21000+ Important MCQs for UPSC
21000+ MCQs for UPSC are available here. You can learn these questions for your better preparation. Questions are available with its correct answer. You can check the correct answer of any questions by clicking the option or show answer button.
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Explanation: The cell is the fundamental unit of life; tissues, organs, and organ systems are higher-level assemblies of cells. Therefore, cell is the correct and most basic unit.
Explanation: Insulin, produced by pancreatic beta cells, lowers blood glucose by promoting cellular uptake and storage. Glucagon raises blood glucose, adrenaline increases glucose availability in stress, and cortisol raises blood sugar during long-term stress.
Explanation: Heterotrophs obtain energy and carbon by consuming organic matter (other organisms). Autotrophs/producers make their own organic compounds (e.g., via photosynthesis). Phototrophs use light as an energy source but can be autotrophs or heterotrophs depending on carbon source.
Explanation: Natural selection is the differential survival and reproduction of organisms due to variation in heritable traits. Organisms do not 'want' traits; individuals generally do not change their DNA in response to needs within a lifetime (that would be Lamarckian), and species do change over time via evolution, so options 1, 2, and 4 are incorrect.
Explanation: Antibiotics target bacteria (their cell walls, protein synthesis, etc.). They are not effective against viruses (which require antivirals), fungi (treated with antifungals), or prions (abnormal proteins) — these require different treatments.
Explanation: Fats (lipids) store the most energy per gram and serve as long-term energy reserves in animals. Glycogen is a short-term carbohydrate storage in animals. Starch is plant storage, and protein is used mainly for structure and enzymes, not primary energy storage.
Explanation: B cells differentiate into plasma cells that secrete antibodies specific to antigens. T cells assist or kill infected cells but do not secrete antibodies. Macrophages phagocytose pathogens, and neutrophils are innate immune phagocytes — none primarily produce antibodies.
Explanation: Crossing over during prophase I of meiosis exchanges DNA between homologous chromosomes, creating new allele combinations. Independent assortment also creates variation by random segregation of chromosome pairs, but it does not exchange segments. DNA replication copies genetic material; binary fission is a form of asexual reproduction in prokaryotes.