NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions


The Gram (-) bacteria detect and respond to the chemicals in their surroundings by

  • muramic acid

  • lipopolysaccharide

  • volutin granules

  • porin



In cell wall of Gram-negative bacteria, the peptidoglycan layer is very thin. The outer membrane is a bilayered structure consisting chiefly of phospholipids, proteins and lipo-polysaccharides. The permeability of outer membrane to nutrients is provided by proteins called porins, which form channels in the membrane.


One of the characteristic of sieve tube is

  • it is a part of phloem

  • function is transport of inorganic solutes

  • it is dead cell

  • sieve plate is not present


it is a part of phloem

The phloem consists of sieve elements companion cells, phloem fibres and phloem parenchyma. Sieve tube members are long, slender, tube-like cells joined end to end to form long tubular channels, the sieve tubes.


Plants purify air by which process?

  • Photorespiration

  • Photosynthesis

  • Photophosphorylation

  • Transpiration



During photosynthesis, carbon dioxide is reduced into carbohydrates and oxygen is liberated, ie, plants purify air by process of photosynthesis.

Photorespiration is a respiratory process by which they take up oxygen in the light and give out some carbon dioxide, contrary to the general pattern of photosynthesis. It takes place in higher plants.

Photophosphorylation is the synthesis of ATP from ADP and phosphate that occurs in a plant using radiant energy absorbed during photosynthesis.

Transpiration is the process by which moisture is carried through plants from roots to small pores on the underside of leaves, where it changes to vapor and is released to the atmosphere. It is the evaporation of water from plant leaves.


Which one of the following statement correctly define the term homonym?

  • Identical name of two different taxon

  • Two or more names belonging to the same taxon

  • When species name repeats the generic name

  • Other name of a taxon given in a language other than the language of zoological/ botanical nomenclature


Identical name of two different taxon

Homonym is a Latin name which is identical to that of a different organism. It is specific or generic name that has been used for two or more different organisms Or it is a specific or generic name that is identical for two different taxon.

For eg, Echidna is used for spiny anteater and also for moray eels.


Chromosomes replicate in which stage of meiosis?

  • Prophase- I

  • Prophase- II

  • Telophase- I

  • Interphase



Interphase is a phase of cell cycle where cell prepares itself for division. It consists of 3 phases: G1 phase, S phase and G2 phase.

During S or Synthesis phase, all the chromosomes get replicated. Each chromosome consists of two sister chromatids.

In eukaryotic DNA, histone and non- histone proteins are known as chromatin. It consists of thread- like structures known as chromosomes. Hence, the replication of DNA in the chromosomes initiates in S- phase of interphase.


Dimorphism of chloroplast is found in

  • C3 - plants

  • C4 - plants

  • CAM plants

  • Both (b) and (c)


C4 - plants

C4 plants have Kranz anatomy. The chloroplasts of the mesophyll cells are smaller and have well developed grana, while the chloroplasts of bundle sheath cells are agranal, ie, dimorphic chloroplasts are found in Cplants.


Mesoglia is seen in between

  • ectoderm and endoderm

  • ectoderm and mesoderm

  • mesoderm and endoderm

  • just below mesoderm


ectoderm and endoderm

The coelenterates are diploblastic animals. They have two germ layers, the ectoderm and endoderm. Between these two layers, a thin, delicate, transparent and non-cellular mesogloea is present. Mesoglea is present in Diploblastic animals (a) between ectoderm and endoderm. However, in triploblastic animals (b) mesoderm is present between ectoderm and endoderm.


A substance that induces dormancy of seed is

  • ABA

  • GA

  • thio-urea

  • cytokinin



ABA or Abscisic Acid induces dormancy in buds and seeds. The buds as well as seeds sprout only when abscisic acid is overcome by gibberellins.


Which of the following is called stress hormone?

  • Abscisic acid

  • Auxin

  • Cytokinin

  • Gibberellic acid


Abscisic acid

Abscisic acid is also called stress hormone because the production of this hormone is stimulated by drought, water logging and other adverse environmental conditions.


Which of the following element is responsible for Minamata disease?

  • Hg

  • Pb

  • Cd

  • Fe



Minamata disease is caused due to mercury. It is a disease of the central nervous system (CNS). It occurs due to poisoning caused by long- term consumption, in large amounts, of fish and shellfish from Minamata Bay. Mercury, is changed to water soluble dimethyl, mercury, which undergoes biomagnification. This disease is characterized by diarrhoea, haemolysis, impairment of various senses numbness of lips tongue, limbs etc.