Class 12th Biology 2011 Set3 Delhi Board Paper Solution

Section 1

Q1	Mention the role of the codons AUG and UGA during protein synthesis.
Q2	Normally one embryo develops in one seed but when an orange seed is squeezed many embryos of different shapes and sizes are seen. Mention how it has happened.
Q3	Why green plants are not found beyond a certain depth in the ocean?
Q4	Write the scientific name of the microbe used for fermenting malted cereals and fruit juices.
Q5	Name the type of cell division that takes place in the zygote of an organism exhibiting haplontic life cycle.
Q6	How can bacterial DNA be released from the bacterial cell for biotechnology experiments?
Q7	Name the event during cell division cycle that results in the gain or loss of chromosome.
Q8	Write the importance of cryopreservation ín conservation of biodiversity.

Section 2

Q9	State the dual role of deoxyribonucleoside triphosphates during DNA replication.
Q10	Differentiate between albuminous and non-alburninous seeds, giving one example of each.
Q11	Explain how a hereditary disease can be corrected. Give an example of first successful attempt made towards correction of such diseases.
Q12	Justify with the help of an example where a deliberate attempt by humans has led to the extinction of a particular species.
Q13	Explain the role of Ti plasmids in biotechnology.
Q14	Study the graph given below. Explain how is oxygen concentration affected in the river when sewage is discharged into it.
Q15	Name the two types of immune systems in a human body. Why are cell mediated and humoral immunities so called? OR Write the scientific names of the causal organisms of elephantiasis and ringworm in humans. Mention the body parts affected by them.
Q16	State the functions of primary and secondary lymphoid organs in humans.
Q17	Why is CuT considered a good contraceptive device to space children?
Q18	Explain the process of RNA interference.

Section 3

Q19	(a) Identify A and B illustrations in the following: (b) Write the term given to A and C. (c) Expand PCR. Mention its importance in biotechnology.
Q20	Name the type of interaction seen in each of the following examples: (i) Ascaris worms living in the intestine of human (ii) Wasp pollinating fig inflorescence (iii) Clown fish living among the tentacles of sea-anemone (iv) Mycorrhizae living on the roots of higher plants (v) Orchid growing on a branch of a mango tree (vi) Disappearance of smaller barnacles when Balanus dominated in the Coast of Scotland.
Q21	Why do you see two different types of replicating strands in the given DNA replication form? Explain. Name these strands.
Q22	Draw a diagram of a male gametophyte of an angiosperm. Label any four parts. Why is sporopollenin considered the most resistant organic material?
Q23	How are dominance, codominance and incomplete dominance patterns of inheritance different from each other?
Q24	(a) Sickle celled anaemia in humans is a result of point mutation. Explain. (b) Write the genotypes of both the parents who have produced a sickle celled anaemic offspring.
Q25	(a) Why do farmers prefer biofertilisers to chemical fertilizers these days? Explain. (b) How do Anabaena and mycorrhiza act as biofertilisers?
Q26	(a) Name the stage of Plasmodium that gains entry into the human body. (b) Trace the stages of Plasmodium in the body of female Anopheles after its entry. (c) Explain the cause of periodic recurrence of chill and high fever during malarial attack in humans. OR Trace the events that occur in human body to cause immunodeficiency when HIV gains entry into the body.
Q27	What is inbreeding depression and how is it caused in organisms? Write any two advantages of inbreeding.

Section 4

Q28	(a) Describe the stages of oogenesis in human females. (b) Draw a labelled diagram of human ovum released after ovulation. OR (a) When and where does spermatogenesis occur in a human male? (b) Draw a diagram of a mature human male gamete. Label the following parts: acrosome, nucleus, middle piece and tail. (c) Mention the functions of acrosome and middle piece.
Q29	(a) Explain primary productivity and the factors that influence it. (b) Describe how oxygen and chemical composition of detritus control decomposition do. OR (a) What is El Nino effect? Explain how it accounts for biodiversity loss. (b) Explain any three measures that you as an individual would take, to reduce environmental pollution.
Q30	Explain the salient features of Hugo de Vries theory of mutation. How is Darwins theory of natural selection different from it? Explain. OR (a) Name the primates that lived about 15 million years ago. List their characteristic features. (b) 1. Where was the first man-like animal found? 2. Write the order in which Neanderthals, Homo habilis and Homo erectus appeared on earth. State the brain capacity of each one of them. 3. When did modern Homo sapiens appear on this planet?