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Biology 57/1/2 2018-2019 CBSE (Science) Class 12 Question Paper Solution

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Biology [57/1/2]
Marks: 70Academic Year: 2018-2019
Date: March 2019
Duration: 2h
  • Section A contains questions number 1 to 5, very short answer type questions of one mark each.
  • Section B contains questions number 6 to 12, short answer type I questions of two marks each.
  • Section C contains questions number 13 to 24, short answer type II questions of three marks each.
  • Section D contains question number 25 to 27, long answer type questions of five marks each.

SECTION - A
[1]1
[1]1.1

Answer the following question.
What are 'flocs', formed during secondary treatment of sewage?

Concept: Microbes in Sewage Treatment
Chapter: [3.03] Microbes in Human Welfare
OR
[1]1.2

Answer the following question.
Write any two places where methanogens can be found.

Concept: Microbes in Production of Biogas
Chapter: [3.03] Microbes in Human Welfare
[1]2

Answer the following question.
How did Charles Darwin express 'fitness'?

Concept: Darwin'S Contribution
Chapter: [2.03] Evolution
[1]3

Answer the following question.
At what stage does the meiosis occur in an organism exhibiting haploidic life cycle and mention the fate of the products thus produced.

Concept: Sexual Reproduction - Post-fertilisation Events - the Zygote
Chapter: [1.01] Reproduction in Organisms
[1]4
[1]4.1

Answer the following question.
Name the layer of the atmosphere that is associated with 'good ozone'.

Concept: Ozone - Ozone Depletion in the Stratosphere
Chapter: [5.04] Environmental Issues
OR
[1]4.2

Answer the following question.
Mention the term used to describe a population interaction between an orchid growing on a forest tree.

Concept: Population - Population Interactions
Chapter: [5.01] Organisms and Populations
[1]5

Answer the following question.
British geneticist R.C. Punnett developed a graphical representation of a genetic cross called “Punnett Square”. Mention the possible result this representation predicts of the genetic cross carried.

Concept: Inheritance of Two Genes - Linkage and Crossing Over
Chapter: [2.01] Principles of Inheritance and Variation
SECTION - B
[2]6

Answer the following question.
Express the process of pollination in Vallisneria.

Concept: Pre-fertilisation - Structures and Events - Pollination
Chapter: [1.02] Sexual Reproduction in Flowering Plants
[2]7
[2]7.1

Answer the following question.
Differentiate between the roles of B-lymphocytes and T-lymphocytes in generating immune responses.

Concept: Concept of Immunity
Chapter: [3.01] Human Health and Diseases
OR
[2]7.2

Answer the following question:
The principle of vaccination is based on the property of the "memory" of the immune system. Taking one suitable example, justify the statement.

Concept: Concept of Immunity
Chapter: [3.01] Human Health and Diseases
[2]8

Answer the following question.
How would the gene flow or genetic drift affect the population in which either of them happens to take place?

Concept: Gene Flow and Genetic Drift
Chapter: [2.03] Evolution
[2]9

Answer the following question.
Why is crossbreeding in animals practiced? How is a breed Hisardale developed?

Concept: Animal Husbandry
Chapter: [3.02] Strategies for Enhancement in Food Production
[2]10

Answer the following question.
β galactosidase enzyme is considered a better selectable marker. Justify the statement.

Concept: Tools of Recombinant Dna Technology - Cloning Vectors
Chapter: [4.01] Biotechnology - Principles and Processes
[2]11
[2]11.1

Answer the following question.
Mention four significant services that a healthy forest ecosystem provide.

Concept: Ecosystem – Structure and Function
Chapter: [5.02] Ecosystem
OR
[2]11.2

Answer the following question:
Substantiate with the help of one example that in an ecosystem mutualists
(i) tend to co-evolve and
(ii) are also one of the major causes of biodiversity loss.

Concept: Biodiversity - Loss of Biodiversity
Chapter: [5.03] Biodiversity and Its Conservation
[2]12

Answer the following question.
List any four ways by which GMOs have been useful for enhanced crop output.

Concept: Biotechnological Applications in Agriculture
Chapter: [4.02] Biotechnology and Its Application
SECTION - C
[3]13
[3]13.1

Differentiate between geitonogamy and xenogamy.

Concept: Pre-fertilisation - Structures and Events - Pollination
Chapter: [1.02] Sexual Reproduction in Flowering Plants
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OR
[3]13.2

Answer the following question.
Write the difference in the characteristics of the progeny produced as a result of the two processes.

Concept: Pre-fertilisation - Structures and Events - Pollination
Chapter: [1.02] Sexual Reproduction in Flowering Plants
[3]14
[2]14.1

Write two differences between Homo erectus and Homo habilis

Concept: Origin and Evolution of Man
Chapter: [2.03] Evolution
[1]14.2

Rearrange the following from early to late geologic periods:
Carboniferous, Silurian, Jurassic.

Concept: Introduction of Evolution and Origin of Universe and Earth
Chapter: [2.03] Evolution
[3]15
[3]15.1

Answer the following question.
Explain the mechanism of DNA replication with the help of a replication fork. What role does the enzyme ONA-ligase play in a DNA replication fork?

Concept: Search for Genetic Material - Genetic Material is DNA
Chapter: [2.02] Molecular Basis of Inheritance
OR
[3]15.2

Answer the following question.
Construct and label a transcription unit from which the RNA segment given below has been transcribed. Write the complete name of the enzyme that transcribed this RNA. 

Concept: Transcription - Types of RNA and the Process of Transcription
Chapter: [2.02] Molecular Basis of Inheritance
[3]16
[3]16.1

Answer the following question.
Compare in any three ways the chromosomal theory of inheritance as proposed by Sutton and Bovery with that of experimental results on pea plant presented by Mendel.

Concept: Inheritance of Two Genes - Chromosome Theory of Inheritance
Chapter: [2.01] Principles of Inheritance and Variation
OR
[3]16.2
[2]16.2.1

Answer the following question.
Explain linkage and recombination as put forth by T.H. Morgan based on his observations with the Drosophila melanogaster crossing experiment.

Concept: Inheritance of Two Genes - Linkage and Crossing Over
Chapter: [2.01] Principles of Inheritance and Variation
[1]16.2.2

Answer the following question.
Write the basis on which Alfred Sturtevant explained gene mapping.

Concept: Human Genome Project
Chapter: [2.02] Molecular Basis of Inheritance
[3]17
[3]17.1

Draw a label diagram.
Draw a labeled diagram to show the interrelationship of four accessory ducts in a human male reproductive system. 

Concept: The Male Reproductive System
Chapter: [1.03] Human Reproduction
OR
[3]17.2

Draw a label diagram.
Draw a sectional view of the human ovary showing the different stages of developing follicles, corpus luteum, and ovulation.

Concept: The Female Reproductive System
Chapter: [1.03] Human Reproduction
[3]18
[1]18.1

How does the activity of each one of the following help in organic farming?
Mycorrhiza

Concept: Microbes as Biocontrol Agents
Chapter: [3.03] Microbes in Human Welfare
[1]18.2

How does the activity of each one of the following help in organic farming?
Cyanobacteria

Concept: Microbes as Biofertilisers
Chapter: [3.03] Microbes in Human Welfare
[1]18.3

How does the activity of each one of the following help in organic farming?
Rhizobium

Concept: Agrochemicals and Their Effects
Chapter: [5.04] Environmental Issues
[3]19

Answer the following question.
Two children, A and B aged 4 and 5 years respectively visited a hospital with a similar genetic disorder. The girl A was provided enzyme-replacement therapy and was advised to revisit periodically for further treatment. The girl, B was, however, given a therapy that did not require revisit for further treatment.

Name the ailments the two girls were suffering from?

Concept: Concept of Mutation
Chapter: [2.01] Principles of Inheritance and Variation
[3]20

Answer the following question:
While on a visit to a pond in the city-neighborhood, the visitors were delighted to find a large expanse of water covered with colorful algal mass.  

As a student of biology, do you agree with their delight? Give reasons in support of your answer.

Concept: Water Pollution and Its Control - Introduction of Water Pollution and Its Control
Chapter: [5.04] Environmental Issues
[3]21
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[2]21.1

Match the microbes listed under Column-A with the products mentioned under Column-B. 

  Column -A     Column -B 
(H)  Peniciffium notatum  (i)   Statin 
(I)  Trichoderma polysporum    (ii) ethanol
(J)  Monascus purpures (iii)   antibiotic
(K) Saccharomyces cerevisia  (iv) Cyclosporin-A
Concept: Introduction of Microbes in Human Welfare
Chapter: [3.03] Microbes in Human Welfare
[1]21.2

Answer the following question:
Why does 'Swiss Cheese' develop large holes?

Concept: Microbes in Household Products
Chapter: [3.03] Microbes in Human Welfare
[3]22

Answer the following question.
Beekeeping practice is a good income generating industry.
Write the different points to be kept in mind for successful beekeeping.
Write the scientific name of the most common Indian species used for the purpose.

Concept: Animal Husbandry
Chapter: [3.02] Strategies for Enhancement in Food Production
[3]23

Answer the following question.
Mention the special adaptations evolved in parasites and why?

Concept: Common Diseases in Humans
Chapter: [3.01] Human Health and Diseases
[3]24
[3]24.1

Answer the following question:
Describe the formation of recombinant DNA by the action of EcoRI.

Concept: Processes of Recombinant Dna Technology
Chapter: [4.01] Biotechnology - Principles and Processes
OR
[3]24.2

Answer the following question:
Describe the process of amplification of the "gene of interest" using the PCR technique.

Concept: Processes of Recombinant Dna Technology
Chapter: [4.01] Biotechnology - Principles and Processes
SECTION - D
[5]25
[5]25.1

Answer the following question.
Where does the process of megasporogenis start in an angiosperm? Describe the process up to the formation of an embryo sac.

Concept: Pre-fertilisation - Structures and Events - The Pistil, Megasporangium (Ovule) and Embryo Sac
Chapter: [1.02] Sexual Reproduction in Flowering Plants
OR
[5]25.2
[3]25.2.1

Answer the following question.
Explain the process of fertilization in humans.

Concept: Introduction of Sexual Reproduction
Chapter: [1.01] Reproduction in Organisms
[2]25.2.2

Answer the following question.
Name the embryonic stage that gets implanted in human females. Explain the process of implantation.

Concept: Fertilisation and Implantation
Chapter: [1.03] Human Reproduction
[5]26
[3]26.1

Answer the following question.
What is "population" according to you as a biology student?

Concept: Population Explosion and Birth Control
Chapter: [1.04] Reproductive Health
[2]26.2

Answer the following question.
"The size of a population for any species is not a static parameter." Justify the statement with specific reference to fluctuations in the population density of a region in a given period of time.

Concept: Population - Population Attributes
Chapter: [5.01] Organisms and Populations
OR
[5]26.3
[1]26.3.1

Answer the following question.
What is hydrarch succession?

Concept: Ecological Succession
Chapter: [5.02] Ecosystem
[2]26.3.2

Answer the following question.
Compare the pioneer species and climax communities of hydrarch and xerarch succession respectively.

Concept: Ecological Succession
Chapter: [5.02] Ecosystem
[2]26.3.3

Answer the following question.
List the factors upon which the type of invading pioneer species depends on secondary hydrarch succession. Why is the rate of this succession faster than that of primary succession? 

Concept: Ecological Succession
Chapter: [5.02] Ecosystem
[5]27
[5]27.1

Answer the following question.
Differentiate between incomplete dominance and co-dominance. Substantiate your answer with one example of each.

Concept: Inheritance of One Gene - Law of Segregation - Co-dominance
Chapter: [2.01] Principles of Inheritance and Variation
OR
[5]27.2
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[3]27.2.1

Write the contributions of the following scientists in deciphering the genetic code.
George Gamow; Hargobind Khorana; Marshall Nirenberg; Severo Ochoa

Concept: Genetic Code - Introduction of Genetic Code
Chapter: [2.02] Molecular Basis of Inheritance
[2]27.2.2

Answer the following question.
State the importance of a Genetic code in protein biosynthesis.

Concept: Genetic Code - Introduction of Genetic Code
Chapter: [2.02] Molecular Basis of Inheritance

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