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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Question #1581
Assertion (A): Plants wilt in salty soil.
Reason (R): High salinity causes water to move out of root cells by osmosis.
A. A false, R true.
B. Both A and R are true, but R is not the correct explanation.
C. Both A and R are true, and R is the correct explanation.
D. A true, R false.
Discuss
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Correct Answer: Option C

Explanation:
Saline soil has lower water potential, causing exosmosis from root cells, leading to plasmolysis and wilting. R correctly explains A.
This question belongs to: Science Biology
Question #1582
Which of the following statements about the lymphatic system is correct?
A. It circulates blood throughout the body.
B. It returns interstitial fluid to the bloodstream.
C. Lymph nodes produce red blood cells.
D. The thymus is a secondary lymphoid organ.
Discuss
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Correct Answer: Option B

Explanation:
The lymphatic system drains excess tissue fluid (lymph) back to the venous blood. Blood circulation is the cardiovascular system; lymph nodes filter lymph; thymus is a primary lymphoid organ.
This question belongs to: Science Biology
Question #1583
Identify the INCORRECT statement about chromosomes and genes:
A. Genes are segments of DNA that code for proteins.
B. Humans have 46 chromosomes in each somatic cell.
C. All mutations are harmful.
D. Alleles are alternative forms of a gene.
Discuss
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Correct Answer: Option C

Explanation:
Mutations can be beneficial, neutral, or harmful. They are the source of genetic variation. Other statements are correct.
This question belongs to: Science Biology
Question #1584
Consider the following statements about the nervous system:
1. The central nervous system consists of the brain and spinal cord.
2. The peripheral nervous system includes cranial and spinal nerves.
3. The autonomic nervous system controls voluntary actions.
Which of the above is/are correct?
A. 1, 2, and 3
B. 1 and 2 only
C. 1 and 3 only
D. 2 and 3 only
Discuss
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Correct Answer: Option B

Explanation:
CNS = brain + spinal cord; PNS = nerves. Autonomic NS controls involuntary actions, so 3 is incorrect. Thus, 1 and 2 are correct.
This question belongs to: Science Biology
Question #1585
Assertion (A): The leaves of cacti are reduced to spines.
Reason (R): Spines reduce water loss by transpiration.
A. Both A and R are true, but R is not the correct explanation.
B. Both A and R are true, and R is the correct explanation.
C. A false, R true.
D. A true, R false.
Discuss
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Correct Answer: Option B

Explanation:
Cacti, xerophytes, have spiny leaves to minimize surface area and transpiration, conserving water. Thus, R correctly explains A.
This question belongs to: Science Biology
Question #1586
Which of the following statements about DNA and RNA is correct?
A. Both DNA and RNA are double-stranded.
B. DNA contains ribose sugar.
C. Uracil is present in RNA instead of thymine.
D. RNA contains deoxyribose sugar.
Discuss
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Correct Answer: Option C

Explanation:
RNA uses uracil in place of thymine, and ribose sugar. DNA is double-stranded with deoxyribose and thymine. Thus, C is correct.
This question belongs to: Science Biology
Question #1587
Identify the correct statement about the human respiratory system:
A. Alveoli are surrounded by capillaries for gas exchange.
B. Inhalation is a passive process.
C. The diaphragm relaxes during inhalation.
D. The trachea branches into two bronchioles.
Discuss
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Correct Answer: Option A

Explanation:
Alveoli have a rich capillary network for O₂/CO₂ exchange. Inhalation is active (diaphragm contracts), trachea divides into two bronchi (not bronchioles).
This question belongs to: Science Biology
Question #1588
Consider the following statements about antibodies:
1. They are produced by T-lymphocytes.
2. They are also called immunoglobulins.
3. They specifically bind to antigens.
Which of the above is/are correct?
A. 1, 2, and 3
B. 1 and 3 only
C. 2 and 3 only
D. 1 and 2 only
Discuss
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Correct Answer: Option C

Explanation:
Antibodies are produced by B-lymphocytes (plasma cells), not T-cells. They are immunoglobulins that bind specific antigens. Thus, 2 and 3 are correct.
This question belongs to: Science Biology
Question #1589
Assertion (A): Pea plants were chosen by Mendel for his experiments.
Reason (R): Pea plants have many contrasting characters and are self-pollinating.
A. A false, R true.
B. Both A and R are true, and R is the correct explanation.
C. Both A and R are true, but R is not the correct explanation.
D. A true, R false.
Discuss
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Correct Answer: Option B

Explanation:
Mendel selected Pisum sativum because it had distinct contrasting traits, was easy to cultivate, and was naturally self-pollinating, allowing controlled crosses. R explains A correctly.
This question belongs to: Science Biology
Question #1590
Which of the following statements about sex determination in humans is correct?
A. Males produce two types of sperm: X-bearing and Y-bearing.
B. Sex is determined by autosomal chromosomes.
C. Females have XY chromosomes.
D. The mother’s egg determines the sex of the child.
Discuss
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Correct Answer: Option A

Explanation:
Human males are XY and produce X and Y sperm; females are XX. The sperm determines sex. Thus, C is correct.
This question belongs to: Science Biology
Question #1591
Identify the INCORRECT statement about the endocrine system:
A. The pancreas produces insulin and glucagon.
B. The thyroid gland produces thyroxine.
C. The pituitary gland controls other endocrine glands.
D. The adrenal medulla produces cortisol.
Discuss
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Correct Answer: Option D

Explanation:
The adrenal medulla produces adrenaline and noradrenaline; cortisol is produced by the adrenal cortex. So B is incorrect.
This question belongs to: Science Biology
Question #1592
Consider the following statements about ecosystem:
1. Producers are autotrophs.
2. Consumers are heterotrophs.
3. Decomposers recycle nutrients.
Which of the above is/are correct?
A. 1 and 3 only
B. 1, 2, and 3
C. 2 and 3 only
D. 1 and 2 only
Discuss
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Correct Answer: Option B

Explanation:
All are correct: producers make food, consumers eat other organisms, decomposers break down dead matter and return nutrients.
This question belongs to: Science Biology
Question #1593
Assertion (A): Humans are ureotelic.
Reason (R): The liver converts ammonia to urea, which is excreted in urine.
A. Both A and R are true, and R is the correct explanation.
B. A true, R false.
C. Both A and R are true, but R is not the correct explanation.
D. A false, R true.
Discuss
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Correct Answer: Option A

Explanation:
Ammonia, toxic, is converted to less toxic urea in the liver via the urea cycle, then excreted by kidneys. Thus, humans excrete urea (ureotelic). R explains A.
This question belongs to: Science Biology
Question #1594
Which of the following statements about the cell cycle is correct?
A. Mitosis is the longest phase of the cell cycle.
B. The S phase is when DNA synthesis occurs.
C. Cytokinesis occurs before prophase.
D. DNA replication occurs during the G2 phase.
Discuss
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Correct Answer: Option B

Explanation:
In the S (synthesis) phase of interphase, DNA is replicated. G2 is preparation for mitosis. Interphase is the longest. Cytokinesis follows telophase.
This question belongs to: Science Biology
Question #1595
Identify the correct statement about mutations:
A. Silent mutations always change the protein sequence.
B. Mutations can be inherited if they occur in germ cells.
C. Mutations cannot be spontaneous.
D. All mutations are caused by radiation.
Discuss
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Correct Answer: Option B

Explanation:
Germline mutations can be passed to offspring. Mutations can be spontaneous or induced; silent mutations do not change the amino acid sequence.
This question belongs to: Science Biology
Question #1596
Consider the following statements about the liver:
1. It stores glycogen.
2. It secretes bile.
3. It produces insulin.
Which of the above is/are correct?
A. 1 and 3 only
B. 1 and 2 only
C. 2 and 3 only
D. 1, 2, and 3
Discuss
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Correct Answer: Option B

Explanation:
The liver stores glycogen and produces bile. Insulin is produced by the beta cells of the pancreas. So 3 is incorrect.
This question belongs to: Science Biology
Question #1597
Assertion (A): ATP is the energy currency of the cell.
Reason (R): It stores energy in its high-energy phosphate bonds.
A. Both A and R are true, and R is the correct explanation.
B. A false, R true.
C. A true, R false.
D. Both A and R are true, but R is not the correct explanation.
Discuss
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Correct Answer: Option A

Explanation:
ATP has two high-energy anhydride bonds that release energy when hydrolyzed, driving cellular processes. R correctly explains A.
This question belongs to: Science Biology
Question #1598
Which of the following statements about ecological pyramids is correct?
A. The pyramid of biomass is always upright in terrestrial ecosystems.
B. The pyramid of energy is always upright.
C. The pyramid of numbers is always upright.
D. The pyramid of energy can be inverted.
Discuss
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Correct Answer: Option B

Explanation:
Energy pyramids are always upright because energy decreases at higher trophic levels. Pyramids of numbers and biomass can be inverted (e.g., tree ecosystem, aquatic).
This question belongs to: Science Biology
Question #1599
Identify the INCORRECT statement about the human ear:
A. The cochlea is responsible for balance.
B. The eardrum vibrates in response to sound waves.
C. The ossicles amplify sound vibrations.
D. The auditory nerve carries impulses to the brain.
Discuss
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Correct Answer: Option A

Explanation:
The cochlea is for hearing; the vestibular apparatus (semicircular canals, utricle, saccule) is for balance. So C is incorrect.
This question belongs to: Science Biology
Question #1600
Consider the following statements about carbohydrates:
1. Glucose is a monosaccharide.
2. Sucrose is a disaccharide.
3. Cellulose is a storage polysaccharide in plants.
Which of the above is/are correct?
A. 1 and 3 only
B. 1, 2, and 3
C. 1 and 2 only
D. 2 and 3 only
Discuss
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Correct Answer: Option C

Explanation:
Glucose is a monosaccharide, sucrose a disaccharide (glucose+fructose). Cellulose is a structural polysaccharide, not storage; starch is storage. So 3 is incorrect.
This question belongs to: Science Biology

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