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Biology 57/3/2 2018-2019 CBSE (Science) Class 12 Question Paper Solution

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Biology [57/3/2]
Marks: 70 Academic Year: 2018-2019
Date: March 2019
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SECTION - A
[1] 1

Why are cucurbit plants said to be monoecious ?

Concept: Reproduction in Organisms (Questions)
Chapter: [0.01] Reproduction in Organisms
[1] 2
[1] 2.a

Name the pollutant attributed to be the cause of ‘ozone-hole’ over the Antarctica region.

Concept: Ozone Layer Depletion - Ozone Depletion in the Stratosphere
Chapter: [0.04] Environmental Issues
OR
[1] 2.b

List the greenhouse gases other than carbon dioxide.

Concept: Greenhouse Effect and Climate Change
Chapter: [0.04] Environmental Issues
[1] 3
[1] 3.a

Write the scientific name of the organism Alexander Fleming worked on and discovered the first antibiotic.
Was the organism he worked on a fungus or a bacterium ?

Concept: Microbes in Human Welfare
Chapter: [0.03] Microbes in Human Welfare [0.03] Microbes in Human Welfare
OR
[1] 3.b

Suggest a method to overcome excessive inbreeding depression.

Concept: Animal Husbandry (Livestock)
Chapter: [0.02] Strategies for Enhancement in Food Production
[1] 4

According to de-Vries what is saltation?

Concept: Mechanism of Organic Evolution
Chapter: [0.03] Evolution
[1] 5

Differentiate between a DNA and a RNA nucleotide.

Concept: Search for Genetic Material - Properties of Genetic Material (DNA Versus RNA)
Chapter: [0.02] Molecular Basis of Inheritance
SECTION - B
[2] 6

Where exactly is the filiform apparatus present in the embryo-sac of an angiosperm ?
States its function.

Concept: Development of Female Gametophytes
Chapter: [0.02] Sexual Reproduction in Flowering Plants
[2] 7

Explain the role of histones in forming a nucleosome.

Concept: Packaging of DNA Helix
Chapter: [0.02] Molecular Basis of Inheritance
[2] 8
[2] 8.a

What is ‘Ori’ ? State its importance during cloning of a vector.

Concept: Tools of Recombinant Dna Technology - Cloning Vectors
Chapter: [0.01] Biotechnology - Principles and Processes
OR
[2] 8.b

Explain the importance of ‘Selectable marker’, with the help of a suitable example.

Concept: Tools of Recombinant Dna Technology - Cloning Vectors
Chapter: [0.01] Biotechnology - Principles and Processes
[2] 9

What is ‘carrying capacity’ of a species in a habitat ? Why is logistic growth model considered more realistic?

Concept: Population Growth
Chapter: [0.01] Organisms and Populations
[2] 10
[2] 10.a

Why has the Indian Government set up the organisation named GEAC ? Give any two reasons.

Concept: Ethical Issues
Chapter: [0.02] Biotechnology and Its Application
OR
[2] 10.b

Give a schematic representation of the transformation of a pro-insulin into insulin.

Concept: Biotechnological Applications in Medicine
Chapter: [0.02] Biotechnology and Its Application
[2] 11

Explain the relationship between B-lymphocytes and T-lymphocytes developing an immune response.

Concept: Immunity
Chapter: [0.01] Human Health and Diseases
[2] 12

“The pyramid of biomass is not always upright.” Explain the statement.

Concept: Ecological Pyramids
Chapter: [0.02] Ecosystem
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SECTION - C
[3] 13

Draw a T.S. of a young anther of an angiosperm. Label the different layers of the wall and write their functions.

Concept: Pre-fertilization in Plant: Structure and Events - Stamen, Microsporangium and Pollen Grain
Chapter: [0.02] Sexual Reproduction in Flowering Plants
[3] 14
[1] 14.a

Why should a bacterium be made ‘competent’ ?

Concept: Tools of Recombinant Dna Technology - Competent Host (For Transformation with Recombinant Dna)
Chapter: [0.01] Biotechnology - Principles and Processes
[2] 14.b

Explain the role of ‘microinjection’ and ‘gene gun’ in biotechnology

Concept: Tools of Recombinant Dna Technology - Competent Host (For Transformation with Recombinant Dna)
Chapter: [0.01] Biotechnology - Principles and Processes
[3] 15

How do desert lizards cope with the variations in their environment ? Explain.

Concept: Adaptations and Its Types
Chapter: [0.01] Organisms and Populations
[3] 16
[1.5] 16.a

Name and explain the mode of action of any two types of IUDs.

Concept: Population Explosion and Birth Control
Chapter: [0.04] Reproductive Health
[1.5] 16.b

List the advantges of using ‘Saheli’ as a contraceptive.

Concept: Population Explosion and Birth Control
Chapter: [0.04] Reproductive Health
[3] 17
[2] 17.a

Write the scientific name of the source plant and the part from which opiods are extracted. What is it commonly and chemically called ?

Concept: Drugs and Alcohol Abuse - Effects of Drug/Alcohol Abuse
Chapter: [0.01] Human Health and Diseases
[1] 17.b

Where in the human body are its specific receptors located ? How do opioids affect the human body ?

Concept: Drugs and Alcohol Abuse - Effects of Drug/Alcohol Abuse
Chapter: [0.01] Human Health and Diseases
[3] 18
[1.5] 18.a

How does the human body respond when vaccine is introduced into it?

Concept: Immunity
Chapter: [0.01] Human Health and Diseases
[1.5] 18.b

It is said that vaccinations are a must for a healthy society. Justify.

Concept: Immunity
Chapter: [0.01] Human Health and Diseases
[3] 19
[3] 19.a

What is heterogamety ? Explain the mechanism of sex determinatin in Drosophila.

Concept: Sex Determination
Chapter: [0.01] Principles of Inheritance and Variation
OR
[3] 19.b

Explain the process of making heterogeneous nuclear RNA (hnRNA) into a fully functional mRNA in eukaryotes. Where does this process occur in the cell?

Concept: Protein synthesis - Transcription - Types of RNA and the Process of Transcription
Chapter: [0.02] Molecular Basis of Inheritance
[3] 20

Write any six salient features of the human genome as drawn from the human genome project.

Concept: Human Genome Project
Chapter: [0.02] Molecular Basis of Inheritance
[3] 21

“Appearance of melanised moths post-industrialisation in England is a classic example of evolution by natural selection.” Explain.

Concept: Evidence of Organic Evolution
Chapter: [0.03] Evolution
[3] 22
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[3] 22.a

Explain any three remedial measures to overcome the acute air pollution in our cities.

Concept: Prevention of Air Pollution
Chapter: [0.04] Environmental Issues
OR
[3] 22.b

Write any three ways by which noise pollution affects the human body adversely. List any three steps that should be followed in order to reduce noise pollution.

Concept: Noise Pollution
Chapter: [0.04] Environmental Issues
[3] 23
[1] 23.a

What is the primary productivity of an ecosystem and how is it expressed?

Concept: Productivity
Chapter: [0.02] Ecosystem
[2] 23.b

Explain what does the equation given below show :
NPP = GPP – R

Concept: Productivity
Chapter: [0.02] Ecosystem
OR
[1] 23.c

Name the type of detritus that decomposes faster. List any two factors that enhance the rate of decomposition.

Concept: Decomposition
Chapter: [0.02] Ecosystem
[2] 23.d

Write the different steps taken in humification and mineralisation during the process of decomposition.

Concept: Decomposition
Chapter: [0.02] Ecosystem
[3] 24
[3] 24.a

Write any two biochemical/molecular diagonostic procedures for early detection of viral infection. Explain the principle of any one of them.

Concept: Biotechnological Applications in Medicine
Chapter: [0.02] Biotechnology and Its Application
OR
[3] 24.b

Describe the steps that are followed during secondary treatment of sewage.

Concept: Biotechnological Applications in Medicine
Chapter: [0.02] Biotechnology and Its Application
SECTION D
[5] 25
[5] 25.a

Explain the changes that occur in the ovary and uterus during menstrual cycle in human females. Mention the influence of pituitary and ovarian hormones in bringing these changes.

Concept: Menstrual Cycle (Ovarian Cycle)
Chapter: [0.03] Human Reproduction
OR
[5] 25.b

Compare the characteristic features of insect pollinated and wind pollinated flowers. Explain how the respective features assist in pollination.

Concept: Pre-fertilization in Plant: Pollination
Chapter: [0.02] Sexual Reproduction in Flowering Plants
[5] 26
[1] 26.a

Write the specific name of the genus Plasmodium that causes one of the most serious types of diseases in humans. Name the disease.

Concept: Common Diseases in Humans
Chapter: [0.01] Human Health and Diseases
[2] 26.b

Describe the events in the life cycle of Plasmodium which take place in the female Anopheles.

Concept: Common Diseases in Humans
Chapter: [0.01] Human Health and Diseases
[2] 26.c

Explain what happens in the RBCs of the humans when Plasmodium gains entry into them. How does the human body gets affected?

Concept: Common Diseases in Humans
Chapter: [0.01] Human Health and Diseases
OR
[5] 26.d

Explain the interrelationship between organic farming and biofertilizers, with the help of any three suitable examples.

Concept: Microbes as Biofertilizers
Chapter: [0.03] Microbes in Human Welfare
[5] 27
[2.5] 27.a

How would you find out whether a given tall garden pea plant is homozygous or heterzygous? Substantiate your answer with the help fo Punnett squares.

Concept: Monohybrid Cross - Inheritance of One Gene
Chapter: [0.01] Principles of Inheritance and Variation
[2.5] 27.b

Given below are the F2 – phenotypic ratios of two independently carried monohybrid crosses :
(i) 1 : 2 : 1
(ii) 3 : 1
Mention what does each ratio suggest.

Concept: Monohybrid Cross - Inheritance of One Gene
Chapter: [0.01] Principles of Inheritance and Variation
OR
[5] 27.c

(a) Why did Hershey and Chase use radioactive 32P and 35S in their experiments? Explain.
(b) Following the experiments conducted by them, write what conclusion did they arrive at and how ?

Concept: Search for Genetic Material - Introduction of Search for Genetic Material
Chapter: [0.02] Molecular Basis of Inheritance

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