Subject

Biology

Class

NEET Class 12

Test Series

Take Zigya Full and Sectional Test Series. Time it out for real assessment and get your results instantly.

Test Yourself

Practice and master your preparation for a specific topic or chapter. Check you scores at the end of the test.

 Multiple Choice QuestionsMultiple Choice Questions

51.

Assertion : Saccharomyces cerevisiae produces acetic acid.

Reason : Trichoderma polysporum produces blood cholestrol lowering agent.

  • If both assertion and reason are true and reason is the correct explanation of assertion.

  • If both assertion and reason are hue 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.

Yeast (Saccharomyces cerevisiae) is used for commercial production of ethanol. A bioactive molecule, cyclosporin A which is used as an immunosuppressive agent in organ-transplant patients, is produced by the fungus Trichoderma polysporum.


52.

Assertion :Now-a-days, the biodiversity is declining with an accelerated rate.

Reason : Exotic species are considered to be a major cause of extinction of species.

  • If both assertion and reason are true and reason is the correct explanation of assertion.

  • If both assertion and reason are hue 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 hue but reason is not the correct explanation of assertion.

There are four major causes of species extinction due to human interference.

  1. habitat loss and fragmentation
  2. over- exploitation
  3. alien species invasions
  4. co- extinctions

The exotic species are considered to be second major cause of extinction of species (the first being habitat destruction).


53.

Assertion : Periodic abstinence is a natural method where couples abstain from coitus.

Reason : Coitus from day 5-10 should be avoided because this is the time of ovulation.

  • If both assertion and reason are true and reason is the correct explanation of assertion.

  • If both assertion and reason are hue 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.

Periodic abstinence is a natural method of birth control in which the couples avoid or abstain from coitus (copulation or intercourse) from day 10 to 17 of the menstrual cycle because ovulation occurs during this period. The chances of fertilization are very high during this period, therefore, it is called the fertile period.


54.

Assertion: While working on Staphylococci, Alexander Fleming observed that Penicillin nolatum inhibits the growth of the bacteria.

Reason : This inhibiting chemical was commercially extracted and its full potential was established by Alexander Fleming.

  • If both assertion and reason are true and reason is the correct explanation of assertion.

  • If both assertion and reason are hue 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.

Alexander Fleming while working on Staphylococci bacteria, once observed a mould growing in one of his unwashed culture plates around which Staphylococci could not grow. He found out that it was due to a chemical produced by the mould and he named it Penicillin after the mould Penicillium notatum. However, its full potential as an effective antibiotic was established much later by Ernest Chain and Howard Florey.


55.

Assertion : Rice field is an ecosystem for plants and animals.

Reason : Gut of human/animals is an ecosystem for flora and fauna.

  • If both assertion and reason are true and reason is the correct explanation of assertion.

  • If both assertion and reason are hue 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 hue but reason is not the correct explanation of assertion.

The human digestive system consist of about trillions of micro- organisms colonising the gut. Therefore, it is said to be rich in flora and fauna. The micro-orgnaisms perform various functions such as-

  1. fermenting unused energy substrates
  2. training the immune system
  3. preventing growth of pathogenic bacteria
  4. regulating the development of gut producing vitamins for the host.

Fish culture is done in combination with a rice crop, so that they are grown in the water. Therefore, it is an ecosystem inhabitaing plants and animals.


56.

A large quantity of urban sewage is drained to nearby village river. Which among the given conditions would happen after mixing of sewage into the river?

(i) Biochemical oxygen demand (BOD) of receiving water body increases.

(ii) Dissolved oxygen of receiving water body decreases.

(iii) It will not cause mortality among fishes and other aquatic creatures.

(iv) It will lead to nutrient enrichment of receiving water body.

  • (i), (ii) and (iii)

  • (i), (ii) and (iv)

  • (ii) and (iii)

  • (iii) and (iv)


B.

(i), (ii) and (iv)

Sewage having biodegradable organic matter is released into water body, micro- organisms involved in biodegradation consumes lot of oxygen to decompose the sewage. This results in a sharp decline in dissolved oxygen downstream from the point of sewage discharge and hence increases biological oxygen demand (BOD). 

Presence of large amount of nutrients in water causes excessive growth of planktonic  algae known as algal bloom. It causes deterioration of water quality and fish mortality.


57.

Which of the following is a secondary pollutant?

  • Carbon dioxide

  • Nitrogen oxides

  • Peroxyacyl nitrates

  • All of these


C.

Peroxyacyl nitrates

Secondary air pollutants are photochemically produced from primary pollutants and are thus called photochemical oxidants. Ozone, peroxyacyl nitrates, aldehydes and phenols are produced due to photochemical reactions between nitrogen oxides and unsaturated hydrocarbons.


58.

Chromatin is made up of

  • DNA and protein

  • DNA and histone

  • DNA, RNA, protein

  • RNA, histone and oil bodies


C.

DNA, RNA, protein

Nucleus contains nucleoli and chromatin network. Chromatin contains DNA and some basic proteins called histones, some nonhistone proteins and also RNA.


59.

Assertion : Only a boy child could be born with a substitution of glutamic acid by valine on 6 codon of beta-chain of haemoglobin.

Reason : The gene for the above mutation is found on Y-chromosome.

  • If both assertion and reason are true and reason is the correct explanation of assertion.

  • If both assertion and reason are hue 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.

Sickle cell anaemia is an autosomal recessive hereditary disorder in which the erythrocytes become sickle-shaped under oxygen deficiency as during strenuous exercise and at high altitudes. The disease is caused by the formation of an abnormal haemoglobin called haemoglobin- S. It differs from normal haemoglobin in only one amino acid- 6th amino acid of β- chain. Glutamic acid is replaced by valine due to substitution of T by A in the second position of the triplet codon (CTC) which is changed to CAC in the β- haemoglobin gene on chromosome 11.


60.

Assertion: In a regular medical examination of a small population, a 35 years old lady was found to have higher levels of oestrogens, progesterone in her blood.

Reason : The lady is 12 weeks pregnant.

  • If both assertion and reason are true and reason is the correct explanation of assertion.

  • If both assertion and reason are hue 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.

Human chorionic gonadotrophin (hCG) hormone is secreted by the trophoblast cells and is assayed during pregnancy test. It helps in maintaining the mother's corpus luteum. Corpus luteum prevents menstruation and ovulations by secreting oestrogens and progesterones. 

Around 10th week of pregnancy, hCG secretion is declined by placenta, menstruation stops and the amount of estrogens and progesterone exceeds the amount secreted by ovaries. High levels of estrogen and progesterone inhibits the level of FSH and LH and prevents ovulation. It also maintains the uterus and prepare it for labor and delivery.