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 91 of 103
Question #1801
Consider statements about genetics: 1. The human genome contains 23 pairs of chromosomes. 2. Sex is determined by the Y chromosome. 3. All mutations are harmful. 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:
Human somatic cells are diploid, containing 23 pairs of chromosomes (22 pairs of autosomes and 1 pair of sex chromosomes). The presence of the Y chromosome determines male sex (XY), while its absence results in female sex (XX). Mutations are random changes in DNA; while some are harmful, many are neutral, and some can be beneficial, providing the genetic variation necessary for evolution. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1802
Consider statements about evolution: 1. The theory of use and disuse was given by Lamarck. 2. The theory of natural selection was given by Darwin. 3. The theory of mutation was given by Hugo de Vries. 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 C

Explanation:
Jean-Baptiste Lamarck proposed the theory of inheritance of acquired characters, based on the use and disuse of organs. Charles Darwin proposed the theory of evolution by natural selection, emphasizing survival of the fittest. Hugo de Vries, a Dutch botanist, proposed the mutation theory of evolution after working on evening primrose, stating that evolution occurs via sudden, large mutations (saltations). All statements are correct.
This question belongs to: Science Biology
Question #1803
Consider statements about ecology: 1. A population includes all species in an area. 2. A community includes only interacting populations. 3. An ecosystem includes both biotic and abiotic components. Which are correct?
A. 2 only
B. 1 and 3 only
C. 1 and 2 only
D. 1, 2 and 3
Discuss
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Correct Answer: Option A

Explanation:
A population consists of individuals of a single species living in a specific area, not all species. A community comprises all the interacting populations of different species living together in a defined area. An ecosystem is a functional unit of nature encompassing both the biotic (living community) and abiotic (physical environment) components, interacting as a system. Only statement 2 is strictly correct in its definition.
This question belongs to: Science Biology
Question #1804
Consider statements about environment: 1. Carbon dioxide is a greenhouse gas. 2. Methane is a greenhouse gas. 3. Oxygen is a major greenhouse gas. 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:
Greenhouse gases trap heat in the Earth's atmosphere, contributing to the greenhouse effect and global warming. Carbon dioxide (CO2) and methane (CH4) are potent greenhouse gases emitted through human activities like fossil fuel combustion and agriculture. Oxygen (O2) and nitrogen (N2), which make up the majority of the atmosphere, are not greenhouse gases as they do not absorb infrared radiation. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1805
Consider statements about microorganisms: 1. Bacteria reproduce by binary fission. 2. Viruses have their own metabolic machinery. 3. Fungi have a cell wall made of chitin. 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 B

Explanation:
Bacteria are prokaryotes that primarily reproduce asexually through binary fission, where a single cell divides into two identical daughter cells. Fungi are eukaryotes characterized by having cell walls primarily composed of chitin, a tough polysaccharide. Viruses lack cellular structure and metabolic machinery; they are obligate parasites that rely entirely on the host cell's machinery for replication. Thus, statements 1 and 3 are correct.
This question belongs to: Science Biology
Question #1806
Consider statements about biotechnology: 1. DNA fingerprinting is used in forensics. 2. Insulin was the first genetically engineered human hormone. 3. Bt brinjal is resistant to herbicides. 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:
DNA fingerprinting analyzes unique patterns in an individual's DNA (VNTRs) and is widely used in forensics for identifying criminals or establishing paternity. Human insulin (Humulin) was the first genetically engineered therapeutic protein, produced in E. coli in 1982. Bt brinjal is genetically modified to express Bt toxin for resistance against specific insect pests (like the fruit and shoot borer), not herbicides. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1807
Consider statements about animal husbandry: 1. Silkworms feed on mulberry leaves. 2. Honeybees communicate through the waggle dance. 3. Fish farming is called sericulture. 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:
The domesticated silkworm, Bombyx mori, is a monophagous insect that feeds exclusively on the leaves of the mulberry plant (Morus alba). Honeybees perform a 'waggle dance' on the honeycomb to communicate the direction and distance of food sources to other worker bees. Fish farming is called pisciculture or aquaculture; sericulture specifically refers to the rearing of silkworms for silk production. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1808
Consider statements about scientists: 1. Robert Hooke coined the term 'cell'. 2. Antonie van Leeuwenhoek discovered the cell nucleus. 3. Matthias Schleiden proposed that all plants are made of cells. 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 D

Explanation:
Robert Hooke observed cork tissue in 1665 and coined the term 'cell' to describe the box-like structures. Matthias Schleiden, a botanist, concluded in 1838 that all plants are composed of cells, forming a core tenet of the cell theory. The cell nucleus was discovered by Robert Brown in 1831, not Antonie van Leeuwenhoek, who is famous for discovering living microorganisms. Thus, statements 1 and 3 are correct.
This question belongs to: Science Biology
Question #1809
Consider statements about cell division: 1. Crossing over occurs in prophase I of meiosis. 2. Anaphase I involves the separation of homologous chromosomes. 3. Telophase II results in four diploid cells. 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:
During prophase I of meiosis, homologous chromosomes pair up and crossing over (exchange of genetic material) occurs at the pachytene stage. In anaphase I, the homologous chromosomes separate and move to opposite poles, while sister chromatids remain attached. Telophase II is the final stage of meiosis II, resulting in four genetically distinct haploid cells, not diploid cells. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1810
Consider statements about plant biology: 1. Xylem vessels are dead at maturity. 2. Phloem sieve tubes are living at maturity. 3. Cambium is responsible for primary growth. 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:
Xylem vessels and tracheids are dead, hollow cells at functional maturity, providing a continuous tube for water transport. Phloem sieve tube elements are living cells at maturity, though they lack a nucleus, and are responsible for transporting organic nutrients. Cambium (vascular and cork) is a lateral meristem responsible for secondary growth (increase in girth), while apical meristems are responsible for primary growth (increase in length). Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1811
Consider statements about human anatomy: 1. The sternum is located in the chest. 2. The clavicle is the collar bone. 3. The scapula is the shoulder blade. 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:
The sternum, or breastbone, is a flat bone located in the center of the chest, to which the ribs attach. The clavicle, commonly known as the collarbone, connects the arm to the body, running horizontally above the first rib. The scapula, or shoulder blade, is a flat, triangular bone located on the upper back, forming the posterior part of the shoulder girdle. All statements are correct.
This question belongs to: Science Biology
Question #1812
Consider statements about human physiology: 1. The pancreas secretes both digestive enzymes and hormones. 2. The liver secretes bile, which contains digestive enzymes. 3. The gall bladder stores and concentrates bile. 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:
The pancreas is a mixed gland; its exocrine part secretes digestive enzymes (trypsin, lipase, amylase), and its endocrine part (Islets of Langerhans) secretes hormones (insulin, glucagon). The liver continuously secretes bile, but bile does not contain digestive enzymes; it contains bile salts that emulsify fats. The gall bladder stores and concentrates this bile before releasing it into the duodenum. Thus, statements 1 and 3 are correct.
This question belongs to: Science Biology
Question #1813
Consider statements about human diseases: 1. Common cold is caused by a virus. 2. Typhoid is transmitted through contaminated food and water. 3. Plague is transmitted by the bite of a rat flea. 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 C

Explanation:
The common cold is a viral infection of the upper respiratory tract, primarily caused by rhinoviruses. Typhoid fever, caused by Salmonella typhi, is transmitted via the fecal-oral route through contaminated food and water. Plague, caused by Yersinia pestis, is a zoonotic disease transmitted to humans primarily by the bite of infected rat fleas (Xenopsylla cheopis). All three statements are correct.
This question belongs to: Science Biology
Question #1814
Consider statements about human immunity: 1. IgG is the most abundant antibody in blood. 2. IgE is involved in allergic reactions. 3. IgA is found in mucosal secretions. 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 B

Explanation:
Immunoglobulin G (IgG) is the most abundant antibody in blood plasma, providing long-term immunity and crossing the placenta. Immunoglobulin E (IgE) is present in small amounts and binds to mast cells, triggering the release of histamine during allergic reactions. Immunoglobulin A (IgA) is predominantly found in mucosal secretions like saliva, tears, and breast milk, providing localized mucosal immunity. All statements are correct.
This question belongs to: Science Biology
Question #1815
Consider statements about human nutrition: 1. Proteins are made of amino acids. 2. Carbohydrates are made of fatty acids. 3. Fats are made of glycerol and fatty acids. 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 D

Explanation:
Proteins are complex macromolecules composed of long chains of amino acids linked by peptide bonds. Fats (triglycerides) are lipids composed of one glycerol molecule esterified to three fatty acid chains. Carbohydrates are composed of simple sugars (monosaccharides) like glucose, not fatty acids. Thus, statements 1 and 3 are correct, while statement 2 is false.
This question belongs to: Science Biology
Question #1816
Consider statements about vitamins: 1. Vitamin D is synthesized in the skin upon sunlight exposure. 2. Vitamin B12 is the only vitamin containing a metal ion. 3. Vitamin A 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 D3 (cholecalciferol) is synthesized in the epidermis of the skin when 7-dehydrocholesterol is exposed to ultraviolet B (UVB) radiation from sunlight. Vitamin B12 (cobalamin) is unique among vitamins as it contains the metal ion cobalt in its structure. Vitamin K, not Vitamin A, is essential for the synthesis of blood clotting factors. Vitamin A is crucial for vision and immunity. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1817
Consider statements about genetics: 1. DNA is transcribed into mRNA. 2. mRNA is translated into protein. 3. tRNA carries amino acids to the ribosome. 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 B

Explanation:
Transcription is the process where the genetic information in a DNA sequence is copied into a complementary messenger RNA (mRNA) molecule by RNA polymerase. Translation is the process where the mRNA sequence is decoded by ribosomes to synthesize a specific polypeptide (protein). Transfer RNA (tRNA) molecules act as adapters, carrying specific amino acids to the ribosome based on the mRNA codon. All statements are correct.
This question belongs to: Science Biology
Question #1818
Consider statements about evolution: 1. The fossil record provides evidence for evolution. 2. Embryological similarities support common ancestry. 3. Biogeography shows species distribution is random. 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:
The fossil record shows a chronological sequence of life forms, providing direct evidence of evolutionary changes over time. Embryological similarities, such as the presence of pharyngeal slits and a notochord in early vertebrate embryos, support the idea of common ancestry. Biogeography, the study of species distribution, shows that species are not randomly distributed but are related to their geographic origins and evolutionary history. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1819
Consider statements about ecology: 1. A food chain shows the flow of energy. 2. A food web shows interconnected food chains. 3. Decomposers are the primary producers. 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:
A food chain is a linear sequence showing the transfer of energy and matter from one organism to another through consumption. A food web is a complex, interconnected network of multiple food chains, representing the realistic feeding relationships in an ecosystem. Decomposers (bacteria and fungi) are saprotrophs that break down dead organic matter; primary producers are autotrophs (plants, algae) that synthesize their own food. Thus, statements 1 and 2 are correct.
This question belongs to: Science Biology
Question #1820
Consider statements about environment: 1. The Montreal Protocol addresses ozone depletion. 2. The Kyoto Protocol addresses greenhouse gas emissions. 3. The Ramsar Convention addresses wetland conservation. 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 B

Explanation:
The Montreal Protocol is an international treaty designed to protect the ozone layer by phasing out the production of substances like CFCs. The Kyoto Protocol is an international agreement linked to the UNFCCC, committing state parties to reduce greenhouse gas emissions to combat global warming. The Ramsar Convention is the international treaty for the conservation and sustainable use of wetlands, recognizing their ecological importance. All statements are correct.
This question belongs to: Science Biology

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