Subject

Biology

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

1.

One common example of simple reflex is

  • tying your shoe laces while talking to another person and not looking at them

  • watering of mouth at the sight of a favourite food

  • climbing up a stairs in dark without stumbling

  • closing of eyes when strong light is flashed across them.


D.

closing of eyes when strong light is flashed across them.

Simple or unconditional reflexes are present in an individual right from birth. They are specific, predictable, purposeful and have survival value, e.g. breast feeding and swallowing in newly born babies and blinking of eyes are examples of unconditioned reflexes.

(a), (b) and (c) are the examples of conditional reflexes and are not present at birth but develop later in life through learning habit.


2.

Which one of the following is a matching pair

  • Lubb - Sharp closure of AV valves at the beginning of ventricular systole

  • Dup - Sudden opening of semilunar valves at the beginning of ventricular diastole

  • Pulsation of the radial artery - Valves in the blood vessels

  • Initiation of the heart beat - Purkinje fibres


A.

Lubb - Sharp closure of AV valves at the beginning of ventricular systole

Lubb (first sound, systolic sound) is the first heart sound which is low pitched, not very loud, of long duration (about 0.15 seconds) and is produced partly due to closure of atria-ventricular valves (tricuspid and bicuspid) and partly by the contraction of the muscles in the ventricles


3.

Injury to vagus nerve in humans is not likely to affect

  • tongue movements

  • gastrointestinal movements

  • pancreatic secretion

  • cardiac movements.


A.

tongue movements

Vagus nerve arises from the side of medulla oblongata. It innervates the larynx, trachea, oesophagus, stomach, lungs, heart and intestines. It is a mixed nerve. It controls the visceral sensations and visceral movements, i.e., heart beat, respiratory movements, peristalsis, sound production, etc. Movement of the tongue is controlled by hypoglossal nerve as it innervates the muscles of the tongue.


4.

Select one of the following pairs of important features distinguishing Gnetum from Cycas and Pinus and showing affinities with angiosperms.

  • Perianth and two integuments

  • Embryo development and apical meristem

  • Absence of resin duct and leaf venation

  • Presence of vessel elements and absence of archegonia


D.

Presence of vessel elements and absence of archegonia

Unlike Cycas and Pinus, Gnetum shows the occurrence of vessel elements and the absence of archegonia. Archegonia are altogether absent in the female gametophyte and vessels occur in the xylem along with the tracheids in the secondary wood. Thus Gnetum shows affinities with angiosperms. Besides it resembles angiosperms in several other aspects like presence oftetrasporic embryo sac, free nuclear divisions in the embryo sac, two cotyledonous embryo etc.


5.

During the life-cycle, Fasciola hepatica (liver fluke) infects its intermediate host and primary host at the following larval stages respectively

  • redia and miracidium

  • cercaria and redia

  • metacercaria and cercaria

  • miracidium and metacercaria.


D.

miracidium and metacercaria.

Life cycle of F. hepatica is complete and completed in two hosts. Primary host, in which the adult fluke lives, is sheep. While the intermediate host, in which numerous larval stages are passed, is a snail (Lymnaea, Planorbis, etc.). This type of life cycle, involving two different kinds of hosts, is termed digenetic.

Miracidium larva is the larval stage involved in life cycle. When suitable conditions become available, the encapsulated embryo, in 4-15 days, differentiates into a miracidium larva. It hatches out and swims in water. Metacercaria develops into adult fluke only inside its definitive host or sheep. The latter gets infection by grazing on leaves and grass blades to which the cysts are attached. Metacercaria survives action of host's gastric juice as its cyst is insoluble in it. Cyst wall finally dissolves in proximal part of intestine and liberates the larva.


6.

Cattle fed with spoilt hay of sweet clover which contains dicumarol

  • are healthier due to a good diet

  • catch infections easily

  • may suffer vitamin K deficiency and prolonged bleeding

  • may suffer from beri-beri due to deficiency of vitamin B1


C.

may suffer vitamin K deficiency and prolonged bleeding

Dicumarol is an anticoagulant found in spoilts sweet clover causes hemorrhage and other symptoms of bleeding disorder by disrupting vitamin K metabolism and preventing the activation of prothrombin and certain other clotting factors by the liver.


7.

Which one of the following methods is commonly used to maintain the genetic traits of a given plant

  • By propagating through seed germination

  • By propagating through vegetative multiplication

  • By generating hybrids through intergeneric pollination

  • By treating the seeds with gamma radiations


B.

By propagating through vegetative multiplication

The propagation through vegetative multiplication is used to maintain the genetic traits of a given plant. It gives rise to genetically uniform population or clone. In case of plants propagated through seeds, variations creep in due to chance segregation of genes during meiosis and their chance combination during fertilization.


8.

Phytohormones are

  • hormones regulating growth from seed to adulthood

  • growth regulators synthesised by plants and influencing physiological process

  • hormones regulating flowering

  • hormones regulating secondary growth.


B.

growth regulators synthesised by plants and influencing physiological process

Growth regulators are organic substances, other than nutrients, which in low concentration regulate growth, differentiation and development by promoting or inhibiting the same. Phytohormones are growth regulators produced naturally in plants and translocated to another region for regulating one or more physiological reactions when present in low concentration. Phytohormone can have a promoting or inhibiting effect on a process


9.

You are required to draw blood from a patient and to keep it in a test tube for analysis of blood corpuscles and plasma. You are also provided with the following four types of test tubes. Which of these will you not use for the purpose

  • Test tube containing calcium bicarbonate

  • Chilled test tube

  • Test tube containing heparin

  • Test tube containing sodium hydroxide


C.

Test tube containing heparin

Clotting of collected blood can be prevented by ­

1) coating test tubes with silicon (which produce non wettable surface similar in its smoothness to endothelial lining of blood vessels).

2) adding chelating agents (includes trisodium citrate, sodium oxalate and sodium EDTA) which remove calcium which is important for blood coagulation, and prevent blood clotting.

3) adding heparin, most powerful anticoagulant which acts indirectly by activating plasma antithrombin III. Heparin is effective both in vivo and in vitro. Whereas the option a, b and d are effective in vitro. Heparinized blood is not suitable for blood counts (as it alters the shape of RBC's and WBC's which affects blood testing), Fragility testing and complement fixation tests.


10.

A patient of diabetes mellitus excretes glucose in urine even when he is kept in a carbohydrate free diet. It is because

  • fats are catabolised in adipose tissues to form glucose

  • amino acids are catabolised in kidney to form glucose

  • amino acids are discharged in blood stream from liver

  • glycogen from muscles is released in blood stream.


A.

fats are catabolised in adipose tissues to form glucose

A patient of diabetes mellitus is unable to produce or fail to utilize insulin hormone. Thus, he is unable to store glucose in the form of glycogen. Hence, he started to excrete glucose in the urine. A patient is kept in carbohydrate free diet yet he excretes glocose in urine because high level of glucose not only depends on dietary carbohydrates but also on glycogenolysis (degradation of glycogen in liver) and gluconeogenesis (breakdown of fats into glucose in adipose tissues and coversion of muscle lactate into glucose via cori cycle).