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 57 of 103
Question #1121
The scientist who proposed the 'germ plasm theory' to disprove Lamarckism was:
A. Alfred Wallace
B. August Weismann
C. Hugo de Vries
D. Charles Darwin
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Correct Answer: Option B

Explanation:
August Weismann proposed the germ plasm theory, stating that only changes in germ cells (sperm/egg) are inherited, not somatic changes. He cut off tails of mice for many generations but offspring had normal tails, disproving inheritance of acquired characters.
This question belongs to: Science Biology
Question #1122
The type of fruit that develops without fertilization, such as banana, is called:
A. Parthenocarpic fruit
B. True fruit
C. Aggregate fruit
D. Multiple fruit
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Correct Answer: Option A

Explanation:
Parthenocarpy is the development of fruit without fertilization, leading to seedless fruits like commercial banana, navel orange, and some grapes. It can be natural or induced by hormones. True fruits develop from ovary after fertilization.
This question belongs to: Science Biology
Question #1123
The element that is a component of the oxygen-carrying protein in blood is:
A. Magnesium
B. Phosphorus
C. Iron
D. Calcium
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Correct Answer: Option C

Explanation:
Iron is the central atom of heme in hemoglobin, essential for binding oxygen. Magnesium is in chlorophyll, calcium in bones and signaling, phosphorus in ATP and bones.
This question belongs to: Science Biology
Question #1124
The disease caused by the bacterium Salmonella typhi is:
A. Tuberculosis
B. Dysentery
C. Typhoid
D. Cholera
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Correct Answer: Option C

Explanation:
Typhoid fever is caused by Salmonella typhi, transmitted via contaminated food/water, causing high fever, abdominal pain, and rose spots. Widal test is used for diagnosis. Cholera is Vibrio cholerae, TB Mycobacterium, dysentery Shigella or Entamoeba.
This question belongs to: Science Biology
Question #1125
The process by which plants lose water in the form of liquid from hydathodes is:
A. Evaporation
B. Transpiration
C. Guttation
D. Bleeding
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Correct Answer: Option C

Explanation:
Guttation is the exudation of water droplets containing dissolved minerals from hydathodes at leaf margins, driven by root pressure when transpiration is low. Transpiration is vapor loss, bleeding is sap from cut tissue.
This question belongs to: Science Biology
Question #1126
The vitamin deficiency that leads to megaloblastic anemia is:
A. Vitamin A and K
B. Vitamin B₉ and B₁₂
C. Vitamin C and E
D. Vitamin B₁ and B₂
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Correct Answer: Option B

Explanation:
Folate (B₉) and vitamin B₁₂ are required for DNA synthesis. Deficiency leads to impaired cell division in bone marrow, producing large, immature erythrocytes (megaloblasts), causing megaloblastic anemia. Iron deficiency causes microcytic anemia.
This question belongs to: Science Biology
Question #1127
The organ that detoxifies alcohol and drugs is the:
A. Stomach
B. Liver
C. Pancreas
D. Kidney
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Correct Answer: Option B

Explanation:
The liver contains enzymes (cytochrome P450 system) that metabolize and detoxify alcohol, drugs, and other xenobiotics, converting them to less toxic, excretable forms. The kidneys excrete waste, stomach digests, pancreas secretes enzymes.
This question belongs to: Science Biology
Question #1128
The type of immunity that is present from birth is:
A. Innate immunity
B. Passive immunity
C. Active immunity
D. Adaptive immunity
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Correct Answer: Option A

Explanation:
Innate (natural) immunity is non-specific, present at birth, and provides the first line of defense. It includes physical barriers (skin), phagocytes, and chemical defenses. Adaptive immunity is acquired and specific.
This question belongs to: Science Biology
Question #1129
The technique used to amplify DNA in a test tube is:
A. Southern blotting
B. Sequencing
C. PCR
D. Gel electrophoresis
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Correct Answer: Option C

Explanation:
Polymerase chain reaction (PCR) uses Taq polymerase, primers, and thermal cycling to make millions of copies of a specific DNA sequence. Southern blotting detects DNA, electrophoresis separates, sequencing reads bases.
This question belongs to: Science Biology
Question #1130
The hormone that regulates the body's response to long-term stress is:
A. Insulin
B. Thyroxine
C. Adrenaline
D. Cortisol
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Correct Answer: Option D

Explanation:
Cortisol, from the adrenal cortex, is a glucocorticoid that increases blood glucose, suppresses inflammation, and aids the body's adaptation to prolonged stress. Adrenaline is for acute stress, thyroxine metabolism, insulin glucose.
This question belongs to: Science Biology
Question #1131
The disease caused by the fungus Aspergillus fumigatus is:
A. Aspergillosis
B. Histoplasmosis
C. Ringworm
D. Candidiasis
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Correct Answer: Option A

Explanation:
Aspergillosis is an opportunistic fungal infection, often affecting the lungs, caused by inhalation of Aspergillus spores. Candidiasis is by Candida, ringworm by dermatophytes, histoplasmosis by Histoplasma.
This question belongs to: Science Biology
Question #1132
The process by which plants produce offspring from vegetative parts is:
A. Fertilization
B. Sexual reproduction
C. Vegetative propagation
D. Pollination
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Correct Answer: Option C

Explanation:
Vegetative propagation is asexual reproduction using stems (runners, tubers), roots, or leaves, producing clones. Examples: potato (tuber), strawberry (runner). Sexual reproduction involves seeds from pollination/fertilization.
This question belongs to: Science Biology
Question #1133
The scientist who discovered the bacterium that causes tuberculosis is:
A. Louis Pasteur
B. Edward Jenner
C. Joseph Lister
D. Robert Koch
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Correct Answer: Option D

Explanation:
Robert Koch identified Mycobacterium tuberculosis as the causative agent of tuberculosis in 1882, applying his postulates. He also discovered the cholera bacillus. Pasteur worked on vaccines, Jenner smallpox, Lister antisepsis.
This question belongs to: Science Biology
Question #1134
The hormone that stimulates the release of bile from the gall bladder is:
A. Secretin
B. Cholecystokinin
C. Gastrin
D. Motilin
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Correct Answer: Option B

Explanation:
Cholecystokinin (CCK), released from the duodenal mucosa in response to fatty chyme, causes contraction of the gall bladder and relaxation of the sphincter of Oddi, releasing bile. Secretin stimulates bicarbonate.
This question belongs to: Science Biology
Question #1135
The animal that has a closed circulatory system is:
A. Earthworm
B. Snail
C. Cockroach
D. Butterfly
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Correct Answer: Option A

Explanation:
Earthworms (annelids) have a closed circulatory system with blood contained within vessels. Cockroach, snail, and butterfly have open circulatory systems where hemolymph bathes organs directly.
This question belongs to: Science Biology
Question #1136
The pigment that absorbs light in photosystem I is primarily:
A. Chlorophyll b
B. P700
C. Xanthophyll
D. P680
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Correct Answer: Option B

Explanation:
P700, a specialized chlorophyll a, is the reaction center of photosystem I, absorbing far-red light (700 nm). P680 is the reaction center of photosystem II. Chlorophyll b and xanthophyll are accessory pigments.
This question belongs to: Science Biology
Question #1137
The disease caused by the bacterium Clostridium tetani is:
A. Gangrene
B. Botulism
C. Tetanus
D. Leprosy
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Correct Answer: Option C

Explanation:
Tetanus (lockjaw) is caused by a neurotoxin produced by Clostridium tetani, which enters through wounds and causes painful muscle spasms. Botulism is C. botulinum, gas gangrene C. perfringens, leprosy M. leprae.
This question belongs to: Science Biology
Question #1138
The vitamin that is essential for the synthesis of prothrombin is:
A. Vitamin A
B. Vitamin D
C. Vitamin K
D. Vitamin C
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Correct Answer: Option C

Explanation:
Vitamin K is required for the gamma-carboxylation of prothrombin (factor II) and other clotting factors, enabling them to bind calcium and participate in coagulation. Deficiency leads to bleeding.
This question belongs to: Science Biology
Question #1139
The structure that is the site of fertilization in flowering plants is the:
A. Ovule
B. Ovary
C. Style
D. Stigma
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Correct Answer: Option A

Explanation:
Fertilization occurs within the ovule, where the pollen tube delivers two sperm cells. One fuses with the egg to form the zygote, the other with polar nuclei to form endosperm. The stigma receives pollen, style is the path, ovary contains ovules.
This question belongs to: Science Biology
Question #1140
The technique used to analyze the transcriptome of a cell is:
A. Transcriptomics
B. Proteomics
C. Metabolomics
D. Genomics
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Correct Answer: Option A

Explanation:
Transcriptomics studies the complete set of RNA transcripts (transcriptome) produced by the genome under specific conditions. It often uses microarrays or RNA-seq. Genomics is DNA, proteomics proteins, metabolomics metabolites.
This question belongs to: Science Biology

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