Plus Two Biology (Bot + Zoo) | Practice Model Question Paper PDF with Answer key | SET 2

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I. Answer any 3 questions from 1 – 5. Each carries 1 score. (3 x 1 = 3)

1) Name the first transgenic cow that produces human protein enriched milk.

✅ Rosie.

2) Name the principle which states that two closely related species competing for the same resources cannot co-exist indefinitely and the competitively inferior one will be eliminated eventually.

✅ Gause’s ‘Competitive Exclusion Principle’.

3) The first discovered restriction endonuclease is ……………………

✅ Hind II

4) Vertical distribution of different species occupying different levels is called ……………………

✅ Stratification.

5) Microsporangium is surrounded by four wall layers. Name the layer which nourishes developing pollen grains.

✅ Tapetum

II. Answer any 9 questions from 6 – 16. Each carries 2 scores. (9 x 2 = 18)

6) Bt. Cotton is a well-known example of application of Biotechnology in Agriculture. Bt. Cotton reduces use of pesticides. Explain.


Bt. Cotton is genetically modified to produce a natural insecticide, the Bt toxin, derived from the bacterium Bacillus thuringiensis. This makes the cotton plant resistant to certain pests, reducing the need for chemical pesticides.
7) Anitha is studying about a circular DNA which has the following sequence.

5’ → GGAATTCC → 3’
3’ → CCTTAAGG → 5’

She wishes to add a new segment of DNA into it.

a. Identify the technology she planned.
b. Suggest the specific enzyme to make a cut in the DNA with above sequence.


a. Recombinant DNA technology.

b. A restriction enzyme called EcoRI.

8) Adenosine deaminase (ADA) deficiency is a hereditary disease where ADA which is crucial for functioning of immune system is absent. Explain how ADA deficiency can be treated.


ADA deficiency can be treated through enzyme replacement therapy or gene therapy.

In enzyme replacement therapy, patients receive regular injections of functional ADA enzyme.

In gene therapy, a functional ADA gene is introduced into the patient's cells, restoring the production of ADA enzyme.

9) Density of a population in a given habitat during a given period fluctuates due to changes in 4 basic processes- Natality, Mortality, Immigration & Emigration.

a. Differentiate Natality and Mortality.
b. Differentiate Immigration & Emigration.


(a) Natality (B): It is the number of births in a population during a given period.
Mortality (D): It is the number of deaths in a population during a given period.

(b) Immigration (I): It is the number of individuals of the same species that have come into the habitat from elsewhere during a given time period.
Emigration (E): It is the number of individuals of the population who left the habitat and gone elsewhere during a given time period.

10) Match the following:


11) Pond is a self-sustainable unit. Some organisms related to pond ecosystem is listed below:

Tadpole, fish, water, plants, kingfisher

a. Construct a food chain with the listed organisms.
b. Point out trophic level of each organism in the constructed food chain.


a. Plants → Tadpole → Fish → Kingfisher

b. Trophic levels of each organism:

Plants: Trophic Level 1 (Producers)
Tadpole: Trophic Level 2 (Primary Consumers)
Fish: Trophic Level 3 (Secondary Consumers)
Kingfisher: Trophic Level 4 (Tertiary Consumers)

12) Two students, Unni and Kannan studied inter-specific interactions between different species. Can you help them by naming the interaction between species in different cases?


Case No. 1: Mutualism
Case No. 2: Competition
Case No. 3: Predation/Parasitism
Case No. 4: Commensalism
13) The given figure represents the reactions associated with PCR.

a. Expand PCR.
b. Name the steps A, B, C in the process.


(a) Polymerase Chain Reaction.

(b) Steps:

A= Denaturation
B= Annealing
C= Extension

14) Correct the following statements considering the underlined part.

a. Ovary develops into seed.
b. In flowering plants, zygote is formed inside the microsporangium.
c. Ovules develop into fruit.
d. Primary endosperm cell (PEC) develops into embryo.


a. Ovary develops into fruit.
b. In flowering plants, zygote is formed inside the ovule.
c. Ovaries develop into fruit.
d. Zygote develops into embryo.
15) Population growth may be exponential or logistic. Differentiate between them.


Exponential Growth:

• Population increases at a constant rate.
• Unrestricted growth under ideal conditions.
• Shown by a J-shaped curve.

Logistic Growth:

• Population growth slows as it approaches carrying capacity.
• Limited resources cause a plateau in growth.
• Shown by an S-shaped curve.

16) Given below a schematic representation with circles and squares which shows four factors/processes influence the population density. Write the factors in circles and squares.


III. Answer any 3 questions from 17 – 20. Each carries 3 scores. (3 x 3 = 9)

17) (a) While learning trophic levels in class-room, teacher asked you to explain ‘standing crop’. Explain.

(b) Distinguish between mutualism and parasitism. Give one example for each.


(a) The amount of living material in a trophic level at a given time is called standing crop. It is measured as the biomass (mass of living organisms) or the number in a unit area.

(b) Mutualism and parasitism.

Mutualism: It’s a type of symbiotic relationship where both species benefit. E.g., bees and flowers. Bees get nectar from flowers, and in return, they help in pollination.
Parasitism: It’s a type of symbiotic relationship where one species (the parasite) benefits at the expense of the other (the host). E.g., Ticks feed on the dog’s blood.

18) Raju is a diabetic patient who takes insulin injections regularly. The insulin used by such patients is produced by genetically engineered organisms. Write different steps involved in the production of insulin by genetic engineering.


In 1983, Eli Lilly company prepared two DNA sequences corresponding to A & B chains of human insulin and introduced them in plasmids of E. coli to produce insulin chains. Chains A & B were combined by creating disulfide bonds to form human insulin (Humulin).

• The human insulin gene is isolated from a human cell.
• The insulin gene is inserted into a plasmid of E. coli to form a recombinant DNA.
• Recombinant DNA plasmid is introduced into E. coli.
E. coli multiply and produce insulin.
• Insulin is extracted and purified for medical use.

19) Three different flowers are given.

(i) Maize      (ii) Vallisneria      (iii) Rose

a) Group them based on pollinating agents.
b) Mention one adaptation of each flower related with the agents of pollination.


a) Grouping based on pollinating agents:

• Maize: Wind Pollinated (Anemophily)
• Vallisneria: Water Pollinated (Hydrophily)
• Rose: Insect Pollinated (Entomophily)

b) Adaptations related to pollination:

• Maize: It has long and feathery stigmas to catch pollen grains from the wind.
• Vallisneria: It has long stalked female flowers that reach the water surface to catch pollen grains.
• Rose: It has bright colour and sweet fragrance to attract insects.

20) Diagram shows a typical agarose gel showing migration of DNA fragments.
a. Which of the bands has largest and smallest DNA fragments?
b. How can you make fragments of DNA for electrophoresis?
c. Explain separation of DNA fragments using electrophoresis.


(a) a is largest DNA fragments and e is smallest DNA fragments.

(b) DNA is fragmented using restriction endonucleases that cut DNA at specific sequences.

(c) DNA fragments are loaded into agarose gel, and an electric current is applied. DNA is negatively charged, so it moves towards the anode. Smaller fragments move faster while larger fragments move slower and travel less distance. This results in separation of DNA fragments based on size.


I. Answer any 3 questions from 1 – 5. Each carries 1 score. (3 x 1 = 3)

1) The gene flow by chance causing change in frequency is called ...................

✅ Genetic drift

2) Name the process of differentiation of spermatids to spermatozoa.

✅ Spermiogenesis

3) Ovulation occurs on ............... of the Menstrual cycle.

(a) 10th day          (b) 14th day
(c) 1-5th day         (d) 15-28th day

✅ (b) 14th day

4) Who popularized the term Biodiversity?

✅ Edward Wilson

5) Swiss cheese has large holes due to production of CO2 by a bacterium called ................

Propionibacterium sharmani

II. Answer any 9 questions from 6 – 16. Each carries 2 scores. (9 x 2 = 18)

6) a) Expand BAC and YAC.
b) Mention any two salient features of human genome.


(a) BAC: Bacterial Artificial Chromosome
YAC: Yeast Artificial Chromosome

(b) Salient features of human genome:

• Human genome contains 3164.7 million nucleotide bases.
• Total number of genes= about 30,000.
• Average gene consists of 3000 bases, but sizes vary.
• 99.9% nucleotide bases are same in all people. Only 0.1% difference makes every individual unique.

7) Observe the figure given below:
(a) Identify the disorder and its genetic constitution.
(b) Write any two symptoms of this disorder.


(a) Turner’s syndrome. Genetic constitution: 44A + X0
(b) Sterile, Ovaries are rudimentary. Lack of secondary sexual characters. Dwarf. Mentally retarded (Any 2).
8) (a) “Microbes can be used for energy purposes”. Do you agree? Justify.
(b) Name any two microbes used as biofertilizers.


(a) Yes. Methanogens are the microbes that can be used for biogas production.
(b) Rhizobium, Azotobacter, Cyanobacterium, Mycorrhiza etc. (any 2)
9) Match the following:


10) Observe the diagram given.
a. Identify the molecule. Which cell produces this?
b. Mention its importance.


(a) An antibody. It is produced by B-lymphocytes (B-cells).
(b) These are the proteins to fight the pathogens. i.e., gives immunity.
11) (a) Briefly explain the theory of Abiogenesis.
(b) Who experimentally disproved this theory?


(a) It states that life came out of decaying and rotting matter like straw, mud etc.
(b) Louis Pasteur disproved this theory.
12) Write down the single word for the following.

a. Blastocyst becomes embedded in the endometrium.
b. Mammary glands produce milk towards the end of pregnancy.
c. Cap-like structure at the tip of sperm head.
d. Yellow-coloured structure developed from ruptured Graafian follicle after ovulation.


(a) Implantation
(b) Lactation
(c) Acrosome
(d) Corpus luteum
13) Expand:      (i) GIFT          (ii) ICSI


(i) GIFT: Gamete Intra Fallopian Transfer
(ii) ICSI: Intra Cytoplasmic Sperm Injection
14) Distinguish between divergent evolution and convergent evolution.


Divergent evolution: It is the evolution by which related species become less similar to survive and adapt in different environmental condition.
Convergent evolution: It is the evolution by which unrelated species become more similar to survive and adapt in similar environmental condition.
15) Write down any 4 salient features of genetic code.


Salient features of genetic code:

• Triplet code. 61 codons code for amino acids. UAA, UAG & UGA are stop codons (Termination codons).
• Genetic code is universal.
• No punctuations b/w adjacent codons.
• An amino acid is coded by many codons. So the code is degenerate.

16) To find out the unknown genotype of violet flowered pea plant, a researcher done the following cross. Observe the diagram and answer the following questions.
a. What would be the above cross is called? Define it.
b. Mention its significance.


(a) Test cross. It is the cross between F1 hybrid with a recessive parent.
(b) It is used to find out the unknown genotype of a character.

III. Answer any 3 questions from 17 – 20. Each carries 3 scores. (3 x 3 = 9)

17) Understanding the warning signs of drug/alcohol abuse is important to save the people in Adolescence period.

a. Mention any three such warning signs.
b. Mention any three ways for prevention and control of drug/alcohol abuse.


(a) Warning signs:

• Drop in academic performance and absence from school.
• Lack of interest in personal hygiene.
• Withdrawal and isolation.
• Depression, fatigue, aggressive and rebellious behaviour.
• Change in sleeping and eating habits.

(b) Prevention and control:
• Avoid undue peer pressure.
• Education and counselling.
• Seeking help from parents and peers.
• Looking for danger signs.
• Seeking professional and medical help.

18) T.H Morgan conducted some experiments using Drosophila melanogaster and made important observations regarding linkage and recombination.

a. Define linkage and recombination.
b. Mention his any two conclusions from this experiment.


(a) Linkage is the physical association of genes on a chromosome.
Recombination is the generation of non-parental gene combinations.

(b) He found that
• When two genes were situated on same chromosome, proportion of parental gene combinations was much higher than the non-parental type. It is due to linkage.
• Genes of white eye & yellow body were very tightly linked and showed only 1.3% recombination.
• Genes of white eye & miniature wing were loosely linked and showed 37.2% recombination.
• Tightly linked genes show low recombination. Loosely linked genes show high recombination.

19) (a) Mention any two examples for co-extinction.
(b) Biodiversity (species richness) is highest in tropics. Give any two reasons.
(c) Define the term hotspots.


(a) Extinction of the parasites when the host is extinct.
In co-evolved plant-pollinator mutualism, extinction of one causes the extinction of the other.

(b) Biodiversity (species richness) is highest in tropics because

• Tropics had more evolutionary time.
• Relatively constant environment (less seasonal).
• They receive more solar energy which contributes to greater productivity.

(c) Hotspots are the regions with very high species richness, high degree of endemism but most threatened.

20) (a) Prepare a flowchart showing the Central Dogma of Molecular Biology.
(b) Name the initiator codon and the amino acid coded by it.


(a) Central Dogma of Molecular Biology:
(b) AUG is the initiator codon. Methionine is the amino acid coded by it.

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