Subject

Biology

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

51.

Assertion: A gene from Bacillus thuringiensis is incorporated in plant genome to increase their yield.

Reason: Bacillus thuringiensis has Bt toxin producing gene, which kills the larva of insects

  • 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

Bacillus thuringiensis is a bacterium found in soil worldwide. Several strains can infect and kill insects. Due to this property, through genetic engineering, gene coding for insecticide is incorporated into plant genome. Plant having this gene are insect resistant thus high yielding e.g. Bt cotton is usually resistant to bollworm disease of cotton. It is the first genetically modified crop of India. This produces its own insecticide, as it contain a gene from soil bacterium Bacillus thuringiensis.


52.

Assertion: Blood group 'O' have anti-A & antiB antibodies.

Reason: It does not have any antigens.

  • 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.


B.

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

ABO blood groups are determined by the gene I (iso agglutinin). There are three alleles, IA, IB and IO of this gene. Proteins produced by the IA and IB alleles are called A antigen and B antigen. People with blood group A have the A antigen on the surface of their RBCs, and antibodies against antigen Bin their plasma. Persons with blood group B have B antigen on their RBCs, and antibodies against A antigen in their plasma. Individuals with AB blood group have both antigen A and antigen B on their RBCs, and no antibodies for either of the antigens in their plasma. Type O individuals are without A and B antigens on their RBCs, but have antibodies for both these antigens in their plasma.


53.

Assertion: Algal blooms are formed in nutrientless water.

Reason: Algal blooms in water turn it unfit for human consumption, but cause enormous growth of fish.

  • 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.

Algal blooms are a result of eutrophication. Eutrophication involves change in biological
productivity and nutrient content of a water body. They are harmful for both humans and aquatic
organisms. Eutrophication results in higher BOD and reduced dissolved oxygen in water body.
It causes death of fish and other aquatic animals.


54.

Assertion: Sporozoites of malarial parasite enter in the human body due to biting of freshly born female Anopheles mosquito, whose mother was a carrier of malarial parasite.

Reason: Male and female gametocytes of malarial parasites are formed in the human intestine

  • 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.


B.

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

A healthy person acquires infection when a female Anopheles mosquito, containing infective stages of parasite (sporozoites) in its salivary glands, bites him for sucking his blood. The mosquito punctures the host's skin by its proboscis and first introduces some saliva into blood stream. Along with saliva, thousands of sporozoites contained therein are also inoculated. Sporozoites represent the infective forms of parasite.


55.

Assertion: In some species of asteraceae and poaceae seeds are formed without fertilization.

Reason: Formation of fruit without fertilization is called parthenocarpy.

  • 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.


B.

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

Formation of seeds without fertilization is called apomixis. It leads to clonal reproduction in which all offsprings are by and large genetically identical to the parent. The egg contains a full complement of genes and does not need to fuse with a sperm to produce a zygote. Apomixis provides for the perpetuation of traits favourable to individual survival but eliminates the longer-term evolutionary advantage of biparental inheritance. In Asteraceae, various genera and individual species of the order asterales are known to reproduce by apomixis (the setting of seeds without fertilization), either completely or in addition to normal sexual means.

In poaceae about 35 genera produce seeds without fertilization. On the other hand, parthenocarpy is development of fruits without fertilization. The fruit resembles a normally produced fruit but is seedless, e.g. pineapple, banana, cucumber, grape, orange, grapefruit etc.


56.

Assertion: Now-a-days amniocentesis is banned.

Reason: Amniocentesis gives the information of any abnormality in the foetus and many other complications regarding pregnancy can be detected.

  • 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.


B.

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

Amniocentesis is a foetal sex determination and disorder test based on the chromosomal pattern in the amniotic fluid surrounding the developing embryo. The amniotic fluid contains cells from foetus skin and respiratory tract.

These cells are cultured and are used to determine chromosomal abnormalities (Down's syndrome, Klinefelter's syndrome, etc.) and metabolic disorders (phenylketonuria, sickle cell anaemia, etc.) of the foetus. But now-a-days instead of positive uses of amniocentesis it is being used for female foeticide. Sex of the foetus is determined using amniocentesis and then if it turns out to been a female one, foetus is aborted. That is why amniocentesis has been banned in India.


57.

Assertion: A geneticist crossed two plants, he got 50% tall and 50% dwarf progenies.

Reason: It follows Mendelian law as one of the parent plant might be heterozygous.

  • 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

It can be explained as follows

or 50% tall, 50% dwarf progeny


58.

Which of the following features can be said to be a true defining feature of living beings without any exception

  • They can digest their food.

  • All of them can reproduce.

  • They can regenerate.

  • They can respond to external stimuli.


D.

They can respond to external stimuli.

All organisms, from the prokaryotes to the most complex eukaryotes can sense and respond to environmental cues eg. Photoperiod affects reproduction in seasonal breeders, both· plants and animals. Consciousness therefore, becomes the defining property of living organisms.


59.

Assertion: A mangrove tree growing in marshy place has pneumatophores.

Reason: Pneumatophores help in better anchorage to marshy soil.

  • 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

Mangroves which form shallow littoral forests near sea shores areas are halophytes. Mangrove grow in physiologically dry environment (water is available in plenty but in the form of strong salt solution). These plants develop shallow rootings due to water logged environment where oxygen scarcity prevails. To ensure proper aeration in root system, plants produce respiratory roots or pneumatophores which are negatively geotropic peg-like projections above ground with numerous pores or lenticels for gaseous exchange:


60.

Assertion: Corpus luteum is produced by Graafian follicle after ovulation.

Reason: It secretes estrogen which is necessary to maintain pregnancy.

  • 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.


B.

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

After ovulation, the empty Graafian follicle contains a blood clot which is called corpus haemorrhagic. Its granulosa cells continue to proliferate, develop yellow carotene pigment or lutein and get converted into lutein cells. This converts the ruptured follicle into yellow body called corpus luteum. It becomes a temporary endocrine gland secreting progesterone with small quantity of estrogen.