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Biology Abroad (Set 1) 2018-2019 CBSE (Science) Class 12 Question Paper Solution

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Biology [Abroad (Set 1)]
Marks: 70 Academic Year: 2018-2019
Date: March 2019
Duration: 2h
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(i) There are total 27  questions and four  sections in the question paper. All questions are compulsory.

(ii) Section contains questions number to 5, very short answer type questions of one mark each.

(iii) Section B contains questions number 6 to 12, short answer type I questions of two marks each.

(iv) Section contains questions number 13 to 24, short answer type II questions of three marks each.

(v) Section D contains question number 25 to 27, long answer  type questions of five marks each.

(vii) There is no overall choice in the question paper, however, an internal choice is provided in two questions of one  mark, two questions of two marks, four questions of three marks and all the three questions of five marks. In these questions, an  examinee is to attempt any one of the two given alternatives.

(vii) Wherever  necessary, the diagram  drawn should be neat and properly labelled.


Section A
[1] 1

State from where do the signals for parturition originate in human females.

Concept: Parturition and Lactation
Chapter: [1.03] Human Reproduction
[1] 2
[0.5] 2.1

Name the pattern of inheritance where F1 phenotype

resembles only one of the two parents.

Concept: Drugs and Alcohol Abuse - Prevention and Control
Chapter: [3.01] Human Health and Diseases
[0.5] 2.2

Name the pattern of inheritance where F1 phenotype

does not resemble either of the two parents and is in between the two.

Concept: Monohybrid Cross - Inheritance of One Gene - Law of Segregation - Incomplete Dominance
Chapter: [2.01] Principles of Inheritance and Variation
[1] 3
[1] 3.1

According to the Hardy-Weinberg principle, the allele frequency of a population remains constant. How do you interpret the change of frequency of alleles in a population?

Concept: Hardy Weinberg’s Principle
Chapter: [2.03] Evolution
OR
[1] 3.2

Coelacanth was caught in South Africa. State the significance of the discovery of Coelacanth in the evolutionary history of vertebrates.

Concept: Pre-fertilization in Plant: Pollination
Chapter: [1.02] Sexual Reproduction in Flowering Plants
[1] 4
[1] 4.1

State the functions of mast cells in allergy response.

Concept: Immunity
Chapter: [3.01] Human Health and Diseases
OR
[1] 4.2

State the function of interpherons.

Concept: Immunity
Chapter: [3.01] Human Health and Diseases
[1] 5

What is the cell that receives a recombinant gene called?

Concept: Process and Principles of Biotechnology
Chapter: [4.01] Biotechnology - Principles and Processes [4.01] Biotechnology - Principles and Processes
Section B
[2] 6

Name a disorder a human suffers from as a result of the monosomy of the sex chromosome. Give the karyotype and write the symptoms.

Concept: Genetic Disorders
Chapter: [2.01] Principles of Inheritance and Variation [2.01] Principles of Inheritance and Variation
[2] 7
[2] 7.1

In the T.S. of a mature anther given below, identify "a" and "b" and mention their functions.

Concept: Pre-fertilization in Plant: Structure and Events - The Pistil, Megasporangium (Ovule) and Embryo Sac
Chapter: [1.02] Sexual Reproduction in Flowering Plants
OR
[2] 7.2

What is cleistogamy? Write one advantage and one disadvantage of it, to the plant.

Concept: Introduction of Sexual Reproduction in Flowering Plants
Chapter: [1.02] Sexual Reproduction in Flowering Plants
[2] 8

State the role of the thymus as a lymphoid organ. Name the cells that are released from it and mention their function.

Concept: Immunity
Chapter: [3.01] Human Health and Diseases
[2] 9

"Artificial insemination helps overcome several problems of normal mating in cattle". Do you agree? Support your answer with any three reasons.

Concept: Transgenic Animals
Chapter: [4.02] Biotechnology and Its Application
[2] 10

Name and explain the interaction that is seen between clownfish and sea anemones.

Concept: Population Interactions
Chapter: [5.01] Organisms and Populations
[2] 11

Write the relationship between productivity, gross primary productivity, net primary productivity, and secondary productivity.

Concept: Productivity
Chapter: [5.02] Ecosystem
[2] 12

Justify the need for the signing of the 'Montreal Protocol' by the participating nations in 1987.

Concept: Ozone Layer Depletion - Ozone Depletion in the Stratosphere
Chapter: [5.04] Environmental Issues
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Section C
[3] 13
[3] 13.1

Emasculation and bagging are the two important steps carried during artificial hybridization to obtain superior varieties of desired plants. Explain giving reasons, in which types of flowers and at what stages are the two processes carried out.

Concept: Artificial Hybridization
Chapter: [1.02] Sexual Reproduction in Flowering Plants
OR
[3] 13.2

State what is apomixis. Write its significance. How can it be commercially used?

Concept: Polyembryony
Chapter: [1.02] Sexual Reproduction in Flowering Plants
[3] 14
[3] 14.1
[1.5] 14.1.1

Draw a sectional view of human ovary. Label the following parts :

(i) Primary Follicle
(ii) Secondary oocyte
(iii) Graafian follicle
(iv) Corpus luteum
Concept: Microscopic Anatomy of Ovary
Chapter: [1.03] Human Reproduction
[1.5] 14.1.2

Name the hormones influencing the follicular development of corpus luteum.

Concept: Development of Female Gametophytes
Chapter: [1.02] Sexual Reproduction in Flowering Plants
OR
[3] 14.2
[1] 14.2.1
Draw an L.S. of pistil showing pollen tube entering into the embryo sac. Label the following :
(i) Nucellus
(ii) Antipodals
(iii) Synergids
(iv) Micropyle
Concept: Pre-fertilization in Plant: Pollination
Chapter: [1.02] Sexual Reproduction in Flowering Plants
[2] 14.2.2
Write the function of the following :
Synergids
Concept: Development of Female Gametophytes
Chapter: [1.02] Sexual Reproduction in Flowering Plants

Write the function of the following :
Micropyle

Concept: Seed
Chapter: [1.02] Sexual Reproduction in Flowering Plants
[3] 15
[3] 15.1

Given below is the representation of a relevant part of the amino acid composition of the β-chain of hemoglobin, related to the shape of human red blood cells.

(a) Is this representation of the sequence of amino acids indicating a normal human or a sufferer from certain blood related genetic diseases? Give reasons in support of your answer.

(b) Why is the disease referred to as a Mendelian disorder? Explain.

Concept: Deviations from Mendelism - Incomplete Dominance, Co-dominance, Multiple Alleles and Inheritance of Blood Groups, Pleiotropy
Chapter: [2.01] Principles of Inheritance and Variation
OR
[3] 15.2
[1.5] 15.2.1

Name the kind of diseases/disorders and any two symptoms that are likely to occur in humans if Mutation in the gene that codes for an enzyme phenylalanine hydroxylase occurs.

Concept: Reproductive Health
Chapter: [1.04] Reproductive Health [1.04] Reproductive Health [1.04] Reproductive Health [1.04] Reproductive Health
[1.5] 15.2.2

Name the kind of diseases/disorders and any two symptoms that are likely to occur in humans if The karyotype is XXY

Concept: Reproductive Health
Chapter: [1.04] Reproductive Health [1.04] Reproductive Health [1.04] Reproductive Health [1.04] Reproductive Health
[3] 16

Name the technique and the property of plant cells that can help to grow somaclones of certain desired varieties of apple. Explain how somaclones of apple can be obtained in the lab so as to get the desired variety on a large scale.

Concept: Tissue Culture
Chapter: [3.02] Strategies for Enhancement in Food Production
[3] 17

Study the graph given below and answer the question that follows:

(i) The curve 'b' is described by the following equation :

`"dN"/"dt" = "r""N" {"K-N"/"K"}`
What does 'K' stand for in this equation? Mention its significance.

(ii) Which one of the two curves is considered a more realistic one for most of the animal populations?

(iii) Which curve would depict the population of a species of deer if there are no predators in the habitat? Why is it so?

Concept: Population Explosion and Birth Control
Chapter: [1.04] Reproductive Health
[3] 18

"A very small sample of tissue or even a drop of blood can help determine paternity." Provide a scientific explanation to substantiate how it is possible.

Concept: DNA Fingerprinting Technique
Chapter: [2.02] Molecular Basis of Inheritance
[3] 19

Explain the phenomena of dominance, multiple allelism and co-dominance taking human ABO blood group as an example.

Concept: Deviations from Mendelism - Incomplete Dominance, Co-dominance, Multiple Alleles and Inheritance of Blood Groups, Pleiotropy
Chapter: [2.01] Principles of Inheritance and Variation
[3] 20

Name the genus to which baculoviruses belong. Describe their role in integrated pest management programmes.

Concept: Animal Husbandry (Livestock)
Chapter: [3.02] Strategies for Enhancement in Food Production
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[3] 21
[1] 21.1

Give a reason why :
DNA cannot pass into a host cell through the cell membrane.

Concept: The Genetic Material is a DNA
Chapter: [2.02] Molecular Basis of Inheritance
[1] 21.2

Give a reason why :
Proteases are added during the isolation of DNA for genetic engineering.

Concept: Process and Principles of Biotechnology
Chapter: [4.01] Biotechnology - Principles and Processes [4.01] Biotechnology - Principles and Processes
[1] 21.3

Give a reason why :
Single cloning site is preferred in a vector.

Concept: Tools of Recombinant Dna Technology - Restriction Enzymes
Chapter: [4.01] Biotechnology - Principles and Processes
[3] 22

State the medicinal value and the bioactive molecules produced by Penicillium notatum.

Concept: Microbes in Industrial Production
Chapter: [3.03] Microbes in Human Welfare

State the medicinal value and the bioactive molecules produced by Monascus purpureus.

Concept: Microbes in Industrial Production
Chapter: [3.03] Microbes in Human Welfare

State the medicinal value and the bioactive molecules produced by Trichoderma polysporum.

Concept: Microbes in Industrial Production
Chapter: [3.03] Microbes in Human Welfare
[3] 23
[3] 23.1

Describe the role of high temperature.

Concept: Biotechnological Applications in Medicine
Chapter: [4.02] Biotechnology and Its Application

Describe the role of primers.

Concept: Biotechnological Applications in Medicine
Chapter: [4.02] Biotechnology and Its Application

Describe the role of bacterium Thermus aquaticus in carrying the process of polymerase chain reaction.

Concept: Biotechnological Applications in Medicine
Chapter: [4.02] Biotechnology and Its Application
OR
[3] 23.2

How does the β-galactosidase coding sequence act as a selectable marker? Why is it a preferred selectable marker to antibiotic resistance genes? Explain.

Concept: Tools of Recombinant Dna Technology - Cloning Vectors
Chapter: [4.01] Biotechnology - Principles and Processes
[3] 24

Answer the following question based on Meselson and Stahl's experiment on E. coli :

Write the name of the chemical substance used as the only source of nitrogen in the experiment.

Concept: Microbes in Industrial Production
Chapter: [3.03] Microbes in Human Welfare

Answer the following question based on Meselson and Stahl's experiment on E. coli :

Why did they allow the synthesis of the light and the heavy DNA molecules in the organism?

Concept: Introduction of Molecular Basis of Inheritance
Chapter: [2.02] Molecular Basis of Inheritance

Answer the following question based on Meselson and Stahl's experiment on E. coli :

How did they distinguish the heavy DNA molecules from the light DNA molecules? Explain.

Concept: Introduction of Molecular Basis of Inheritance
Chapter: [2.02] Molecular Basis of Inheritance

Answer the following question based on Meselson and Stahl's experiment on E. coli :

Write the conclusion the scientists arrived at, at the end of the experiment.

Concept: Introduction of Molecular Basis of Inheritance
Chapter: [2.02] Molecular Basis of Inheritance
Section D
[5] 25
[5] 25.1

Describe the process of megasporogenesis up to fully developed embryo sac formation in an angiosperm.

Concept: Pre-fertilization in Plant: Structure and Events - The Pistil, Megasporangium (Ovule) and Embryo Sac
Chapter: [1.02] Sexual Reproduction in Flowering Plants
OR
[5] 25.2

Given below is the diagram of a human ovum surrounded by a few sperms. Study the diagram and answer the following questions :

(a) Which one of the sperms would reach the ovum earlier?
(b) Identify 'D' and 'E'. Mention the role of 'E'.
(c) Mention what helps the entry of sperm into the ovum and write the changes occurring in the ovum during the process.
(d) Name the specific region in the female reproductive system where the event represented in the diagram takes place.

Concept: Pre-fertilization in Plant: Structure and Events - The Pistil, Megasporangium (Ovule) and Embryo Sac
Chapter: [1.02] Sexual Reproduction in Flowering Plants
[5] 26
[5] 26.1

Study the schematic representation of the genes involved in the lac operon given below and answer the questions that follow :

p i p o z y a

(a) Identify and name the regulatory gene in this operon. Explain its role in 'switching off' the operon.

(b) Why is the lac operon's regulation referred to as negative regulation?

(c) Name the inducer molecule and the products of the genes 'z' and 'y' of the operon. Write the functions of these gene products.

Concept: Regulation of Gene Expression - The Lac Operon
Chapter: [2.02] Molecular Basis of Inheritance
OR
[5] 26.2
[2.5] 26.2.1

How does the Hardy-Wienberg equation explain genetic equilibrium?

Concept: Hardy Weinberg’s Principle
Chapter: [2.03] Evolution
[2.5] 26.2.2

Describe how this equilibrium is disturbed that may lead to the founder effect.

Concept: Gene Flow and Genetic Drift
Chapter: [2.03] Evolution
[5] 27
[5] 27.1

Study the flow chart given below and complete the equation that follows by identifying 1, 2, 3 and 4.

Nt + 1 = Nt + {(1+ 2) − (3 + 4)}

Concept: Population - Population Attributes
Chapter: [5.01] Organisms and Populations

Mention the different ways by which the population density of different species can be measured.

Concept: Population - Population Attributes
Chapter: [5.01] Organisms and Populations
OR
[5] 27.2
[2.5] 27.2.1

'The pyramid of energy is always upright.' Explain

Concept: Ecological Pyramids
Chapter: [5.02] Ecosystem
[2.5] 27.2.2

Explain with the help of labelled diagrams, the difference between an upright pyramid of biomass and an inverted pyramid of biomass.

Concept: Ecological Pyramids
Chapter: [5.02] Ecosystem
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