Class -XII  Sample Paper

Time : 3 hrs.                     MM.: 70

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.

Section A (1×8 = 8)

1. The following statements describe the wind-pollinated plants. Which one of

these statements is incorrect?

(i)       The pollen grains are sticky.

(ii)      Stamens are well exposed.

(iii)     Flowers often have a single ovule.

2. Write the formula to calculate allele frequency in future generations according to

Hardy – Weinberg genetic equilibrium.

3. “Pranay suffered from measles at the age of 10 years. There are rare chances of his

getting infected with the same disease for the rest of his life.” Give reason for the


4. Give the name of the carcinogenic dye which is used to stain gel to make the DNA

visible under UV light.

5. Which main technique and instrument is used to isolate DNA from a plant cell?

6. How is the action of  normal endonuclease enzymes different from that of

restriction endonucleases?

7. ‘Eutrophication’ is the natural aging of a lake. Mention  another  feature which

defines this term.

8. How are standing crop and biomass related to each other?

Section B (2 × 10 = 20)

9. What do you understand by amniocentasis? Why is there a statutory ban on this?

Give reason.

10. A non-haemophilic couple was informed by their doctor that there is possibility of

a haemophilic child being born to them. Draw a checker board and find out the

percentage of possibility of such a child among the progeny.

11. How do Darwin’s finches illustrate adaptive radiation?

12. In a particular plant species, majority of the plants bear purple flowers. Very few

plants bear white flowers. No intermediate colours are observed. If you are given a

plant bearing purple flowers, how would you ascertain that it is a pure breed for

that trait? Explain.

13. Why is the introduction of genetically engineered lymphocytes  into an  ADA

deficiency patient not a permanent cure? Suggest a possible permanent cure.

14. In which technique do we use Taq polymerase enzyme and why?

15. Differentiate between a detrivore and a decomposer giving an example of each.116

16. DDT content in the water of a lake that supplies drinking water to the nearby

villages is found to be 0.004 ppm. The pelicans of that area are reported to have 2.6

ppm of DDT. Why has the concentration increased in these birds? What possible

harm will this cause to the bird population? Name the phenomenon.

17. The gradual and predictable change in the species composition of a given area is

called ecological succession. What do you understand with the pioneer and climax

community in this context?

18. Write the names of causal organisms of the following:

a) Typhoid

b) Pneumonia

c) Elephantiatis  (Filariasis)

d) Amoebiasis


Expand the following:



Section – C (3 × 9 = 27)

19.Study the graph given above  showing the levels of ovarian hormones during

menstruation  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 fertilized)

20. Expand the following and explain any one of them.

a) IVF                                         b) ZIFT

c) IUI                                                    d) MTP

21. What is the genetic basis for proof that codon is a triplet and is read in a

contiguous manner without punctuations?

22. What is satellite DNA in a genome? Explain their role in DNA fingerprinting.

23. “Microbes play a dual role when used for sewage treatment as they not only help

to retrieve usable water but also generate fuel”. Explain.

24. What does BOD of a water body stand for? How is it related to water pollution?

25. A vector is engineered with three features which facilitate its cloning within the

host cell. List the three features and explain each one of them.

26. Interspecific interactions of two species of any population may be beneficial,

detrimental or neutral. Explain each of them with the help of suitable examples.

27. Water is very essential for life.  List any three features that enable  plants and

animals to survive in water scarce environment.


(a) What would be the consequence of failure of the electrostatic precipitator of a

thermal plant?

(b) Mention any four methods by which vehicular air pollution can be


Section D (5 × 3 = 15)

28. (a) Draw a labelled diagram of sectional view of human ovary showing different

stages of oogenesis.

(b) Where is morula formed in humans? Explain the process of its development

from the zygote.


(a) Draw a labelled diagram of the sectional view of a typical anatropous ovule.

(b) Mention the fate of all the components of the embryo sac after fertilization?

29. (a) Write what DNA replication refers to.

(b) State the properties of DNA replication model.

(c) List any three enzymes involved in the process along with their functions.


Inheritance patterns of flower colour in garden pea plant and snap dragon

differ. Why is the difference observed? Explain the difference with the help of

crosses in their inheritance patterns.

30. Aditya participated in a group discussion in his school on “The ill effects of

Tobacco on Human Health”.  In the evening he goes with his family for dinner

and insists on sitting in the “Non-Smoking Area” to which his father (who is a

heavy smoker) objects.

(a) In this situation, who wins your support – Aditya’s concern for health &

environment or his father’s objection? Justify giving two reasons.     (2)

(b) Suggest any three effective propaganda campaigns  for anti-tobacco

awareness.  (3)