Subject

Biology

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

51.

Assertion: Parturition is induced by neural signal in maternal pituitary.

Reason: At the end of gestation period, the maternal pituitary releases prolactin which causes uterine contractions.

  • 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.


D.

If both assertion and reason are false.

The process of delivery of the foetus (childbirth) is called parturition. Parturition is induced by a complex neuroendocrine mechanism. The signals for parturition originate from the fully developed foetus and the placenta which induce mild uterine contractions called foetal ejection reflex This triggers release of oxytocin from the maternal pituitary. Oxytocin acts on the uterine muscles and causes stronger uterine contractions, which in turn stimulate further secretion of oxytocin. The stimulatory reflex between the uterine contractions and oxytocin secretion continues resulting in stronger and stronger contractions. This leads to expulsion of the baby out of the uterus through the birth canal.


52.

Assertion: BOD of a river polluted by sewage is more than 20 ppm.

Reason: Polluted river contains excess of organic matter.

  • 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. 

Degree of impurity of water due to organic matter is measured in terms of BOD (Biochemical oxygen demand). BOD is the oxygen in milligrams required for five days in one litre of water at 20°C for the microorganisms to metabolise organic waste. It is measured in the milligrams of oxygen taken up in one litre of sewage. The effluent that is legally allowed to be discharged into a river or stream should be such that BOD at 20°C should not be more than 20 ppm, i.e., 20 mg per litre.


53.

An example of gene therapy is

  • production of injectable hepatitis B vaccine

  • production of vaccines in food crops like potatoes which can be eaten

  • introduction of gene for adenosine deaminase in persons suffering from Severe Combined Immuno Deficiency (SCID)

  • production of test tube babies by artificial insemination and implantation of fertilised eggs


C.

introduction of gene for adenosine deaminase in persons suffering from Severe Combined Immuno Deficiency (SCID)

Gene therapy is the method of correction of genetic defect by delivery of normal gene to replace the faulty gene. The first clinical gene therapy was given to a 4-year old girl with adenosine deaminase (ADA) deficiency. Deficiency of ADA causes SCID.


54.

Assertion: Darwin's finches are a classical example of natural selection.

Reason: Darwin explained that the difference in size and shape of the beaks of the species was a result ofthe adaptation ofthe species to different food habits.

  • 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. 

Darwin's finches represent an excellent example of adaptive radiation. Darwin's finches showed wide variations in beak shape and size from island to island. Darwin deduced that these variations made the finches better adapted to take advantage of the food in their particular local environment - thin, sharp beaks prevailing where the birds' main food was insects and grubs, and large claw shaped beaks where their diet was buds, fruits and nuts.


55.

Assertion: Mast cells in the human body release excessive amounts of inflammatory chemicals which cause allergic reactions.

Reason: Allergens in the environment on reaching human body stimulate mast cells in certain individuals.

  • 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. 

Mast cells act on body's defense mechanism. When some allergens like different pollutants, smog, smoke, pollen grains etc. come in contact with mast cells, they stimulate the mast cells. The allergic reaction is triggered by cross linking of IgE molecules on the surface of mast cells by allergen and ultimately mast cells release excessive amounts of inflammatory chemicals which cause allergic reactions.


56.

Assertion: GM foods are facing widespread resistance by the people.

Reason: GM foods have mutated genes which cause infections and allergies.

  • 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 GM crops are fast becoming a part of agriculture throughout the world because of their contribution to the increased crop productivity and to global food, feed and fiber security, besides their use in health-care and industry.

However, GM foods are facing widespread resistance by the people from all over the world. It is because transgenes in commercial crops can endanger native species. For example, the gene for Bt toxin expressed in pollen might endanger pollinators like honeybees. These crops cause problems in human health by supplying allergens and transfer of antibiotic resistance markers. The GM crops may change the fundamental vegetable nature of plants as the genes from animals (e.g., fish or mouse) are being introduced into crop plants. GM foods also have a bad effect on environment and biodiversity.


57.

Assertion: In recombinant DNA technology, human genes are often transferred into bacteria (prokaryotes) or yeasts (eukaryotes).

Reason: Both bacteria and yeasts multiply very fast to form huge populations which express the desired gene.

  • 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 recombinant DNA technology, widely used hosts for replication and amplification of recombinant DNA are prokaryotic E. coli and the eukaryotic yeast. They replicate very fast to form huge populations which express the desired gene. Yeast artificial chromosomes (YACs) are important cloning tools for the analysis of complex genome such as that of humans. They allow the maintenance, propagation and analysis of such genome in an experimentally tractable system, the yeast.


58.

Assertion: Filarial worm is transmitted to humans by Culex mosquito.

Reason: Culex prefers to breed in fresh water.

  • 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.


C.

If assertion is true but reason is false. 

Wuchereria (W.bancrofti and W.malayi), the filarial worms cause a slowly developing chronic inflammation of the organs in which they live for many years, usually the lymphatic vessels of the lower limbs, and the disease is called filariasis. The pathogen spreads from one human being to another through mosquitoes like Culex and to a less extent by Anopheles and Aedes. The parasite resides in lymph vessels, connective tissues and mesentery. It is manifestated by lymphoedema accompanied by thickening of subcutaneous tissues and skin so that there is permanent swelling mostly of feet, legs, thighs, scrotal sacs, breast etc. In Culex and other mosquitoes females are blood sucking while males suck juices of flowers and fruits. Female Culex carries filarial worm from one person to another. It prefers to breed in dirty water near human habitation.


59.

Apomixis is

  • formation of seeds by fusion of gametes

  • formation of seeds without syngamy and meiosis

  • formation of seeds with syngamy but no meiosis

  • none of the above


B.

formation of seeds without syngamy and meiosis

Apomixis (Gk. apo-without, mixismixing) is a mode of reproduction which does not involve formation of zygote through gametic fusion. It is, therefore, akin to asexual reproduction. In plants apomixis commonly mimics sexual reproduction but produces seeds without fertilisation, e.g., some species of Asteraceae and grasses.


60.

A small rise in the body temperature of humans is corrected by

(i) sweating
(ii) dilating the skin arteries
(iii) constricting the skin arteries
(iv) increased tension of muscles in the skin

  • (i) only

  • (ii) only

  • (i) and (ii)

  • (iii) and (iv)


C.

(i) and (ii)

A small rise in body temperature is detected by sensory receptors in the skin and by special neurons, which monitor blood temperature, in the hypothalamus itself. When the neural centre of the hypothalamus involved in lowering body temperature receives information that body temperature is too high, it commands the arteries of the skin to dilate so that more blood, and therefore more heat, reaches the surface where heat can be lost. A large rise in body temperature causes the hypothalamus to command both an extreme dilation in the arteries of the skin and the release of sweat from the body