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 51 of 103
Question #1001
The type of root that grows from the stem or leaves is called:
A. Primary root
B. Adventitious root
C. Taproot
D. Fibrous root
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Correct Answer: Option B

Explanation:
Adventitious roots arise from non-root tissues like stems, leaves, or branches. Examples: prop roots of banyan, stilt roots of maize, aerial roots of orchids. Taproot and fibrous roots develop from the radicle.
This question belongs to: Science Biology
Question #1002
The organ that produces the hormone insulin is the:
A. Pancreas
B. Thyroid
C. Spleen
D. Liver
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Correct Answer: Option A

Explanation:
The beta cells of the pancreatic islets of Langerhans produce insulin, which lowers blood glucose by promoting cellular uptake and glycogen synthesis. The liver stores glucose, the spleen filters blood, the thyroid regulates metabolism.
This question belongs to: Science Biology
Question #1003
The process by which water is lost from plants as liquid droplets through hydathodes is:
A. Transpiration
B. Precipitation
C. Evaporation
D. Guttation
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Correct Answer: Option D

Explanation:
Guttation occurs when root pressure forces water out through special pores (hydathodes) at leaf tips/margins, forming droplets, usually at night or early morning. Transpiration is vapor loss, evaporation from wet surfaces, precipitation is rain.
This question belongs to: Science Biology
Question #1004
The blood cells that initiate blood clotting are:
A. Lymphocytes
B. Thrombocytes (platelets)
C. Erythrocytes
D. Leukocytes
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Correct Answer: Option B

Explanation:
Platelets adhere to damaged vessel walls, aggregate, and release clotting factors, forming a plug and initiating the coagulation cascade. RBCs carry oxygen, WBCs fight infection, lymphocytes are immune cells.
This question belongs to: Science Biology
Question #1005
The vitamin that is required for the synthesis of collagen is:
A. Vitamin A
B. Vitamin D
C. Vitamin C
D. Vitamin K
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Correct Answer: Option C

Explanation:
Vitamin C is a cofactor for enzymes that hydroxylate proline and lysine in procollagen, essential for proper collagen triple helix formation. Deficiency results in weak collagen and scurvy. Vitamin A is for vision, D for calcium, K for clotting.
This question belongs to: Science Biology
Question #1006
The organelle that contains oxidative enzymes and is involved in photorespiration is:
A. Peroxisome
B. Lysosome
C. Mitochondria
D. Chloroplast
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Correct Answer: Option A

Explanation:
Peroxisomes contain enzymes like glycolate oxidase that participate in photorespiration, along with chloroplasts and mitochondria. They also detoxify peroxides. Lysosomes digest, mitochondria respire, chloroplasts photosynthesize.
This question belongs to: Science Biology
Question #1007
The process that converts light energy into chemical energy in plants is:
A. Photosynthesis
B. Fermentation
C. Respiration
D. Translocation
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Correct Answer: Option A

Explanation:
Photosynthesis captures light energy via chlorophyll and converts CO₂ and H₂O into glucose and O₂. Respiration releases energy from glucose, fermentation is anaerobic, translocation is movement of solutes.
This question belongs to: Science Biology
Question #1008
The structure that prevents food from entering the trachea is the:
A. Tongue
B. Epiglottis
C. Uvula
D. Glottis
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Correct Answer: Option B

Explanation:
The epiglottis is a cartilage flap that covers the glottis (laryngeal opening) during swallowing, directing food into the esophagus and protecting the airway. The tongue manipulates food, the uvula prevents nasal regurgitation.
This question belongs to: Science Biology
Question #1009
The hormone that induces ovulation in females is:
A. Progesterone
B. FSH
C. LH
D. Estrogen
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Correct Answer: Option C

Explanation:
A mid-cycle surge in luteinizing hormone (LH) triggers the final maturation and release of the secondary oocyte from the Graafian follicle (ovulation). FSH stimulates follicle growth, estrogen proliferates uterine lining, progesterone maintains it.
This question belongs to: Science Biology
Question #1010
The technique used to study the internal structures of cells using electron beams is:
A. Chromatography
B. Electron microscopy
C. Light microscopy
D. Spectrophotometry
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Correct Answer: Option B

Explanation:
Electron microscopes use beams of electrons to achieve much higher resolution than light microscopes, enabling visualization of organelles and macromolecular complexes. Types include TEM (internal) and SEM (surface). Light microscopes use visible light, spectrophotometry measures absorbance, chromatography separates.
This question belongs to: Science Biology
Question #1011
The element that is a component of hemoglobin is:
A. Iron
B. Magnesium
C. Calcium
D. Zinc
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Correct Answer: Option A

Explanation:
Iron (Fe²⁺) is at the center of the heme group in hemoglobin, enabling reversible oxygen binding. Calcium is in bones, magnesium in chlorophyll, zinc in many enzymes. Iron deficiency leads to anemia.
This question belongs to: Science Biology
Question #1012
The type of fruit that develops from a single flower with multiple carpels fused together is:
A. Simple fruit
B. Multiple fruit
C. Aggregate fruit
D. Accessory fruit
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Correct Answer: Option A

Explanation:
A simple fruit develops from a single ovary of a single flower, which may be a single carpel or fused carpels (e.g., tomato, peach). Aggregate fruits develop from separate carpels of one flower (e.g., strawberry). Multiple fruits from many flowers (e.g., pineapple).
This question belongs to: Science Biology
Question #1013
The organism that causes sleeping sickness is transmitted by:
A. Tick
B. Tsetse fly
C. Housefly
D. Mosquito
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Correct Answer: Option B

Explanation:
African sleeping sickness (trypanosomiasis) is caused by Trypanosoma brucei and transmitted by the bite of the tsetse fly (Glossina). Malaria is by mosquito, typhoid by housefly (mechanical), Lyme disease by tick.
This question belongs to: Science Biology
Question #1014
The type of joint that allows movement in one plane, like the elbow and knee, is:
A. Hinge
B. Ball and socket
C. Saddle
D. Pivot
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Correct Answer: Option A

Explanation:
Hinge joints (ginglymus) permit flexion and extension only, like a door hinge. The elbow, knee, and interphalangeal joints are examples. Ball-and-socket (hip) multiaxial, pivot (neck) rotation, saddle (thumb) biaxial.
This question belongs to: Science Biology
Question #1015
The male reproductive part of a flower is the:
A. Stamen
B. Pistil
C. Sepal
D. Petal
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Correct Answer: Option A

Explanation:
The stamen is the male reproductive organ, consisting of an anther (producing pollen) and a filament. The pistil (carpel) is the female part, petals attract pollinators, sepals protect the bud.
This question belongs to: Science Biology
Question #1016
The vitamin that is a component of coenzyme A is:
A. Folic acid
B. Biotin
C. Thiamine
D. Pantothenic acid
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Correct Answer: Option D

Explanation:
Pantothenic acid (vitamin B₅) is a component of coenzyme A (CoA), which is essential for the metabolism of carbohydrates, fats, and proteins via the Krebs cycle and fatty acid synthesis. Thiamine is TPP, biotin for carboxylation, folic acid for one-carbon transfer.
This question belongs to: Science Biology
Question #1017
The scientist who demonstrated that fermentation is caused by yeast was:
A. Eduard Buchner
B. Antonie van Leeuwenhoek
C. Alexander Fleming
D. Louis Pasteur
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Correct Answer: Option D

Explanation:
Louis Pasteur proved that fermentation is caused by living yeast cells, not spontaneous chemical reactions. Buchner later showed that cell-free extracts could ferment sugar, discovering enzymes. Fleming discovered penicillin, Leeuwenhoek observed microbes.
This question belongs to: Science Biology
Question #1018
The process that moves food through the esophagus by rhythmic contractions is:
A. Segmentation
B. Mastication
C. Peristalsis
D. Emulsification
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Correct Answer: Option C

Explanation:
Peristalsis is a wave-like series of muscular contractions and relaxations that propels food through the digestive tract. Segmentation mixes contents in the intestine, emulsification breaks fat globules, mastication is chewing.
This question belongs to: Science Biology
Question #1019
The organelle that stores calcium ions in muscle cells is the:
A. Nucleus
B. Sarcoplasmic reticulum
C. Mitochondria
D. Golgi apparatus
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Correct Answer: Option B

Explanation:
The sarcoplasmic reticulum is a specialized smooth endoplasmic reticulum in muscle cells that stores and releases calcium ions, which trigger muscle contraction. Mitochondria produce ATP, Golgi processes proteins, nucleus controls gene expression.
This question belongs to: Science Biology
Question #1020
The phenomenon where a single gene mutation affects multiple traits is:
A. Epistasis
B. Codominance
C. Pleiotropy
D. Polygenic inheritance
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Correct Answer: Option C

Explanation:
Pleiotropy is when one gene influences several distinct phenotypic characteristics. Example: sickle cell disease (mutant hemoglobin affects RBC shape, causing anemia, pain, organ damage). Polygenic traits involve many genes, codominance both alleles expressed, epistasis gene interaction.
This question belongs to: Science Biology

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