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 86 of 103
Question #1701
Consider statements about the cell wall: 1. Plant cell walls are made of cellulose. 2. Fungal cell walls contain chitin. 3. Bacterial cell walls contain peptidoglycan. Which 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 A

Explanation:
The cell wall composition varies across kingdoms. Plant cell walls are primarily composed of cellulose, a complex polysaccharide. Fungal cell walls are characterized by the presence of chitin, providing structural rigidity. Bacterial cell walls consist of peptidoglycan (murein). Therefore, all three statements accurately describe the cell wall composition of these respective groups.
This question belongs to: Science Biology
Question #1702
Consider statements about the nucleus: 1. It is bounded by a single membrane. 2. It contains the nucleolus. 3. Nuclear pores allow RNA export. Which 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 D

Explanation:
The nucleus is bounded by a double membrane called the nuclear envelope, not a single membrane. It houses the nucleolus, which is the site of ribosomal RNA synthesis. The nuclear envelope is perforated by nuclear pores that regulate the bidirectional transport of molecules, including the export of mRNA to the cytoplasm. Thus, statements 2 and 3 are correct.
This question belongs to: Science Biology
Question #1703
Consider statements about the endoplasmic reticulum: 1. Rough ER has ribosomes attached. 2. Smooth ER synthesizes lipids. 3. Rough ER is involved in detoxification. Which are correct?
A. 1 and 2 only
B. 1, 2 and 3
C. 1 and 3 only
D. 2 and 3 only
Discuss
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Correct Answer: Option A

Explanation:
The rough endoplasmic reticulum (RER) has ribosomes attached to its cytoplasmic surface, making it appear rough, and is primarily involved in protein synthesis and modification. The smooth endoplasmic reticulum (SER) lacks ribosomes and is the major site for lipid synthesis and detoxification of drugs. Statement 3 is incorrect as detoxification is a function of SER.
This question belongs to: Science Biology
Question #1704
Consider statements about the Golgi apparatus: 1. It has cis and trans faces. 2. It modifies and packages proteins. 3. It synthesizes ATP. Which are correct?
A. 2 and 3 only
B. 1, 2 and 3
C. 1 and 3 only
D. 1 and 2 only
Discuss
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Correct Answer: Option D

Explanation:
The Golgi apparatus consists of flattened membranous sacs called cisternae. It has a forming cis face near the ER and a maturing trans face directed towards the plasma membrane. It primarily modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles. It does not synthesize ATP; that is the function of mitochondria.
This question belongs to: Science Biology
Question #1705
Consider statements about ribosomes: 1. They are non-membranous organelles. 2. Prokaryotic ribosomes are 80S. 3. They are the site of protein synthesis. Which are correct?
A. 2 and 3 only
B. 1 and 3 only
C. 1 and 2 only
D. 1, 2 and 3
Discuss
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Correct Answer: Option B

Explanation:
Ribosomes are dense, spherical, non-membranous structures composed of RNA and proteins. They are the cellular factories for protein synthesis. Prokaryotic ribosomes are 70S (50S + 30S subunits), while eukaryotic cytoplasmic ribosomes are 80S (60S + 40S subunits). Therefore, statements 1 and 3 are correct, but statement 2 is false.
This question belongs to: Science Biology
Question #1706
Consider statements about the cytoskeleton: 1. Microtubules are made of tubulin. 2. Microfilaments are made of actin. 3. Intermediate filaments are made of cellulose. Which 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 D

Explanation:
The cytoskeleton provides structural support and is composed of three main types of filaments. Microtubules are hollow tubes made of the protein tubulin. Microfilaments are solid rods composed of actin. Intermediate filaments are made of various fibrous proteins like keratin, not cellulose, which is a plant cell wall component. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1707
Consider statements about cell division: 1. Mitosis results in four daughter cells. 2. Meiosis involves two successive divisions. 3. Crossing over occurs in mitosis. Which are correct?
A. 1, 2 and 3
B. 2 only
C. 1 and 3 only
D. 1 and 2 only
Discuss
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Correct Answer: Option B

Explanation:
Mitosis is an equational division resulting in two genetically identical diploid daughter cells, not four. Meiosis is a reductional division involving two successive stages, meiosis I and meiosis II, producing four haploid cells. Crossing over, the exchange of genetic material, occurs exclusively during the pachytene stage of prophase I in meiosis, not in mitosis. Only statement 2 is correct.
This question belongs to: Science Biology
Question #1708
Consider statements about five kingdom classification: 1. Monera includes all prokaryotes. 2. Protista includes unicellular eukaryotes. 3. Fungi are photosynthetic autotrophs. Which are correct?
A. 1, 2 and 3
B. 2 and 3 only
C. 1 and 2 only
D. 1 and 3 only
Discuss
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Correct Answer: Option C

Explanation:
R.H. Whittaker's five kingdom classification places all prokaryotic organisms in Kingdom Monera and unicellular eukaryotes in Kingdom Protista. Fungi are a distinct kingdom characterized by heterotrophic nutrition, primarily saprophytic or parasitic, and possess chitinous cell walls. They are not photosynthetic autotrophs. Therefore, statements 1 and 2 are correct, while 3 is incorrect.
This question belongs to: Science Biology
Question #1709
Consider statements about viruses: 1. They possess both DNA and RNA. 2. They are obligate intracellular parasites. 3. They can be crystallized. Which are correct?
A. 1 and 2 only
B. 1 and 3 only
C. 1, 2 and 3
D. 2 and 3 only
Discuss
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Correct Answer: Option D

Explanation:
Viruses are unique entities containing either DNA or RNA, never both simultaneously, enclosed in a protein capsid. They are obligate intracellular parasites, requiring a host cell's machinery to replicate. Despite being biological entities, they can be crystallized like chemicals, as demonstrated by W.M. Stanley with TMV. Thus, statements 2 and 3 are correct.
This question belongs to: Science Biology
Question #1710
Consider statements about bryophytes: 1. They are called amphibians of the plant kingdom. 2. They possess vascular tissues. 3. They require water for fertilization. Which are correct?
A. 2 and 3 only
B. 1 and 3 only
C. 1, 2 and 3
D. 1 and 2 only
Discuss
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Correct Answer: Option B

Explanation:
Bryophytes are termed amphibians of the plant kingdom because they live on land but require water for the swimming of male gametes to reach the egg during fertilization. They lack true vascular tissues (xylem and phloem), which first appear in pteridophytes. Therefore, statements 1 and 3 are correct, but statement 2 is false.
This question belongs to: Science Biology
Question #1711
Consider statements about gymnosperms: 1. They bear naked seeds. 2. They are mostly evergreen trees. 3. They undergo double fertilization. Which are correct?
A. 1 and 3 only
B. 2 and 3 only
C. 1 and 2 only
D. 1, 2 and 3
Discuss
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Correct Answer: Option C

Explanation:
Gymnosperms are seed-producing plants where the ovules are not enclosed in an ovary; hence, the seeds are naked. They are predominantly perennial, evergreen, woody trees like pines and cedars. Double fertilization and the formation of triploid endosperm are unique characteristics of angiosperms, not gymnosperms. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1712
Consider statements about angiosperms: 1. They have enclosed seeds. 2. They exhibit double fertilization. 3. All angiosperms are trees. Which are correct?
A. 1, 2 and 3
B. 1 and 3 only
C. 1 and 2 only
D. 2 and 3 only
Discuss
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Correct Answer: Option C

Explanation:
Angiosperms are flowering plants where seeds are enclosed within a mature ovary (fruit). They are characterized by double fertilization, where one male gamete fuses with the egg and the other with the secondary nucleus. They exhibit immense diversity in habit, ranging from tiny aquatic Wolffia to massive trees, so not all are trees. Statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1713
Consider statements about plant stems: 1. Nodes are the regions where leaves arise. 2. Internodes are the regions between nodes. 3. All stems grow underground. Which are correct?
A. 2 and 3 only
B. 1 and 2 only
C. 1, 2 and 3
D. 1 and 3 only
Discuss
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Correct Answer: Option B

Explanation:
The stem is characterized by the presence of nodes, which are the junctions where leaves and buds arise, and internodes, the segments between two nodes. While some stems are modified to grow underground (like potatoes or onions) for storage or perennation, the primary and most common form of the stem is aerial, growing above the ground. Statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1714
Consider statements about leaves: 1. The flat part is called the lamina. 2. Stomata are more abundant on the upper epidermis in dicots. 3. The petiole attaches the leaf to the stem. Which are correct?
A. 2 and 3 only
B. 1, 2 and 3
C. 1 and 2 only
D. 1 and 3 only
Discuss
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Correct Answer: Option D

Explanation:
A typical leaf consists of the leaf base, petiole (stalk), and lamina (leaf blade). In dicotyledonous leaves, stomata are generally more abundant on the lower epidermis to reduce excessive water loss from direct sunlight, unlike monocots where they may be equal. Therefore, statements 1 and 3 are correct, while statement 2 is incorrect.
This question belongs to: Science Biology
Question #1715
Consider statements about photosynthesis: 1. Light reactions occur in the grana. 2. The Calvin cycle occurs in the stroma. 3. Oxygen is released from CO2. Which are correct?
A. 1, 2 and 3
B. 2 and 3 only
C. 1 and 2 only
D. 1 and 3 only
Discuss
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Correct Answer: Option C

Explanation:
Photosynthesis consists of light-dependent reactions occurring in the thylakoid membranes (grana) where water is split, releasing oxygen, and light-independent reactions (Calvin cycle) occurring in the stroma where CO2 is fixed. The oxygen released during photosynthesis comes from the photolysis of water, not from carbon dioxide. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1716
Consider statements about plant hormones: 1. Auxins promote apical dominance. 2. Gibberellins cause bolting in rosette plants. 3. Cytokinins promote leaf senescence. Which 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:
Auxins produced at the apex suppress the growth of lateral buds, maintaining apical dominance. Gibberellins induce rapid stem elongation or bolting in rosette plants before flowering. Cytokinins actually delay or prevent senescence (aging) of leaves by promoting nutrient mobilization, known as the Richmond-Lang effect. Therefore, statements 1 and 2 are correct, while 3 is false.
This question belongs to: Science Biology
Question #1717
Consider statements about plant tissues: 1. Parenchyma cells have thin cell walls. 2. Collenchyma provides mechanical support. 3. Sclerenchyma cells are living at maturity. Which 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:
Parenchyma is a simple permanent tissue with thin-walled, living cells primarily involved in storage and photosynthesis. Collenchyma cells have thickened corners and provide mechanical support and flexibility to growing parts. Sclerenchyma consists of dead cells at maturity with heavily lignified walls, providing rigid strength. Thus, statements 1 and 2 are correct, but 3 is incorrect.
This question belongs to: Science Biology
Question #1718
Consider statements about human digestion: 1. Saliva contains the enzyme ptyalin. 2. The stomach secretes hydrochloric acid. 3. Bile is produced by the gall bladder. Which are correct?
A. 1 and 2 only
B. 2 and 3 only
C. 1, 2 and 3
D. 1 and 3 only
Discuss
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Correct Answer: Option A

Explanation:
Salivary glands secrete saliva containing salivary amylase (ptyalin) which begins starch digestion. The stomach's gastric glands secrete HCl, creating an acidic medium for pepsin action. Bile is synthesized continuously by the liver, stored, and concentrated in the gall bladder, but not produced by it. Therefore, statements 1 and 2 are correct, while 3 is false.
This question belongs to: Science Biology
Question #1719
Consider statements about the small intestine: 1. Villi increase the surface area for absorption. 2. The duodenum receives bile and pancreatic juice. 3. The ileum is the first part of the small intestine. Which are correct?
A. 1, 2 and 3
B. 2 and 3 only
C. 1 and 2 only
D. 1 and 3 only
Discuss
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Correct Answer: Option C

Explanation:
The small intestine is highly specialized for absorption, with circular folds, villi, and microvilli massively increasing its surface area. The duodenum is the first, shortest part, receiving the hepatopancreatic duct carrying bile and pancreatic juice. The ileum is the third and final part, connecting to the large intestine. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1720
Consider statements about the human heart: 1. The left ventricle has the thickest wall. 2. The tricuspid valve is between the left atrium and ventricle. 3. The SA node is the natural pacemaker. Which are correct?
A. 1, 2 and 3
B. 1 and 3 only
C. 1 and 2 only
D. 2 and 3 only
Discuss
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Correct Answer: Option B

Explanation:
The left ventricle has the thickest muscular wall to pump blood at high pressure into the systemic circulation. The sinoatrial (SA) node generates impulses spontaneously, acting as the natural pacemaker. The tricuspid valve is located between the right atrium and right ventricle; the bicuspid (mitral) valve is on the left side. Thus, statements 1 and 3 are correct.
This question belongs to: Science Biology

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