Class 12th Biology 2018 Set1 Delhi Board Paper Solution

Section 1

Q1	Write the dual purpose served by Deoxyribonucleoside triphosphates in polymerisation.
Q2	Name two diseases whose spread can be controlled by the eradication of Aedes mosquitoes.
Q3	How do cytokine barriers provide innate immunity in humans?
Q4	Write the Names of the following: A 15 mya primate that was ape-like
Q4	Write the Names of the following: A 2 mya primate that lived in East African grasslands
Q5	Mention the chemical change that proinsulin undergoes, to be able to act as mature insulin.

Section 2

Q6	Your advice is sought to improve the nitrogen content of the soil to be used for cultivation of a non-leguminous terrestrial crop. (a) Recommend two microbes that can enrich the soil with nitrogen. (b) Why do leguminous crops not require such enrichment of the soil?
Q7	With the help of an algebraic equation, how did Hardy-Weinberg explain that in a given population the frequency of occurrence of alleles of a gene is supposed to remain the same through generations?
Q7	Although a prokaryotic cell has no defined nucleus, yet DNA is not scattered through the cell. Explain.
Q8	How did a citizen group called Friends of Arcata Marsh, Arcata, California, USA, help to improve water quality of the marshland using integrated Waste Water Treatment? Explain in four steps.
Q9	You have obtained a high yielding variety of tomato. Name and explain the procedure that ensures retention of the desired characteristics repeatedly in large populations of future generations of the tomato crop.
Q10	Name the source plant of heroin drug. How is it obtained from the plant.
Q10	Write the effects of heroin on the human body.

Section 3

Q11	Draw a diagram of a mature human sperm. Label any three parts and write their functions.
Q12	Expand VNTR and describe its role in DNA fingerprinting.
Q12	List any two applications of DNA fingerprinting technique.
Q13	Differentiate between Parthenocarpy and parthenogenesis. Give one example of each.
Q14	Medically it is advised to all young mother that breastfeeding is the best for their newborn babies. Do you agree? Give reasons in support of your answer.
Q15	Explain the mechanism of ‘sex determination’ in birds. How does it differ from that of human beings?
Q16	How has the development of bioreactor helped in biotechnology?
Q16	Name two commonly used bioreactors. State the importance of using a bioreactor.
Q17	Explain the roles of the following with the help of an example each in recombinant DNA technology: (a) Restriction enzymes (b) Plasmids
Q18	Explain out-breeding, out crossing and cross-breeding practices in animal husbandry.
Q19	Organic farmers prefer biological control of diseases and pests to the use of chemicals for the same purpose. Justify.
Q19	Give an example of a bacterium, a fungus and an insect that are used as biocontrol agents.
Q20	Differentiate between analogous and homologous structures.
Q20	Select and write analogous structures from the list given below: (i) Wings of butterfly and birds (ii) Vertebrae hearts (iii) Tendrils of bougainvillea and cucurbita (iv) Tubers of sweet potato and potato
Q21	“India has greater ecosystem diversity than Norway.” Do you agree with the statement? Give reasons in support of your answer.
Q21	Write the difference between genetic biodiversity and species biodiversity that exists at all the levels of biological organisation.
Q22	How has the use of Agrobacterium as vectors helped in controlling Meloidegyne incognitia infestation is tobacco plants? Explain in correct sequence.

Section 4

Q23	Looking at the deteriorating air quality because of air pollution in many cities of the country, the citizens are very much worried and concerned about their health. The doctors have declared health emergency in the cities where the air quality is very severely poor. (a) Mention any two major causes of air pollution. (b) Write any two harmful effects of air pollution to plants and humans. (c) As a captain of your school Eco-club, suggest any two programmes you would plan to organise in the school so as to bring awareness among the students on how to check air pollution in and around the school.
Q24	Describe any two devices in a flowering plant which prevent both autogamy and geitonogamy.
Q24	Explain the events upto double fertilisation after the pollen tube enters one of the synergids in an ovule of an angiosperm.
Q24	Explain menstrual cycle in human females.
Q24	How can the scientific understanding of the menstrual cycle of human females help as a contraceptive measure?
Q25	Write the scientific name of the organism Thomas Hunt Morgan and his colleagues worked with for their experiments. Explain the correlation between linkage and recombination with respect to genes as studied by them.
Q25	How did Sturtevant explain gene mapping while working with Morgan?
Q25	State the ‘Central dogma’ as proposed by Francis Crick. Are there any exceptions to it? Support your answer with a reason and an example.
Q25	Explain how the biochemical characterisation (nature) of ‘Transforming Principle’ was determined, which was not defined from Griffith’s experiments.
Q26	Following are the responses of different animals to various abiotic factors. Describe each one with the help of an example. (i) Regulate (ii) Conform (iii) Migrate (iv) Suspend
Q26	If 8 individuals in a population of 80 butterflies die in a week, calculate the death rate of population of butterflies during that period.
Q26	What is a trophic level in an ecosystem? What is ‘standing crop’ with reference to it?
Q26	Explain the role of the ‘first trophic level’ in an ecosystem.
Q26	How is the detritus food chain connected with the grazing food chain in a natural ecosystem?