Subject

Biology

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

11.

The blood calcium level is lowered by the deficiency of 

  • parathormone

  • thyroxine

  • calcitonin

  • calcitonin


A.

parathormone

The chief cells of the parathyroids secrete parathormone. Its deficiency causes the lowering of blood calcium level. This increases the excitability of nerves and muscles causing cramps and convulsions. This caused parathyroid tetany characterised by sustained contractions of the muscles of larynx, face, hands and feet.

Calcitonin is secreted when calcium level is high in blood it has an opposite action to that of parathyroid hormone and lowers the calcium level by suppressing the release of calcium ions from the bones.

Thyroxine is secreted from the thyroid gland. It regulates the metabolic rate of the body and thus, maintain basal metabolic rate, stimulate protein synthesis and therefore, promote the growth of the body tissue.

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12.

The rupture and fractionation do not usually occur in the water column in vessel/tracheids during the ascent of sap because of 

  • lignified thick walls

  • cohesion and adhesion

  • weak gravitational pull

  • weak gravitational pull


B.

cohesion and adhesion

The Vertical conduction of water from root to aerial parts of the plant is called ascent of sap. The water molecules remain joined to each other due to a force of attraction called cohesion force. This attraction is due to the presence of hydrogen bonds between them. The magnitude of this force is very high, therefore, the continuous water column in the xylem cannot be broken easily due to the force of gravity or other obstructions offered by internal tissues in the upward movement of water. This adhesive property of water, ie, the attraction between the water molecules and the walls of xylem ensures the continuity of water column in xylem.

Due to transpiration water evaporates to outer atmosphere through stomata. As a result leaf cells develop low water potential and water from leaf veins moves into leaf cells. They xylem of the main stem. A pressure (pull) is thus, exerted by all the leaves on the stems, which is called transpiration pull. This is strong enough to pull up the column of water to a great height.

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13.

The length of different internodes in a culm of sugarcane is variable because of

  • shoot apical meristem

  • position of axillary buds

  • size of leaf lamina at the node below each internode

  • size of leaf lamina at the node below each internode


D.

size of leaf lamina at the node below each internode

Intercalary meristem is prsent away from apical meristem in primary permanent tissue. It is present at the base of internodes, eg, in family-Gramineae or at the base of leaves, eg, Pinus or at the base of the node, eg, Mentha. Intercalary meristem is responsible for the increase in length. 
The shoot apical meristem present at the apices of the shoot is self-determining and autonomous organising centre. The primary growth and differentiation of primary tissue are entirely due to this meristem as it continuously divides giving rise to new cells. These are the apical meristems that increase the length of the plant but not internodes variability. 

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14.

Which one of the following is linked to the discovery of Bordeaux mixture as a popular fungicide?

  • Bacterial leaf blight of rice

  • Downy mildew of grapes

  • Loose smut of wheat

  • Loose smut of wheat


B.

Downy mildew of grapes

Bordeaux mixture was discovered by Millardet in France in 1882. It is prepared by dissolving 40 g of copper sulphate and 40 g of calcium hydroxide in 5 L of water. It was first used to control downy mildew disease of grape-vine that is caused by a fungus Plasmopara viticola. Black rust of wheat is caused by Puccinia graminis Tritici. The use of fungicide Dithane Z- 78 and Dithane M- 45 control the disease even at a lower concentration.
Loose smut of wheat is caused by Ustilago tritici. The use of fungicides (systemic fungicide like D- 735 and F- 461)give the quite encouraging result.

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15.

Which one of the following is heterosporous? 

  • Dryopteris 

  • Salvinia

  • Adiantum

  • Adiantum


B.

Salvinia

Heterospory is the production of spores of two different sizes and two different developmental patterns. Small spores are called microspores and larger as megaspore. Microspores germinate to produce the male gametophyte or microgametophyte that bear male sex organs while megaspores germinate to form female gametophyte or megagametophytes that bear archegonia or female sex organs. It is most important evolutionary development in the vascular plants because it has ultimately lead to seed development eg, Selaginella, Marselia Salvinia, Azolla, isoetes.

Dryopteris is homosporous a 32-64 haploid spores are produced in each sporangium.
Adiantum is also homosporous. The spores are the pioneer structures of the gametophytic generation.

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16.

Endosperm is consumed by developing embryo in the seed of 

  • coconut

  • castor

  • pea

  • pea


C.

pea

Endosperm, if present acts as the food storage tissue of a seed. The seeds with endosperm are called endospermic or albuminous (eg Cocos nucifera, Ricinus Communis, Zea mays and other cereals, while those without endosperm are called non-endospermic or exalbuminous seeds (eg, Brassica campestris, Arachis hypogea, Pisum Sativum).

In castor (Ricinus communis) the endosperm is whitish soft mass rich with oil reserve food material. 

The endosperm in maize is yellowish in colour, the outermost layer of endosperms is called aleurone layer, which is rich in protein.

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17.

The fleshy receptacle of  syconus of fig encloses a number of 

  • achenes

  • samaras

  • berries

  • berries


A.

achenes

Syconus is a composite fruit develops from the hypanthodium inflorescence, eg, Ficus carica, Ficus Benghalensis. The flask-shaped receptacle encloses female flowers that give rise to achene - like fruits. This fruit possesses a small pore protected by scaly leaves. THe receptacle that becomes fleshy is edible.

Samara is a single-seeded, dry indehiscent fruit. Its pericarp becomes membranous and flat-like wings that help in dispersal, eg Ulmus Holoptelia indica.


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18.

Dry indehiscent single-seeded fruit formed from bicarpellary syncarpous inferior ovary is 

  • Caryopsis

  • cypsela

  • Adiantum

  • Adiantum


B.

cypsela

Cypsela is dry, indehiscent, single-seeded fruit develops from an unilocular, single ovulate inferior ovary of bicarpellary, syncarpous, gynoecium possessing basal placentation. The fruit wall develops from pericarp and thalamus and is thin and remains attached to the seed at one point, eg, Helianthus.

Caryopsis are dry, indehiscent, the small single-seeded fruit develops from unilocular single ovule, superior ovary of the multi carpellary gynoecium. It differs from typical achenes as their pericarp is completely fused with the seed coat or testa, eg, Poaceae.

Cremocarp is bilocular and two seeded schizocarpic fruits (small, dry) developed from the inferior ovary of bis carpellary, syncarpous gynoecium possessing persistent stylopodium, eg, Apiaceae.

Berry is fleshy, indehiscent, few to multi-seeded fruit derived from multi carpellary syncarpous gynoecium.The fleshy pericarp of berry consists of epicarp. Mesocarp and endocarp.

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19.

Which one of the following is the correct difference between rod cells and cone cells of our retina? 

  • Features

    Rod cells

    Cone cells

    Visual acuity

    High

    Low

  • Features

    Rod cells

    Cone cells

    Visual Pigment contained

    Iodeosin

    Rhodopsin

  • Features

    Rod cells

    Cone cells

    Overall function

    Vision in poor light

    Colour vision and detailed vision in bright light

  • Features

    Rod cells

    Cone cells

    Overall function

    Vision in poor light

    Colour vision and detailed vision in bright light


C.

Features

Rod cells

Cone cells

Overall function

Vision in poor light

Colour vision and detailed vision in bright light

The retina is the neural and sensory layer of the eyeball. A small, oval yellowish area of the retina lying exactly opposite the centre of the cornea is named the macula lutea or yellow spot, which has at its middle a shallow depression the fovea centrails. The foveacentrails has cone cells only. It is devoid or rods and blood vessels. The rods contain the rhodopsin (visual purple) pigment and enable to animals to see in darkness. Therefore. present in large number in nocturanal animals.The cones contain the iodopsin (visual violet) pigment and chiefly concerned with distinction in colour and light vision during daytime.

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20.

Which one of the followings in birds, indicates their reptilian ancestry?

  • Scales on their hind limbs

  • Four chambered heart

  • Two special chambers crop and gizzard in their digestive tract


C.

Two special chambers crop and gizzard in their digestive tract

Nearly a century ago, T H Huxley called birds 'glorified reptiles' thereby meaning that birds have evolved from some reptilian ancestor. Both birds and reptiles lay the same type of eggs, which are deposited outside water. Eggs are large and telolecithal. The ovum is surrounded by albumen, an egg membrane and a thick hard calcareous shell, which are all secreted by special glands located in the walls of the oviduct. 

Birds like mammals have a completely four-chambered heart with double circulation, in which there is no mixing of pure and impure blood., All birds have horny epidermal scales confined to the lower parts of their legs and feet, which are exactly like the epidermal scales of the reptiles. Besides birds are covered by feathers, which are homologous to the reptilian horny scales as they have a similar origin and develop from similar germ buds.

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