12th Biology Paper Solutions Set 3 : CBSE Delhi Previous Year 2010

General Instructions:
(i) All questions are compulsory.
(ii) This question paper consists of four Sections A, B, C and D. Section A contains 8 questions of one mark each, Section B is of 10 questions of two marks each, Section C is of 9 questions of three marks each and Section D is of 3 questions of five marks each.
(iii) There is no overall choice. However, an internal choice has been provided in one question of 2 marks, one question of 3 marks and two questions of 5 marks weightage. A student has to attempt only one of the alternatives in such questions.
(iv) Wherever necessary, the diagrams drawn should be neat and properly labelled.
Q1 :

Mention one positive and one negative application of amniocentesis.


Answer :

Positive impact of amniocentesis:

It is used for detecting foetal abnormalities or genetic diseases during pregnancy.

Negative impact of amniocentesis:

It is used for determining the sex of foetus which, in turn, can lead to female foeticide.

Q2 :

How do animals like fish and snails avoid summer related unfavourable conditions?


Answer :

Fishes and snails undergo aestivation or summer sleep to avoid summer-related unfavourable conditions.

Q3 :

In a pond there were 200 frogs. 40 more were born in a year. Calculate the birth rate of the population.


Answer :

Birth rate = 40/200 = 0.2 off springs per frog per year

Q4 :

Mention two functions of the codon AUG.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q5 :

Name a molecular diagnostic technique to detect the presence of a pathogen in its early stage of infection.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q6 :

Name the scientist who disproved spontaneous generation theory.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q7 :

What is it that prevents a child to suffer from a disease he/she is vaccinated against? Give one reason.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q8 :

Why is the enzyme cellulose used for isolating genetic material from plant cells but not for animal cells?


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q9 :

Where does triple fusion take place in a flowering plant? Why is it so called? Mention its significance.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q10 :

Why certain regions have declared as biodiversity “hot spots” by environmentalists of the world? Name any two “hot spot” regions of India.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q11 :

A moss plant produces a large number of antherozoids but relatively only a few egg cells. Why?


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q12 :

Why is the introduction of genetically engineered lymphocytes into a ADA deficiency patient not a permanent cure? Suggest a possible permanent cure.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q13 :

Study the given food chain and answer the questions that follow:

(i) Give reasons why there is a continuous increase in the DDT content in different trophic levels of the chain.

(ii) Name the phenomenon responsible for the increase in DDT content.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q14 :

Honey collection improves when beehives are kept in crop-fields during flowering season. Explain.

OR

How does addition of a small amount of curd to fresh milk help formation of curd? Mention a nutritional quality that gets added to the curd.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q15 :

Name the type of food chains responsible for the flow of larger fraction of energy in an aquatic and a terrestrial ecosystem respectively. Mention one difference between the two food chains.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q16 :

Name the host and the site where the following occur in the life-cycle of a malarial parasite:

(a) Formation of gametocytes

(b) Fusion of gametocytes


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q17 :

Why are F2 phenotypic and genotypic ratios same in a cross between red-flowered snapdragon and white-flowered snapdragon plants. Explain with the help of a cross.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q18 :

How does the floral pattern of Mediterranean orchid Ophrys guarantee cross pollination?


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q19 :

During his studies on genes in Drosophila that were sex-linked T.H. Morgan found F2 − population phenotypic ratios deviated from expected 9:3:3:1. Explain the conclusion he arrived at.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q20 :

Describe the termination process of transcription in bacteria.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q21 :

How does RNA interference help in developing resistance in tobacco plant against nematode infection?


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q22 :

Draw a longitudinal section of a post − pollinated Pistil showing entry of pollen tube into a mature embryo-sac. Label filiform apparatus, chalazal end, Hilum, antipodals, male gametes and secondary nucleus.

OR

Draw a labelled sectional view of seminiferous tubule of a human male.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q23 :

Explain the efforts which must be put in to improve health, hygiene and milk yield of cattle in a dairy farm.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q24 :

Explain convergent and divergent evolution with the help of one example of each.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q25 :

Eco RI is used cut a segment of foreign DNA and that of a vector DNA to form a recombinant DNA. Show with the help of schematic diagrams.

(i)The set of palindronic nucleotide sequence of base pairs the Eco RI will recognise in both the DNA segments. Mark the site at which Eco RI will act and cut both the segments.

(ii)Sticky ends formed on both the segments where the two DNA segments will join later to form a recombinant DNA.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q26 :

An antibody molecule is represented as H2L2. Explain.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q27 :

Identify a, b, c, d, e and f in the table given below:

Organism

Bioactive molecule

Use

1.

Monascus perpureus (Yeast)

2.

Antibiotic

3.

Cyclosporin A


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q28 :

When and where are primary oocytes formed in a human female? Trace the development of these oocytes till ovulation (in menstrual cycle). How do gonadotropins influence this developmental process?

OR

(a)Explain the events taking place at the time of fertilization of an ovum in a human female.

(b)Trace the development of zygote upto its implantation in the uterus.

(c)Name and draw a labelled sectional view of the embryonic stage that gets implanted.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q29 :

Draw and explain a logistic curve for a population of density (N) at time (t) whose intrinsic rate of natural increase is (r) and carrying capacity is (k).

OR

Describe the process of decomposition of detritus under the following heads: Fragmentation; leaching; catabolism; humification and mineralization.


Answer :

Please Register/Login to get access to all solutions Facebook Login
Q30 :

Write the symptoms of haemophilia and sickle-cell anaemia in humans.

Explain how the inheritance pattern of the two diseases differ from each other.

OR

(a) Write Hardy-Weinberg principle.

(b) Explain the three different ways the natural selection can affect the frequency of a heritable trait in a population shown in the graph given below.


Answer :

Please Register/Login to get access to all solutions Facebook Login

12th Biology Paper Solutions Set 3 : CBSE Delhi Previous Year 2013 will be available online in PDF book soon. The solutions are absolutely Free. Soon you will be able to download the solutions.