Subject

Biology

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

11.

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.


B.

scion

Grafting is the technique ofjoining parts of two plants so as to form a composite plant. One plant has a strong root system called the stock, and the other plant having better flower or fruit yield is known as scion. When a scion is grafted to a stock the root system of the plant has the genotype of stock and fruits produced show genotypes of the scion


12.

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.


B.

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

Myxomycetes, also called Mycetozoa, phylum of funguslike organisms within the kingdom Protista, commonly known as true slime molds. They exhibit characteristics of both protozoans (one-celled microorganisms) and fungi.


13.

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


D.

protect nitrogenase from oxygen

Rhizobium is the nitrogen fixing bacteria present in root nodules of leguminous plants. Roots of a legume secrete chemical attractants flavonoids and betaines. Bacteria collect over the root hairs, release nod factors that causes curling of root hairs around the bacteria, degradations of cell wall and formation of an infection thread enclosing bacteria. The infected cortical cells differentiate and start dividing. It produces swelling of nodules and the infected cells enlarge. Bacteria stop dividing and form irregular polyhedral structures called bacteroids. The host cells develops a pinkish coloured pigment called leghaemoglobin. It is an oxygen scavenger and protects nitrogenase from oxygen. Symbiotic nitrogen fixation requires co-operations of 'Nod' genes of legumes, 'nod' 'nif' and 'fix' genes of bacteria.


14.

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.


B.

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

Angiogram is an X-ray diagnostic procedure used to visualize the blood vessels following injection of a contrast substance into an artery. It is used to image arteries in the brain, heart, kidneys, gastrointestinal tract, aorta, neck (carotids), chest, limbs and pulmonary circuit. Coronary angiography is performed to detect obstruction in the coronary arteries, which can lead to heart attack. It may be performed if you have unstable angina, a typical chest pain, aortic stenosis, or unexplained heart failure


15.

Avena curvature test is a bioassay for examining the activity of

  • auxins

  • cytokinins

  • gibberellins

  • ethylene.


A.

auxins

Bioassay is a testing of biological activity like growth response of a substance by employing plant part. Avena curvature test is a bioassay for examining the activity of auxins. It is based upon experiments of Went. 10° curvature is produced by auxin concentration of150 g/lit at 250C and 90% relative humidity. It can measure auxin upto 300g/litre. Auxin from shoot tip or any other plant organ is allowed to diffuse in a standard size agar block. 15- 30 mm long oat coleoptile grown in dark is held vertically over water. 1 mm tip of colcoptile is removed without injuring the primary leaf. After 3 hours a second decapitation is carried out for 4mm distance. Primary leaf is now pulled loose and agar block supported against it at the tip of decapitated coleoptile. After 90- 100 mm the coleoptile is found to have bent. The curvature is measured


16.

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


D.

Sealing mechanism on wounding

Sieve elements are a component of phloem tissue and are responsible for conduction of food in plants. A sieve tube element has peripheral layer of cytoplasm without any nucleus. The central part is occupied by a network of canals which contain fibrils of p-protein. The protein is vibratite and is believed to actively participate in the transport of nutrients. One general property of its ability to form a gel and it functions as a puncture repair substance forming a plug at any site of damage in sieve element, thus preventing loss of food materials being translocated by the phloem. Thus it is believed to have scaling function on wounding.


17.

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.


A.

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.


18.

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


D.

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

Chromatophores are internal membrane systems present in photosynthetic prokaryotes. These develop as membrane lined sacs or thylakoids from plasma membrane. Thylakoid membranes contain photosynthetic pigments in cyanobacteria and purple bacteria. Small sacs or granules containing pigments phycobilin are attached to these membranes. In green bacteria chromatophores are covered by non-unit, non-lipid protein membrane. They are sometimes called chlorosomes.


19.

"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.


D.

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

The system of classification of seed plants presented by Bentham and Hooker, represented. the most well developed classification of natural system.

The classification was published in 3 volumes of Genera plantarum'. The system divided phanerogams or seed plants into 3 classes dicotyledons, gymnospermae and monocotyledons. Dicotyledons were further subdivided into 3 subclasses - polypetalae, gamopetalae and monochlamydae based on the presence or absence of petals and their fusion. They were further divided into series, orders and families. No orders were recognised within monochlamydae and monocotyledons, the series being directly divided into families. But the system had a lot of demerits within it. He did not know the affinities of the families placed under 'Ordines anomate' and the families were tentativily grouped together. So, a few orders were not placed satisfactorily in the classification. Monochlamydae is an unnatural assemblage of taxa, which belongs elsewhere. The creation of this group has resulted in the separation of many closely related families


20.

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


B.

cambium for secondary growth

Grafting is the technique of joining parts of two plants so as to form a composite plant. Grafting is carried out during period of active growth and rapid healing between two related plants having vascular cambium. One plant has strong root system and the other plant possesses better flower or fruit yield. The former is called stock and the latter is known as scion or graft. Vascular cambium are the lateral meristem found in those vascular plants that exhibit secondary growth. It forms secondary xylem and secondary phloem mostly by periclinal division.