Plus Two Biology (Bot + Zoo) | Practice Model Question Paper PDF with Answer key | SET 4

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

1) Fill up the blanks with appropriate terms in the given pyramid of trophic level:

✅ a. Primar consumer

b. Secondary consumer

2) Observe the relation in the first pair and fill up the blank in the second.

Cry I Ac: Control cotton bollworm

……………….: Control corn borer

✅ cryIAb

3) Fill up the blanks after reading the statement:

The post fertilization events in angiosperms.

Zygote : Embryo

Ovule : ………………

Ovary : ………………

✅ Ovule: Seed        Ovary: Fruit

4) Sucker fish and shark live in close association is a classic example of ……………….

✅ Commensalism

5) In PCR, repeated amplification is achieved by the use of a thermostable DNA polymerase isolated from a bacterium called .....................

Thermus aquaticus

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

6) Population interactions:
Where '+' beneficial interaction
'-' detrimental interaction
'0' neutral interaction

Observe the interactions of populations of 3 species as shown in the table. Name the interactions between:

a. Species x and species y in case 1

b. Species y and species z in case 2

c. Species x and species z in case 3

d. Species y and species z in case 1


Population interactions:

a. Mutualism

b. Parasitism/Predation

c. Competition

d. Commensalism

7) Pre-fertilization events of sexual reproduction in all organisms are gametogenesis and gamete transfer. What are the post fertilization events?


Post-fertilization events in sexual reproduction include:

Endosperm development: Primary endosperm cell divides repeatedly to form a triploid endosperm tissue.

Embryogeny: The zygote develops into an embryo.

Seed and Fruit formation: The ovules develop into seeds and the ovary develops into a fruit.

8) Observe the sketch of stirred-tank bioreactor and label the parts A, B, C and D.


A= Motor

B= Foam braker

C= Flat bladed impeller

D= Culture broth.

9) Briefly explain Somatic hybridisation.


Somatic hybridization is the fusion of protoplasts from two different varieties of plants with desirable characters to get hybrid protoplasts. It is grown to form a new plant called somatic hybrids.

Protoplasts can be isolated after digesting the cell walls of plant cells.

E.g. Tomato protoplast + Potato protoplast → pomato.

10) Emasculation and Bagging are two steps of a crop improvement program called Artificial hybridisation. Explain them.


Emasculation and Bagging.

Emasculation: Removal of anthers from the bisexual flower bud of female parent before the anther dehisces.

Bagging: Here, emasculated flowers are covered with a bag to prevent contamination of its stigma with unwanted pollen.

11) Observe the cloning vector and explain the following:

a. ori        b. rop


a) Ori (Origin of Replication) is a specific sequence in the DNA where replication begins. Any piece of DNA linked to this sequence can replicate within host cells.

b) rop: Codes for the proteins involved in the replication of plasmid.

12) Biotechnology has important application in the field of Molecular Diagnosis. Justify with two examples.


Yes. Biotechnology has important application in the field of Molecular Diagnosis. For example,

a. Polymerase Chain Reaction (PCR): It is used to detect HIV in suspected patients, gene mutations in suspected cancer patients etc.

b. ELISA (Enzyme Linked Immuno-Sorbent Assay): It is used to detect infection by pathogen or the antibodies synthesized against the pathogen.

13) a) Define Verhulst-Pearl Logistic Growth.

b) Write the equation to describe this.


a) A population with limited resources shows initially a lag phase, phases of acceleration & deceleration and finally an asymptote. This type of population growth is called Verhulst-Pearl Logistic Growth.


14) What is meant by competition in population interaction? Give one example.


It is a process in which fitness of one species (r value) is significantly lower in presence of another species. Here, both species are harmed (-).

E.g., Flamingoes & fishes in some shallow South American lakes compete for zooplankton.

15) Define the terms:

(a) Trophic level

(b) Food web.


(a) Trophic Level: It refers to the position an organism in a food chain.

(b) Food Web: It is a complex network of interconnecting food chains that shows the feeding relationships.

16) Briefly explain the processes fragmentation and leaching.


Fragmentation: It is the breakdown of detritus into smaller particles by detritivores (e.g. earthworm).

Leaching: It is the process in which water soluble inorganic nutrients go down into soil horizon and precipitate as unavailable salts.

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

17) Plus Two students of a school on their study tour collected flowers showing the following character:

1) Flowers are with light pollen grains

2) Colourful flowers

3) Nectar producing flowers

4) Flowers with feathery stigma

a. Arrange the characters under different pollination groups in the given table.

b. Write the name of 2 flowers pollinating through water.


a. Pollination groups.
b. Vallisneria & Hydrilla.
18) a) Mention any two features that are required to facilitate cloning into a vector.

b) Since DNA is a hydrophilic molecule, it cannot pass through cell membranes. So bacterial cells are made ‘competent’ to take up alien DNA or plasmid. Prepare a flowchart showing the steps of this process.


a) Origin of Replication (Ori), Selectable Marker, Cloning Sites etc.

b) Treat bacterial cells with a specific concentration of a divalent cation (e.g. calcium) → DNA enters the bacterium through pores in cell wall → Incubate the cells with recombinant DNA on ice → Place them briefly at 42°C (heat shock) → Put them back on ice → Bacteria take up recombinant DNA.

19) (a) Rani wrote name of the following organisms in her notebook. Arrange the terms in a food chain sequence.

Man, hen, earthworm, mango-tree

(b) Explain food chain and name the types of food chain.


(a) Mango-tree → Earthworm → Hen → Man.

(b) The chain of feeding relationship between different organisms is called a food chain. It is 2 types:

Grazing Food Chain (GFC): Here, primary consumer feeds on living plants (producer).

Detritus Food Chain (DFC): Here, primary consumer feeds on dead organic matter (detritus).

20) Match the following:



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

1) Note the relationship between first two terms and suggest a suitable term for the fourth place.

a. Sperm: Seminiferous tubules Ovum: ……………

b. Progesterone: Corpus luteum HCG: ……………

✅ a. Ovarian follicles        b. Placenta

2) Given are two unlabelled diagrams depicting invertebrate and vertebrate diversity. What do A and B stand for?

✅ A= Insects        B= Fishes

3) Select the Assisted Reproductive Technique that uses an early embryo with up to 8 blastomeres.

a. ZIFT        b. IUT        c. GIFT        d. IUI

✅ a. ZIFT

4) Name the phenomenon where both phenotypic and genotypic ratios are found to be same.

✅ Incomplete dominance

5) Expand SNPs.

✅ Single Nucleotide Polymorphisms.

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

6) Symbols used in human pedigree analysis and their meanings are provided in the table. Fill the blanks with suitable symbols or meanings.


a. Male

b. ⚪

c. Sex unspecified

d. ⬛

7) Observe the graph given.
a) What do A and B stand for?

b) Mention one function A and B.


a) A= Estrogen        B= Progesterone

b) Estrogen stimulates proliferation of ruptured uterine endometrium.

Progesterone helps to maintain the endometrium for implantation and other events of pregnancy.

8) A DNA molecule which contains most of its nitrogen in the form of 15N is allowed to replicate in a medium containing the nitrogen source 14N.

a. What will be the percentage of DNA strands that contain 15N after 2 rounds of replication?

b. Who conducted this experiment and what conclusion they reached from this experiment?


a) After 2 rounds of replication, 25% of the DNA strands will contain 15N.

b) The experiment was conducted by Matthew Meselson and Franklin Stahl.

Their conclusion was that DNA replication is semi-conservative, meaning each new DNA molecule consists of one parental strand and one newly synthesized strand.

9) Match the following:


10) A list of human diseases is given below. Categorize them into distinct groups with suitable titles.

Ascariasis, Typhoid, Diphtheria, Malaria, Pneumonia, Amoebiasis, Elephantiasis


Human diseases:

Bacterial diseases: Typhoid, Pneumonia, Diphtheria

Protozoan diseases: Malaria, Amoebiasis

Helminth diseases: Ascariasis, Elephantiasis

11) Raju had lost his mother at birth. He is unhealthy and prone to diseases easily. In his doctor’s opinion, Raju’s ill health is due to lack of drinking mother’s milk. How will you justify the doctor’s opinion in the light of your knowledge of immunity?


Mother's milk especially colostrum provides essential antibodies and immune factors that contribute to the development of the infant's immune system. Antibodies in the milk protect the baby from infections and diseases. The lack of these immune-boosting elements in Raju's early life made him unhealthy and prone to diseases.
12) Central dogma of molecular biology is given in the diagram.
a. What do A, B and C stand for?

b. In which organisms, the central dogma is reversed?


a) A= Replication

    B= Transcription

    C= Translation

b) Retroviruses

13) Certain facts related to a human disorder are given.

• It is an inborn error in metabolism.

• It is inherited as an autosomal recessive trait.

• The affected person is mentally retarded.

a. Name the disorder.

b. What are the physiological processes behind this mental retardation?


a) Phenylketonuria.

b) The affected individual lacks the enzyme phenylalanine hydroxylase. As a result, phenylalanine accumulates and converts into phenyl pyruvic acid and other derivatives. They accumulate in brain resulting in mental retardation.

14) A genetic cross is represented below.
a. Identify the given cross and mention the ratio.

b. Elaborate upon the significance of such a cross.


a. Test cross.

Ratio is 1:1.

b. Test cross is used to find out unknown genotype of a character.

15) Mention any four factors that affect Hardy-Weinberg equilibrium.


Gene migration, genetic drift, mutation, genetic recombination and natural selection.
16) Some terms related to biodiversity conservation are given. Arrange these terms under two suitable headings.

Biosphere reserves, National parks, Zoological parks, Wildlife sanctuaries, Cryopreservation of gametes, Seed banks, Botanical gardens, Sacred groves


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

17) Diagram shown below is a surgical method used for female sterilization.

a. Name the surgical method and mention how it works.

b. Mention one advantage and one disadvantage of this method.

c. Name two contraceptives that can be used as emergency contraceptives.


a) Tubectomy.

It blocks gamete transport thereby prevents fertilization and conception.

b) Advantage: Highly effective.

Disadvantage: Reversibility is poor.

c) Progestogens or progestogen-oestrogen combinations & IUDs.

18) Observe the diagram provided and identify the process.

a. Label A, B, C and D.

b. Why are gametes produced haploid even though the gamete mother cells are diploid?


a) A= Primary oocyte

B= First polar body

C= Secondary oocyte

D= Ovum (Ootid)

b) Gametes are produced as haploid cells by meiosis. When haploid gametes fuse during fertilization, the resulting zygote restores the diploid chromosome number.

19) Given below is the diagram of a replication fork drawn by a student.

a. Redraw the diagram correctly and label it.

b. Why does discontinuous synthesis of DNA occur in one strand?


Replication fork. a.
b. Discontinuous synthesis of DNA occurs in one strand because DNA polymerase can only add nucleotides in a 5' to 3' direction. As the replication fork opens, this strand is synthesized in short, discontinuous fragments.
20) Observe the diagrammatic representation and answer the questions:

a. Explain the phenomenon shown in the figure.

b. How can it be considered as evidence of evolution?

c. Write any other example for this phenomenon. Explain.


a) Adaptive radiation of marsupials of Australia.

It is the evolution of different species from an ancestor in a geographical area starting from a point and radiating to other areas of geography (habitats).

b) Adaptive radiation is considered as evidence of evolution because it explains how a single ancestral species can diversify into multiple species.

c) Darwin’s finches. Despite having a common ancestor, they have evolved different beak shapes and sizes, enabling them to utilize different foods.

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