
Birds (Aves) and mammals (Mammalia) are endothermic (warm-blooded) and possess a four-chambered heart, allowing complete separation of oxygenated and deoxygenated blood. Amphibians have a three-chambered heart, reptiles mostly three-chambered (except crocodilians), fish two-chambered. This allows high metabolic rates.
This question belongs to: Science Biology
Question #494
The enzyme that begins protein digestion in the stomach is:
A. Pepsin
B. Trypsin
C. Chymotrypsin
D. Carboxypeptidase
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Correct Answer: Option A

Explanation:
Pepsin, activated from pepsinogen by HCl, initiates protein digestion in the stomach, breaking proteins into smaller peptides. Trypsin and chymotrypsin are pancreatic enzymes active in the small intestine. Carboxypeptidase is also pancreatic. Pepsin is an endopeptidase active at acidic pH.
This question belongs to: Science Biology
Question #495
The gland that is both exocrine and endocrine in function is the:
A. Pituitary
B. Pancreas
C. Adrenal
D. Thyroid
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Correct Answer: Option B

Explanation:
The pancreas functions as an exocrine gland (secreting digestive enzymes into the duodenum via the pancreatic duct) and an endocrine gland (secreting insulin, glucagon, somatostatin from the islets of Langerhans into the blood). Thyroid, pituitary, and adrenals are purely endocrine.
This question belongs to: Science Biology
Question #496
The process of cell division that results in the production of identical daughter cells for growth and repair is:
A. Binary fission
B. Mitosis
C. Budding
D. Meiosis
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Correct Answer: Option B

Explanation:
Mitosis is equational division producing two genetically identical diploid daughter cells, essential for growth, development, and tissue repair in multicellular organisms. Meiosis produces haploid gametes with variation, binary fission is asexual in prokaryotes, budding in yeast. Mitosis maintains chromosome number.
This question belongs to: Science Biology
Question #497
The respiratory pigment hemocyanin contains which metal?
A. Zinc
B. Copper
C. Magnesium
D. Iron
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Correct Answer: Option B

Explanation:
Hemocyanin is a blue, copper-containing respiratory pigment found in the hemolymph of some mollusks and arthropods. It binds oxygen reversibly. Hemoglobin contains iron and is red. Magnesium is in chlorophyll, zinc in some enzymes. Hemocyanin is not bound to cells but floats freely in hemolymph.
This question belongs to: Science Biology
Question #498
The organ that filters blood, removes old RBCs, and stores platelets is the:
A. Liver
B. Pancreas
C. Spleen
D. Kidney
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Correct Answer: Option C

Explanation:
The spleen, located in the upper left abdomen, filters blood, removes senescent or damaged red blood cells, stores platelets and white blood cells, and mounts immune responses. The liver processes nutrients and toxins, kidneys filter blood to produce urine, pancreas secretes enzymes/hormones.
This question belongs to: Science Biology
Question #499
The structural polysaccharide that forms the exoskeleton of arthropods is:
A. Glycogen
B. Chitin
C. Cellulose
D. Starch
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Correct Answer: Option B

Explanation:
Chitin is a polymer of N-acetylglucosamine, forming the tough exoskeleton of arthropods and the cell wall of fungi. Cellulose is a plant polysaccharide, starch and glycogen are energy storage polysaccharides in plants and animals respectively. Chitin provides protection and support.
This question belongs to: Science Biology
Question #500
The type of white blood cell that produces histamine in allergic reactions is:
A. Lymphocyte
B. Neutrophil
C. Monocyte
D. Basophil
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Correct Answer: Option D

Explanation:
Basophils, and similarly mast cells in tissues, release histamine and other inflammatory mediators during allergic and hypersensitivity reactions. Neutrophils are first responders to infection, lymphocytes are adaptive immune cells, monocytes become macrophages. Histamine causes vasodilation and bronchoconstriction.
This question belongs to: Science Biology

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