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 92 of 103
Question #1821
Consider statements about microorganisms: 1. Lactobacillus is used in curd formation. 2. Saccharomyces is used in bread making. 3. Aspergillus is used in the production of citric acid. Which are correct?
A. 1, 2 and 3
B. 1 and 2 only
C. 2 and 3 only
D. 1 and 3 only
Discuss
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Correct Answer: Option A

Explanation:
Lactobacillus is a lactic acid bacterium that ferments lactose in milk, producing lactic acid that coagulates proteins to form curd. Saccharomyces cerevisiae (baker's yeast) undergoes anaerobic respiration, producing CO2 gas that causes bread dough to rise. Aspergillus niger, a fungus, is widely used in industrial fermentation for the large-scale production of citric acid. All statements are correct.
This question belongs to: Science Biology
Question #1822
Consider statements about biotechnology: 1. Agrobacterium tumefaciens is a natural plant genetic engineer. 2. Bt toxin is active in the acidic gut of insects. 3. RNAi is used to silence specific genes. Which are correct?
A. 1, 2 and 3
B. 2 and 3 only
C. 1 and 3 only
D. 1 and 2 only
Discuss
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Correct Answer: Option C

Explanation:
Agrobacterium tumefaciens is a soil bacterium that naturally transfers a segment of its Ti plasmid into plant cells, making it a natural genetic engineer used to create transgenic plants. RNA interference (RNAi) is a cellular defense mechanism used in biotechnology to silence specific mRNA molecules, preventing gene expression. Bt toxin is inactive in the insect gut until it encounters the alkaline pH, which solubilizes and activates it. Thus, statements 1 and 3 are correct.
This question belongs to: Science Biology
Question #1823
Consider statements about animal husbandry: 1. MOET is used for cattle improvement. 2. Artificial insemination allows the use of superior bull semen. 3. Crossbreeding reduces genetic diversity. 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 C

Explanation:
Multiple Ovulation Embryo Transfer (MOET) is a reproductive technology used in cattle to rapidly multiply the offspring of superior females. Artificial insemination (AI) allows farmers to use semen from genetically superior bulls without keeping the animal, improving herd quality. Crossbreeding involves mating animals of different breeds to combine desirable traits and increase heterozygosity, thereby increasing, not reducing, genetic diversity in the population. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1824
Consider statements about scientists: 1. Edward Jenner is the father of immunology. 2. Alexander Fleming discovered penicillin. 3. Louis Pasteur discovered the structure of DNA. 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:
Edward Jenner is considered the father of immunology for pioneering the concept of vaccination by developing the smallpox vaccine. Alexander Fleming discovered the first antibiotic, penicillin, from the fungus Penicillium notatum in 1928. Louis Pasteur made monumental contributions to microbiology and vaccination, but the structure of DNA was discovered by James Watson and Francis Crick in 1953. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1825
Consider statements about cell biology: 1. The Golgi apparatus packages materials for secretion. 2. The smooth ER is involved in lipid synthesis. 3. The rough ER is involved in lipid synthesis. 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:
The Golgi apparatus consists of cisternae that modify, sort, and package proteins and lipids received from the ER for secretion or delivery to other organelles. The smooth endoplasmic reticulum (SER) lacks ribosomes and is the primary site for the synthesis of lipids, including phospholipids and steroids. The rough endoplasmic reticulum (RER) has ribosomes attached and is primarily involved in protein synthesis, not lipid synthesis. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1826
Consider statements about plant biology: 1. The root hair zone is the primary area for water absorption. 2. The zone of elongation is responsible for cell division. 3. The root cap protects the apical meristem. 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:
The root is divided into zones. The root hair zone contains epidermal extensions (root hairs) that vastly increase surface area, making it the primary region for water and mineral absorption. The zone of cell division (meristematic zone) is at the very tip, where active mitosis occurs; the zone of elongation is where cells expand in length, pushing the root tip forward. The root cap is a thimble-like structure protecting the delicate apical meristem as it pushes through soil. Thus, statements 1 and 3 are correct.
This question belongs to: Science Biology
Question #1827
Consider statements about human anatomy: 1. The femur is the longest bone in the body. 2. The stapes is the smallest bone in the body. 3. The hyoid bone is attached to another bone by a joint. Which 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 D

Explanation:
The femur (thigh bone) is the longest, heaviest, and strongest bone in the human skeleton. The stapes (stirrup) is a small bone in the middle ear and is the smallest bone in the human body. The hyoid bone is a U-shaped bone in the neck that supports the tongue; it is unique because it is not articulated (jointed) with any other bone, but is suspended by muscles and ligaments. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1828
Consider statements about human physiology: 1. The sinoatrial node is the pacemaker of the heart. 2. The atrioventricular node delays the impulse before it reaches the ventricles. 3. The Purkinje fibers distribute the impulse to the ventricular muscle. Which are correct?
A. 1, 2 and 3
B. 2 and 3 only
C. 1 and 3 only
D. 1 and 2 only
Discuss
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Correct Answer: Option A

Explanation:
The cardiac conduction system ensures coordinated heartbeats. The sinoatrial (SA) node generates the electrical impulse, acting as the natural pacemaker. The impulse reaches the atrioventricular (AV) node, which delays it slightly to allow the atria to fully contract and empty into the ventricles. The impulse then travels down the Bundle of His to the Purkinje fibers, which rapidly distribute it throughout the ventricular myocardium, causing ventricular contraction. All statements are correct.
This question belongs to: Science Biology
Question #1829
Consider statements about human diseases: 1. Ascariasis is caused by a roundworm. 2. Ringworm is caused by a fungus. 3. Amoebiasis is caused by a bacterium. Which are correct?
A. 1 and 2 only
B. 1, 2 and 3
C. 2 and 3 only
D. 1 and 3 only
Discuss
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Correct Answer: Option A

Explanation:
Ascariasis is a helminthic infection caused by the intestinal roundworm Ascaris lumbricoides. Ringworm (dermatophytosis) is a superficial fungal infection of the skin, hair, or nails caused by dermatophytes like Microsporum. Amoebiasis is an intestinal infection caused by the protozoan parasite Entamoeba histolytica, not a bacterium. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1830
Consider statements about human immunity: 1. Innate immunity is non-specific. 2. Acquired immunity is specific. 3. Secondary immune response is weaker than primary. Which are correct?
A. 1, 2 and 3
B. 1 and 2 only
C. 2 and 3 only
D. 1 and 3 only
Discuss
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Correct Answer: Option B

Explanation:
Innate immunity is the non-specific, inborn defense mechanism present from birth, providing immediate but general protection against pathogens. Acquired (adaptive) immunity is highly specific, targeting particular antigens and developing memory. The secondary immune response, occurring upon re-exposure to the same antigen, is much faster, stronger, and more prolonged than the primary response due to the presence of memory cells. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1831
Consider statements about human nutrition: 1. Essential amino acids cannot be synthesized by the body. 2. Saturated fats are liquid at room temperature. 3. Dietary fiber aids in digestion. 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 A

Explanation:
Essential amino acids (like lysine, tryptophan) cannot be synthesized by the human body and must be obtained through the diet. Dietary fiber (roughage) is indigestible plant material that adds bulk to stool, promotes peristalsis, and aids in digestion and preventing constipation. Saturated fats have no double bonds between carbon atoms, making them solid at room temperature (like butter); unsaturated fats are liquid (like oils). Thus, statements 1 and 3 are correct.
This question belongs to: Science Biology
Question #1832
Consider statements about vitamins: 1. Vitamin A is fat-soluble. 2. Vitamin C is water-soluble. 3. Vitamin D deficiency causes scurvy. 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 B

Explanation:
Vitamins A, D, E, and K are fat-soluble vitamins, meaning they are absorbed along with fats in the diet and can be stored in the body's fatty tissue and liver. Vitamin C and the B-complex vitamins are water-soluble, meaning they dissolve in water and are not stored in significant amounts. Vitamin D deficiency causes rickets in children and osteomalacia in adults; scurvy is caused by Vitamin C deficiency. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1833
Consider statements about genetics: 1. A gene is a segment of DNA that codes for a protein. 2. Alleles are alternative forms of a gene. 3. The phenotype is the genetic makeup of an organism. 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:
A gene is a specific sequence of nucleotides in DNA that serves as the fundamental unit of heredity, typically coding for a specific protein or RNA molecule. Alleles are different versions or alternative forms of the same gene that occupy the same locus on homologous chromosomes and determine variations in a trait. The genotype is the genetic makeup of an organism, while the phenotype is the observable physical or biochemical characteristics. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1834
Consider statements about evolution: 1. Genetic drift is a random change in allele frequencies. 2. Gene flow occurs through migration. 3. Natural selection is a random process. 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:
Genetic drift is the random fluctuation of allele frequencies in a population, particularly significant in small populations, due to chance events. Gene flow (migration) is the transfer of alleles from one population to another through the movement of individuals or gametes. Natural selection is a non-random, deterministic process where individuals with traits better suited to their environment have higher survival and reproductive success. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1835
Consider statements about ecology: 1. Primary productivity is the rate of biomass production by producers. 2. Secondary productivity is the rate of new biomass creation by consumers. 3. Decomposition rate is independent of temperature. Which are correct?
A. 1 and 2 only
B. 1 and 3 only
C. 2 and 3 only
D. 1, 2 and 3
Discuss
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Correct Answer: Option A

Explanation:
Primary productivity is the rate at which autotrophs (producers) convert solar energy into chemical energy (biomass) through photosynthesis. Secondary productivity is the rate at which heterotrophs (consumers) assimilate food to create new organic matter (biomass). Decomposition is a biological process carried out by microbes, and its rate is highly dependent on environmental factors like temperature, moisture, and oxygen availability; warmer temperatures generally increase decomposition. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1836
Consider statements about environment: 1. Biochemical Oxygen Demand (BOD) measures organic pollution. 2. Eutrophication is caused by excess nutrients. 3. Biological magnification decreases at higher trophic levels. 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 B

Explanation:
Biochemical Oxygen Demand (BOD) measures the amount of dissolved oxygen required by aerobic bacteria to decompose organic matter in water; high BOD indicates severe organic pollution. Eutrophication is the excessive enrichment of water bodies with nutrients (like nitrates and phosphates), leading to algal blooms and oxygen depletion. Biological magnification is the progressive increase in the concentration of non-biodegradable toxins (like DDT) at each successive trophic level, not a decrease. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1837
Consider statements about microorganisms: 1. Cyanobacteria are photosynthetic prokaryotes. 2. Mycorrhiza is a symbiotic association between fungi and plant roots. 3. Nitrosomonas is a denitrifying bacterium. 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:
Cyanobacteria (blue-green algae) are photosynthetic, oxygenic prokaryotes that play a crucial role in nitrogen fixation in aquatic and terrestrial ecosystems. Mycorrhiza is a mutualistic symbiotic association between a fungus and the roots of a vascular plant, where the fungus aids in nutrient absorption and the plant provides carbohydrates. Nitrosomonas is a nitrifying bacterium that converts ammonia to nitrite; denitrifying bacteria like Pseudomonas convert nitrates to nitrogen gas. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1838
Consider statements about biotechnology: 1. PCR can amplify a specific DNA sequence. 2. Gel electrophoresis separates DNA fragments by size. 3. Restriction enzymes join DNA fragments. Which are correct?
A. 1 and 3 only
B. 1 and 2 only
C. 1, 2 and 3
D. 2 and 3 only
Discuss
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Correct Answer: Option B

Explanation:
Polymerase Chain Reaction (PCR) is a powerful technique used to exponentially amplify a specific segment of DNA using primers and a thermostable DNA polymerase. Gel electrophoresis is a method used to separate DNA, RNA, or protein molecules based on their size and charge by applying an electric field through a gel matrix. Restriction enzymes are molecular scissors that cut DNA at specific sequences; DNA ligase is the enzyme that joins DNA fragments together. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1839
Consider statements about animal husbandry: 1. Poultry birds are reared for meat and eggs. 2. Dairy animals are reared for milk production. 3. Sericulture involves rearing honeybees. Which are correct?
A. 2 and 3 only
B. 1 and 2 only
C. 1 and 3 only
D. 1, 2 and 3
Discuss
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Correct Answer: Option B

Explanation:
Poultry farming involves the commercial rearing of birds, primarily chickens, for the production of meat (broilers) and eggs (layers). Dairy farming focuses on the breeding, rearing, and management of cattle, buffaloes, and other mammals for the production of milk and milk products. Sericulture is the rearing of silkworms (Bombyx mori) for silk production; the rearing of honeybees is called apiculture. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1840
Consider statements about scientists: 1. Charles Darwin proposed the theory of evolution. 2. Gregor Mendel proposed the laws of inheritance. 3. Robert Hooke discovered the cell nucleus. 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:
Charles Darwin, an English naturalist, proposed the theory of evolution by natural selection in his book 'On the Origin of Species'. Gregor Mendel, an Austrian monk, conducted experiments on pea plants and proposed the fundamental laws of inheritance (segregation and independent assortment). Robert Hooke discovered cells in cork tissue; the cell nucleus was discovered later by Robert Brown. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology

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