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 19 of 103
Question #361
Which of the following tissues provides mechanical strength and flexibility to plant organs?
A. Parenchyma
B. Collenchyma
C. Sclerenchyma
D. Xylem
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Correct Answer: Option B

Explanation:
Collenchyma is a simple permanent tissue with living cells, unevenly thickened primary cell walls (cellulose and pectin), providing mechanical support and flexibility, especially in young stems and leaf petioles. Parenchyma is for storage and metabolism, sclerenchyma is dead, rigid with lignified walls, xylem conducts water.
This question belongs to: Science Biology
Question #362
The movement of molecules from a region of higher concentration to a region of lower concentration without a membrane is:
A. Simple diffusion
B. Osmosis
C. Facilitated diffusion
D. Active transport
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Correct Answer: Option A

Explanation:
Simple diffusion is the passive movement of molecules (e.g., O₂, CO₂) from high to low concentration without the need for a membrane protein or energy. Osmosis specifically refers to water movement across a semipermeable membrane. Facilitated diffusion uses channel or carrier proteins but no energy. Active transport requires energy (ATP).
This question belongs to: Science Biology
Question #363
The structure that connects the fetus to the uterine wall and allows nutrient exchange is the:
A. Umbilical cord
B. Placenta
C. Amnion
D. Yolk sac
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Correct Answer: Option B

Explanation:
The placenta is a temporary organ formed by both fetal (chorion) and maternal (endometrium) tissues. It facilitates the exchange of oxygen, nutrients, and waste products between mother and fetus, and produces hormones (e.g., hCG, progesterone). The umbilical cord connects the fetus to the placenta. The amnion surrounds the embryo.
This question belongs to: Science Biology
Question #364
Which of the following diseases can be prevented by the BCG vaccine?
A. Tuberculosis
B. Poliomyelitis
C. Measles
D. Diphtheria
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Correct Answer: Option A

Explanation:
BCG (Bacille Calmette-Guérin) is a live attenuated vaccine derived from Mycobacterium bovis, used against tuberculosis, primarily in children. Polio vaccine (OPV/IPV) prevents poliomyelitis, DPT prevents diphtheria, pertussis, tetanus, and MMR prevents measles, mumps, rubella. BCG is often administered at birth in TB-endemic countries.
This question belongs to: Science Biology
Question #365
The inorganic molecule that is a cofactor for many enzymes, including DNA polymerase, and is essential for nerve function is:
A. Magnesium
B. Iron
C. Zinc
D. Calcium
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Correct Answer: Option A

Explanation:
Magnesium (Mg²⁺) is a crucial cofactor for ATP-utilizing enzymes, including DNA polymerase, and is essential for nucleic acid structure, nerve impulse transmission, and muscle contraction. Iron is for hemoglobin, zinc for many enzymes and transcription factors, calcium for bones and signaling. Magnesium is the central atom in chlorophyll.
This question belongs to: Science Biology
Question #366
Which characteristic is exclusive to living organisms and not observed in non-living entities?
A. Increase in mass
B. Magnetism
C. Consciousness
D. Crystallization
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Correct Answer: Option C

Explanation:
Consciousness is the defining property of living organisms, allowing them to sense and respond to stimuli. Non-living objects can increase in mass (e.g., crystal growth), crystallize, or exhibit magnetism, but they lack consciousness. Reproduction and metabolism are also key characteristics, but consciousness is the most fundamental feature. Thus, only living things possess this ability.
This question belongs to: Science Biology
Question #367
The scientific name of the lion is:
A. Canis lupus
B. Felis catus
C. Panthera tigris
D. Panthera leo
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Correct Answer: Option D

Explanation:
Panthera leo is the binomial name for the lion. Panthera tigris is the tiger, Felis catus is the domestic cat, and Canis lupus is the grey wolf. The genus Panthera includes roaring cats: lion, tiger, jaguar, and leopard. Binomial nomenclature uses a capitalized genus and lowercase species epithet, both italicized.
This question belongs to: Science Biology
Question #368
The branch of biology dealing with the study of algae is called:
A. Bryology
B. Pteridology
C. Phycology
D. Mycology
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Correct Answer: Option C

Explanation:
Phycology (algology) is the study of algae, which are photosynthetic eukaryotic organisms ranging from unicellular to multicellular forms. Mycology deals with fungi, bryology with mosses and liverworts, and pteridology with ferns. Algae include green algae, red algae, brown algae, and diatoms, and are important primary producers in aquatic ecosystems.
This question belongs to: Science Biology
Question #369
Which of the following is an example of a non-living thing that can grow by accretion?
A. Mushroom
B. Bacteria
C. Coral reef
D. Mango tree
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Correct Answer: Option C

Explanation:
Coral reefs grow by accumulation of calcium carbonate skeletons secreted by living coral polyps, but the reef structure itself is non-living. It increases in mass externally (accretion). Mushrooms, mango trees, and bacteria exhibit intrinsic growth by cell division, characteristic of living organisms. Thus, coral reef growth is non-living accumulation.
This question belongs to: Science Biology
Question #370
Who is known as the 'Father of Botany'?
A. Theophrastus
B. Aristotle
C. Darwin
D. Linnaeus
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Correct Answer: Option A

Explanation:
Theophrastus (c. 371–287 BCE), a student of Aristotle, is called the Father of Botany for his works 'Historia Plantarum' and 'De Causis Plantarum', in which he classified and described hundreds of plants. Aristotle is the Father of Zoology. Linnaeus developed binomial nomenclature. Darwin proposed natural selection. Theophrastus laid the early foundations of plant science.
This question belongs to: Science Biology
Question #371
Which of the following cell organelles is capable of self-replication?
A. Rough endoplasmic reticulum
B. Golgi apparatus
C. Lysosome
D. Mitochondria
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Correct Answer: Option D

Explanation:
Mitochondria and chloroplasts contain their own DNA and ribosomes (70S) and can replicate by binary fission, a feature supporting their endosymbiotic origin. Golgi apparatus, lysosomes, and rough ER cannot self-replicate; they are part of the endomembrane system and arise from pre-existing membranes. Mitochondria are thus semi-autonomous organelles.
This question belongs to: Science Biology
Question #372
In which phase of mitosis does the nuclear envelope reform around the chromosomes?
A. Prophase
B. Anaphase
C. Telophase
D. Metaphase
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Correct Answer: Option C

Explanation:
During telophase, the chromatids reach the poles, decondense, and the nuclear envelope reassembles around each set, forming two daughter nuclei. The spindle disappears. Prophase involves nuclear envelope breakdown, metaphase aligns chromosomes, and anaphase separates chromatids. Cytokinesis often overlaps with telophase, dividing the cytoplasm.
This question belongs to: Science Biology
Question #373
The site of protein synthesis in a cell is the:
A. Mitochondria
B. Ribosome
C. Nucleus
D. Golgi apparatus
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Correct Answer: Option B

Explanation:
Ribosomes are the molecular machines where mRNA is translated into a polypeptide chain (protein). They consist of two subunits (large and small) and are found free in the cytoplasm or attached to rough ER. The nucleus stores genetic information, Golgi modifies and packages proteins, mitochondria produce ATP. Thus, protein synthesis occurs at ribosomes.
This question belongs to: Science Biology
Question #374
Assertion (A): Plant cells possess a large central vacuole. Reason (R): The vacuole stores waste products and maintains turgor pressure.
A. Both A and R are true, and R is the correct explanation.
B. Both A and R are true, but R is not the correct explanation.
C. A is true, but R is false.
D. A is false, but R is true.
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Correct Answer: Option A

Explanation:
Mature plant cells contain a large central vacuole that stores water, ions, pigments, and waste products, and is critical for maintaining turgor pressure against the cell wall, providing structural support. The vacuole can occupy up to 90% of cell volume. The reason correctly explains the function of the vacuole, so both statements are true and linked.
This question belongs to: Science Biology
Question #375
Which of the following is absent in a prokaryotic cell?
A. Ribosomes
B. Nuclear membrane
C. Plasma membrane
D. Nucleoid
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Correct Answer: Option B

Explanation:
Prokaryotes lack a true nucleus and nuclear membrane; their genetic material is concentrated in a nucleoid region. They possess ribosomes (70S), a plasma membrane, and usually a cell wall. The absence of membrane-bound organelles is a defining feature distinguishing them from eukaryotes. Thus, the nuclear membrane is absent.
This question belongs to: Science Biology
Question #376
During glycolysis, glucose is converted into:
A. Citric acid
B. Acetyl CoA
C. Pyruvate
D. Ethanol
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Correct Answer: Option C

Explanation:
Glycolysis, occurring in the cytoplasm, breaks down one molecule of glucose (6C) into two molecules of pyruvate (3C), producing a net gain of 2 ATP and 2 NADH. This is the first step of both aerobic and anaerobic respiration. Pyruvate then enters the mitochondria for further oxidation in the Krebs cycle if oxygen is available.
This question belongs to: Science Biology
Question #377
The process by which a cell engulfs a solid particle is termed:
A. Osmosis
B. Phagocytosis
C. Pinocytosis
D. Exocytosis
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Correct Answer: Option B

Explanation:
Phagocytosis ('cell eating') is a type of endocytosis where the cell membrane extends pseudopodia around a solid particle (e.g., bacterium) and engulfs it into a phagosome, which later fuses with a lysosome for digestion. Pinocytosis is 'cell drinking' of fluids. Exocytosis is secretion. Osmosis is water movement across a membrane.
This question belongs to: Science Biology
Question #378
Which of the following is a defining characteristic of meiosis?
A. Involves one division
B. Crossing over occurs
C. Produces identical daughter cells
D. Produces diploid cells
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Correct Answer: Option B

Explanation:
Meiosis is characterized by two successive divisions producing haploid gametes, and involves genetic recombination through crossing over during prophase I. Mitosis produces identical diploid cells with one division. Crossing over and independent assortment generate genetic variation. Therefore, crossing over is unique to meiosis.
This question belongs to: Science Biology
Question #379
The organelle involved in lipid metabolism and detoxification is:
A. Rough ER
B. Lysosome
C. Golgi apparatus
D. Smooth ER
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Correct Answer: Option D

Explanation:
Smooth endoplasmic reticulum (SER) lacks ribosomes and is involved in synthesis of lipids, steroid hormones, and detoxification of drugs and toxins via cytochrome P450 enzymes. Rough ER is for protein synthesis, Golgi for packaging, lysosomes for digestion. SER is abundant in liver and gonadal cells.
This question belongs to: Science Biology
Question #380
In the five-kingdom classification, eukaryotic unicellular organisms with various modes of nutrition are placed in:
A. Plantae
B. Protista
C. Fungi
D. Monera
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Correct Answer: Option B

Explanation:
Kingdom Protista includes diverse unicellular eukaryotes like protozoans, slime molds, and unicellular algae. They can be autotrophic, heterotrophic, or mixotrophic. Monera contains prokaryotes, Fungi are multicellular eukaryotes (except yeast) with absorptive nutrition, Plantae are multicellular autotrophs. Protista is a paraphyletic group in modern cladistics but used in the five-kingdom system.
This question belongs to: Science Biology

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