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Question Paper Solutions - Biology 2015 - 2016-CBSE 12th-Class 12 CBSE (Central Board of Secondary Education)

Alternate Sets

    

Marks: 70
[1]1

A male honeybee has 16 chromosomes whereas its female has 32 chromosomes. Give one reason.

Chapter: [7.02] Chromosomal Basis of Inheritance
Concept: Inheritance of Two Genes - Chromosome Theory of Inheritance
[1]2

Mention the role of ‘genetic mother’ in MOET.

Chapter: [3.02] Strategies for Enhancement in Food Production
Concept: Animal Husbandry
[1]3

What is biopiracy?

Chapter: [4.02] Biotechnology and Its Application
Concept: Ethical Issues
[1]4

Mention two advantages for preferring CNG over diesel as an automobile fuel.

Chapter: [5.04] Environmental Issues
Concept: Air Pollution and Its Control - Introduction of Air Pollution and Its Control
[1]5

Write the probable differences in eating habits of Homo habilis and Homo erectus.

Chapter: [7.01] Origin and the Evolution of Life
Concept: Origin and Evolution of Man
[1]6

A single pea plant in your kitchen garden produces pods with viable seeds, but the individual papaya plant does not. Explain.

Chapter: [2.01] Principles of Inheritance and Variation
Concept: Elementary Idea of Polygenic Inheritance
[1]7

Following are the features of genetic codes. What does each one indicate?
Stop codon; Unambiguous codon; Degenerate codon; Universal codon.

Chapter: [2.02] Molecular Basis of Inheritance
Concept: Transcription - Introduction of Transcription
[1]8

Suggest four important steps to produce a disease resistant plant through conventional plant breeding technology.

Chapter: [3.01] Enhancement in Food Production
Concept: Plant Breeding
[2]9

Name a genus of baculovirus.

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

Why are baculovirus considered good bio-control agents?

Chapter: [3.03] Microbes in Human Welfare
Concept: Microbes as Biocontrol Agents
[2]10 | Attempt any one of the following
[2]10.1

Explain the relationship between CFC’s and Ozone in the stratosphere.

Chapter: [5.04] Environmental Issues
Concept: Ozone - Ozone Depletion in the Stratosphere
[2]10.2

Why are scared groves highly protected?

Chapter: [5.03] Biodiversity and Its Conservation
Concept: Biodiversity Conservation
[2]11 | Attempt any one of the following
[2]11.1

Name the organic material exine of the pollen grain is made up of. How is this material advantageous to pollen grain?

Chapter: [1.02] Sexual Reproduction in Flowering Plants
Concept: Pre-fertilisation - Structures and Events - Stamen, Microsporangium and Pollen Grain

Still it is observed that it does not form a continuous layer around the pollen grain. Give reason.

Chapter: [1.02] Sexual Reproduction in Flowering Plants
Concept: Pre-fertilisation - Structures and Events - Stamen, Microsporangium and Pollen Grain

How are ‘pollen banks’ useful?

Chapter: [1.02] Sexual Reproduction in Flowering Plants
Concept: Pre-fertilisation - Structures and Events - Stamen, Microsporangium and Pollen Grain
[2]11.2

Mention the problems that are taken care of by Reproduction and Child Health Care programme.

Chapter: [1.04] Reproductive Health
Concept: Reproductive Health - Problems and Strategies

What is amniocentesis and why there is a statutory ban on it?

Chapter: [1.04] Reproductive Health
Concept: Reproductive Health - Problems and Strategies
[2]12

What is a test cross?

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

How can test cross decipher the heterozygosity of a plant?

Chapter: [2.01] Principles of Inheritance and Variation
Concept: Deviations from Mendelism - Incomplete Dominance, Co-dominance, Multiple Alleles and Inheritance of Blood Groups, Pleiotropy
[2]13

What do 'Y' and 'B' stand for in 'YAC' and 'BAC' used in Human Genome Project (HGP).

Mention their role in the project.

Chapter: [8.01] Genetic Engineering and Genomics
Concept: Human Genome Project

Write the percentage of the total human genome that codes for proteins and the percentage of discovered genes whose functions are known as observed during HGP.

Chapter: [8.01] Genetic Engineering and Genomics
Concept: Human Genome Project

Expand 'SNPs' identified by scientists in HGP

Chapter: [8.01] Genetic Engineering and Genomics
Concept: Human Genome Project
[2]14

Differentiate between homology and analogy. Give one example of each.

Chapter: [2.03] Evolution
Concept: Evidences for Evolution
[2]15

It is generally observed that the children who had suffered from chicken – pox in their childhood may not contract the same disease in their adulthood. Explain giving reasons the basics of such immunity in an individual. Name this kind of immunity.

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

What are interferons?

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

Mention role of interferons

Chapter: [3.01] Human Health and Diseases
Concept: Concept of Immunity
[2]16

Write the two limitations of traditional breeding technique that led to the promotion of micropropagation.

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

Mention two advantages of micro propagation.

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

Give two examples where micropropagation is commercially adopted

Chapter: [3.02] Strategies for Enhancement in Food Production
Concept: Tissue Culture
[2]17

How do organic farmers control pests? Give two examples.

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

State the difference in organic farmers approach from that of conventional pest control methods.

Chapter: [3.03] Microbes in Human Welfare
Concept: Microbes as Biocontrol Agents
[2]18

Name the selectable markers in the cloning vector pBR322? Mention the role they play.

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

Why is the coding sequence of an enzyme β - galactosidase a preferred selectable marker in comparison to the ones named above?

Chapter: [4.01] Biotechnology - Principles and Processes
Concept: Tools of Recombinant Dna Technology - Cloning Vectors
[3]19

Why must a cell be made ‘competent’ in biotechnology experiments? How does calcium ion help in doing so?

Chapter: [4.01] Biotechnology - Principles and Processes
Concept: Tools of Recombinant Dna Technology - Competent Host (For Transformation with Recombinant Dna)

State the role of 'biolistic gun' in biotechnology experiments.

Chapter: [4.01] Biotechnology - Principles and Processes
Concept: Tools of Recombinant Dna Technology - Competent Host (For Transformation with Recombinant Dna)
[3]20

Explain enzyme – replacement therapy to treat adenosine deaminase deficiency. Mention two disadvantages of this procedure.

Chapter: [4.02] Biotechnology and Its Application
Concept: Biotechnological Applications in Medicine
[3]21

Name and explain the type of interaction that exists in mycorrhizae and between cattle egret and cattle.

Chapter: [3.03] Microbes in Human Welfare
Concept: Microbes as Biocontrol Agents
[3]22

Differentiate between primary and secondary succession provided one example of each.

Chapter: [5.02] Ecosystem
Concept: Ecological Succession
[3]23

A large number of married couples the world over are childless. It is shocking to know that in India the female partner is often blamed for the couple being childless.
(a) Why in your opinion the female partner is often blamed for such situations in India? Mention any two values that you as a biology student can promote to check this social evil.
(b) State any two reasons responsible for the cause of infertility.
(c) Suggest a technique that can help the couple to have a child where the problem is with male partner

Chapter: [1.04] Reproductive Health
Concept: Infertility
[3]24 | Attempt any one of the following
[3]24.1

Explain the menstrual phase in a human female. State the levels of ovarian and pituitary hormones during this phase.

Chapter: [1.03] Human Reproduction
Concept: Menstrual Cycle

Why is follicular phase in the menstrual cycle also referred as proliferative phase? Explain.

Chapter: [1.03] Human Reproduction
Concept: Menstrual Cycle

Explain the events that occur in a graafian follicle at the time of ovulation and thereafter.

Chapter: [1.03] Human Reproduction
Concept: Menstrual Cycle

Draw a graafian follicle and label antrum and secondary oocyte

Chapter: [1.03] Human Reproduction
Concept: Menstrual Cycle
[3]24.2

As a senior biology student you have been asked to demonstrate to the students of secondary level in your school, the procedure (s) that shall ensure cross – pollination in a hermaphrodite flower. List the different steps that you would suggest and provide reasons for each of the item.

Chapter: [2] Flowering Plants
Concept: Pre-fertilisation - Structures and Events - Pollination

Draw a diagram of a section of a megasporangium of an angiosperm and label funiculus, Micropyle, embryosac and nuclleus.

Chapter: [2] Flowering Plants
Concept: Pre-fertilisation - Structures and Events - Pollination
[3]25 | Attempt any one of the following
[3]25.1

Describe Meselson and Stahl’s experiment that was carried in 1958 on E.Coli. Write the conclusion they arrived at after the experiment.

Chapter: [2.02] Molecular Basis of Inheritance
Concept: Replication - The Experimental Proof
[3]25.2

Describe the process of transcription in bacteria

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

Explain the processing the hnRNA needs to undergo before becoming functional mRNA eukaryotes.

Chapter: [2.02] Molecular Basis of Inheritance
Concept: Transcription - Introduction of Transcription
[3]26 | Attempt any one of the following
[3]26.1

(a) Name the two growth models that represent population growth and draw the respective growth curves they represent.

(b) State the basics for the difference in the shape of these curves

(c) Which one of the curves represents the human population growth at present? Do you think such a curve is sustainable? Give reason in support of your answer.

Chapter: [5.01] Organisms and Populations
Concept: Population - Population Attributes
[3]26.2

Taking an example of a small pond, explain how the four components of an ecosystem function as a unit.

Chapter: [5.02] Ecosystem
Concept: Ecosystem – Structure and Function

Name the type of food chain that exists in a pond.

Chapter: [5.02] Ecosystem
Concept: Ecosystem – Structure and Function
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