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 94 of 103
Question #1861
Consider statements about human immunity: 1. Skin acts as a physical barrier. 2. White blood cells fight infections. 3. Antibiotics are effective against viruses. 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 D

Explanation:
The skin and mucous membranes form the first line of defense (innate immunity), acting as physical barriers that prevent pathogens from entering the body. White blood cells (leukocytes), including phagocytes and lymphocytes, are the cellular components of the immune system that identify, attack, and destroy pathogens. Antibiotics are drugs designed to kill or inhibit the growth of bacteria; they are completely ineffective against viruses, which lack the cellular machinery targeted by antibiotics. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1862
Consider statements about human nutrition: 1. A balanced diet contains all essential nutrients. 2. Malnutrition can be caused by overeating. 3. Water is not a nutrient. 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 C

Explanation:
A balanced diet provides all the essential nutrients (carbohydrates, proteins, fats, vitamins, minerals, and water) in the correct proportions required for optimal health and growth. Malnutrition refers to deficiencies, excesses, or imbalances in a person's intake of energy and/or nutrients; therefore, overeating (leading to obesity) is a form of malnutrition. Water is an essential nutrient, crucial for hydration, transport, and chemical reactions, though it provides no calories. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1863
Consider statements about vitamins: 1. Vitamin A deficiency causes night blindness. 2. Vitamin B1 deficiency causes beriberi. 3. Vitamin C deficiency causes rickets. 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 A

Explanation:
Vitamin A is essential for the synthesis of rhodopsin, a visual pigment; its deficiency leads to night blindness, the inability to see in low light. Vitamin B1 (thiamine) is crucial for carbohydrate metabolism; its deficiency causes beriberi, characterized by nerve and heart dysfunction. Vitamin C deficiency causes scurvy, characterized by bleeding gums and poor wound healing; rickets is caused by a deficiency of Vitamin D, leading to soft, weak bones in children. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1864
Consider statements about genetics: 1. DNA is the genetic material in most organisms. 2. RNA is the genetic material in some viruses. 3. Proteins are the genetic material in all cells. 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 A

Explanation:
DNA (deoxyribonucleic acid) is the universal genetic material in all cellular organisms (prokaryotes and eukaryotes) and many viruses, storing hereditary information. Some viruses, known as RNA viruses (like HIV, influenza, and TMV), use RNA (ribonucleic acid) as their genetic material instead of DNA. Proteins are the products of gene expression and perform various cellular functions, but they are never the genetic material in any cell or virus. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1865
Consider statements about evolution: 1. Evolution is a change in allele frequencies over time. 2. Speciation is the formation of new species. 3. Evolution always leads to more complex organisms. 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:
Evolution, at its most fundamental genetic level, is defined as the change in the frequency of alleles within a population over successive generations. Speciation is the evolutionary process by which populations evolve to become distinct, reproductively isolated species. Evolution does not have a predetermined goal or direction towards complexity; it simply results in adaptation to the current environment, which can sometimes lead to simpler forms (like parasites losing complex structures). Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1866
Consider statements about ecology: 1. A food chain shows a single pathway of energy flow. 2. A food web shows multiple interconnected pathways. 3. Energy is recycled in an ecosystem. 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:
A food chain is a linear, simplified sequence showing the transfer of energy and matter from one organism to another through consumption. A food web is a more realistic, complex network of interconnected food chains, illustrating the multiple feeding relationships and pathways of energy flow in an ecosystem. While nutrients (matter) are continuously recycled in an ecosystem through biogeochemical cycles, energy flows unidirectionally and is eventually lost as heat; it is not recycled. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1867
Consider statements about environment: 1. Deforestation leads to soil erosion. 2. Afforestation helps in carbon sequestration. 3. Plastic is biodegradable. Which are correct?
A. 1 and 2 only
B. 2 and 3 only
C. 1 and 3 only
D. 1, 2 and 3
Discuss
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Correct Answer: Option A

Explanation:
Deforestation, the removal of trees and vegetation, exposes the topsoil to wind and water, leading to severe soil erosion and loss of fertility. Afforestation, the planting of trees in barren areas, increases biomass and helps in carbon sequestration, as trees absorb atmospheric CO2 during photosynthesis, mitigating global warming. Most plastics are synthetic polymers that are non-biodegradable, persisting in the environment for hundreds of years and causing pollution. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1868
Consider statements about microorganisms: 1. Bacteria reproduce asexually by binary fission. 2. Fungi reproduce by spore formation. 3. Viruses can reproduce independently. 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 A

Explanation:
Bacteria are prokaryotes that primarily reproduce asexually through binary fission, a process where a single cell divides into two identical daughter cells. Fungi reproduce both sexually and asexually, but asexual reproduction commonly occurs through the formation and dispersal of spores (like conidia or sporangiospores). Viruses are obligate intracellular parasites; they lack the metabolic machinery for independent reproduction and must hijack a host cell's machinery to replicate. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1869
Consider statements about biotechnology: 1. Genetic engineering involves altering an organism's DNA. 2. Cloning creates an exact genetic copy. 3. Tissue culture is used for plant propagation. 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 D

Explanation:
Genetic engineering (recombinant DNA technology) involves the direct manipulation of an organism's genes using biotechnology to alter its characteristics. Cloning is the process of producing genetically identical copies of a biological entity, such as a gene, cell, or entire organism. Tissue culture (micropropagation) is a technique used to grow plant cells, tissues, or organs in a sterile nutrient medium, allowing for the rapid, large-scale propagation of plants from a small explant. All statements are correct.
This question belongs to: Science Biology
Question #1870
Consider statements about animal husbandry: 1. Dairy farming focuses on milk production. 2. Poultry farming focuses on meat and egg production. 3. Fisheries focus on silk production. 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 C

Explanation:
Dairy farming is the agricultural practice of breeding and raising livestock (like cows and buffaloes) specifically for the long-term production of milk. Poultry farming involves the rearing of domesticated birds (like chickens, ducks, and turkeys) for the production of meat (broilers) and eggs (layers). Fisheries (pisciculture) involves the breeding and rearing of fish and other aquatic organisms for food; silk production is the domain of sericulture (rearing silkworms). Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1871
Consider statements about scientists: 1. Robert Hooke discovered cells. 2. Antonie van Leeuwenhoek discovered bacteria. 3. Charles Darwin proposed the cell theory. 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:
Robert Hooke, in 1665, observed dead cork tissue under a microscope and coined the term 'cell' for the box-like structures he saw. Antonie van Leeuwenhoek, using his superior single-lens microscopes in the 1670s, was the first to observe and describe living microorganisms, including bacteria and protozoa. Charles Darwin proposed the theory of evolution by natural selection; the cell theory was proposed by Matthias Schleiden and Theodor Schwann. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1872
Consider statements about cell biology: 1. The plasma membrane is composed of a phospholipid bilayer. 2. The nucleus contains the cell's genetic material. 3. Mitochondria are the site of photosynthesis. 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:
The plasma membrane (cell membrane) is primarily composed of a phospholipid bilayer with embedded proteins, following the fluid mosaic model, regulating transport in and out of the cell. The nucleus is the membrane-bound organelle that houses the cell's genetic material (DNA) organized into chromosomes. Mitochondria are the site of aerobic cellular respiration and ATP production; chloroplasts are the organelles where photosynthesis occurs in plant cells. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1873
Consider statements about plant biology: 1. Xylem transports water and minerals. 2. Phloem transports food. 3. Cambium is responsible for primary growth. 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:
Xylem is a complex permanent tissue responsible for the unidirectional upward transport of water and dissolved minerals from the roots to the aerial parts of the plant. Phloem is the vascular tissue responsible for the translocation of organic nutrients (primarily sucrose) from sources (leaves) to sinks (roots, fruits), which can be bidirectional. Cambium (vascular and cork) is a lateral meristem responsible for secondary growth (increase in girth); primary growth (increase in length) is driven by apical meristems. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1874
Consider statements about human anatomy: 1. The skeletal system provides support and protection. 2. The muscular system enables movement. 3. The endocrine system produces hormones. 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 D

Explanation:
The skeletal system, composed of bones and cartilage, provides structural support for the body, protects vital internal organs (like the brain and heart), and serves as a site for muscle attachment. The muscular system, consisting of skeletal, smooth, and cardiac muscles, contracts to produce movement of the body and internal organs. The endocrine system comprises glands that secrete hormones directly into the bloodstream to regulate various physiological processes. All statements are correct.
This question belongs to: Science Biology
Question #1875
Consider statements about human physiology: 1. The respiratory system exchanges gases. 2. The circulatory system transports blood. 3. The excretory system removes waste. 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 A

Explanation:
The respiratory system, primarily the lungs, facilitates the exchange of gases (oxygen and carbon dioxide) between the blood and the external environment. The circulatory system, centered around the heart and blood vessels, transports blood containing oxygen, nutrients, hormones, and waste products throughout the body. The excretory system, primarily the kidneys, filters blood to remove metabolic waste products and excess water, excreting them as urine. All statements are correct.
This question belongs to: Science Biology
Question #1876
Consider statements about human diseases: 1. Bacterial diseases can be treated with antibiotics. 2. Viral diseases are often prevented by vaccines. 3. Fungal diseases are caused by protozoa. 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:
Bacterial infections (like tuberculosis, pneumonia) are effectively treated with antibiotics, which target specific bacterial structures or metabolic pathways. Many viral diseases (like polio, measles, influenza) can be prevented through vaccination, which stimulates the immune system to develop memory against the virus. Fungal diseases (like ringworm, candidiasis) are caused by fungi, not protozoa; protozoa cause diseases like malaria and amoebiasis. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1877
Consider statements about human immunity: 1. Active immunity involves the body producing its own antibodies. 2. Passive immunity involves receiving pre-formed antibodies. 3. Vaccination provides passive immunity. 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 D

Explanation:
Active immunity occurs when the body's own immune system is stimulated by an antigen (either through infection or vaccination) to produce its own antibodies and memory cells, providing long-lasting protection. Passive immunity occurs when an individual is directly given pre-formed antibodies (like through mother's milk or antiserum), providing immediate but temporary protection. Vaccination stimulates the body to produce its own immune response, thus providing artificial active immunity, not passive. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1878
Consider statements about human nutrition: 1. Carbohydrates are the main source of energy. 2. Proteins are needed for growth and repair. 3. Fats are not needed for any bodily function. 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:
Carbohydrates are the body's primary and most efficient source of energy, broken down into glucose to fuel cellular activities. Proteins are essential macronutrients composed of amino acids, crucial for the growth, maintenance, and repair of body tissues, as well as forming enzymes and hormones. Fats are essential for numerous bodily functions, including providing concentrated energy, forming cell membranes, insulating the body, and absorbing fat-soluble vitamins. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1879
Consider statements about vitamins: 1. Vitamin A is essential for vision. 2. Vitamin B complex helps in energy metabolism. 3. Vitamin C is essential for blood clotting. 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:
Vitamin A (retinol) is crucial for maintaining healthy vision, particularly in dim light, as it is a component of the visual pigment rhodopsin. The B-complex vitamins (like B1, B2, B3, B5) act as coenzymes and are essential for various metabolic pathways, particularly the conversion of carbohydrates, fats, and proteins into usable energy. Vitamin K, not Vitamin C, is essential for the synthesis of blood clotting factors; Vitamin C is essential for collagen synthesis and immunity. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1880
Consider statements about genetics: 1. Genes are located on chromosomes. 2. DNA replication is semi-conservative. 3. RNA is double-stranded. 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:
Genes are specific sequences of DNA that code for proteins or RNA, and they are arranged linearly on chromosomes within the nucleus. DNA replication is semi-conservative, meaning each newly synthesized DNA molecule consists of one original parental strand and one newly synthesized strand, as proven by the Meselson-Stahl experiment. RNA is typically single-stranded, allowing it to fold into complex shapes and perform various functions, unlike the double-stranded DNA helix. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology

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