Arvind Academy

BIOLOGY SP 4
Class 12 - Biology
Time Allowed: 3 hours Maximum Marks: 70

General Instructions:

1. All questions are compulsory.

2. The question paper has five sections and 33 questions. All questions are compulsory.

3. Section–A has 16 questions of 1 mark each; Section–B has 5 questions of 2 marks each; Section– C has 7

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questions of 3 marks each; Section– D has 2 case-based questions of 4 marks each; and Section–E has 3 questions

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of 5 marks each.

4. There is no overall choice. However, internal choices have been provided in some questions. A student has to

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attempt only one of the alternatives in such questions.
5. Wherever necessary, neat and properly labeled diagrams should be drawn.
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Section A
1. When the number of organisms at successive levels are plotted they assume the shape of a pyramid. This is [1]
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called pyramid of:

a) Both Biomass and Energy b) Number

c) Biomass d) Energy
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2. In a population, the condition at which the rate of addition of new members is more than the rate of individuals [1]
lost indicates:

a) Zero population growth b) Fluctuating growth

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c) Exponential growth d) Declining growth

3. Identify the odd combination of the habitat and the particular animal concerned: [1]

a) Rann of Kutch - Wild ass b) Sunderbans - Bengal tiger

c) Dachigam National Park - Snow leopard d) Periyar - Elephant

4. Which of the following is a STD? [1]

a) Pneumonia b) Malaria

c) Cancer d) Trichomoniasis
5. Enzymes used to join foreign DNA to plasmid is: [1]

a) Endonucleases b) Pectinases

c) Ligases d) Nucleases
6. Which of the following seeds have remained alive for the longest period? [1]

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 a) Yucca gigantea b) Mangifera indica

c) Striga asiatica d) Phoenix dactylifera

7. Select the option that gives the correct description of the process of Natural Selection with respect to the length [1]
of the neck of giraffe.

a) Stabilising selection as giraffes with b) Directional selection as giraffes with longer

medium neck lengths are selected. neck lengths are selected.

c) Stabilising selection as giraffes with longer d) Disruptive selection as giraffes with smaller
neck lengths are selected further. and longer neck lengths are selected.

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8. Picture shown below is an example of:- [1]

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a) Convergent evolution of Australian
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b) Divergent evolution of Australian
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marsupials and placental mammals marsupials and placental mammals

c) Homologous organs of both animals d) Analogous organs of both animals

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9. Healthy ecosystems are the base for a wide range of [1]

a) Economic, environmental and aesthetic b) Only aesthetic goods and services.

goods and services.
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c) Only economic services. d) Only economic goods.

10. On the basis of the sex chromosome shown below, the bird shown is [1]
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a) Female b) Cannot be decided

c) Transgender d) Male
11. Milk is fermented or curdled by: [1]

a) Azotobacter b) Rhizobium

c) Clostridium d) Lactobacillus
12. Which of the following is not required for any of the techniques of DNA fingerprinting available at present? [1]

a) Restriction enzymes b) DNA-DNA hybridization

c) Zinc fingu analysis d) Polymerase chain reaction

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13. Assertion (A): Contraceptives pills are not regular requirements for the maintenance of reproductive health. [1]
Reason (R): Their regular use causes various ill-effects like nausea, abdominal pain, breakthrough bleeding,
irregular menstrual bleeding, or even breast cancer.

a) Both A and R are true and R is the correct b) Both A and R are true but R is not the
explanation of A. correct explanation of A.

c) A is true but R is false. d) A is false but R is true.

14. Assertion (A): Nitrogen-fixing bacteria of legume nodules live in O2-depleted cells. [1]

Reason (R): Leghaemoglobin completely removes O2 from the nodule cells.

a) Both A and R are true and R is the correct b) Both A and R are true but R is not the
explanation of A. correct explanation of A.

c) A is true but R is false. d) A is false but R is true.

15. Assertion (A): Gross primary productivity minus respiration losses is the net primary productivity. [1]

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Reason (R): Net primary productivity is the available biomass for the consumption of heterotrophs.

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a) Both A and R are true and R is the correct b) Both A and R are true but R is not the
explanation of A. correct explanation of A.

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c) A is true but R is false.
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Assertion (A): The primitive atmosphere was reducing once i.e., without oxygen. [1]
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Reason (R): In the primitive atmosphere, oxygen was involved in forming ozone.

a) Both A and R are true and R is the correct b) Both A and R are true but R is not the
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explanation of A. correct explanation of A.

c) A is true but R is false. d) A is false but R is true.

Section B
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17. Explain the changes that milk undergoes when suitable starter/inoculum is added to it. How does the end product [2]
formed prove to be beneficial for human health?
18. Answer the questions based on the dinucleotide show below. [2]
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i. Name the type of sugar to which guanine base is attached to.

ii. Name the linkage connecting the two nucleotides.
iii. Identify the 3' end of the dinucleotide. Give a reason for your answer.
19. Normally one embryo develops in one seed but when an orange seed is squeezed many embryos of different [2]
shapes and sizes are seen. Mention how it has happened?
20. Given below is an incomplete chart showing the influence of hormones on gametogenesis in males. Observe the [2]
chart carefully and fill in the blanks A, B, C and D

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21. How do methanogens help in producing biogas? [2]
OR
Name the enzyme produced by Streptococcus bacterium. Explain its importance in medical sciences.
Section C
22. Observe the diagram for genetic mapping of human DNA and answer the following questions: [3]

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i. Explain DNA polymorphism as the basis of genetic mapping of the human genome.
ii. State the role of VNTR in DNA fingerprinting.
23. A normal couple has their first child, who is haemophilic. Work out a cross to show how it is possible. State the [3]
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possibility of the normal and the haemophilic children, along with their sexes, that can be born to them.
24. Differentiate between an Expanding age pyramid and a Stable age pyramid. Substantiate your answer with [3]
diagrams.
25. The image below eleborates enzyme-replacement therapy. [3]
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i. Explain enzyme-replacement therapy to treat adenosine deaminase deficiency.

ii. Mention two disadvantages of this procedure.
26. How did Dr. David Tilman relate experimentally, the stability of a community and its species richness? Explain. [3]
OR
Alien species are a threat to native species. Justify taking examples of an animal and a plant alien species.
27. How do you express the meaning of words like race, breed, cultivars or variety? [3]
28. Community service department of your school plans a visit to a slum near the school with an objective to [3]

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 educate the slum dwellers with respect to health and hygiene.
i. Why is there a need to organise such visits?
ii. Write the steps you will highlight, as a member of this department, in your interactions with them to enable
them to lead a healthy life.
Section D
29. Read the following text carefully and answer the questions that follow: [4]
The image below shows the menstrual cycle of a human female. On the basis of this cycle:

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i. Explain the menstrual phase in a human female. State the level of ovarian and pituitary hormones during this

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phase. (1)
ii. Why is follicular phase in the menstrual cycle also referred as proliferative phase? Explain. (1)

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iii. Explain the events that occur in a Graafian follicle at the time of ovulation and thereafter. (2)

Draw a Graafian follicle and label antrum and secondary oocyte. (2)
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30. Read the following text carefully and answer the questions that follow: [4]
Aditya went to his home town for summer vacation after a long time. His grandparent’s house is surrounded by
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farmland. Lots of crops were growing nearby. Aditya was excited to visit the farmland. He sought permission
from his mother and were play along with his friends. On returning back he had a running nose, watering eyes,
and continuous sneezing and the symptoms get worse with time.
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i. What do the symptoms signify? (1)

ii. What could be the possible reasons for Aditya’s condition? (1)
iii. Name the few drugs which reduces the symptoms of allergy. (2)
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OR
What are allergens? How do they cause inflammatory response inside human body? (2)
Section E
31. a. Explain any two ways by which apomictic seed can develop. [5]
b. List one advantage and one disadvantage of a apomictic crop.
c. Why do farmers find production of hybrid seeds costly?
OR
A flower of the brinjal plant following the process of sexual reproduction produces 360 viable seeds.

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 Answer the following questions giving reasons.
i. How many ovules are minimally involved?
ii. How many megaspore mother cells are involved?
iii. What is the minimum number of pollen grains that must land on stigma for pollination? OR
iv. How many male gametes are involved in the above case?

32. i. Expand hnRNA. Name the type of cells and the enzyme that transcribes it. [5]
ii. Is it a precursor? Explain the process that it undergoes to become a functional molecule. Name this molecule.
iii. Differentiate between mRNA and tRNA with respect to their roles in the cells.

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OR

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i. What is an operon in a bacterial system?
ii. Draw a schematic self-explanatory diagram of a lac operon in a switched-on condition. Give the correct labelling

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at the respective positions.
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A schematic representation of Polymerase Chain Reaction (PCR) upto the extension stage is given below. [5]
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i. Name the process A

ii. Identify B.
iii. Identify C and mention its importance in PCR.
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i. Why should a cell be made competent to take up an alien DNA? How can a bacterial cell be made competent
using calcium ions? Explain.
ii. 1. State the importance of gel electrophoresis in biotechnology.
2. Explain the principle on which this technique works.
3. Mention why ethidium bromide is used in this technique.

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