Class 12 Biology – Daily Revision MCQ (English Medium)
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In double fertilization of a flowering plant, the second male gamete fuses with which structure?
Chapter 1: Reproduction in Lower and Higher Plants
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Answer: C. The diploid secondary nucleus
This fusion is triple fusion: male gamete + diploid secondary nucleus forms the primary endosperm nucleus (PEN).Which cells of the human testis secrete the male hormone testosterone?
Chapter 2: Reproduction in Lower and Higher Animals
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Answer: A. Interstitial (Leydig) cells
Leydig cells lie between the seminiferous tubules and secrete androgen/testosterone; Sertoli cells only nourish developing sperms.In co-dominance shown by roan cattle, what is the F2 phenotypic ratio of red : roan : white?
Chapter 3: Inheritance and Variation
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Answer: D. 1 : 2 : 1
In co-dominance both alleles express fully, so F2 gives red (RR), roan (RW) and white (WW) in 1:2:1; phenotypic and genotypic ratios are the same.Meselson and Stahl grew E. coli in heavy nitrogen (¹⁵N) and then in ¹⁴N. What did their experiment prove about DNA replication?
Chapter 4: Molecular Basis of Inheritance
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Answer: B. It is semiconservative
The hybrid ¹⁴N-¹⁵N DNA band showed that each new DNA molecule keeps one old strand and one new strand: semiconservative replication.Urey and Miller's spark-discharge experiment gave the first experimental support to which idea?
Chapter 5: Origin and Evolution of Life
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Answer: C. Oparin's theory of chemical evolution
By passing electric sparks through methane, ammonia, hydrogen and water vapour they obtained organic compounds, supporting Oparin's chemical evolution.What is the water potential (ψ) of pure water?
Chapter 6: Plant Water Relation
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Answer: A. Zero
Water potential of pure water is always zero; adding any solute lowers it, so solutions have negative water potential.In which form is most (nearly 70%) of the carbon dioxide transported in human blood?
Chapter 8: Respiration and Circulation
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Answer: B. As bicarbonate ions
About 70% of CO₂ enters RBCs, forms carbonic acid with the help of carbonic anhydrase and is carried as bicarbonate ions.When an infected female Anopheles mosquito bites a person, which stage of Plasmodium enters the human blood?
Chapter 10: Human Health and Diseases
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Answer: D. Sporozoites
The mosquito transfers sporozoites from its salivary glands; they then multiply in liver cells and RBCs.In plant biotechnology, foreign genes are commonly transferred into plant cells through the Ti plasmid of which bacterium?
Chapter 12: Biotechnology
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Answer: A. Agrobacterium tumefaciens
Ti (tumor-inducing) plasmid of A. tumefaciens carries T-DNA that inserts into the plant cell's chromosomes.Which one of the following is among India's four biodiversity hotspots named in the textbook?
Chapter 15: Biodiversity, Conservation and Environmental Issues
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Answer: C. Western Ghats
The book lists India's four hotspots as Western Ghats, Indo-Burma region, Sundaland and Eastern Himalayas.
Class 12: MCQ in other subjects
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All questions are written by PadhaiNotes in our own words from the chapters of the official Maharashtra State Board Balbharati textbook (ebalbharati.in). Each question shows its chapter.