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 53 of 103
Question #1041
The hormone that stimulates milk production after childbirth is:
A. Estrogen
B. Prolactin
C. Progesterone
D. Oxytocin
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Correct Answer: Option B

Explanation:
Prolactin, from the anterior pituitary, promotes mammary gland development and milk synthesis. Oxytocin triggers milk ejection. Estrogen and progesterone prepare breasts during pregnancy but inhibit milk secretion.
This question belongs to: Science Biology
Question #1042
The process of transfer of pollen from anther to stigma of the same flower is:
A. Cross-pollination
B. Geitonogamy
C. Self-pollination
D. Xenogamy
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Correct Answer: Option C

Explanation:
Self-pollination (autogamy) occurs within the same flower. Geitonogamy is pollination between different flowers of the same plant, functionally cross-pollination. Xenogamy is between different plants. Self-pollination leads to genetic uniformity.
This question belongs to: Science Biology
Question #1043
The fluid that accumulates in tissues causing edema when lymphatic drainage is impaired is:
A. Lymph
B. Serum
C. Synovial fluid
D. Plasma
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Correct Answer: Option A

Explanation:
Lymph is interstitial fluid that has entered lymphatic capillaries. When lymph vessels are blocked (e.g., filariasis), lymph accumulates, causing swelling (lymphedema). Plasma is blood fluid, synovial in joints, serum is plasma without clotting factors.
This question belongs to: Science Biology
Question #1044
The scientist who discovered the bacterium that causes cholera was:
A. John Snow
B. Filippo Pacini
C. Louis Pasteur
D. Robert Koch
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Correct Answer: Option B

Explanation:
Filippo Pacini first observed Vibrio cholerae in 1854, but Robert Koch later independently identified it and demonstrated its role. Koch is often credited, but Pacini's discovery was earlier. John Snow linked cholera to water.
This question belongs to: Science Biology
Question #1045
The vitamin deficiency that leads to pernicious anemia is:
A. Vitamin C
B. Vitamin B₁
C. Vitamin B₆
D. Vitamin B₁₂
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Correct Answer: Option D

Explanation:
Pernicious anemia is a megaloblastic anemia caused by vitamin B₁₂ deficiency, often due to lack of intrinsic factor needed for its absorption. B₁ deficiency causes beriberi, B₆ deficiency dermatitis and neuropathy, C scurvy.
This question belongs to: Science Biology
Question #1046
The element that is the central atom in chlorophyll is:
A. Iron
B. Magnesium
C. Cobalt
D. Calcium
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Correct Answer: Option B

Explanation:
Magnesium is the central atom in the porphyrin ring of chlorophyll, essential for light absorption in photosynthesis. Iron is in heme, calcium structural, cobalt in vitamin B₁₂.
This question belongs to: Science Biology
Question #1047
The type of muscle found in the walls of the digestive tract is:
A. Skeletal
B. Smooth
C. Cardiac
D. Voluntary
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Correct Answer: Option B

Explanation:
Smooth muscle is non-striated, involuntary, and forms the muscular layer of the digestive tract (esophagus, stomach, intestines), responsible for peristalsis. Skeletal muscle is voluntary and striated, cardiac is heart-specific.
This question belongs to: Science Biology
Question #1048
The process by which bacteria exchange genetic material via a bacteriophage is:
A. Transformation
B. Binary fission
C. Conjugation
D. Transduction
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Correct Answer: Option D

Explanation:
Transduction is the transfer of bacterial DNA by a bacteriophage (virus). Transformation is uptake of free DNA, conjugation is direct transfer via pilus, binary fission is reproduction.
This question belongs to: Science Biology
Question #1049
The structure that produces ribosomes in the nucleus is the:
A. Nucleolus
B. Nucleoplasm
C. Nuclear pore
D. Chromatin
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Correct Answer: Option A

Explanation:
The nucleolus is a dense region within the nucleus where ribosomal RNA (rRNA) is transcribed and ribosomal subunits are assembled. Chromatin is DNA-protein complex, nucleoplasm is the fluid, nuclear pores regulate transport.
This question belongs to: Science Biology
Question #1050
The animal that has a three-chambered heart is:
A. Human
B. Pigeon
C. Crocodile
D. Frog
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Correct Answer: Option D

Explanation:
Amphibians like frogs have a three-chambered heart (two atria, one ventricle) with some mixing of blood. Humans and pigeons have four-chambered hearts, crocodiles uniquely have a four-chambered heart among reptiles.
This question belongs to: Science Biology
Question #1051
The technique of using radioactive probes to detect specific DNA sequences on a membrane is:
A. Southern blotting
B. Flow cytometry
C. PCR
D. ELISA
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Correct Answer: Option A

Explanation:
Southern blotting involves separation of DNA fragments by gel electrophoresis, transfer to a membrane, and hybridization with a labeled probe. PCR amplifies DNA, ELISA detects proteins, flow cytometry analyzes cells.
This question belongs to: Science Biology
Question #1052
The condition caused by excess growth hormone after puberty is:
A. Acromegaly
B. Gigantism
C. Dwarfism
D. Cretinism
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Correct Answer: Option A

Explanation:
Acromegaly is the enlargement of bones and soft tissues due to overproduction of growth hormone in adults after growth plates have fused. Gigantism occurs in childhood, dwarfism GH deficiency, cretinism congenital hypothyroidism.
This question belongs to: Science Biology
Question #1053
The type of root that is modified for food storage, as in carrot and radish, is:
A. Adventitious root
B. Taproot
C. Fibrous root
D. Prop root
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Correct Answer: Option B

Explanation:
Carrot and radish are examples of modified taproots where the primary root swells to store food. Prop roots are adventitious (banyan), fibrous roots are fine and branching (grasses), adventitious arise from stems/leaves.
This question belongs to: Science Biology
Question #1054
The hormone that stimulates the gall bladder to release bile is:
A. Motilin
B. Gastrin
C. Cholecystokinin (CCK)
D. Secretin
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Correct Answer: Option C

Explanation:
CCK, released from the duodenum in response to fats, stimulates contraction of the gall bladder and release of bile, and also stimulates pancreatic enzyme secretion. Gastrin stimulates HCl, secretin bicarbonate, motilin GI motility.
This question belongs to: Science Biology
Question #1055
The organ that produces clotting factors and albumin is the:
A. Spleen
B. Pancreas
C. Kidney
D. Liver
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Correct Answer: Option D

Explanation:
The liver synthesizes most plasma proteins, including albumin (osmotic pressure) and clotting factors (I, II, VII, IX, X). The kidneys produce erythropoietin and active vitamin D, pancreas digestive enzymes, spleen filters.
This question belongs to: Science Biology
Question #1056
The pigment that gives the blue color to cyanobacteria is:
A. Phycocyanin
B. Carotene
C. Phycoerythrin
D. Chlorophyll a
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Correct Answer: Option A

Explanation:
Phycocyanin is a blue phycobiliprotein pigment present in cyanobacteria (blue-green algae), along with chlorophyll a. Phycoerythrin is red, carotene orange. Phycobilins are accessory pigments that capture light energy for photosynthesis.
This question belongs to: Science Biology
Question #1057
The scientist who proposed the 'lock and key' model was:
A. Hans Krebs
B. Daniel Koshland
C. Peter Mitchell
D. Emil Fischer
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Correct Answer: Option D

Explanation:
Emil Fischer proposed the lock-and-key model in 1894 to explain enzyme specificity. Koshland modified it to induced fit. Krebs discovered the citric acid cycle, Mitchell chemiosmosis.
This question belongs to: Science Biology
Question #1058
The vitamin that acts as a coenzyme in transamination reactions is:
A. Niacin
B. Riboflavin
C. Pyridoxine (B₆)
D. Thiamine
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Correct Answer: Option C

Explanation:
Pyridoxal phosphate (PLP), the active form of vitamin B₆, is a coenzyme for transaminases (ALT, AST), decarboxylases, and other enzymes in amino acid metabolism. Thiamine in decarboxylation of keto acids, riboflavin in redox, niacin in NAD/NADP.
This question belongs to: Science Biology
Question #1059
The term used for organisms that can synthesize their own food from inorganic substances is:
A. Autotrophs
B. Parasites
C. Heterotrophs
D. Saprotrophs
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Correct Answer: Option A

Explanation:
Autotrophs (self-feeders) include photoautotrophs (plants, algae, cyanobacteria) and chemoautotrophs (some bacteria). They produce organic matter from CO₂. Heterotrophs depend on others, saprotrophs decompose dead matter, parasites live on hosts.
This question belongs to: Science Biology
Question #1060
The enzyme that removes RNA primers during DNA replication is:
A. Ligase
B. DNA polymerase III
C. Primase
D. DNA polymerase I
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Correct Answer: Option D

Explanation:
In prokaryotes, DNA polymerase I has 5'→3' exonuclease activity that removes RNA primers and fills the gaps with DNA. DNA pol III extends strands, ligase joins, primase synthesizes primer.
This question belongs to: Science Biology

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