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 32 of 103
Question #621
The substance that makes the fungal cell wall rigid is:
A. Peptidoglycan
B. Lignin
C. Chitin
D. Cellulose
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Correct Answer: Option C

Explanation:
Fungal cell walls contain chitin, a strong, flexible polysaccharide also found in arthropod exoskeletons. Cellulose is in plant walls, peptidoglycan in bacterial walls, lignin in secondary plant walls. Chitin provides structural support and protection against environmental stress.
This question belongs to: Science Biology
Question #622
The human disease characterized by the formation of amyloid plaques in the brain is:
A. Multiple sclerosis
B. Epilepsy
C. Parkinson's disease
D. Alzheimer's disease
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Correct Answer: Option D

Explanation:
Alzheimer's disease is a progressive neurodegenerative disorder marked by extracellular amyloid-beta plaques and intracellular neurofibrillary tangles of tau protein, leading to memory loss and cognitive decline. Parkinson's involves dopamine neuron loss, multiple sclerosis demyelination, epilepsy seizures.
This question belongs to: Science Biology
Question #623
The process of formation of blood cells is called:
A. Hemostasis
B. Hematopoiesis
C. Hemolysis
D. Hematuria
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Correct Answer: Option B

Explanation:
Hematopoiesis is the production of formed elements of blood (red cells, white cells, platelets) from hematopoietic stem cells in the bone marrow. Hemolysis is RBC destruction, hemostasis is stopping bleeding, hematuria is blood in urine. Erythropoietin stimulates RBC production.
This question belongs to: Science Biology
Question #624
The type of root that develops from any part of the plant other than the radicle is called:
A. Primary root
B. Taproot
C. Fibrous root
D. Adventitious root
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Correct Answer: Option D

Explanation:
Adventitious roots arise from stem, leaf, or other non-root tissues, unlike taproots and fibrous roots that develop from the radicle. Examples: prop roots of banyan, stilt roots of maize, aerial roots of orchids. They can serve support, aeration, or additional absorption.
This question belongs to: Science Biology
Question #625
The part of the neuron that is usually myelinated and conducts impulses away from the cell body is the:
A. Synapse
B. Cell body
C. Dendrite
D. Axon
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Correct Answer: Option D

Explanation:
The axon is a long, slender projection of the neuron that carries nerve impulses (action potentials) away from the soma to other neurons, muscles, or glands. Axons are often insulated by a myelin sheath. Dendrites receive signals, the cell body contains the nucleus, the synapse is the junction.
This question belongs to: Science Biology
Question #626
The technique used to measure the amount of light absorbed by a substance is:
A. Spectrophotometry
B. Chromatography
C. Electrophoresis
D. Centrifugation
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Correct Answer: Option A

Explanation:
Spectrophotometry quantifies the concentration of a substance by measuring the absorbance of light at specific wavelengths. Chromatography separates mixtures, electrophoresis separates charged molecules, centrifugation separates by density/size. Spectrophotometers are widely used in biochemical and clinical labs.
This question belongs to: Science Biology
Question #627
The bacterium used in the production of Swiss cheese (for holes) is:
A. Propionibacterium shermanii
B. Lactobacillus acidophilus
C. Penicillium roqueforti
D. Streptococcus thermophilus
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Correct Answer: Option A

Explanation:
Propionibacterium shermanii ferments lactate to propionic acid, acetic acid, and CO₂ during cheese ripening; the CO₂ forms the characteristic holes (eyes) in Swiss cheese. Lactobacillus and Streptococcus are starter cultures for acid production, Penicillium roqueforti is used for blue cheese.
This question belongs to: Science Biology
Question #628
The process of protein synthesis on ribosomes is called:
A. Translation
B. Transformation
C. Transcription
D. Replication
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Correct Answer: Option A

Explanation:
Translation is the ribosome-mediated synthesis of a polypeptide chain according to the mRNA template. tRNA molecules bring amino acids, and peptide bonds form. Replication duplicates DNA, transcription synthesizes RNA from DNA, transformation is genetic uptake by bacteria.
This question belongs to: Science Biology
Question #629
The scientist who discovered the antibiotic streptomycin was:
A. Louis Pasteur
B. Selman Waksman
C. Robert Koch
D. Alexander Fleming
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Correct Answer: Option B

Explanation:
Selman Waksman and his team isolated streptomycin from the soil bacterium Streptomyces griseus in 1943. It was the first effective antibiotic against tuberculosis. Fleming discovered penicillin, Pasteur developed rabies vaccine, Koch identified tuberculosis bacillus. Waksman coined the term 'antibiotic'.
This question belongs to: Science Biology
Question #630
The membrane that lines the thoracic cavity and covers the lungs is the:
A. Meninges
B. Pericardium
C. Peritoneum
D. Pleura
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Correct Answer: Option D

Explanation:
The pleura consists of visceral pleura (adhering to lungs) and parietal pleura (lining chest wall), with pleural fluid between them reducing friction during breathing. Pericardium surrounds the heart, peritoneum lines the abdominal cavity, meninges cover the brain and spinal cord.
This question belongs to: Science Biology
Question #631
The hormone that stimulates milk ejection during breastfeeding is:
A. Estrogen
B. Progesterone
C. Oxytocin
D. Prolactin
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Correct Answer: Option C

Explanation:
Oxytocin, released from the posterior pituitary in response to suckling, causes contraction of myoepithelial cells around mammary alveoli, forcing milk into ducts (let-down reflex). Prolactin stimulates milk synthesis. Estrogen and progesterone inhibit milk secretion during pregnancy.
This question belongs to: Science Biology
Question #632
The process of removing the anthers from a bisexual flower to prevent self-pollination is called:
A. Tagging
B. Hybridization
C. Bagging
D. Emasculation
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Correct Answer: Option D

Explanation:
Emasculation is the removal of stamens (anthers) from a bisexual flower before anthesis to prevent self-fertilization in artificial hybridization experiments. Bagging covers the flower to prevent contamination, tagging labels the cross. Emasculation ensures that only desired pollen is used.
This question belongs to: Science Biology
Question #633
The part of the seed that emerges first during germination and develops into the root is the:
A. Plumule
B. Cotyledon
C. Radicle
D. Hypocotyl
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Correct Answer: Option C

Explanation:
The radicle is the embryonic root, and it is the first structure to emerge from the seed coat during germination, growing downward to anchor the plant and absorb water. The plumule becomes the shoot, hypocotyl connects radicle to cotyledons, cotyledons are seed leaves.
This question belongs to: Science Biology
Question #634
The element that is the central atom in the vitamin B₁₂ (cobalamin) molecule is:
A. Magnesium
B. Zinc
C. Iron
D. Cobalt
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Correct Answer: Option D

Explanation:
Vitamin B₁₂ contains a cobalt ion at the center of its corrin ring structure, hence the name cobalamin. It is essential for DNA synthesis and nervous system function. Iron is in heme, magnesium in chlorophyll, zinc in many enzymes. B₁₂ is unique in having a metal-carbon bond.
This question belongs to: Science Biology
Question #635
The form in which glucose is stored in liver and muscle cells is:
A. Starch
B. Cellulose
C. Sucrose
D. Glycogen
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Correct Answer: Option D

Explanation:
Glycogen is a highly branched polysaccharide of glucose, the storage form in animals, found mainly in the liver and skeletal muscles. Starch is the plant equivalent. Cellulose is structural in plants, sucrose is a disaccharide. Glycogen can be rapidly mobilized to maintain blood glucose.
This question belongs to: Science Biology
Question #636
The technique used to determine the nucleotide sequence of DNA is:
A. DNA sequencing
B. Southern blotting
C. PCR
D. Gel electrophoresis
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Correct Answer: Option A

Explanation:
DNA sequencing determines the precise order of nucleotides in a DNA fragment. Sanger's dideoxy chain-termination method and next-generation sequencing are common. PCR amplifies DNA, gel electrophoresis separates by size, Southern blotting detects specific sequences. Sequencing is fundamental in genomics.
This question belongs to: Science Biology
Question #637
The organism that causes 'black rust' of wheat is a:
A. Fungus
B. Bacterium
C. Mycoplasma
D. Virus
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Correct Answer: Option A

Explanation:
Black stem rust of wheat is caused by the fungus Puccinia graminis tritici, a basidiomycete that produces reddish-brown uredospores and black teliospores. It requires barberry as an alternate host. It is a major disease causing significant crop losses.
This question belongs to: Science Biology
Question #638
The fluid that surrounds the brain and spinal cord is:
A. Lymph
B. Cerebrospinal fluid
C. Synovial fluid
D. Pleural fluid
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Correct Answer: Option B

Explanation:
Cerebrospinal fluid (CSF) is a clear fluid produced by the choroid plexus in the ventricles of the brain. It cushions the CNS, provides buoyancy, removes waste, and maintains chemical stability. Synovial fluid is in joints, pleural fluid in chest cavity, lymph in lymphatic vessels.
This question belongs to: Science Biology
Question #639
The pigment present in rod cells of the retina that is responsible for vision in dim light is:
A. Rhodopsin
B. Melanin
C. Hemoglobin
D. Iodopsin
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Correct Answer: Option A

Explanation:
Rhodopsin (visual purple) is a photopigment in rod cells consisting of opsin and retinal (from vitamin A). It bleaches upon absorbing light, initiating signal transduction for vision in low light. Cone cells contain iodopsin for color vision. Melanin is skin pigment, hemoglobin carries oxygen.
This question belongs to: Science Biology
Question #640
The bacterium that causes peptic ulcers is:
A. Vibrio cholerae
B. Helicobacter pylori
C. Salmonella enterica
D. Escherichia coli
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Correct Answer: Option B

Explanation:
Helicobacter pylori colonizes the gastric mucosa, causing chronic inflammation, peptic ulcers, and increasing the risk of gastric cancer. It survives stomach acid by secreting urease, which converts urea to ammonia, neutralizing acid. Treatment involves antibiotics and acid suppressants.
This question belongs to: Science Biology

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