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 49 of 103
Question #961
The infective stage of the malarial parasite in humans is:
A. Merozoite
B. Trophozoite
C. Gametocyte
D. Sporozoite
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Correct Answer: Option D

Explanation:
The sporozoite is the motile infective stage injected by the female Anopheles mosquito into the human host. It invades liver cells. Gametocytes are the stage taken up by the mosquito, merozoites are released from liver and infect RBCs.
This question belongs to: Science Biology
Question #962
The vitamin that acts as an antioxidant and protects cell membranes from damage is:
A. Vitamin A
B. Vitamin C
C. Vitamin K
D. Vitamin E
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Correct Answer: Option D

Explanation:
Vitamin E (tocopherol) is a lipid-soluble antioxidant that scavenges free radicals and prevents lipid peroxidation of cell membranes. Vitamin C is water-soluble antioxidant, A is for vision, K for clotting.
This question belongs to: Science Biology
Question #963
The hormone that stimulates the reabsorption of sodium and water in the kidney is:
A. Natriuretic peptide
B. Aldosterone
C. Antidiuretic hormone (ADH)
D. Renin
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Correct Answer: Option B

Explanation:
Aldosterone, secreted by the adrenal cortex, increases sodium reabsorption (and water follows) and potassium secretion in the distal tubule and collecting duct. ADH increases water reabsorption only. Renin is an enzyme, natriuretic peptides inhibit sodium reabsorption.
This question belongs to: Science Biology
Question #964
The type of immunity that occurs after recovery from an infection is:
A. Natural active immunity
B. Artificial passive immunity
C. Artificial active immunity
D. Natural passive immunity
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Correct Answer: Option A

Explanation:
Natural active immunity develops when a person is exposed to a live pathogen, develops an immune response, and creates memory cells. Artificial active is from vaccination. Passive immunity involves receiving antibodies.
This question belongs to: Science Biology
Question #965
The process by which nitrogen gas is converted to ammonia by bacteria is called:
A. Denitrification
B. Nitrogen fixation
C. Nitrification
D. Ammonification
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Correct Answer: Option B

Explanation:
Biological nitrogen fixation, carried out by symbiotic (Rhizobium) and free-living (Azotobacter) bacteria, reduces atmospheric N₂ to ammonia. Nitrification converts ammonia to nitrates, denitrification returns N₂ to air, ammonification releases ammonia from organic matter.
This question belongs to: Science Biology
Question #966
Which of the following is the largest part of the human brain?
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 prominent part of the brain, divided into left and right hemispheres, responsible for higher functions like thought, memory, and voluntary movement. The cerebellum coordinates movement, medulla controls vital functions.
This question belongs to: Science Biology
Question #967
The technique of producing many identical copies of a plant from a single tissue is:
A. Cross-pollination
B. Hybridization
C. Tissue culture (micropropagation)
D. Selective breeding
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Correct Answer: Option C

Explanation:
Tissue culture (micropropagation) involves growing plant cells/tissues on a sterile nutrient medium to regenerate whole plants, producing clones. Hybridization is crossing varieties, cross-pollination is natural or artificial pollination, selective breeding chooses parents.
This question belongs to: Science Biology
Question #968
The animal that has a four-chambered stomach for rumination is:
A. Cat
B. Cow
C. Dog
D. Pig
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Correct Answer: Option B

Explanation:
Ruminants like cows, sheep, and goats have a four-chambered stomach (rumen, reticulum, omasum, abomasum) to digest cellulose via microbial fermentation. Cats and dogs have simple stomachs, pigs are monogastric.
This question belongs to: Science Biology
Question #969
The chemical name of vitamin B₂ is:
A. Pyridoxine
B. Niacin
C. Thiamine
D. Riboflavin
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Correct Answer: Option D

Explanation:
Riboflavin is vitamin B₂, a component of coenzymes FAD and FMN involved in redox reactions. Thiamine is B₁, niacin is B₃, pyridoxine is B₆. Riboflavin deficiency causes angular stomatitis.
This question belongs to: Science Biology
Question #970
The blood group that lacks both antigens A and B is:
A. O
B. AB
C. B
D. A
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Correct Answer: Option A

Explanation:
Blood group O has neither A nor B antigens on the red blood cells, but has both anti-A and anti-B antibodies in plasma. It is the universal donor for red cells. Group AB has both antigens, A has A antigen, B has B antigen.
This question belongs to: Science Biology
Question #971
The structure in the female reproductive system that produces eggs is the:
A. Uterus
B. Vagina
C. Fallopian tube
D. Ovary
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Correct Answer: Option D

Explanation:
Ovaries are the primary female gonads that produce ova (eggs) and secrete sex hormones estrogen and progesterone. The uterus supports embryo development, the fallopian tubes transport eggs, the vagina is the birth canal.
This question belongs to: Science Biology
Question #972
The process by which atmospheric CO₂ is fixed into organic compounds by plants is:
A. Photosynthesis
B. Combustion
C. Decomposition
D. Respiration
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Correct Answer: Option A

Explanation:
Photosynthesis converts CO₂ and water into glucose using light energy, fixing carbon. Respiration releases CO₂, combustion burns organic matter, decomposition breaks down dead matter. Photosynthesis is the main route of carbon entry into the biosphere.
This question belongs to: Science Biology
Question #973
The enzyme that breaks down starch into maltose in the mouth is:
A. Pepsin
B. Lipase
C. Salivary amylase
D. Rennin
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Correct Answer: Option C

Explanation:
Salivary amylase (ptyalin) initiates starch digestion in the mouth, hydrolyzing it into maltose and dextrins. Pepsin digests protein, lipase fats, rennin curdles milk. Amylase works optimally at neutral pH.
This question belongs to: Science Biology
Question #974
The lymphatic system consists of lymph, lymph nodes, and:
A. Capillaries only
B. Veins
C. Arteries
D. Lymphatic vessels
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Correct Answer: Option D

Explanation:
The lymphatic system includes lymph, lymphatic capillaries, vessels, ducts, and lymphoid organs (nodes, spleen, thymus). It returns tissue fluid to the blood, absorbs fats, and defends against pathogens.
This question belongs to: Science Biology
Question #975
The type of joint found between the vertebrae is:
A. Cartilaginous joint
B. Ball and socket joint
C. Suture
D. Hinge joint
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Correct Answer: Option A

Explanation:
Intervertebral discs are fibrocartilaginous joints (symphyses) that allow slight movement and absorb shock. Hinge joints are in knee/elbow, ball-and-socket in hip/shoulder, sutures are immovable fibrous joints in skull.
This question belongs to: Science Biology
Question #976
The process by which bacteria reproduce is:
A. Mitosis
B. Meiosis
C. Budding
D. Binary fission
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Correct Answer: Option D

Explanation:
Binary fission is a type of asexual reproduction in prokaryotes where the cell divides into two identical daughter cells after DNA replication. Mitosis and meiosis are eukaryotic. Budding occurs in yeast and some bacteria.
This question belongs to: Science Biology
Question #977
The pigment that is essential for vision in low light is:
A. Hemoglobin
B. Iodopsin
C. Rhodopsin
D. Melanin
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Correct Answer: Option C

Explanation:
Rhodopsin (visual purple) in rod cells of the retina consists of opsin and retinal (derived from vitamin A). It bleaches in light, triggering nerve impulses. It is highly sensitive, enabling night vision. Iodopsin is in cones for color vision.
This question belongs to: Science Biology
Question #978
The scientist who discovered the vaccine for rabies was:
A. Louis Pasteur
B. Robert Koch
C. Jonas Salk
D. Edward Jenner
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Correct Answer: Option A

Explanation:
Louis Pasteur developed the first rabies vaccine in 1885, using dried spinal cords from infected rabbits. Jenner developed smallpox vaccine, Koch identified tuberculosis bacterium, Salk developed inactivated polio vaccine.
This question belongs to: Science Biology
Question #979
The structure that connects the bones and allows movement is:
A. Joint
B. Ligament
C. Cartilage
D. Tendon
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Correct Answer: Option A

Explanation:
A joint (articulation) is where two or more bones meet, allowing varying degrees of movement. Tendons connect muscle to bone, ligaments bone to bone, cartilage cushions. Joints are classified as fibrous, cartilaginous, or synovial.
This question belongs to: Science Biology
Question #980
The deficiency of vitamin A causes:
A. Night blindness
B. Pellagra
C. Beri-beri
D. Scurvy
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Correct Answer: Option A

Explanation:
Vitamin A is essential for the synthesis of rhodopsin. Deficiency leads to impaired dark adaptation (night blindness) and eventually xerophthalmia. Beri-beri is B₁ deficiency, pellagra B₃, scurvy vitamin C.
This question belongs to: Science Biology

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