Subject

Biology

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

11.

How many genome types are present in a typical green plants cell

  • More than five

  • More than ten

  • Two

  • Three


C.

Two

Since a typical green plant is diploid, therefore it has two sets of chromosomes. So the number of genome will be two, because genome is the entire set of gene carried by a gamete or present in the haploid cell of a particular organism.


12.

The cells of the quiescent centre are characterised by

  • having dense cytoplasm and prominent nuclei

  • having light cytoplasm and small nuclei

  • dividing regularly to add to the corpus

  • dividing regularly to add to tunica


B.

having light cytoplasm and small nuclei

In the apices ofsome roots, (e.g., Zea mays, maize), there is a central region of cells which normally does not divide. This central inactive region was called quiescent centre by FE.A.L. Clowes (1959, 1961).

The cells of this region have lesser amounts of RNA and DNA so they have small nuclei. These cells also have a lower rate of protein synthesis. Mitochondria and endoplasmic reticulum arc less developed. The cells of the quiescent centre arc usually inactive. However, if already existing meristematic cells are injured or become inactive due to any other reason, the cells ofquiescent centre become active.


13.

Enzymes, vitamins and hormones can be classified into a single category of biological chemicals because of all of these

  • enhance oxidative metabolism

  • are conjugated proteins

  • are exclusively synthesised in the body of a living organism as at present

  • help in regulating metabolism.


D.

help in regulating metabolism.

Enzymes are protein that, in small amounts, speed up the rate of a biological reactions and help in regulating metabolism. Hormones are also metabolic regulator and help in stimulation or inhibition of one or more physiological processes. Vitamines are accessory food factors which are required in small quantity for controlling metabolism and body functioning.


14.

Assertion: Protoplasmic continuity is maintained in perforated septum.

Reason: Usually a small pore remains in the centre of the septum.

  • If both assertion and reason are true and reason is the correct explanation of assertion

  • If both assertion and reason are true but reason is not the correct explanation of assertion

  • If assertion is true but reason is false

  • If both assertion and reason are false.


A.

If both assertion and reason are true and reason is the correct explanation of assertion

In all the septate fungi except basidiomycetes (dolipore septum), the septa are seldom complete. They arc perforated and contain plasmodesmata or small central pores. Septal pores allow protoplasmic continuity betweenadjacent cells. This is useful for quick translocation of nutrients to all part of the body. Mobilisation of reserve materials from older parts to younger parts and from vegetative hyphae to reproductive hyphac.


15.

Chlorenchyma is known to develop in the

  • cytoplasm of Chlorella

  • mycelium of a green mould such as Aspergillus

  • spore capsule of a moss

  • pollen tube of Pinus


C.

spore capsule of a moss

Chlorenchyma or assimilatory parenchyma are parenchymatous cells that possess abundantchloroplasts in them. They are capable of photosynthesis. A spore capsule of moss can perform photosynthesis because of the presence of chlorenchyma cells in them.


16.

Ectophloic siphonostele is found in

  • Osmunda and Equisetum

  • Marsilea and Botrychium

  • Adiantum and Cucurbitaceae

  • Dicksonia and Maidenhair fern.


A.

Osmunda and Equisetum

Stele is a column containing vascular tissues which is surrounded by pericycle and separated from ground tissue by endodermis. Siphonostcle is medullated protostele or protostele with a central non-vascular pith. Leaf gaps are absent.

Siphonostelc is of two types: In Ectophloic siphonostele, central pith is surrounded successively by xylem, phloem, pericycle and endodermis. In amphiphloic siphonostele there is a central pith and xylem is surrounded on either side by phloem, pericycle and endodermis. It is found in Osmunda and Equisetum.


17.

In succulent plants the stomata open in nightand close in day. Which among the following would be best hypothesis to explain the mechanism of stomatal action in night only.

  • CO2 accumulates, reduces pH, stimulate enzymes resulting in accumulation of sugars.

  • Increase in CO2 concentration, conversion of organic acids into starch resulting in the increased conversion into sugars resulting in K+ transport.

  • Low CO2 concentration accumulates organic acids resulting in the increased concentration of cell sap.

  • CO2 used up, increase pH results in accumulation of sugars.


B.

Increase in CO2 concentration, conversion of organic acids into starch resulting in the increased conversion into sugars resulting in K+ transport.

In CAM plants stomata open at night. In theseplants night acidification occurs. i.e., malic acid is
synthesised during night due to incomplete oxidation of carbohydrates.
In night. 2 C6H12O6+ 3 O23 C4H6O5+ 3H2O
(malic acid)

leads to opening of stomata

At night malic acid formed in guard cells dissociates into H and malate ions. K ion exchange from subsidiary cells with H ions. Thus due to accumulation of K ions osmotic pressure of guard cells increases, endosmosis occurs andguard cells become turgid due to which stomata opens. The malic acid at clay time breaks into CO2 and pyruvic acid thus increasing the concentration of CO2 in mesophyll cells. This is utilised in Calvin cycle to form sugar which is finally converted into starch.


18.

Thermococcus, Methanococcus and Methanobacterium exemplify

  • bacteria whose DNA is relaxed or positively supercoiled but which have a cytoskeleton as well as mitochondria

  • bacteria that contain a cytoskeleton and ribosomes

  • archaebacteria that contains protein homologous to eukaryotic core histones

  • archaebacteria that lack any histones resembling those found in eukaryotes but whose DNA is negatively supercoiled


D.

archaebacteria that lack any histones resembling those found in eukaryotes but whose DNA is negatively supercoiled

Thermococcus, Methanococcus and Methanobacterium exemplify archaebacteria that lack any histones resembling those found in eukaryotes but whose DNA is negatively supercoiled. Archaebacteria do not have a nucleus, the genetic material floats freely in the cytoplasm. They consist of ribosomal RNA. DNA contains a single, circular molecule, which is compact and tightly wound. No protein is associated with DNA. The archaebacterial cell may contain plasmids, which are small, circular pieces of DNA and have a highly negatively supercoiled DNA.


19.

Assertion: The primary protenema of moss by death and decay of cells may break into fragments.

Reason: Each fragment gives rise to leafy gametophyte.

  • If both assertion and reason are true and reason is the correct explanation of assertion

  • If both assertion and reason are true but reason is not the correct explanation of assertion

  • If assertion is true but reason is false

  • If both assertion and reason are false.


A.

If both assertion and reason are true and reason is the correct explanation of assertion

The haploid spores on germination gives rise to alga-like filamentous branched portion called primary protonema. This protonema develops buds, from which leafy gametophyte arises. Sometimes this primary protonema breaks up into small fragments accidentally and these fragments give rise to leafy gametophores.


20.

Cut surfaces of fruit and vegetables often become dark because

  • dirty knife makes it dark

  • oxidation of tannic acid in the presence of trace of iron from the knife makes it dark

  • dust of the air makes it dark

  • none of the above.


B.

oxidation of tannic acid in the presence of trace of iron from the knife makes it dark

When fresh fruits and vegetables are peeled or cut open, the enzyme called polyphenol oxidase (also called tyrosinase) contained in the cells is exposed to and reacts with the oxygen in the air. The reaction that occurs, which is called oxidation, is what turns the fruits and vegetables brown.