Board Paper of Class 12-Science 2008 Biology (SET 1) - Solutions

(a) Expand IUD.

(b) Why is hormone releasing IUD considered a good contraceptive to space children?

Name the interaction in each of the following:

(a) Cuscuta growing on a shoe flower plant

(b) Mycorrhiza living on the roots of higher plants

(c) Clown fish living among the tentacles of sea anemone

(d) Koel laying her eggs in crow’s nest

A plant of Antirrhinum majus with red flowers was crossed with another plant of the same species with white flowers. The plants of the F₁ generation bore pink flowers. Explain the pattern of inheritance with the help of a cross.

OR

A woman with blood group O married a man with AB group. Show the possible blood groups of the progeny. List the alleles involved in this inheritance.

Why do sportspersons often fall a victim to cocaine addiction?

State the difference between the first trophic level of detritus food chain and grazing food chain.

Coconut palm is monoecious while date palm is dioecious. Why are they called so?

How can DNA segments, separated by gel electrophoresis, be visualised and isolated?

How do Darwin’s finches illustrate adaptive radiation?

Name the blank spaces a, b, c, and d from the table given below:

Type of microbe	Scientific name	Commercial product
Bacterium	a	Lactic acid
Fungus	b	Cyclosporine A
c	Monascus purpureus	Statin
Fungus	Penicillium notatum	d

DDT content in the water of a lake that supplies drinking water to the nearby villages is found to be 0.003 ppm. The kingfishers of that area are reported to have 3 ppm of DDT. Why has the concentration increased in these birds? What harm will this cause to the bird population? Name the phenomenon.

(a)

Read the graph given above and correlate the uterine events that take place according to the hormonal levels on

(i) 6 − 15 days

(ii) 16 − 25 days

(iii) 26 − 28 days (if the ovum is not fertilised)

(b) Specify the sources of the hormones mentioned in the graph.

Explain the role of baculoviruses as biological control agents. Mention their importance in organic farming.

Study the population growth curves shown above.

(i) Identify curves ‘a’ and ‘b’.

(ii) Mention the conditions responsible for the curves ‘a’ and ‘b’ respectively.

(iii) Give the necessary equation of the curve ‘b’.

Why is Agrobacterium tumefaciens a good cloning vector? Explain.

OR

Explain the importance of (a) ori (b) amp^R and (c) rop in the E. coli vector shown below:

(a) Name the infective stage of Plasmodium which Anopheles mosquito takes in along with the blood meal from an infected human.

(b) Why does the infection cause fever in humans?

(c) Give a flow chart of the part of the life-cycle of this parasite passed in the insect.

A factory drains its waste water into the nearby lake. It has caused algal bloom.

(a) How was the algal bloom caused?

(b) What would be the consequences?

(c) Name the phenomenon that caused it.

(a) Draw a schematic labelled diagram of a fertilised embryo sac of an Angiosperm.

(b) Describe the stages in embryo development in a dicot plant.

OR

(a) Draw a labelled diagram of a sectional view of human seminiferous tubule.

(b) Differentiate between gametogenesis in human males and females on the basis of:

(i) Time of initiation of the process

(ii) Products formed at the end of the process

Explain the steps involved in the production of genetically engineered insulin.

OR

(a) Name the nematode that infests and damages tobacco roots.

(b) How are transgenic tobacco plants produced to solve this problem?

What is ‘semi-conservative’ DNA replication? How was it experimentally proved and by whom?

OR

A homozygous tall pea plant with green seeds is crossed with a dwarf pea plant with yellow seeds.

(i) What would be the phenotype and genotype of F₁?

(ii) Work out the phenotypic ratio of F₂ generation with the help of a Punnett square.