Class 12th Biology 2012 Set2 Delhi Board Paper Solution

Section 1

Q1	Cucurbits and papaya plants bear staminate and pistillate flowers. Mention the categories they are put under separately on the basis of the type of flowers they bear.
Q2	A garden pea plant (A) produced inflated yellow pod, and another plant (B) of the same species produced constricted green pods. Identify the dominant traits.
Q3	Write what do phytophagous insects feed on.
Q4	What is the interaction called between cuscuta and shoe flower blush?
Q5	When do the oogenesis and the spermatogenesis initiate in human females and males respectively?
Q6	How does smoking tobacco in human lead to oxygen deficiency in their body?
Q7	State the significance of the study of fossils in evolution.
Q8	Name the following: (a) The semi-dwarf variety of wheat is high-yielding and disease-resistant. (b) Any one inter-specific hybrid mammal.

Section 2

Q9	(a) Highlight the role of thymus as a lymphoid organ. (b) Name the cells that are released from the above mentioned gland. Mention how they help in immunity.
Q10	Why do clown fish and sea anemone pair up? What is this relationship called?
Q11	Some organisms suspend their metabolic activities to survive in unfavourable conditions. Explain with the help of any four examples.
Q12	(a) State the role of DNA ligase in biotechnology. (b) What happens when Meloidegyne incognitia consumes cells with RNAi gene?
Q13	Draw a schematic diagram of a part of double stranded dinucleotide DNA chain having all the four nitrogenous bases and showing the correct polarity.
Q14	Name the parasite that causes filariasis in human. Mention its two diagnostic symptoms. How is this disease transmitted to others?
Q15	Name the source of streptokinase. How does this bio-reactor molecule function in our body? OR How do mycorrhizae act as biofertilizers? Explain. Name a genus of fungi that forms a mycorrhizal association with plants.
Q16	(a) State the difference between meiocyte and gamete with respect to chromosome number. (b) Why is a whiptail lizard referred to as parthenogenetic?
Q17	Explain the work carried out by Cohen and Boyer that contributed immensely in biotechnology.
Q18	Where is sporopollenin present in plants? State its significance with reference to its chemical nature.

Section 3

Q19	Write the function of each of the following (a) Middle piece in human sperm. (b) Tapetum in anthers. (c) Luteinizing hormone in human males.
Q20	Given below is the representation of amino acid composition not the relevant translated portion of -chain of haemoglobin, related to the shape of human red blood cells. (a) Is this representation indicating a normal human or a sufferer from certain related genetic disease? Give reason in support of your answer. (b) What difference would be noticed in the phenotype of the normal and the sufferer related to this gene? (c) Who are likely to suffer more from the defect related to the gene represented the males, the females or both males and females equally? And why?
Q21	Draw a schematic sketch of pBR 322 plasmid and label the following in it: (a) Any two restriction sites. (b) Ori and rop genes. (c) An antibiotic resistant gene.
Q22	It is established that RNA is the first genetic material. Explain giving three reasons. OR (a) Name the enzyme responsible for the transcription of tRNA and the amino acid the initiator tRNA gets linked with. (b) Explain the role of initiator tRNA in initiation of protein synthesis.
Q23	Study a part of the life cycle of malarial parasite given below. Answer the questions that follow: (a) Mention the roles of A in the life cycle of the malarial parasite. (b) Name the event C and the organ where this event occurs. (c) Identify the organ B and name the cells being released from it.
Q24	State the theory of Biogenesis. How does Millers experiment support this theory?
Q25	Name the genes responsible for making Bt cotton plants resistant to bollworm attack. How do such plants attain resistance against bollworm attacks? Explain.
Q26	How does an algal bloom cause eutrophication of a water body? Name the weed that can grow in such a eutrophic lake.
Q27	Name the two different categories of microbes naturally occurring in sewage water. Explain their role in cleaning sewage water into usable water.

Section 4

Q28	(a) Draw a pyramid of numbers of a situation where a large population of insects feed upon a very big tree. The insects in turn, are eaten by small birds which in turn are fed upon by big birds. (b) Differentiate giving reasons, between the pyramid of biomass of the above situation and the pyramid of numbers that you have drawn. OR (a) What are the two types of desirable approaches to conserve biodiversity? Explain with examples bringing out the difference between the two types. (b) What is the association between the bumble bee and its favourite orchid ophrys? How would extinction or change of one would affect the other?
Q29	What is the inheritance pattern observed in the size of starch grains and seed shape of Pisum sativum? Workout the monohybrid cross showing the above traits. How does this pattern of inheritance deviate from that of Mendelian law of dominance? OR State the aim and describe Messelson and Stahls experiment.
Q30	The following is the illustration of the sequence of ovarian events (a - i) in a human female. (i) Identify the figure that illustrates ovulation and mention the stage of oogenesis it represents. (ii) Name the ovarian hormone and the pituitary hormone that have caused the above mentioned event. (iii) Explain the changes that occur in the uterus simultaneously in anticipation. (iv) Write the difference between c and h. (v) Draw a labeled sketch of the structure of a human ovum prior to fertilization. OR How does the megaspore mother cell develop into 7-celled, 8 nucleate embryo sac in an angiosperm? Draw a labeled diagram of a mature embryo sac.