NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions



Tadpoles of frog can be made to grow as giant sized tadpoles, if they are

  • administered antithyroid substance like thiourea

  • administered large amounts of thyroxine

  • reared on a diet rich in egg yolk

  • reared on a diet rich in both egg yolk and glucose.


administered antithyroid substance like thiourea

Thyroxine, the principal hormone, of thyroid gland, is required for tissue differentiation and metamorphosis (the rapid transformation from the larval to the adult form) in amphibians. Thyroxine triggers a response from the hypothalamus, (probably by a genetic mechanism) followed by the production and release of TSH (Thyroid stimulating hormone), thus metamorphosis begins and tadpoles metamorphose into frogs. Thiourea is an organic compound of carbon, nitrogen, sulphur and hydrogen, with the formula CSN2H4, or (NH2)2CS. It is similar to urea, except that oxygen atom is replaced by a sulphur atom.


The given figure shows an angiogram of the coronary blood vessel. Which one of the following statements correctly describes, what is being done

  • It is coronary artery which has a cancerous growth that is being removed.

  • It is coronary artery which is blocked by a plaque and the same is being cracked.

  • It is coronary vein in which the defective valves are being opened.

  • It is coronary vein blocked by a parasite (blood fluke) that is being removed.


Grafting is successful in dicots but not in monocots because the dicots have

  • vascular bundles arranged in a ring

  • cambium for secondary growth

  • vessels with elements arranged end to end

  • cork cambium


In the sieve elements, which one of the following is the most likely function of P-proteins

  • Deposition of callose on sieve plates

  • Providing energy for active translocation

  • Autolytic enzymes

  • Sealing mechanism on wounding


Myxomycetes are

  • saprobes or parasites, having mycelia, asexual reproduction by fragmentation, sexual reproduction by fusion of gametes

  • slimy mass of multinucleate protoplasm, having pseudopodia-like structures for engulfing food, reproduction through fragmentation or zoospores

  • prokaryotic organisms, cellular or acellular, saprobes or autotrophic, reproduce by binary fission

  • eukaryotic, single-celled or filamentous, saprobes or autotrophic, asexual reproduction by fusion of two cells or their nuclei.

16. 'Ordines Anomali' of Bentham and Hooker includes
  • seed plants showing abnormal forms of growth and development

  • plants described only in fossil state

  • plants described in the literature but which Bentham and Hooker did not see in original

  • a few orders which could not be placed satisfactorily in the classification.


A scion is grafted to a stock. The quality of fruits produced will be determined by the genotype of

  • stock

  • scion

  • both stock and scion

  • neither stock nor scion.


In prokaryotes, chromatophores are

  • specialized granules responsible for colouration of cells

  • structures responsbile for organizing the shape of the organism

  • inclusion bodies lying free inside the cells for canying out various metabolic activities

  • internal membrane systems that may become extensive and complex in photosynthetic bacteria


The function of leghaemoglobin during biological nitrogen fixation in root nodules of legumes is to

  • convert atmospheric N2 to NH3

  • convert ammonia to nitrite

  • transport oxygen for activity of nitrogenase

  • protect nitrogenase from oxygen


Avena curvature test is a bioassay for examining the activity of

  • auxins

  • cytokinins

  • gibberellins

  • ethylene.