CBSE Class 12 Biology Solved Practice Paper 2017: Set – II

Question1:  Meiosis has to occur for production of haploid gametes in diploid organisms.  Justify.

Sol. Meiosis reduces the chromosome number to half in daughter cells and thereby, produces haploid gametes from diploid organisms.

Question 2: Compare and contrast characters of Ramapithecus and Dryopithecus.

Sol. Both Dryopithecus and Ramapithecus were hairy and walked like gorillas and chimpanzees. Ramapithecus was more man-like while Dryopithecus was more ape-like.

Question 3:  Name the cross that leads to production of mules. Mention the significance of the process.

Sol.  Interspecific hybridization. It leads to production of progeny having desirable characters of both parents.

Question 4: What does the second amendment of the Indian Patents Bill take into consideration?

Sol.  It considers patent terms emergency provisions and research and development initiative.

Question 5:  Why should the motor vehicles equipped with catalytic converter use unleaded petrol?

Sol.  Motor vehicles equipped with catalytic converter should use unleaded petrol because lead in the petrol inactivates the catalyst.

Question 6: Production of unisexual flowers prevents autogamy but not geitonogamy while dioecy prevents both autogamy and geitonogamy. Explain.

Sol.  If the unisexual flowers are present on the same plant (monoecious), it would prevent autogamy but not geitonogamy. Since dioecy refers to presence of male and female flowers on different plants, it would prevent both autogamy and geitonogamy.

Question 7:  Same polypeptide chain can be encoded by DNA with more than one type of nucleotide sequence of DNA. Explain.
Sol.  Degeneracy of genetic code allows one amino acid to be encoded by multiple codons; hence, same polypeptide chain can be encoded by DNA with more than one type of nucleotide sequence of DNA.

Question 8: Mention the breeding strategy used to develop the improved breeds of cattle through conventional animal breeding techniques.

Sol. Superior males and superior females of the same breed are identified and mated in pairs and the progeny of superior males and females among them are identified for further mating.

Question 9:  Use of biocontrol measures greatly reduces dependence on toxic chemicals and pesticides. Justify with one example.

Sol. The Ladybird and Dragonflies are useful to get rid of aphids and mosquitoes, respectively and thus, there is no need of use of those toxic insecticides.

Question 10: The ‘Sixth Extinction’ presently in progress different from the previous episodes. How?

OR

The number of species waiting to be saved from extinction far exceeds the conservation resources available. Give one solution to address this problem.

Sol. The current Sixth species extinction rates are estimated to be 100 to 1,000 times faster than in the pre-human times and anthropogenic activities are responsible for the faster rates.

OR

The problem can be addressed by targeting the biodiversity conversation in ‘biodiversity hotspots’ regions with very high levels of species richness and high degree of endemism.