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NCERT Exemplar Class 12 Biology Chapter 11 Biotechnology: Principles and Processes are part of NCERT Exemplar Class 12 Biology. Here we have given NCERT Exemplar Class 12 Biology Chapter 11 Biotechnology: Principles and Processes. https://www.cbselabs.com/ncert-exemplar-problems-class-12-biology-biotechnology-principles-processes/

NCER Exemplar Class 12 Biology Chapter 11 Biotechnology: Principles and Processes

Multiple Choice Questions
Single Correct Answer Type

1. Rising of dough is due to
(a) Multiplication of yeast (b) Production of CO₂
(c) Emulsification (d) Hydrolysis of wheat flour starch into sugars.
Answer. (b) Dough, which is used for making dosa and idli is fermented by bacteria. The puffed up appearance of dough is due to the production of CO₂ gas. Dough which is used for making bread, is fermented by fungi Saccharomyces cerevisiae (Baker’s yeast)

2. An enzyme catalysing the removal of nucleotides from the ends of DNA is
(a) Endonuclease (b) Exonuclease
(c) DNAligase (d) Hind-II
Answer. (b) Exonucleases remove nucleotides from the ends of the DNA whereas endonucleases make cuts at specific positions within the DNA.

3. The transfer of genetic material from one bacterium to another through the mediation of a vector like virus is termed as
(a) Transduction (b) Conjugation
(c) Transformation (d) Translation
Answer. (a) The transfer of genetic material from one bacterium to another through the mediation of a vector like virus is termed as transduction.

4. Which of the given statement is correct in the context of observing DNA separated by agarose gel electrophoresis?
(a) DNA can be seen in visible light
(b) DNA can be seen without staining in visible light
(c) Ethidium bromide stained DNA can be seen in visible light
(d) Ethidium bromide stained DNA can be seen under exposure to UV light
Answer. (d) The separated DNA fragments can he visualised only after staining the DNA with a compound known as ethidium bromide followed by exposure to ultraviolet radiation (we cannot see pure DNA fragments in the visible light and without staining).

5. ‘Restriction’ in Restriction enzyme refers to
(a) Cleaving of phosphodiester bond in DNA by the enzyme
(b) Cutting of DNA at specific position only
(c) Prevention of the multiplication of bacteriophage in bacteria
(d) All of the above
Answer. (c)‘Restriction’inRestrictionenzymereferstopreventionofthemultiplication of bacteriophage in bacteria.

6. Which of the following is not required in the preparation of recombinant DNA molecule?
(a) Restriction endonuclease (b) DNA ligase
(c) DNA fragments (d) E. coli
Answer. (d) Genetic engineering or r-DNA technology can be accomplished only if we have the key tools:
(1) Restriction enzymes (2) Polymerase enzymes
(3) Ligases (4) Vectors
(5) Host organism

7. In agarose gel electrophoresis, DNA molecules are separated on the basis of their
(a) Charge only (b) Size only
(c) Charge to size ratio (d) Both charge and size
Answer. (d) The differential mobility of DNA depends upon charge and size of DNA.

8. The most important feature in a plasmid to be used as a vector is
(a) Origin of replication (on)
(b) Presence of a selectable marker
(c) Presence of sites for restriction endpnuclease
(d) Its size
Answer. (a) The most important feature in a plasmid to be used as a vector is origin of replication (ori).

9. While isolating DNA from bacteria, which of the following enzymes is not used?
(a) Lysozyme (b) Ribonuclease
(c) Deoxyribonuclease (d) Protease
Answer. (c) While isolating DNA from bacteria lysozyme, ribonuclease and protease, enzymes is used.

10. Which of the following has popularised the PCR (polymerase chain reactions)?
(a) Easy availability of DNA template
(b) Availability of synthetic primers
(c) Availability of cheap deoxyribonucleotides
(d) Availability of ‘Thermostable’ DNA polymerase
Answer. (d) If the process of replication ‘of DNA is repeated many times, the segment of DNA can be amplified to approximately billion times i.e., 1 billion copies are made. Such repeated amplification is achieved by the use of a thermostable DNA polymerase (isolated from a thermophilic bacterium Thermits aquaticus), which is active during the high temperature induced denaturation of double stranded DNA.

11. An antibiotic resistance gene in a vector usually helps in the selection of
(a) Competent cells (b) Transformed cells
(c) Recombinant cells (d) None of the above
Answer. (b) An antibiotic resistance gene in a vector usually helps in the selection of transformed cells.

12. Significance of ‘heat shock’ method in bacterial transformation is to facilitate
(a) Binding of DNA to the cell wall
(b) Uptake of DNA through membrane transport proteins
(c) Uptake of DNA through transient pores in the bacterial cell wall
(d) Expression of antibiotic resistance gene
Answer. (c) Significance of ‘heat shock’ method in bacterial transformation is to facilitate uptake of DNA through transient pores in the bacterial cell wall.

13. The role of DNA ligase in the construction of a recombinant DNA molecule is
(a) Formation of phosphodiester bond between two DNA fragments
(b) Formation of hydrogen bonds between sticky ends of DNA fragments
(c) Ligation of all purine and pyrimidine bases .
(d) None of the above
Answer. (a) The role of DNA ligase in the construction of a recombinant DNA molecule is formation of phosphodiester bond between two DNA fragments.

14. Which of the following is not a source of restriction endonuclease?
(a) Haemophilus influenzae (b) Escherichia coli
(c) Entamoeba coli . (d) Bacilliusquifacieus
Answer. (c) Haemophilus influenzae, Escherichia coli and Bacillius quifacieus are source of restriction endonuclease.

15. Which of the following steps are catalysed by Taq polymerase in a PCR reaction?
(a) Denaturation of template DNA
(b) Annealing of primers to template DNA
(c) Extension of primer end on the template DNA
(d) All of the above
Answer. (c) Taq polymerase is used between annealing and extension, help in extension of primer end on the template DNA.

16. A bacterial cell was transformed with a recombinant DNA that was generated using a human gene. However, the transformed cells did not produce the desired protein. Reasons could be
(a) Human gene may have intron which bacteria cannot process
(b) Amino acid codons for humans and bacteria are different
(c) Human protein is formed but degraded by bacteria
(d) All of the above .
Answer. (a) A bacterial cell was transformed with a recombinant DNA that was generated using a human gene However, the transformed cells did not produce the desired protein because human gene may have intron which bacteria cannot process.

17. Which of the following should be chosen for best yield if one were to produce a recombinant protein in large amounts?
(a) Laboratory flask of largest capacity
(b) A stirred-tank bioreactor without inlets and outlets
(c) A continuous culture system
(d) Any of the above
Answer. (c)

• After having cloned the gene of interest and having optimised the conditions to induce the expression of the target protein one has to consider producing it on a large scale. Small volume cultures cannot yield appreciable quantities of products.
•  To produce in large quantities the development of bioreactors, where large volume (100-1000 litres) of culture (continuous) can be processed, was required.

18. Who among the following was awarded the Nobel Prize for the development of PCR technique?
(a) Herbert Boyer (b) Hargovind Khurana
(c) KaryMullis (d) Arthur Komberg
Answer. (c) Karv Mullis was awarded the Nobel Prize for the development of PCR technique.

19. Which of the following statements does not hold true for restriction enzyme?
(a) It recognises a palindromic nucleotide sequence
(b) It is an endonuclease .
(c) It is isolated from viruses
(d) It produces the same kind of sticky ends in different DNA molecules
Answer. (c) Restriction enzyme:

• recognises a palindromic nucleotide sequence
• is an endonuclease isolated from bacteria
• produces the same kind of sticky ends in different DNA molecules

Very Short Answer Type Questions
1. How is copy number of the plasmid vector related to yield of recombinant protein?
Answer. Higher the copy number of vector plasmid, higher the copy number of gene and consequently, protein coded by the gene is produced in high amount.

2. Would you choose an exonuclease while producing a recombinant DNA molecule?
Answer. No, as exonuclease acts on the free ends of linear DNA molecule. Therefore, instead of producing DNA fragments with sticky ends, it will shorten or completely degrade the DNA fragment containing the gene of interest, and the circular plasmid (vector) will not get cut as it lacks free ends.

3. What does ‘H’ in ‘d’ and ‘III’ refer to in the enzyme Hind III?
Answer. ‘H’ from name of genus Haemophilus, ‘d’ from name of strain Rd. TIT indicates the order in which the enzyme were isolated from Rd strain of bacteria.

4. Restriction enzymes should not have more than one site of action in the cloning site of a vector. Comment.
Answer. If the restriction enzymes have more than one recognition site in a vector, than the vector itself will get fragmented on treatment with the restriction enzyme.

5. What does ‘competent’ refer to in competent cells used in transformation experiments?
Answer. Competent means bacterial cells, on treatment with CaCl₂, are made capable of taking up foreign DNA.

6. What is the significance of adding proteases at the time of isolation of genetic material (DNA)?
Answer. Role of proteases is to degrade the proteins present inside a cell (from which DNA is being isolated). If the proteins are not removed from DNA preparation then they could interfere with any downstream treatment of DNA (such action of restriction endonuclease, DNA ligase etc).

7. While doing a PCR, ‘denaturation’ step is missed. What will be its effect on the process?
Answer. If denaturation of double-stranded DNA does not take place, then primers will not be able to anneal to the template, no extension will take place, hence no amplification will occur.

8. Name a recombinant vaccine that is currently being used in vaccination program.
Answer. Hepatitis B recombinant vaccine-engerix is used for vaccination of hepatitis virus.

9. Do biomolecules (DNA, protein) exhibit biological activity in anhydrous conditions?
Answer. No, biomolecules like DNA and protein cannot exhibit biological activity in anhydrous conditions. Hence, life is unsustainable without water.

10. What modification is done on the Ti plasmid of Agrobacterium tumifaciens to convert it into a cloning vector?
Answer. The tumor inducing (Ti) plasmid of Agrobacterium tumifaciens has now been modified (disarmed) into a cloning vector which is no more pathogenic to the plants but is still able to use the mechanisms to deliver genes of our interest into a variety of plants.

Short Answer Type Questions
1. What is meant by gene cloning?
Answer. Gene cloning refers to a process in which a gene of interest is ligated to a vector. The recombinant DNA thus produced is introduced in a host cell by transformation. Each cell gets one DNA molecule and when the transformed cell grows to a bacterial colony, each cell in the colony has a copy of the gene. This is precisely gene cloning.

2. Both a wine maker and a molecular biologist who had developed a recombinant vaccine claim to be biotechnologists. Who in your opinion is correct?
Answer. Both. As biotechnology is a very wide area which deals with techniques of using a ‘natural’ organism (or its parts) as well as genetically modified organism to produce products and processes useful for mankind. A wine maker employs a strain-of yeast to produce wine by fermentation (a natural phenomenon), while the molecular biologist has cloned gene for the antigen (that is used as vaccine) in an organism which allows the production of the antigen in large amount. .

3. A recombinant DNA molecule was created by ligating a gene to a plasmid vector. By mistake, an exonuclease was added to the tube containing the recombinant DNA. How does this affect the next step in the experiment, i.e. bacterial transformation?
Answer. The experiment will not likely to be affected as recombinant DNA molecule is circular closed, with no free ends. Hence, it will not be a substrate for exonuclease enzyme which removes nucleotides from the free ends of DNA.

4. Restriction enzymes that are used in the construction of recombinant DNA
are endonucleases which cut* the DNA at ‘specific-recognition sequence’. What would be the disadvantage if they do not cut the DNA at specific- recognition sequence? .
Answer. If the restriction enzymes would cut DNA at random sites instead of at specific sites, then the DNA fragments obtained will not have ‘sticky ends’. In the absence of sticky ends, construction of recombinant DNA molecule would not be possible.

5. A plasmid DNA and a linear DNA (both are of the same size) have one site for a restriction endonuclease. When cut and separated on agarose gel electrophoresis, plasmid shows one DNA band while linear DNA shows two fragments. Explain.
Answer. It is because plasmid is a circular DNA molecule. When cut with enzyme, it becomes linear but does not get fragmented. Whereas, a linear DNA molecule gets cut into two fragments. Hence, a single DNA band is observed for plasmid while two DNA bands are observed for linear DNA in agarose gel.

6. How does one visualise DNA on an agarose gel?
Answer. A compound called Ethidium Bromide stains DNA, which on irradiating with Ultraviolet, fluoresce gives orange light. Hence, DNA fragments appear as orange band in the presence of Ethidium Bromide and UV.

7. A plasmid without a selectable marker was chosen as vector for cloning a gene. How does this affect the experiment?
Answer. In a gene, cloning experiment, first a recombinant DNA molecule is constructed, where the gene of interest is ligated to the vector (the step would not be affected) and introduced inside the host cell (transformation). Since, not all the cells get transformed with the recombinant/plasmid DNA, in the absence of selectable marker, it will be difficult to distinguish between transformants and non-transformant, because role of selectable marker is in the selection of transformants.

8. A mixture of fragmented DNA was electrophoresed in an agarose gel. After staining the gel with ethidium bromide, no DNA bands were observed. What could be the reason?
Answer. The reasons are as follows:
(i) DNA sample that was loaded on the gel may have got contaminated with nuclease (exo-or endo-or both) and completely degraded.
(ii) Electrodes were put in opposite orientation in the gel assembly that is anode towards the wells (where DNA sample is loaded). Since DNA molecules are-negatively charged, they move towards anode and hence move out of the gel instead of moving into the matrix of gel.
(iii) Ethidium bromide was not added at all or was not added in sufficient concentration and so DNA was not visible.

9. Describe the role of CaCl₂ in the preparation of competent cells.
Answer. CaCl₂ is known to increase the efficiency of DNA uptake to produce transformed bacterial cells. The divalent Ca²⁺ ions supposedly create transient pores on the bacterial cell wall by which the entry of foreign DNA is facilitated into the bacterial cells.

10. What would happen when one grows a recombinant bacterium in a bioreactor but forget to add antibiotic to the medium in which the recombinant is growing?
Answer. In the absence of antibiotic, there will be no pressure on recombinants to retain the plasmid (containing the gene of your interest). Since, maintaining a high copy number of plasmids is a metabolic burden to the microbial cells, will thus tend to lose the plasmid.

11. Identify and explain steps ‘A’, ‘B’ and ‘C’ in the PCR diagram given below.

Answer. A—Denaturation
B—Annealing
C—Extension of primers

12. Name the regions marked A, B and C.

Answer. A—Bam HI
B—Pst I .
C—Ampicillin resistance gene (amp^R)

Long Answer Type Questions
1. For selection of recombinants, insertional inactivation of antibiotic marker has been superseded by insertional inactivation of a marker gene coding for a chromogenic substrate. Give reasons.
Answer. Selection of recombinants due to inactivation of antibiotics is a laborious process as it requires:
(i) a vector with two antibiotic resistance marker
(ii) preparation of two kinds of media plate, with one antibiotic each.
Transformed cells are first plated on that antibiotic plate which has not been insertionally inactivated (ampicillin) and incubated overnight for growth of transformants. For selection of recombinants, these transformants are Replica plated on second antibiotic (tetracycline) plate (which got inactivated due to insertion of gene). Non-recombinants grow on both the plates (one carrying ampicillin and the other carrying tetracycline) while recombinants will grow only on ampicillin plate.
This entire exercise is laborious and takes more time (two overnight incubation) as well. However, if we choose the second option (insertional inactivation of a marker that produces colour in the presence of a chromogenic compound), we can distinguish between the recombinants and non-recombinants on a single medium plate (containing one antibiotic and the chromogenic compound) after overnight growth.
Hence I would choose a marker which produces a coloured compound but gets inactivated due to insertion of foreign DNA.

2. Describe the role of Agrobacterium tumafaciens in transforming a plant cell.
Answer. Agrobacterium tumafaciens harbours a mega plasmid called Ti-plasmid.
This has a T-DNA region flanked by left border and right border sequence. The T-DNA gets transferred and integrates with the host plant DNA. This property of Ti-plasmid has been exploited for cloning of gene of interest and stably integrating them in the plant genese. Therefore, by using Ti-plasmid or its derivatives, recombinant plant cells with desired genes of interest stably integrated in the plant genome has been successfully produced.

3. Illustrate the design of a bioreactor. Highlight the difference between a flask in your laboratory and a bioreactor which allows cells to grow in a continuous culture system.
Answer. Small volume cultures cannot yield appreciable quantities of products. To produce in large quantities, the development of bioreactors, where large volumes (100-1000 litres) of culture can be processed, was required. Thus, bioreactors can be thought of as vessels in which raw materials are biologically converted into specific products, individual enzymes, etc., using microbial plant, animal or human cells. A bioreactor provides the optimal conditions for achieving the desired product by providing optimum growth conditions (temperature, pH, substrate”, salts, vitamins, oxygen).

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NCERT Exemplar Class 12 Biology Chapter 12 Biotechnology and its Applications are part of NCERT Exemplar Class 12 Biology. Here we have given NCERT Exemplar Class 12 Biology Chapter 12 Biotechnology and its Applications. https://www.cbselabs.com/ncert-exemplar-problems-class-12-biology-biotechnology-applications/

NCERT Exemplar Class 12 Biology Chapter 12 Biotechnology and its Applications

Multiple Choice Questions
Single Correct Answer Type

1. Bt cotton is not
(a) A GM plant
(b) Insect resistant
(c) A bacterial gene expressing system
(d) Resistant to all pesticides
Answer. (d) Bt cotton is a GM plant, insect resistant and a bacterial gene expressing system.

2. C-peptide of human insulin is
(a) A part of mature insulin molecule
(b) Responsible for formation of disulphide bridges
(c) Removed during maturation of pro-insulin to insulin
(d) Responsible for its biological activity.
Answer. (c) C-peptide of human insulin is removed during maturation of pro-insulin to insulin. •

3. GEAC stands for
(a) Genome Engineering Action Committee
(b) Ground Environment Action Committee
(c) Genetic Engineering Approval Committee .
(d) Genetic and Environment Approval Committee
Answer. (c) GEAC stands for Genetic Engineering Approval Committee.

4. α -1 antitrypsin is
(a) An antacid
(b) An enzyme
(c) Used to treat arthritis
(d) Used to treat emphysema. 
Answer. (d) α -1 antitrypsin is used to treat emphysema.

5. A probe which is a molecule used to locate specific sequences in a mixture of, DNA or RNA molecules could be
(a) A single stranded RNA
(b) A single stranded DNA
(c) Either RNA or DNA
(d) Can be ssDNA but not ssRNA
Answer. (c) A single stranded DNA or RNA, tagged with a radioactive molecule is called Probe. .

6. Choose the correct option regarding Retrovirus:
(a) An RNA virus that can synthesise DNA during infection
(b) A DNA virus that can synthesise RNA during infection
(c) A ssDNA virus
(d) AdsRNAvirus
Answer. (a) Retrovirus is an RNA virus that can synthesise DNA during infection.

7. The site of production of ADA in the body is
(a) Erythrocytes ‘
(b) Lymphocytes
(c) Blood plasma
(d) Osteocytes
Answer. (b) The site of production of ADA in the body is lymphocytes.

8. A protoxin is
(a) A primitive toxin .
(b) A denatured toxin
(c) Toxin produced by protozoa
(d) Inactive toxin
Answer. (d) Bt toxin is a protein. This toxin does not kill the Bacillus because the Bt toxin protein exists as inactive protoxins but once an insect ingest the inactive toxin, it is converted into an active form of toxin due to the alkaline pH of the gut which solubilise the crystals.

9. Pathophysiology is the
(a) Study of physiology of pathogen
(b) Study of normal physiology of host
(c) Study of altered physiology of host
(d) None of the above
Answer. (c) Pathophysiology is the study of altered physiology of host.

10. The trigger for activation of toxin of Bacillus thuringiensis is
(a) Acidic pH of stomach
(b) High temperature
(c) Alkaline pH of gut
(d) Mechanical action in the insect gut
Answer. (c) The trigger for activation of-toxin of Bacillus thuringiensis is alkaline pH of gut.

11. Golden rice is
(a) A variety of rice grown along the yellow river in China
(b) Long stored rice having yellow colour tint
(c) A transgenic rice having gene for b-carotene
(d) Wild variety of rice with yellow coloured grains.
Answer. (c) Golden rice is a transgenic rice having gene for β-carotene.

12. In RNAi, genes are silenced using
(a) ss DNA (b) ds DNA
(c) dsRNA (d) ssRNA
Answer. (c) RNAi takes place in all eukaryotic organisms as a method of cellular defense. This method involves silencing of a specific mRNA due to the complementary dsRNA molecule that binds to and prevents translation of the mRNA (silencing).

13. The first clinical gene therapy was done for the treatment of
(a) AIDS . (b) Cancer
(c) Cystic fibrosis 
(d) SCID (Severe Combined Immuno Deficiency resulting from deficiency of ADA)
Answer. (d) A first clinical gene therapy was given in 1990 to a 4 year old girl with ADA (Adenosine deaminase) deficiency. ADA deficiency causes SCID (Severe Combined Immuno Deficiency) in which B-lymphocytes and T-lymphocytes are not formed. .

14. ADA is an enzyme which i§ deficient in a genetic disorder SCID. What is the full form of ADA?
(a) Adenosine deoxy aminase (b) Adenosine deaminase
(c) Aspartate deaminase  (d) Arginine deaminase
Answer. (b) ADA stands for Adenosine deaminase.

15. Silencing of a gene could be achieved through the use of
(a) (RNAi) only .(b) Antisense RNA only
(c) By both (d) None of the above
Answer. (c) Silencing of a gene could be achieved through the use of (RNAi) only and Antisense RNA only.

Very Short Answer Type Questions
1. In view of the current food crisis, it is said, that we need another green revolution. Highlight the major limitations of the earlier green revolution.
Answer. Limitations of green revolution:

1. The Green Revolution succeeded in tripling the food supply but yet it was not enough to feed the growing human population. Increased yields have partly been due to the use of improved crop varieties, but mainly due to the use of better management practices and use of agrochemicals (fertilisers and pesticides). However, for farmers in the developing world, agrochemicals are often too expensive, and further increases in yield with existing varieties are not possible using conventional breeding.
2. Use of agrochemicals causes eutrophication in aquatic ecosystems and biomagnification in terrestrial ecosystems.
3. Water logging and soil salinity are some of the problems that have come in the wake of green revolution.

2. Expand GMO. How is it different from a hybrid?
Answer. GMO stands for Genetically Modified Organism. It differs from a hybrid because in a hybrid,cross is done between total genomes of two species or strains, where as in a GMO, foreign gene(s) is introduced in the organism and is usually maintained as extra-chromosomal entity or is integrated into the genome of the organism. .

3. Differentiate between diagnostics and therapeutics. Give one example and for each category.
Answer. A diagnostic technique helps us to identify a disease. Example: ELISA is a test for HIV.
A therapeutic agent on the other hand helps in the treatment of a disease. Example: Antibiotics for bacterial infections.

4. Give the full form of ELISA. Which disease can be detected using it? Discuss the principle underlying the test.
Answer. Enzyme Linked Immuno-sorbent Assay (ELISA) is used for the detection of AIDS. ELISA is based on the principle of antigen-antibody interaction. Infection by pathogen can be detected by the presence of antigens (proteins, glycoproteins, etc.) or by detecting the antibodies synthesised against the pathogen.

5. Can a disease be detected before its symptoms appear? Explain the principle involved.
Answer. Presence of a pathogen (bacteria, viruses, etc.) is normally suspected only when the pathogen has produced a disease symptom. By this time the concentration of pathogen is already very high in the body. However, very low concentration of a bacteria or virus (at a time when the symptoms of the disease are not yet visible) can be detected by amplification of their nucleic acid by PCR.

6. Write a short note on biopiracy highlighting the exploitation of developing countries by the developed countries.
Answer. Biopiracy is the term used to refer to the use of bio-resources by multinational companies and other organisations without proper authorisation from the countries and people concerned without compensatory payment. Most of the industrialised nations are rich financially but poor in biodiversity arid traditional knowledge. In contrast the developing and the underdeveloped world is rich in biodiversity and traditional knowledge related to bio-resources. Traditional knowledge related to bio-resources can be exploited to develop modem applications and can also be used to save time, effort and expenditure during their commercialisation.

7. Many proteins are secreted in their inactive form. This is also hue of many toxic proteins produced by micro organisms. Explain how the mechanism is useful for the organism producing the toxin.
Answer. Many proteins including certain toxins are secreted in their inactive form. They get activated, only when exposed to a specific trigger (pH. temperature etc.). It is advantageous to the bacteria producing it because the bacteria does not get killed due to the action of protein.

8. While creating genetically modified organisms, genetic barriers are not respected. How can this be dangerous in the long run?
Answer. The manipulation of living organisms by the human race cannot go on any further, without regulation. Some ethical standards are required to evaluate the morality of all human activities that might help or harm living organisms. Going beyond the morality of such issues, the biological significance of such things is also important. Genetic modification of organisms can have unpredictable results when such organisms are introduced into the ecosystem.

9. Why has the Indian Parliament cleared the second amendment of the country’s patents bill?
Answer. The Indian Parliament has recently cleared the second amendment of the Indian Patents Bill, that take such issues into consideration, including patent terms emergency provisions and research and development initiative.

10. Give any two reasons why the patent on Basmati should not have gone to an American Company.
Answer. (i) Rice is an important food grain, the presence of which goes back ‘ thousands of years in Asia’s agricultural history. There is an estimated 200,000 varieties of rice in India alone. The diversity of rice in India is one of the richest in the world. Basmati rice is distinct for its unique aroma and flavour and 27 documented varieties of Basmati are grown in India.
(ii) There is a reference to Basmati in ancient texts, folklore and poetry.

11. How was Insulin obtained before the advent of rDNA technology? What were the problems encountered?
Answer. Insulin used for diabetes was earlier extracted from pancreas of slaughtered cattle and pigs. Insulin from an animal source, though caused some patients to develop allergy or other types of reactions to the foreign protein.

12. With respect to understanding diseases,’discuss the importance of transgenic animal models.
Answer. Many transgenic animals are designed to increase our understanding of how genes contribute to the development of disease. These are specially made to serve as models for human diseases so that investigation of new treatments for diseases is made possible. Today transgenic models exist for many human diseases such as cancer, cystic fibrosis, rheumatoid arthritis and Alzheimer’s.

13. Name the first transgenic cow. Which gene was introduced in this cow?
Answer. Rosie was the name of the first transgenic cow. Gene for human alpha lactalbumin was introduced in its gene, which made the milk nutritionally richer.

14. PCR is a useful tool for early diagnosis of an infectious disease. Elaborate.
Answer. PCR is a very sensitive technique which enables the specific amplification of desired DNA from a limited amount of DNA template. Hence, it can detect the presence of an infectious organism in the infected patient at an early stage of infection (even before the infectious organism has multiplied to large number).

15. What is GEAC and what are its objectives?
Answer. GEAC (Genetic Energy Approval Committee) is an Indian government organisation. Its objective are to:
(a) examine the validity of GM (Genetic modification of organism) research.
(b) inspect the safety of introducing GM for public services.

16. For which variety of Indian rice, the patent was filed by a USA Company?
Answer. Indian Basmati was crossed with semi-dwarf variety and was claimed as a new variety for which the patent was filed by a USA company.

17. Discuss the advantages of GMO.
Answer. Plants, bacteria, fungi and animals whose genes have been altered by manipulation are called Genetically Modified Organisms (GMO). GM plants have been useful in many ways. Genetic modification has:

1.  Made crops more tolerant to abiotic stresses (cold, drought, salt, heat).
2.  Reduced reliance on chemical pesticides (pest-resistant crops).
3. Helped to reduce post-harvest losses.
4. Increased efficiency of mineral usage by plants (this prevents early exhaustion of fertility of soil).
5. Enhanced nutritional value of food, e.g., Vitamin ‘A’ enriched rice.

Short Answer Type Questions
1. Gene expression can be controlled with the help of RNA. Explain the method with an example.
Answer. Gene expression can be controlled by using RNA molecule. The technology is called RNA interference or RNAi. It is used to block the expression of certain genes and also referred to as gene silencing. During this process a complementary RNA to the mRN A being produced by the gene is introduced into the cell. This RNA binds to the mRNA making it double stranded and therefore stops translation. Resistance to nematode Meloidegyne incognita in tomato has been achieved by this method.

2. Ignoring our traditional knowledge can we prove costly in the area of biological patenting. Justify.
Answer. Most of the industrialised nations are rich financially but poor in biodiversity and traditional knowledge. In contrast the developing and the underdeveloped world is rich in biodiversity and traditional knowledge related to bio-resources. Traditional knowledge related to bio-resources can be exploited to develop modem applications and can also be used to save time, effort and expenditure during their commercialisation. There has been” growing realisation of the injustice, inadequate compensation and benefit sharing between developed and developing countries. Therefore, some nations are developing laws to prevent such unauthorised exploitation of their bio-resources and traditional knowledge.

3. Highlight any four areas where genetic modification of plants has been useful.
Answer. Plants, bacteria, fungi and animals whose genes have been altered by manipulation_are called Genetically Modified Organisms (GMO). GM plants have been useful in many ways. Genetic modification has
(i) Made crops more tolerant to abiotic stresses (cold, drought, salt, heat).
(ii) Reduced reliance on chemical pesticides (pest-resistant crops).
(iii) Helped to reduce post-harvest losses.
(iv) Increased efficiency of mineral usage by plants (this prevents early exhaustion of fertility of soil).

4. What is a recombinant DNA vaccine? Give two examples.
Answer. A recombinant vaccine is a vaccine produced through recombinant DNA technology. This involves inserting the DNA encoding an antigen that stimulates an immune response into bacterial or mammalian cells. Recombinant DNA technology has allowed the production of antigenic polypeptides of pathogen in bacteria or yeast. Vaccines produced using this .approach allow large scale production and hence greater availability for immunisation, e.g., hepatitis B vaccine (Recombivax HB) produced from yeast. As of June 2015 one human DNA vaccine had been approved for human use, the single-dose Japanese encephalitis vaccine called IMOJEV, released in 2010 in Australia.

5. Why is it that the line of treatment for a genetic disease is different from infectious diseases?
Answer. If a person is born with a hereditary disease, can a corrective therapy be taken for such a disease? Gene therapy is an attempt to do this. Gene therapy is a collection of methods that allows correction of a gene defect that has been diagnosed in a child/embryo.

6. Discuss briefly how a probe is used in molecular diagnostics.
Answer. A single stranded DNA or RNA, tagged with a radioactive molecule (probe) is allowed to hybridise to its complementary DNA in a clone of cells followed by detection using autoradiography. The clone having the mutated gene will hence not appear on the photographic film, because the probe will not have complementarity with the mutated gene.

7. Who was the first patient who was given gene therapy? Why was the given treatment recurrent in nature?
Answer. The first clinical gene therapy was given in 1990 to a 4-year old girl with adenosine deaminase (ADA) deficiency. This enzyme is crucial for the immune system to function. The disorder is caused due to the deletion of the gene for adenosine deaminase. In some children ADA deficiency can be cured by bone marrow transplantation; in others it can be treated by – enzyme replacement therapy, in which functional ADA is given to the patient by injection. But the problem- with both of these approaches that they are not completely curative. As a first step towards gene therapy, lymphocytes from the blood of the patient are grown in a culture outside the body. A functional ADA cDNA (using a retroviral vector) is then introduced into these lymphocytes, which are subsequently returned to the patient. However, as these cells are not immortal, the patient requires “periodic infusion of such genetically engineered lymphocytes. However, if the gene isolate from marrow cells producing ADA is introduced into cells at early embryonic stages, it could be a permanent cure.

8. Taking examples under each category, discuss upstream and downstream processing.
Answer. Upstream processing: Biotechnological processes can be separated into upstream processes and dpwnstream processes. The upstream process is defined as the entire process from DNA isolation and culture expansion of the cells until final product.
Downstream processing: After completion of the biosynthetic stage, the product has to be subjected through a series of processes before it Is ready for marketing as a finished product. The processes include separation and purification, which are collectively referred to as downstream processing. The product has to be formulated with suitable preservatives. Such formulation has to undergo through clinical trials as in case of drugs. Strict quality control testing for each product is also required. The downstream processing and quality control testing vary from product to product.

9. Define Antigen and Antibody. Name any two diagnostic kits based upon them.
Answer. An antigen is a foreign substance that elicits the formation of an antibody. Antibody is a protein that is synthesised in response to an antigen. Antigen and antibody show high degree of specificity in binding each other. Two diagnostic kits based on antigen-antibody interaction are:
(a) ELISA for HIV.
(b) Pregnancy test kits.

10. ELISA technique is based on the principles of antigen-antibody interaction. Can this techique be used in the molecular diagnosis of a genetic disorder, such as phenyketonuria?
Answer. Yes. One can use antibody against the enzyme (that is responsible for the metabolism of phenylalanine) to develop ELISA based diagnostic technique. The patient where the enzyme protein is absent would give negative result in ELISA when compared to normal individual.

11. How is a mature, functional insulin hormone different from its prohormone form?
Answer. Mature functional insulin is obtained by processing of pro-hormone which contains extra peptide called C-peptide. This C-peptide is removed during maturation of pro-insulin to insulin.

12. Gene therapy is an attempt to correct a genetic defect by providing a normal gene into the individual. By this’the normal function can be restored. An alternate method would be to provide the gene product (protein/enzyme) known as enzyme replacement therapy, which would also restore the function. Which in your opinion is a better option? Give reason for your answer.
Answer. Gene therapy is an attempt to correct a genetic defect by providing a normal gene into the individual. By this the normal function can be restored. Alternate method would be to provide the gene product (protein/ enzyme) know as enzyme replacement therapy, which would also restore the function. Which in your opinion is a better option? Give reason for your answer.

13. Transgenic animals are the animals in which a foreign gene is expressed. Such animals can be used to study the fundamental biological process, phenomenon as well as for producing products useful for mankind. Give one example for each type.
Answer. Study of basic biological process—how genes are regulated, how they affect the normal functions of the body and its development. Transgenic cow, Rosie is an example for the second category.

14. When a foreign DNA is introduced into an organism, how is it maintained in the host and how is it transferred to the progeny of the organism?
Answer. Foreign gene is usually ligated to a plasmid vector and introduced in the host. As plasmid replicates, and makes multiple copies of itself, so does the foreign gene gets replicated and its copes are made. When the host organism divides, its progeny also receives the plasmid DNA containing the foreign gene.

15. Bt cotton is resistant to pest, such as lepidopteron, dipterans and coleopterans. Is Bt cotton also resistant to other pests as well?
Answer. Bt cotton is made resistant to only certain specific taxa of pests. It is quite likely that in future,some other pests may infest this Bt cotton plants. It has similar immunisation against small-pox which does not provide immunity against other pathogens like those that cause cholera, typhoid etc.

Long Answer Type Questions
1. A patient is suffering from ADA deficiency. Can he be cured. How?
Answer. The first clinical gene therapy was given in 1990 to a 4-year old girl with adenosine deaminase (ADA) deficiency. This enzyme is crucial for the immune system to function. The disorder is caused due to the deletion of the gene for adenosine deaminase. In some children ADA deficiency can be cured by bone marrow transplantation; in others it can be treated by enzyme replacement therapy, in which functional ADA is given to the patient by injection. But the problem with both of these approaches that they are not completely curative. As a first step towards gene therapy, lymphocytes from the blood of the patient are grown in a culture outside the body. A functional ADA cDNA (using a retroviral vector) is then introduced into these lymphocytes, which are subsequently returned to the patient. However, as these cells are not immortal, the patient requires periodic infusion of such genetically engineered lymphocytes. However, if the gene isolate from marrow cells producing ADA is introduced into cells at early embryonic stages, it could be a permanent cure.

2. Define transgenic animals. Explain in detail any four areas where they can be utilised.
Answer. Transgenic animals are the products of genetic engineering and express specific gene(s) from totally unrelated source. Following are the four main areas where they can be utilised: .
(1) To study normal physiology and development these animals can be used to study as to which factor/gene products are needed at what time of development. By expression of certain genes, they help scientists to understand the normal gene expression at various stages of growth and development. 4
(2) Study of Diseases: Transgenic animals can be created to serve as models for various human diseases. They also help us understand the involvement of various genes in diseases like cancer, Parkinson’s disease etc.
(3) Vaccine safety: Transgenic animals can be used to test vaccines like polio vaccine. Transgenic mice have shown promising results in this area and would replace the vaccine testing on monkeys in the years to come.
(4) Chemical safety testing: Transgenic animals are created which are more sensitive to certain chemicals/drugs. These are used to study the toxicity or side effects of that chemical/drug. The advantage is that we get results faster.

3. You have identified a useful gene in bacteria. Make a flow chart of the steps that you would follow to transfer this gene to a plant.
Answer. After identifying a useful gene in bacteria, following steps should be undertaken:

4. Highlight five areas where biotechnology has influenced our lives.
Answer. The applications of biotechnology include:

1. therapeutics and diagnostics
2. genetically modified crops for agriculture
3. processed food
4. bioremediation
5. waste treatment and energy production.

5. What are the various advantages of using genetically modified plants to increase the overall yield of the crop?
Answer. GM plants have been useful in many ways. Genetic modification has:

1. Made crops more tolerant to abiotic stresses (cold, drought, salt, heat).
2.  Reduced reliance on chemical pesticides (pest-resistant crops).
3. Helped to reduce post-harvest losses.
4. Increased efficiency of mineral usage by plants (this prevents early exhaustion of fertility of soil).
5. Enhanced nutritional value of food>e.g., Vitamin ‘A’ enriched rice.

In addition to these uses, GM has been used to create tailor-made plants to supply alternative resources to industries, in the form of starches, fuels and pharmaceuticals.

6. Explain with the help of one example how genetically modified plants can:
(a) Reduce usage of chemical pesticides .
(b) Enhance nutritional value of food crops
Answer. (a) Reduce usage of chemical pesticides: Bt toxin is produced by a bacterium called Bacillus thuringiensis (Btfor short). Bt toxin gene has been cloned from the bacteria and been expressed in plants to provide resistance to insects without the need for insecticides; in effect created a bio-pesticide. Examples are Bt cotton, Bt com, rice, tomato, potato and soyabean etc.
(b) Enhance nutritional value of food crops: Golden rice is the transgenic variety of basmati rice which gives high yield and rich in vitamin A,
so it is used in the deficiency of vitamin-A causing night blindness and skin disorder.

7. List the disadvantages of insulin obtained from the pancreas of slaughtered cows and pigs:
Answer.

1. Insulin being a hormone is produced in very little amounts in the body.
   Hence, a large number of animals need to be sacrificed for obtaining small quantities of insulin. This makes the cost of insulin very high. [Demand being many fold higher than supply].
2. Slaughtering of animals is also not ethical.
3. There is potential of immune response in humans against the administered insulin which is derived from animals.
4.  There is possibility of slaughtered animals being infested with some infectious micro organism which may contaminate insulin.

8. List the advantages of recombinant insulin.
Answer. Insulin used for diabetes was earlier extracted from pancreas of slaughtered cattle and pigs. Insulin from an animal source, though caused some patients to develop allergy or other types of reactions to the foreign protein. Insulin consists of two short polypeptide chains: chain A and chain B, that are linked together by disulphide bridges. In mammals, including humans, insulin is synthesised as a pro-hormone (like a pro-enzyme, the pro-hormone also needs to be processed before it becomes a fully mature and functional hormone) which contains an extra stretch called the C peptide. This C peptide is not present in the mature insulin and is removed during maturation into insulin. The main challenge for production of insulin using rDNA techniques was getting insulin assembled into a mature form. In 1983, Eli Lilly an American company prepared two DNA sequences corresponding to A and B, chains of human insulin and introduced them in plasmids of E. coli to produce insulin chains. Chains A and B were produced separately, extracted and combined by creating disulfide bonds to form human insulin.

9. What is meant by the term bio-pesticide? Name and explain the mode of action of a popular bio-pesticide.
Answer. Biopesticide is a pesticide which is
(a) not chemical in nature
(b) more specific in action against the pest
(c) safer for environment than chemical pesticides
A popularly known bio-pesticide is Bt toxin, which is produced by a bacterium called Bacillus thuringiensis. Bt toxin gene has been cloned from this bacterium and expressed in plants. Bt toxin protein when ingested by the insect, gets converted to its active form due to the alkaline pH of the gut. The activated toxin binds to the surface of midgut epithelial cells and create pores that cause cell swelling and lysis and eventually kills the insect.

10. Name the five key tools for accomplishing the tasks of recombinant DNA technology. Also mention the functions of each tool.
Answer.

1. Restriction endonucleases: for cutting the desired DNA at desired places
2. Gel electrophoresis: for separating the desired DNA fragments
3. Ligase enzyme: for creating recombinant DNA molecule.
4. DNA delivery system: like electroporation, microinjection, gene gun method.
5. Competent host (usually bacteria/yeast): to take up recombinant DNA.

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NCERT Exemplar Class 12 Biology Chapter 13 Organisms and Populations are part of NCERT Exemplar Class 12 Biology. Here we have given NCERT Exemplar Class 12 Biology Chapter 13 Organisms and Populations. https://www.cbselabs.com/ncert-exemplar-problems-class-12-biology-organisms-populations/

NCERT Exemplar Class 12 Biology Chapter 13 Organisms and Populations

Multiple Choice Questions
Single Correct Answer Type

1. Autecology is the
(a) Relation of a population to its environment
(b) Relation of an individual to its environment
(c) Relation of a community to its environment
(d) Relation of a biome to its environment
Answer. (b) Autecology is the relation of an individual to its environment.

2. Ecotone is
(a) A polluted area
(b) The bottom of a lake
(c) A zone of transition between two communities
(d) A zone of developing community
Answer. (c) Ecotone is a zone of transition between two communities.

3. Biosphere is
(a) A component in the ecosystem
(b) Composed of the plants present in the soil
(c) Life in the outer space
(d) Composed of all living organisms present on earth which interact with the physical environment.
Answer. (d) Biosphere is composed of all living organisms present on earth which interact with the physical environment.

4. Ecological niche is
(a) The surface area of the ocean
(b) An ecologically adapted zone
(c) The physical position and functional role of a species within the community
(d) Formed of all plants and animals living at the bottom of a lake.
Answer. (c) Ecological niche is the physical position and functional role of a species within the community.

5. According to Allen’s Rule, the mammals from colder climates have
(a) Shorter ears and longer limbs (b) Longer ears and shorter limbs
(c) Longer ears and longer limbs (d) Shorter ears and shorter limbs
Answer. (d) According to Allen’s Rule, the mammals from colder climates have shorter ears and shorter limbs.

6. Salt concentration (Salinity) of the sea measured in parts per thousand is
(a) 10-15 (b) 30-70 (c) 0-5 (d) 30-35
Answer. (d) The salt concentrations is measured as salinity in parts per thousand, is less than 5 in inland waters, 30-35 in the sea and greater than 100 percent in some hypersaline lagoons.

7. Formation of tropical forests needs mean annual temperature and mean annual precipitation as
(a) 18-25°C and 150-400 cm (b) 5-15°C and 50-100 cm
(c) 30-50°C and 100-150 cm (d) 5-15°C and 100-200 cm
Answer. (a)

8. Which of the following forest plants controls the light conditions at the ground?
(a) Lianas and climbers  (b) Shrubs
(c) Tall trees (d) Herbs
Answer. (c) Tall trees control the light conditions at the ground.

9. What will happen to a well growing herbaceous plant in the forest if it is transplanted outside the forest in a park?
(a) It will grow normally.
(b) It will grow well because it is planted in the same locality.
(c) It may not survive because of change in its micro climate.
(d) It grows very well because the plant gets more sunlight.
Answer. (c) A well growing herbaceous plant in the forest if it is transplanted outside the forest in a park. It may not survive because of change in its micro climate.

10. If a population of 50 paramoecium present in a pool increases to 150 after an hour, what would be the growth rate of population?
(a) 50 per hour (b) 200 per hour
(c) 5 per hour (d) 100 per hour
Answer. (d)
Initial population of paramecium Pi = 50
After one hour population of paramecium Pf = 150
Growth rate after one hour = Pf – Pi
= 150-50= 100

11. What would be the per cent growth or birth rate per individual per hour for the same population mentioned in the previous question (Question 10)?
(a) 100 (b) 200 (c) 50 (d) 150
Answer. (b)

12. A population has more young individuals compared to the older individuals. What would be the status of the population after some years?
(a) It will decline
(b) It will stabilise
(c) It will increase
(d) It will first decline and then stabilise
Answer. (c) A population has more young individuals compared to the older individuals. It will increase the status of the population after some years.

13. What parameters are used for tiger census in our country’s national parks and sanctuaries?
(a) Pug marks only (b) Pug marks and faecal pellets .
(c) Faecal pellets only (d) Actual head counts
Answer. (b) Sometimes population size is indirectly estimated without actually counting them or seeing them. E.g. ; The tiger census in our National Parks and Tiger Reserves is often based on pug marks and faceal pellets.

14. Which of the following would necessarily decrease the density of a population in a given habitat?
(a) Natality > mortality (b) Immigration > emigration
(c) Mortality and emigration (d) Natality and immigration
Answer. (c) Mortality and emigration would necessarily decrease the density of a population in a given habitat.

15. A protozoan reproduces by binary fission. What will be the number of protozoans in its population after six generations?
(a) 128 (b) 24 (c) 64 (d) 32
Answer. (c)
Population after nth generations = 2n
Population after 6th generations = 26 =64

16. In 2005, for each of the 14 million people present in a country, 0.028 were born and 0.008 died during the year. Using exponential equation, the number of people present in 2015 is predicted as
(a) 25 millions (b) 17 millions
(c) 20 millions (d) 18 millions
Answer. (b)

17. Amensalism is an association between two species where
(a) One species is harmed and other is benefitted
(b) One species is harmed and other is unaffected
(c) One species is benefitted and other is unaffected
(d) Both the species are harmed.
Answer. (b)

18. Lichens are the associations of
(a) Bacteria and fungus (b) Algae and bacterium
(c) Fungus and algae (d) Fungus and virus
Answer. (c) Lichens are the associations of fungus and algae.

19. Which of the following is a partial root parasite? .
(a) Sandal wood (b) Mistletoe
(c) Orobanche (d) Ganoderma
Answer. (a) Sandal Wood is a partial root parasite.

20. Which one of the following organisms reproduces sexually only once in its life time?
(a) Banana plant (b) Mango
(c) Tomato (d) Eucalyptus
Answer. (a) Banana plant organisms reproduce sexually only once in its life time.

Very Short Answer Type Questions
1. Species that can tolerate narrow range of temperature are called
Answer. Stenothermic

2. What are Eurythermic species?
Answer. Species that tolerate wide range of temperature are called Eurythermic . species.

3. Species that can tolerate wide range of salinity are called .
Answer. Euryhaline

4. Define stenohaline species.
Answer. Species that tolerate narrow range of salinity are called stenohaline species.

5. What is the interaction between two species called?
Answer. Interspecific interaction

6. What is commensalism?
Answer. Commensalism is the interaction in which one species benefits and the other is neither harmed nor benefited.

7. Name the association in which one species produces poisonous substance or a change in environmental conditions that is harmful to another species.
Answer. Amensalism

8. What is Mycorrhiza?
Answer. Mycorrhiza is a symbiotic association between a fungus and the roots of higher plants.

9. Emergent land plants that can tolerate the salinities of the sea are called 
Answer. Mangroves

10. Why do high altitude areas have brighter sunlight and lower temperatures as compared to the plains?
Answer. High altitude areas have brighter sunlight because at high altitude there is a very low concentration of dust particles and atmospheric gases which absorbs the sunlight. There is a low atmospheric pressure at high altitudes. Lower atmospheric pressure results in lower temperatures at high altitudes.

11. What is homeostasis?
Answer. To maintain the constancy of internal environment despite varying external environmental conditions is called homeostasis.

12. Define aestivation.
Answer. Aestivation is a state of dormancy characterized by inactivity and a lowered metabolic rate in response to high temperatures and arid conditions.

13. What is diapause and its significance?
Answer. Under unfavourable conditions many zooplankton species in lakes and ponds are known to enter diapause, a stage of suspended development.

14. What would be the growth rate pattern, when the resources are unlimited?
Answer. Exponential.

15. What are the organisms that feed on plant sap and other plant parts called?
Answer. Phytophagous

16. What is high altitude sickness? Write its symptoms.
Answer. If one had ever been to any high altitude place (>3,500m like Rohtang Pass near Manali and Mansarovar .in Tibetan Autonomous Region), thepathological effect caused by acute exposure to low partial pressure of oxygen at high altitude is called altitude sickness. Its symptoms include nausea, fatigue and heart palpitations.

17. Give a suitable example for commensalism.
Answer. Cattle egret and grazing cattle.

18. Define ectoparasite and endoparasite, and give suitable examples.
Answer.

• Parasites that feed on the external surface of the host organism are called ectoparasites. The most familiar examples of this group are the lice on humans and ticks on dogs.
• Endoparasitesare those that live inside the host body at different sites (liver, kidney, lungs, red blood cells, etc.).'”The human liver fluke (a trematode parasite) is an endoparasite.

19. What is brood parasitism? Explain with the help of an example.
Answer. Brood parasitism in birds is a fascinating example of parasitism in which the parasitic bird lays its eggs in the nest of its host and let the host incubate them. During the course of evolution, the eggs of the parasitic bird have evolved to resemble the host’s egg in size and colour to reduce the chances of the host bird detecting the foreign eggs and ejecting them from the nest.

Short Answer Type Questions
1. Why are coral reefs not found in the regions from. West Bengal to Andhra Pradesh but are found in Tamil Nadu and on the east coast of India?
Answer. High salinity, optimal temperature and less siltation are essential to colonise corals. If siltation and fresh water inflow are very high, the corals don’t colonise. In contrast when the siltation and fresh water inflow by the rivers are very less, the coral do colonise.

2. If a fresh water fish is placed in an aquarium containing sea water, will the fish be able to survive? Explain giving reasons.
Answer. If a fresh water fish is placed in an aquarium containing sea water, it will not be able to survive because of the osmotic problems, they would face. Sea water is hypertonic as compared to fish, so it lost water through exosmosis and die due to dehydration.

3. Why do all the fresh water organisms have contractile vacuoles whereas , majority of marine organisms lack them?
Answer. In majority of fresh water organisms, contractile vacuoles is present which help in osmoregulation (remove excess water from body). In marine organism there is no need of removal of water from body (due to hyptonic condition), hence contractile vacuoles are absent.

4. Define heliophytes and sciophytes. Name a plant from your locality that is either heliophyte or sciophyte.
Answer.

• Heliophytes also called sun-loving plants, are those that require for their optimum growth full exposure to the sun. E.g., Mango
• Sciophytes also called shade-loving plants, are those plants that require reduced light intensity. E.g., Lycopodium

5. Why do submerged plants receive weaker illumination than exposed floating plants in a lake?
Answer. Submerged plants receive weaker illumination than exposed floating plants
in a lake because on passing of light through water much more amount of light is lost.

6. In a sea shore, the benthic animals live in sandy, muddy and rocky substrata
and accordingly developed the following adaptations.
a. Burrowing 
b. Building cubes
c. Holdfasts/peduncle
Find the suitable substratum against each adaptation.
Answer. a. Sandy, b. Muddy, c. Rocky

7. Categorise the following plants into hydrophytes, halophytes, mesophytes and xerophytes. Give reasons for your answers.
a. Salvinia b. Opuntia
c. Rhizophora d. Mangifera
Answer. a. Hydrophyte, b. Xerophyte, c. Halophyte, d. Mesophyte

8. In a pond, we see plants which are free-floating; rooted-submerged; footed emergent; rooted with floating leaves. Write the type of plants against each of them.

Answer. a. Submerged, b. Rooted emergent, c. Rooted with floating leaves, d. Free- floating, e. Rooted submerged

9. The density of a population in a habitat per unit area is measured in different units. Write the unit of measurement against the following:
a. Bacteria …………..
b. Banyan …………..
c. Deer …………..
d. Fish …………..
Answer. a. Nos. / Vol; b. Coverage / area; c. Biomass / area; d. Nos. / area; e. Wt. / area

10.

a. Label the three tiers 1, 2, 3 given in the above age pyramid.
b. What type of population growth is represented by the above age pyramid?
Answer. (a)
1. Pre-reproductive pogulation
2. Reproductive population
3. Post-reproductive population
(b) Expanding or growing population

11. In an association of two animal species, one is a termite which feeds on wood and the other is a protozoan Trichonympha present in the gut of the termite. What type of association they establish?
Answer. They shows mutualism.

12. Lianas are vascular plants rooted in the ground and maintain erectness of their stem by making use of other trees for support. They do not maintain direct relation with those trees. Discuss the type of association the lianas have with the trees.
Answer. This association is called commensalism.

13. Give the scientific names of any two micro organisms inhabiting the human intestine.
Answer. 1. Escherichia coli
2. Enterococcusfaecalis

14. What is a tree line?
Answer. When we go up the altitude, beyond a particular height no trees are found and the vegetation comprises only of shrubs and herbs. The altitude beyond which no tree is seen is known as tree line.

15. Define ‘zero population growth rate’. Draw an age pyramid for the same.
Answer. Yes. An inverted bell shaped age pyramid is obtained. The young of pre- reproductive age group individuals are less in number and both pre- reproductive and reproductive stages are in the same level.

16. List any four characters that are employed in human population census.
Answer. 1. Birthrates
2. Death rates
3. Sex ratio
4. Age distribution

17. Give one example for each of the following types.
(a) Migratory animal (b) Camouflaged animal
(c) Predator animal (d) Biological control agent
(e) Phytophagous animal (f) Chemical defense agent
Answer. (a) Migratory animal—Siberian crane, Salmon
(b) Camouflaged animal—Frog, insects
(c) Predator animal—Tiger, sparrow
(d) Biological control agent—Moth (against prickly pear cactus)
(e) Phytophagous animal—Insects like Locusta
(f) Chemical defense agent—Cardiac glycosides produced by Calotropis

18. Fill in the blanks:

Answer.

19. Observe the set of 4 figures A, B, C and D, and answer the following questions: •
(i) Which one of the figures shows mutualism?
(ii) What kind of association is shown in D?
(iii) Name the organisms and the association in C.
(iv) What role is the insect performing in B?

Answer. (i) Figure ‘A’ shows’ mutualism (plant-animal relationship).
(ii) Figure ‘D’ shows predation (leopard killing deer and eating it)
(iii) Figure ‘C’ shows commensalism (cattle egret and grazing cattle)
(iv) In figure ‘B’ insect is phytophagous that feed on sap of the flower.

Long Answer Type Questions
1. Comment on the following figures 1, 2 and 3:
A, B, C, D, G, P, Q, R, S are species

Answer. Fig. 1: It is a single population.and all individuals are of the same species, i.e. A—Individual interact among themselves and their environment.
Fig. 2: It is a community and it contains three populations of species A, B and C. They interact with each other and their environment.
Fig. 3: It is a biome. It contains three communities of which one is in climax and other two are in different stages of development. All three communities are in the same environment and they interact with each other and their environment.

2. An individual and a population has certain characteristics. Name these attributes with definitions.
Answer. A population has certain attributes that an individual organism does not. An individual may have births and deaths, but a population has birth rates and death rates. In a population these rates refer to per capita births and deaths, respectively. The rates, hence, expressed as change in numbers (increase or decrease) with respect to members of the population.
• Another attribute characteristic of a population is sex ratio. An individual is either a male or a female but a population has a sex ratio (e.g., 60 per cent of the population are females and 40 per cent males).
• A population at any given time is composed of individuals of different ages. If the age distribution (per cent individuals of a given age or age group) is plotted for the population, the resulting structure is called an age pyramid. For human population, the age pyramids generally show age distribution of males and females in a combined diagram. The shape of the pyramids reflects the growth status of the population (a) whether it is growing, (b) stable or (c) declining.

3. The following diagrams are the age pyramids of different populations. Comment on the status of these populations.

Answer. Fig. A: It is a pyramid shaped age pyramid. In this figure, the base, i.e., pre-reproductive stage is very large when compared with the reproductive
and past reproductive stages of the population. This type of age structure indicates that the population would increase rapidly.
Fig. B: It is an inverted bell shaped pyramid. In this figure, the pre- reproductive and reproductive stages are same. This type of age structure indicates that the population is stable.
Fig. C: It is ‘Urn’ shaped pyramid. In this figure, the pre-reproductive and reproductive stages are less than the post reproductive stage of this population. In this population, more older people are present. This type of age structure indicates that the population definitely is declining,

4. Comment on the growth curve given below.

Answer. A population growing in a habitat with limited resources show initially a lag phase, followed by phases of acceleration and deceleration and finally an asymptote, when the population density reaches the carrying capacity. A’ plot of N in relation to time (t) results in a sigmoid curve. This type of population growth is called Verhulst-Pearl Logistic Growth and is described by the following equation:

5. A population of Paramoecium caudatum was grown in a culture medium. After 5 days the culture medium became pvercrowded with Paramoecium and had depleted nutrients. What will happen to the population and what type of growth curve will the population attain? Draw the growth curve.
Answer. It shows logistic growth. (See Ans no. 4)

6. Discuss the various types of positive interactions between species.
Answer. Both the species benefit in mutualism. The interaction where one species is benefitted and the other is neither benefitted nor harmed is called commensalism.

7. In an aquarium two herbivorous species of fish are living together and feeding
on phytoplanktons. As per the Gause’s Principle, one of the species is to be eliminated in due course of time, but both are surviving well in the aquarium. Give possible reasons.
Answer. Each species has a specific position or functional role within the community, called niche. According to the Gausse’s principle, no two species can live in the same niche. In this case, two herbivorous species are living in the same niche and feeding on phytoplanktons. It may be because of the availability of sufficient phytoplanktons and or less number of individuals of the fish species. Of the two species might have occurred and though neither of the species have been eliminated, niche overlapping may effect the growth and development of individuals of the species.

8. While living in and on the host species, the animal parasite has evolved certain adaptations. Describe these adaptations with examples.
Answer. In accordance with their life styles, parasites evolved special adaptations such as the loss of unnecessary sense organs, presence of adhesive organs or suckers to cling on to the host, loss of digestive system and high reproductive capacity. The life cycles of parasites are often complex, involving one or two intermediate hosts or vectors to facilitate parasitisation of its primary host.

9. Do you agree that regional and local variations exist within each.biome? Substantiate your answer with suitable example.
Answer. Yes, regional and local variations exist within each biome. Regional and local variations within each biome lead to the formation of a wide variety of habitats. On planet Earth, life exists not just in a few favourable habitats but even in extreme and harsh habitats-^scorching Rajasthan desert, perpetually rain-soaked Meghalaya forests, deep ocean trenches, torrential streams, permafrost polar regions, high mountain tops, boiling thermal springs, and stinking compost pits, to name a few. Even our intestine is a unique habitat for hundreds of species of microbes..

10. Which element is responsible for causing soil salinity? At what concentration does the soil become saline?
Answer. Soil salinity is the salt content in the soil. Salts are a natural component in soils and water. The ions responsible for salination are: Na⁺, K⁺, Ca²⁺, Mg²⁺ and Cl^–.

11. Does light factor affect the distribution of organisms? Write a brief note giving suitable examples of either plants or animals.
Answer. Since plants produce food through photosynthesis, a process which is only possible when sunlight is available as a source of energy, we can quickly understand the importance of light for living organisms, particularly autotrophs. Many species of small plants (herbs and shrubs) growing in forests are adapted to photosynthesise optimally under very low light conditions because they are constantly overshadowed by tall, canopied trees. Many plants are also dependent on sunlight to meet their photoperiodic requirement for flowering. For many animals too, light is important in that they use the diurnal and seasonal variations in light intensity and duration (photoperiod) as cues for timing their foraging, reproductive and migratory activities.

12. Give one example for each of the following:
(i) Eurythermal plant species ………………
(ii) A hot water spring organism ………………
(iii) An organism seen in deep ocean trenches ………………
(iv) An organism seen in compost pit ………………
(v) A parasitic angiosperm ………………
(vi) A stenothermal plant species ………………
(vii) Soil organism ………………
(viii) A benthic animal ………………
(ix) Antifreeze compound seen in antarcticfish ………………
(x) An organism which can conform ………………
Answer. (i) Eurythermal plant species—Red algae
(ii) A hot water spring organism—Thermus aquaticus
(iii) An organism seen in deep ocean trenches—Sea cucumbers
(iv) An organism seen in compost pit—Earthworm
(v) A parasitic angiosperm—Cuscuta reflexa
(vi) A stenothermal plant species—Conifers
(vii) Soil organism—Earthworm
(viii) A benthic animal—Crabs, Sponges
(ix) Antifreeze compound seen in Antarctic fish—Antifreeze glycoproteins orAFGPs
(x) An organism which can conform—Frog

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NCERT Exemplar Class 12 Biology Chapter 10 Microbes in Human Welfare

Multiple Choice Questions
Single Correct Answer Type

1. The vitamin whose content increases following the conversion of milk into curd by lactic acid bacteria is
(a) Vitamin C (b) Vitamin D
(c) Vitamin B₁₂ (d) Vitamin E
Answer. (c) The vitamin B₁₂ content increases following the conversion of milk into curd by lactic acid bacteria (LAB).

2. Wastewater treatment generates a large quantity of sludge, which can be treated by
(a) Anaerobic digesters (b) Floe
(c) Chemicals (d) Oxidation pond
Answer. (a) Wastewater treatment generates a large quantity of sludge, which can be treated by anaerobic sludge digesters.

3. Methanogenic bacteria are not found in
(a) Rumen of cattle (b) Gobar gas plant
(c) Bottom of water-logged paddy fields (d) Activated sludge
Answer. (d) Methanogenic bacteria are found in rumen of cattle, gobar gas plant and bottom of,water-logged paddy fields.

4. Match the following list of bacteria and their commercially important products.

Choose the correct match:
(a) i—B, ii—C, iii—D, iv—A (b) i—B, ii—D, iii—C, iv—A
(c) i—D, ii—C, iii—B, iv—A (d) i—D, ii—A, iii—C, iv—B
Answer. (c)

5. Match the following list of bio active substances and their roles:

Choose the correct match:
(a) i—B, ii—C, iii—A, iv—D (b) i—D, ii—B, iii—A, iv—C
(c) i—D, ii—A, iii—B, iv—C (d) i—C, ii—D, iii—B, iv—A
Answer. (d)

6. The primary treatment of waste water involves the removal of
(a) Dissolved impurities (b) Stable particles
(c) Toxic substances (d) Harmful bacteria
Answer. (b) 10 treatment basically involves physical removal of particles from sewage through: (i) Filtration and (ii) Sedimentation
These are removed in stages:
(i) Initially floating debris is removed by sequential filtration.
(ii) Then the grit (soil and pebbles) are removed by sedimentation

7. BOD of waste water is estimated by measuring the amount of
(a) Total organic matter (b) Biodegradable organic matter
(c) Oxygen evolution (d) Oxygen consumption
Answer. (d) BOD of waste water is estimated by measuring the amount of oxygen consumption.

8. Which one of the following alcoholic drinks is produced without distillation?
(a) Wine (b) Whisky
(c) Rum (d) Brandy
Answer. (a) Wine and beer are produced, withont distillation. Whisky, brandy and rum are produced by distillation.

9. The technology of biogas production from cow dung was developed in India largely due to the efforts of
(a) Gas Authority of India
(b) Oil and Natural Gas Commission
(c) Indian Agricultural Research Institute and Khadi and Village Industries Commission
(d) Indian Oil Corporation
Answer. (c) The technology of biogas production from cow dung was developed in India largely due to the efforts of Indian Agricultural Research Institute and Khadi and Village Industries Commission.

10. The free-living fungus Trichoderma can be used for
(a) Killing insects
(b) Biological control_of plant diseases
(c) Controlling butterfly caterpillars
(d) Producing antibiotics
Answer. (b) The free-living fungus Trichoderma can be used for biological control of plant diseases.

11. What would happen if oxygen availability to activated sludge floes is reduced?
(a) It will slow down the rate of degradation of organic matter.
(b) The center of floes will become anoxic, which would cause death of bacteria and eventually breakage of floes.
(c) Floes would increase in size as anaerobic bacteria would grow around floes.
(d) Protozoa would grow in large numbers.
Answer. (b) If oxygen availability to activated sludge floes is reduced the center of floes will become anoxic, which would cause death of bacteria and eventually breakage of floes.

12. Mycorrhiza does not help the host plant in
(a) Enhancing its phosphorus uptake capacity
(b) Increasing its tolerance to drought
(c) Enhancing its resistance to root pathogens
(d) Increasing its resistance to insects
Answer. (d) Mycorrhiza help the host plant in enhancing its phosphorus uptake capacity, increasing its tolerance to drought and enhancing its resistance to root pathogens.

13. Which one of the following is not a nitrogen-fixing organism?
(a) Anabaena (b) Nostoc
(c) Azdtobacter (d) Pseudomonas
Answer. (d) Anabaena, Nostoc and Azotobacter are the cyanobacteria. All are nitrogen-fixing organism.

14. Big holes in Swiss cheese are made by a
(a) machine
(b) bacterium that produces methane gas
(c) bacterium producing a large amount of carbon dioxide
(d) fungus that releases a lot of gases during its metabolic activities.
Answer. (c) Large holes in Swiss cheese are due to production of large amount of C02
by a bacterium named Proponibacterium sharmanii.

15. The residue left after methane production from cattle dung is
(a) Burnt (b) Buried in landfills
(c) Used as manure (d) Used in civil construction
Answer. (c)

• Thus gobar (excreta/dung) of cattle is rich in these bacteria. Dung can be used for generation of biogas, commonly called gobar gas.
•  The residue left after methane production from cattle dung is used as manure.

16. Methanogens do not produce
(a) Oxygen (b) Methane
(c) Hydrogen sulfide (d) Carbon dioxide
Answer. (a) Methanogens are obligate anaerobes, which produce methane, hydrogen sulfide and carbon dioxide but do not produce oxygen.

17. Activated sludge should have the ability to settle quickly so that it can
(a) Be rapidly pumped back from sedimentation tank to aeration tank
(b) Absorb pathogenic bacteria present in waste water while sinking to the bottom of the settling tank
(c) Be discarded and anaerobically digested
(d) Absorb colloidal organic matter
Answer. (a) Activated sludge should have the ability to settle quickly so that it can be rapidly pumped back from sedimentation tank to aeration tank.

18. Match the items in Column ‘A’ and Column ‘B’ and choose the correct answer.

The correct answer is
(a) i—B, ii—D, iii—C, iv—A (b) i—C, ii—D, iii—B, iv—A
(c) i—D, ii—A, iii—B, iv—C (d) i—C, ii—B, iii—A, iv—D
Answer. (b)

Very Short Answer Type Questions
1.Why does ‘Swiss cheese’ have big holes?
Answer. The large holes in ‘Swiss cheese’ are due to the production of a large amount of C02 by a bacterium named Propionibacterium sharmanii.

2.What are fermentors?
Answer. Even in industry, microbes are used to synthesise a number of products valuable to human beings. Beverages and antibiotics are some of the examples. Production on an industrial scale, requires growing microbes in very large vessels called fermentors.

3.Name a microbe used for statin production. How do statins lower blood cholesterol level?
Answer. Monascus purpureus statins lower blood cholesterol level by competitively inhibiting the enzyme responsible for the synthesis of cholesterol.

4. Why do we prefer to call secondary waste water treatment as biological treatment? .
Answer. The secondary treatment is also called biological treatment because in secondary treatment living organisms like bacteria and fungi are used.

5. What for Nucleopolyhydro viruses are being used now-a-days?
Answer. Necleopolyhydroviruses are used for the biological control of insect pesto.

6. How has the discovery of antibiotics helped mankind in the field of medicine?
Answer. If antibiotics were not discovered bacterial and fungal diseases would not have been controllable.

7. Why is distillation required for producing certain alcoholic drinks?
Answer. Distillation increases the alcohol content in alcoholic drinks.

8. Write the most important characteristic that Aspergillus niger, Clostridium butylicum and Lactobacillus share.
Answer. These all are acid producers. Examples of acid producers are Aspergillus niger (a fungus) of citric acid, Clostridium butylicum (a bacterium) of butyric acid and Lactobacillus (a bacterium) of lactic acid.

9. What would happen if our intestine harbours microbial flora exactly similar to that found in the rumen of cattle?
Answer. If our intestine harbours microbial flora exactly similar to that found in the rumen of cattle then we would be able to digest the cellulose present in our food.

10. Give any two microbes that are useful in biotechnology.
Answer. E.coli and Saccharomyces cerevisae

11. What is the source organism for EcoRI, restriction endonuclease?
Answer. Escherichia coli RY 13.

12. Name any genetically modified crop.
Answer. Bt cotton.

13. Why are blue green algae not popular as biofertilisers?
Answer. Blue green algae are not popular as biofertilisers because they causes algal bloom in polluted water bodies.

14. Which species of Penicillium produces Roquefort cheese?
Answer. Roquefort cheese produced by Penicillium roqueforti.

15. Name the states involved in Ganga action plan.
Answer. Uttarakhand, Uttar Pradesh, Bihar, West Bengal and Jharkhand.

16. Name any two industrially important enzymes.
Answer. Lipase, Amylase.

17. Name an immune immunosuppressive agent.
Answer. Cyclosporin A

18. Give an example of a rod shaped virus.
Answer. Tobacco mosaic virus (TMV).

19. What is the group of bacteria found in both the rumen of cattle and sludge of sewage treatment?
Answer. Methanogens

20. Name a microbe used for the production of Swiss cheese.
Answer. Propionibacterium shaynanii.

Short Answer Type Questions
1. Why are floes important in biological treatment of waste water?
Answer. Secondary treatment or Biological treatment: The primary effluent is passed into large aeration tanks where it is constantly agitated mechanically and air is pumped into it. This allows vigorous growth of useful aerobic microbes into floes (masses of bacteria associated with fungal filaments to form mesh like structures). While growing, these microbes consume the major part of the organic matter in the effluent. This significantly reduces the BOD (biochemical oxygen demand) of the effluent.

2. How has the bacterium Bacillus thuringiensis helped us in controlling caterpillars of insect pests?
Answer. Bacillus thuringiensis products are endotoxin which when ingested and released in the gut of the larvae of insect pest disrupts the insect gut lining thereby killing them.

3. How do mycorrhizal fungi help the plants harbouring them?
Answer. The mycorrhizal fungi absorb phosphorus from the soil and transfer them to the host cells. They also’impart resistance to host plants against root pathogens. They also help plant tolerate salinity and draught.

4. Why are cyanobacteria considered useful in paddy fields?
Answer. Cyanobacteria are autotrophic microbes widely distributed in aquatic and terrestrial environments many of which can fix atmospheric nitrogen, e.g. Anabaena, Nostoc, Oscillatoria, etc. In paddy fields, cyanobacteria serve as an important biofertiliser. Blue green algae also add organic matter to the soil and increase its fertility.

5. How was penicillin discovered?
Answer. Penicillin was an accidental discovery. Sir Alexander Fleming observed that in unwashed culture plates of Staphylococcus, a mould Penicillium was growing. This mould inhibited the-growth of Staphylococcus. Later the antibiotic Penicillin was isolated from this fungus.

6. Name the scientists who were credited for showing the role of Penicillin as an antibiotic.
Answer. Its full potential as an effective antibiotic was established much later by Ernest Chain and Howard Florey. This antibiotic was extensively used to treat American soldiers wounded in World War II. Fleming, Chain and Florey were awarded the Nobel Prize in 1945, for this discovery.

7. How do bioactive molecules of fungal origin help in restoring good health of humans?
Answer. A bioactive molecule, cyclosporin A, that is used as an immunosuppressive agent in organ-transplant patients, is produced by the fungus Trichoderma polysporum. Statins produced by the yeast Monascus purpureus have been commercialised as blood-cholesterol lowering agents. It acts by competitively inhibiting the enzyme responsible for synthesis of cholesterol.

8. What roles do enzymes play in detergents that we use for washing clothes? Are these enzymes produced from some unique microorganisms?
Answer. Microbes are also used for production of enzymes. Lipases are used in detergent formulations and are helpful in removing oily stains from the laundry. Lipases are produced by Candida lipolytica (fungus).

9. What is the chemical nature of biogas? Name an organism which is involved in biogas production.
Answer. The chemical nature of Biogas is methane, CO₂ and H₂. Methanobacterium, a type of methanogen is employed for biogas productioh.

10. How do microbes reduce the environmental degradation caused by chemicals?
Answer. Chakravarthy Bug is a super bug of Pseudomonas with multiple plasmid.
They are helpful in removing oil spills.

11. What is a broad spectrum antibiotic? Name one such antibiotic.
Answer. A broad spectrum antibiotic is one which can inhibit the growth of both G +ve and G -ve bacteria.

12. What are viruses parasitising bacteria called? Draw a well labelled diagram of the same.
Answer. Viruses parasitising bacteria are called bacteriophages.

13. Which bacterium has been used as a clot buster? What is its mode of action?
Answer. Streptokinase produced by the bacterium Streptococcus and modified by
genetic engineering is used as a ‘clot buster’ for removing clots from the blood vessels of patients who have undergone myocardial infarction leading to heart attack.

14. What are biofertilisers? Give two examples.
Answer. Biofertilisers are organisms that enrich the nutrient quality of the soil. The main sources of biofertilisers are bacteria, fungi and cyanobacteria.

Long Answer Questions
1. Why is aerobic degradation more important than anaerobic degradation for the treatment of large volumes of waste waters rich in organic matter? Discuss.
Answer. Secondary treatment or Biological treatment: The primary effluent is passed into large aeration tanks where it is constantly agitated mechanically and air is pumped into it. This allows vigorous growth of useful aerobic microbes into floes (masses of bacteria associated with fungal filaments to form mesh like structures). While growing, these microbes consume the major part of the organic matter in the effluent. This significantly reduces the BOD (biochemical oxygen demand) of the effluent. BOD refers to the amount of the oxygen that would be consumed if all the organic matter in one litre of water were oxidised by bacteria. The sewage water is treated till the BOD is reduced. The BOD test measures the rate of uptake of oxygen by micro¬organisms in a sample of water and thus, indirectly, BOD is a measure of the organic matter present in the water. The greater the BOD of waste water, more is its polluting potential.
Once the BOD of sewage or waste water is reduced significantly, the effluent is then passed into a settling tank where the bacterial ‘floes’ are allowed to sediment. This sediment is called activated sludge. A small part of the activated sludge is pumped back into the aeration tank to serve as the inoculum. The remaining major part of the sludge is pumped into large tanks called anaerobic sludge digesters. Here, other kinds of bacteria, which grow anaerobically, digest the bacteria and the fungi in the sludge. During this digestion, bacteria produce a mixture of gases such as methane, hydrogen sulphide and carbon dioxide. These gases form biogas and can be used as source of energy as it is inflammable.

2. (a) Discuss about the major programs that the Ministry of Environment and Forests, Government of India, has initiated for saving major Indian rivers from pollution.
(b) Ganga has recently been declared the national river. Discuss the implication with respect to pollution of this river.
Answer. (a) The untreated sewage is often discharged directly into rivers leading to their pollution and increase in water-borne diseases. The Ministry of Environment and Forests has initiated Ganga Action Plan and Yamuna Action Plan to save these major rivers of our country from pollution. Under these plans, it is proposed to build a large number of sewage treatment plants so that only treated sewage may be discharged in the rivers.
(b) The Ganga is the largest river in India with an extraordinary religious ‘ importance for Hindus. Situated along its banks are some of the world’s oldest inhabited cities like Varanasi and Patna. It provides water to about 40% of India’s population across 11 states, serving an estimated population of 500 million people or more, which is larger than any other river in the world.
A number of initiatives have been undertaken to clean the river but failed to deliver desired results. After getting elected, India’s Prime minister Narendra Modi affirmed to work for cleaning the river and controlling pollution. Subsequently, Namami Ganga project was announced by the Government in July 2014 budget. An estimated Rs 2,958 crores have been spent till July 2016 in various efforts to clean up the river.

3. Draw a diagrammatic sketch of biogas plant and label its various components given below: Gas Holder, Sludge Chamber, Digester, Dung+water chamber
Answer.

4. Describe the main ideas behind the biological control of pests and diseases.
Answer. Biological control means life against life. It is a natural and ecofriendly
concept. It employs the natural organisms to control the population of pathogens and pests in an ecosystem. Classical examples are Trichoderma which is antagonist against many soil borne plant pathogens. Similarly, Penicillium inhibits the growth of Staphylococcus and therefore has been successfully used in the production of Penicillin antibiotic to control many human bacterial pathogens.

5. (a) What would happen if a large volume of untreated sewage is discharged into a river?
(b) In what way anaerobic sludge digestion is important in sewage treatments?
Answer. (a) Due to increasing urbanisation, sewage is being produced in much larger quantities than ever before. However the number of sewage treatment plants has not increased enough to treat such large quantities. So the untreated sewage is often discharged directly into rivers leading to their pollution and increase in water-borne diseases.
(b) Once the BOD of sewage or waste water is reduced significantly, the effluent is then passed into a settling tank where the bacterial ‘floes’ are allowed to sediment. This sediment is called activated sludge. A small part of the activated sludge is pumped back into the aeration tank to • serve as the inoculum. The remaining major part of the sludge is pumped
into large tanks called anaerobic sludge digesters. Here, other kinds of bacteria, which grow anaerobically, digest the bacteria and the fungi in the sludge. During this digestion, bacteria produce a mixture of gases such as methane, hydrogen sulphide and carbon dioxide. These gases form biogas and can be used as a source of energy as it is inflammable.

6. Which type of food would have lactic acid bacteria? Discuss their useful application.
Answer. Curd. Micro organisms such as lactic acid bacteria (LAB) grow in milk and convert it to curd. During growth, the LAB produce acids that coagulate and partially digest the milk proteins. A small amount of curd added to the fresh milk as inoculum or starter contain millions of LAB, which at suitable temperatures multiply, thus converting milk into curd, which also improves its nutritional quality by increasing vitamin B₁₂. In our stomach too, the LAB play very beneficial role in checking disease causing microbes.

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We hope the NCERT Exemplar Class 12 Biology Chapter 10 Microbes in Human Welfare help you. If you have any query regarding NCERT Exemplar Class 12 Biology Chapter 10 Microbes in Human Welfare, drop a comment below and we will get back to you at the earliest.

NCERT Exemplar Class 12 Biology Chapter 9 Strategies for Enhancement in Food Production are part of NCERT Exemplar Class 12 Biology. Here we have given NCERT Exemplar Class 12 Biology Chapter 9 Strategies for Enhancement in Food Production.

NCERT Exemplar Class 12 Biology Chapter 9 Strategies for Enhancement in Food Production

Multiple Choice Questions
Single Correct Answer Type

1. The chances of contacting bird flu from a properly cooked (above 100°C) chicken and egg are
(a) Very high (b) High
(c) Moderate (d) None
Answer. (d) Properly cooked (above 100°C) chicken and egg have no chances of contacting bird flu.

2. A group of animals which are related by descent and share many similarities are referred to as
(a) Breed (b) Race
(c) Variety (d) Species
Answer. (a) A group of animals which are related by descent and share many similarities are referred to as breed.

3. Inbreeding is carried out in animal husbandry because it
(a) Increases vigour (b) Improves the breed
(c) Increases heterozygosity (d) Increases homozygosity
Answer. (d) Inbreeding is carried out in animal husbandry because it increases homozygosity.

4. Sonalika and Kalyan Sona are varieties of
(a) Wheat (b) Rice
(c) Millet (d) Tobacco
Answer. (a) Sonalika and Kalyan Sona are varieties of wheat.

5. Which one of the following is not a fungal disease?
(a) Rust of wheat (b) SmutofBajra
(c) Black rot of crucifers (d) Red rot of sugarcane
Answer. (c) Black rot of crucifers is a bacterial disease.

6. In virus-infected plants the meristematic tissues in both apical and axillary buds are free of virus because
(a) The dividing cells are virus resistant
(b) Meristems have antiviral compounds
(c) The cell division of meristems are faster than the rate of viral multiplication
(d) Viruses cannot multiply within meristem cell(s).
Answer. (c) In virus-infected plants the meristematic tissues in both apical and axillary buds are free of virus because the cell division of meristems are faster than the rate of viral multiplication.

7. Several South Indian states raise 2-3 crops of rice annually. The agronomic feature that makes this possible is because of
(a) Shorter rice plant (b) Better irrigation facilities
(c) Early yielding rice variety (d) Disease resistant rice variety
Answer. (c) Several South Indian states raise 2-3 crops of rice annually. The agronomic feature that makes this possible is because of early yielding rice variety.

8. Which one of the following combination would a sugarcane farmer look for in the sugarcane crop?
(a) Thick stem, long intemodes, high sugar content and disease resistant
(b) Thick stem, high sugar content and profuse flowering
(c) Thick stem, short internodes, high sugar content, disease resistant
(d) Thick stem, low sugar content, disease resistant.
Answer. (a) Thick stem, long internodes, high sugar content and disease resistant, combination would a sugarcane farmer look for in the sugarcane crop.

9. Fungicides and antibiotics are chemicals that
(a) Enhance yield and disease resistance
(b) Kill pathogenic fungi and bacteria, respectively
(c) Kill all pathogenic microbes
(d) Kill pathogenic bacteria and fungi respectively.
Answer. (b) Fungicides and antibiotics are chemicals that kill pathogenic fungi and bacteria, respectively.

10. Use of certain chemicals and radiation to change the base sequences of genes of crop plants is termed
(a) Recombinant DNA technology (b) Transgenic mechanism (c) Mutation breeding (d) Gene therapy
Answer. (c) Use of certain chemicals and radiation to change the base sequences of genes of crop plants is termed as mutation breeding. Mutations is induced artificially through use of chemicals or radiations like gamma radiations. In mung bean, resistance to yellow mosaic virus and powdery mildew were induced by mutations.

11. The scientific process by which crop plants are enriched with certain desirable nutrients is called
(a) Crop protection (b) Breeding
(c) Bio-fortification (d) Bio-remediation
Answer. (c) Bio-fortification: It is the most practical means to improve public health. In bio-fortification breeding of crops with higher levels of vitamins and minerals or higher protein and healthier fats. In 2000, maize hybrids were developed that had twice the amount of amino acid lysine and tryptophan (MALT). Atlas 66 (Wheat variety), having high protein content has been used as a donor for improving cultivated wheat. Iron fortified rice variety contains over 5 times much Fe.

12. The term‘totipotency’refers to the capacity of a
(a) Cell to generate whole plant (b) Bud to generate whole plant
(c) Seed to germinate (d) Cell to enlarge in size
Answer. (a) The capacity of explant or any cell to generate whole plant is called cellular totipotency. Cellular totipotency is shown by all plant cells. Cellulartotipotency is as demonstrated by F.C. Steward.

13. Given below are a few statements regarding somatic hybridization. Choose the correct statements.
(i) Protoplasts of different cells of the same plant are fused.
(ii) Protoplasts from cells of different species can be fused.
(iii) Treatment of cells with cellulase and pectinase is mandatory.
(iv) The hybrid protoplast contains characters of only one parental protoplast,
(a) (i) and (iii) (b) (i) and (ii)
(c) (i) and (iv) (d) (ii) and (iii)
Answer. (d) Isolated protoplast (surrounded by plasma membranes) from two different varieties can be fused to get hybrid protoplasts which grow to form new plant. The enzyme required to obtain wall free or naked protoplasts are cellulase, hemiceilulase and pectinase, which dissolves cell wall. Somatic cell hybrid (protoplast hybrid) are produced with the help of polyethylene glycol (PEG) and sodium nitrate which promote fusion. In protoplast fusion, chemofusion and electrofusion are employed.

14. An explant is
(a) Dead plant
(b) Part of the plant
(c) Part of the plant used in tissue culture
(d) Part of the plant that expresses a specific gene.
Answer. (c) An explant is a part of the plant used in tissue culture.

15. The biggest constraint of plant breeding is
(a) Availability of desirable gene in the crop and its wild relatives
(b) Infrastructure
(c) Trained manpower
(d) Transfer of genes from unrelated sources
Answer. (a) The biggest constraint of plant breeding is availability of desirable gene in the crop and its wild relatives.

16. Lysine and tryptophan are
(a) Proteins (b) Non-essential amino acids
(c) Essential amino acids (d) Aromatic amino acids
Answer. (c) Lysine and tryptophan are essential amino acids.

17. Micro-propagation is
(a) Propagation of microbes in vitro
(b) Propagation of plants in vitro
(c) Propagation of cells in vitro
(d) Growing plants on smaller scale
Answer. (b) This method of producing thousands of plants through tissue culture is called micro-propagation. Banana, Apple and Tomato are produced on commercial scale using this method.

18. Protoplast is
(a) Another name for protoplasm
(b) An animal cell 
(c) A plant cell without a cell wall
(d) A plant cell
Answer. (c) Protoplast is a plant cell.without a cell wall.

19. To isolate protoplast, one needs
(a) Pectinase (b) Cellulase
(c) Both pectinase and cellulase (d) Chitinase
Answer. (c) The enzyme required to obtain wall free or naked protoplasts are cellulase, hemiceliulase and pectinase, which dissolves cell wall.

20. Which one of the following is a marine fish?
(a) Rohu (b) Hilsa
(c) Catla (d) Common Carp
Answer. (b) Freshwater edible fished: Rohu, Catla and Common carp. Marine edible fishes: Sardines, Hilsa, Mackerel and Pomfrets.

21. Which one of the following products of apiculture is used in cosmetics and polishes?
(a) Honey (b) Oil
(c) Wax (d) Royal jelly
Answer. (c) Wax is a product of apiculture used in cosmetics and polishes.

22. More than 70 per cent of livestock population is in
(a) Denmark . (b) India
(c) China (d) India and China
Answer. (d) More than 70% of the world livestock population is in India and China, but contribution to the world farm produce is only 25% (means productivity per unit is very low).

23. The agriculture sector of India employs about
(a) 50 per cent of the population (b) 70 per cent of the population
(c) 30 per cent of the population (d) 60 per cent of the population
Answer. (d) The agriculture sector of India employs about 60 per cent of the population.

24. 33 percent of India’s (Gross Domestic Product) comes from
(a) Industry (b) Agriculture
(c) Export (d) Small-scale cottage industries.
Answer. (b) 33 percent of India’s (Gross Domestic Product) corner from agriculture.

25. A collection of all the alleles of all the genes of a crop plant is called
(a) Germplasm collection (b) Protoplasm collection
(c) Herbarium (d) Somaclonal collection
Answer. (a) A collection of all the alleles of all the genes of a crop plant is called germplasm collection.

Very Short Answer Type Questions 
1. Millions of chicken were killed in West Bengal, Assam, Orissa and Maharashtra recently, What was the reason?
Answer. Millions of chicken were killed (culled) in West Bengal, Orissa and Maharashtra because they were found to be infected with H5N1 virus, the causal organism of Bird Flu.

2. Can gamma rays used for crop improvement programmes prove to be harmful for health? Discuss.
Answer. Gamma rays used for crop improvement programmes cannot be harmful for health if they are not exposed directly to the human beings. It only induces mutation in the crop varieties.

3. In animal husbandry, if two closely related animals are mated for a few generations, it results in loss of fertility and vigour. Why is this so?
Answer. The phenomenon being referred to is called ‘Inbreeding Depression’ and results in loss of fertility and vigour. This happens because the recessive alleles tend to get together and express harmful effects in the progeny.

4. In the area of plant breeding, it is important not only to preserve the seeds of the variety being cultivated, but also to preserve all its wild relatives. Explain with a suitable example.
Answer. In the area of plant breeding, it is important not only to preserve the seeds of the variety being cultivated, but also to preserve all its wild relatives because several wild relatives of different cultivated species of plants seem to have certain resistant characters but their yields are very low. Hence, there is a need to introduce the resistant genes into the high-yielding cultivated varieties.

5. Name a man-made cereal. Trace how it was developed and where it is used?
Answer. Triticale. It was developed by crossing Triticum aestivum (wheat) and Secale cerale (rye).

6. Fill in the blanks:

Answer. I. Cellulase; II. Somatic hybridization; III. Pomato; IV. Somatic hybrid

7. A few statements are given below followed by a set of terms in a box. Pick the correct term and write it against the appropriate statement.
a. Mating of closely related individuals within the same breed
b. Mating of animals of same breed but having no common ancestors on either side for 4-6 generations
c. Mating of animals of two different species
d. Breeding of animals belonging to different breeds
(i) Cross breeding, (ii) Inter-specific hybridization,
(iii) Out breeding, (iv) Out crossing, (v) Inbreeding
Answer. a. Mating of closely related individuals within the same breed—Inbreeding
b. Mating of animals of same breed but having no common ancestors on either side for 4-6 generations—Out crossing
c. Mating of animals of two different species—Inter-specific hybridization
d. Breeding of animals belonging to different breeds—Cross breeding

8. What is meant by ‘hidden hunger’?
Answer. Consumption of food deficient in nutrients particularly, micronutrients, proteins and vitamins is called hidden hunger.

9. Why are plants obtained by protoplast culture called somatic hybrids?
Answer. Plants obtained by protoplast culture are called somatic hybrids because these are obtained by fusion of somatic cells of two different plants.

10. What is protoplast fusion?
Answer. The ability of protoplasts obtained from two different cells to fuse and form a hybrid protoplast is called protoplast fusion.

11. Why is it easier to culture meristems Compared to permanent tissues?
Answer. Meristems have the capacity of division while permanent tissue have lost the capacity of division.

12. Why are proteins synthesised from SpiruJina called single cell proteins?
Answer. Proteins synthesised from Spirulina are called single cell proteins (SCP) because it is a single celled organism that produce large quantities of food rich in protein, minerals, fats, carbohydrate and vitamins.

13. A person who is allergic to pulses was advised to take a capsule of Spirulina daily. Give the reasons for the advise.
Answer. Humans derive protein from pulses. If a person is allergic to pulses was advised to take a capsule of Spirulina daily because Spirulina is rich in protein.

14. What is aquaculture? Give example of an animal that can be multiplied by aquaculture.
Answer. The rearing of aquatic animals or the cultivation of aquatic plants for food is called aquaculture. Fishes, shell-fish and crustaceans (prawns, crabs, etc.) are the animals that can be multiplied by aquaculture.

15. What are the duties of a veterinary doctor in management of a poultry farm?
Answer. Duties of a veterinary doctor:
1. Veterinary doctor treat disease or injury in animals, which includes diagnosis and treatment.
2. Veterinary doctor is concerned with prophylactic treatment, in order to prevent problems occurring in the future.
3. Veterinary doctor uses vaccination against common animal diseases, such as rabies.
4. Veterinary doctor has important roles in public health and the prevention of zoonoses.

16. Would it be wrong to call plants obtained through micropropagation as ‘clones’? Comment.
Answer. No, it is not wrong because each of the plant will be genetically identical to the original plant from which they were grown, i.e., they are clones/somaclones.

17. How is a somatic hybrid different from a hybrid?
Answer. Isolated’protoplasts from two different varieties of plants can be fused to get hybrid protoplasts, which can be further grown to form a new hybrid plant that is called somatic hybrid. –

18. What is emasculation? Why and when is it done?
Answer. Removal of anther from a bisexual flower is called emasculation. It is used to avoid self-pollination and is used in artificial hybridisation programme. It is done before the dehiscence of anther.

19. Discuss the two main limitations of plant hybridization programme.
Answer. (i) Plant hybridization programme is often constrained by the availability of limited number of disease resistance genes that are present in various crop varieties or wild relatives.
(ii) Several wild relatives of different cultivated species of plants have been shown to have certain resistant character but have very low yield.

20. Interspecific crosses are rare in nature and intergeneric crosses almost unknown. Why?
Answer. The crosses between two different species are called interspecific crosses. As two species are reproductively isolated, the interspecific hybrid is sterile (like mule). Intergenic hybrids are almost non-viable hence intergenic hybrids are almost unknown.

21. Differentiate between pisciculture and aquaculture.
Answer. Pisciculture or fishery is an industry devoted to the catching, processing or selling of fish, shellfish or other aquatic animals.
The rearing of aquatic animals or the cultivation of aquatic plants for food is called aquaculture. .

22. Give two important contributions of Dr. M. S. Swaminathan.
Answer. (i) M.S. Swaminathan developed short-duration high-yielding varieties of rice including scented Basmati.
(ii) He is also known for the development of the concept of crop cafeteria, crop scheduling and genetically improving the yield and quality.

23. The term ‘desirable trait’ can mean different things for different plants.. Justify the statement with suitable examples.
Answer. In millets, resistance to water stress is desirable trait while in mung bean, resistance to yellow mosaic*virus and powdery mildew are desirable traits.

Short Answer Type Questions
1. You are planning to set up a Dairy Farm. Describe the various aspects you would consider before you start the venture.
Answer. Dairying is the management of animals for milk and its products for human consumption.
1. In dairy farm management, we deal with the processes and systems that increase yield and improve quality of milk. Milk yield is primarily dependent on the quality of breeds in the farm.
2. Selection of good breeds having high yielding potential (under the climatic conditions of the area), combined with resistance to diseases is very important.
3. For the yield potential to be realised the cattle have to be well looked after they have to be housed well, should have adequate water and be maintained disease free.
4. The feeding of cattle should be carried out in a scientific manner – with special emphasis on the quality and quantity of fodder.
5. Besides, stringent cleanliness and hygiene (both of the cattle and the handlers) are of paramount importance while milking, storage and transport of the milk and its products.

2. It is said, that diseases are spreading faster due to globalisation and increased movement of people. Justify the statement taking the example of H5N1 virus.
Answer. Diseases are spreading faster due to globalisation and increased movement of people because it is responsible for rapid spreading of infectious diseases.

3. Explain the concept of the Blue Revolution.
Answer. Rapid increase in the fishery industry in recent years is called blue revolution. For example, through aquaculture and pisciculture we have been able to increase the production of aquatic plants and animals, both fresh-water and marine. This has led to the development and flourishing of the fishery industry, and it has brought a lot of income to the farmers in particular and the country in general. We now talk about the ‘Blue Revolution’ which is being implemented along the same lines as ‘Green Revolution’.

4. A farmer was facing the problem of low yield from his farm. He was advised to keep a beehive in the vicinity. Why? How would the beehive help in enhancing yield? .
Answer. Bees are the pollinators of many of our crop species such as sunflower, Brassica, apple and pear. Keeping beehives in crop fields during flowering period increases pollination efficiency and improves the yield beneficial both from the point of view of crop yield and honey yield.

5. Life style diseases are increasing alarmingly in India. We are also dealing with large scale malnutrition in the population. Is there any method by which we can address both of these problems together?
Answer. Lifestyle disorders can be prevented by improving the lifestyle of a person. Taking too much of a stress can lead to heart stroke and paralysis which can be avoided by living in a healthy environment.
Malnutrition is very common in poor people who do not have access to nutritious food and India has a large scale population who are malnutritious. Proper distribution of food and less wasting can help to address both of these problems together.

6. How can we improve the success rate of fertilisation during artificial insemination in animal husbandry programmes?
Answer. The technology is called MOET or Multiple Ovulation Embryo Transfer. During the procedure, a cow is given hormonal treatment so that more than one ovule (6-8 eggs) is produced per cycle. After mating or artificial insemination the embryos at 8-32 celled state are transferred to different surrogate mother cows. The method has been successfully used for cattle, sheep, buffalo etc.

7. What is meant by germplasm collection? What are its benefits?
Answer. The collection of diverse alleles of all the genes of a crop plant is called germplasm collection. It is of great benefits in plant breeding programmes it offers to the breeders, the entire of genes and alleles and the characteristics which they express. The breeder selects the most favourable characters of a particular gene and manipulates its transfer to a desirable parent.

8. Name the improved characteristics of wheat that helped India to achieve green revolution.
Answer. i. Semi-dwarf nature ii. Quick yielding feature iii. High yielding feature iv. Disease resistant feature

9. Suggest some of the features of plants that will prevent insect and pest infestation.
Answer. i. Increasing hair growth on aerial parts of plants.
ii. Rendering the flowers nectarless.
iii. Enabling plants to secrete insect killing chemicals (toxins).

10. It is easier to culture plant cells in vitro as compared to animal cells. Why?
Answer. Plant have meristematic cells that have the capacity of division, so can grow easily in in vitro culture. Animals have mainly differentiated cells that have lost the capacity of division.

11. The culture medium (nutrient medium) can be referred to as a ‘highly enriched laboratory soil’. Justify the statement.
Answer. The culture medium (nutrient medium) can be referred to as a ‘highly enriched laboratory soil’ because in culture medium we must provide a carhon source such as sucrose and also inorganic salts, vitamins, amino acids and growth regulators like auxins, cytpkinins etc. .

12. Is there any relationship between dedifferentiation and the higher degree of success achieved in plant tissue culture experiments?
Answer. Yes, the cells that has lost the capability of division can regain the capacity of division through dedifferentiation. So, in plant tissue culture experiments more success is achieved.

13. “Give me a living cell of any plant and I will give you a thousand plants of the same type”. Is this only a slogan or is it scientifically possible? Write your comments and justify them. 
Answer. It is scientifically possible. By application of tissue culture it is possible to achieve propagation of a large number of plants in very short durations. This method of producing thousands of plants through tissue culture is called micro propagation. Each of these plants will be genetically identical to the original plant from which they were grown, i.e., they are somaclones.

14. What is the difference between n breed and a species? Give an example for each category.
Answer. A group of animals related by descent and similar in most characters like general appearance, features, size, configuration, etc., are said to belong to a breed. Hisardale is a new breed of sheep.
A group of individual that is reproductively isolated from other such group is called species. For examples, Panthera leo (lion) and Mangifera indica are different species.

15. Plants raised through tissue cultures are clones of the ‘parent’ plant. Discuss the utility of these plants.
Answer. Plant raised through tissue cultures are clones of the parent plant that means they are genetically identical to the original plant. They are utilised for maintaining a desirable trait of parent.

16. Discuss the importance of testing of new plant varieties in a geographically vast country like India.
Answer. The newly selected lines are evaluated for their yield and other agronomic traits of quality, disease resistance, etc. This evaluation is done by growing these in the research fields and recording their performance under ideal fertilizer application, irrigation, and other crop management practices. The evaluation in research fields is followed by testing the materials.in fanners’ fields, for at least three growing seasons at several locations in the country, representing all the agroclimatic zones where the crop is usually grown. The material is evaluated in comparison to the best available local crop cultivar-a check or reference cultivar.

17. Define the term ‘stress’ for plants. Discuss briefly the two types of stress encountered by plants.
Answer. Any unfavourable condition for the plant growth and development is called stress. For example, drought, salinity, cold, pest and diseases are different type of stresses.

18. Discuss natural selection and artificial selection. What are the implications of the latter on the process of evolution?
Answer. Artificial selection is the intentional breeding of plants or animals. Selective breeding is a technique used when breeding domesticated animals, such as dogs, pigeons or cattle.
Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in heritable traits of a population over time.

19. Discuss briefly how pure lines are created in animal husbandry.
Answer. Inbreeding is necessary if we want to evolve a pure line in any animal. Inbreeding refers to the mating of more closely related individuals within the same breed for 4-6 generations.

20. What are the physical barriers of a cell in-the protoplast fusion experiment? How are the barriers overcome?
Answer. Cell wall is the most important physical barrier in such experiments. This can be overcomed by treatment with enzymes like cellulase and pectinase which have the ability to digest the cell wall and liberate the naked protoplast surrounded only by the dell membrane.

21. Give few examples of biofortified crops. What benefits do they offer to the society?
Answer. Maize, wheat, rice, bathua, spinach, pulses have biofortified varieties. Maize hybrids have twice the amount of amino acids, fortified wheat variety has high protein content, and fortified rice has high quantity of iron. Consumption of such biofortified foods will enrich the nutritive value of our common foods and will vastly improve public health. Instead of consuming different food items for obtaining different nutrients, if 2 or 3 nutrients can be incorporated into a single crop it offers enormous benefits to human beings and may even help overcome several nutrient deficiency disorders latent in our country.

Long Answer Type Questions
1. You are a Botanist working in the area of plant breeding. Describe the various steps that you will undertake to release a new variety.
Answer. The main steps in breeding a new genetic variety of a crop are:
(i) Collection of variability: Genetic variability is the root of any breeding programme. In many crops pre-existing genetic variability is available from wild relatives of the crop. Collection and preservation of all the different wild varieties, species and relatives of the cultivated species (followed by their evaluation for their characteristics) is a pre-requisite for effective exploitation of natural genes available in the populations. The entire collection (of plants/seeds) having all the diverse alleles for all genes in a given crop is called germplasm collection.
(ii) Evaluation and selection of parents: The germplasm is evaluated so as to identify plants with desirable combination of characters. The selected plants are multiplied and used in the process of hybridisation. Pure lines are created wherever desirable and possible. ‘
(iii) Cross hybridisation among the selected parents: The desired characters have very often to be combined from two different plants (parents), for example high protein quality of one parent may need to be combined with disease resistance from another parent. This is possible by cross hybridising the two parents to produce hybrids that genetically combine the desired characters in one plant. This is a very time-consuming and tedious process since the pollen grains from the desirable plant chosen as male parent have to be collected and placed on the stigma of the flowers selected as female parent (In chapter 2 details on how to make crosses have been described). Also, it is not necessary that the hybrids do combine the desirable characters; usually only one in few hundred to a thousand crosses shows the desirable combination.
(iv) Selection and testing of superior, recombinants: This step consists of selecting, among the progeny of the hybrids, those plants that have the desired character combination. The selection process is crucial to the success of the breeding objective and requires careful scientific evaluation of the progeny. This step yields plants that are superior to both of the parents (very often more than one superior progeny plant may become available). These are self-pollinated for several generations till they reach a state of uniformity (homozygosity), so that the characters will not segregate in the progeny.
(v) Testing, release and commercialisation of new cultivars: The newly selected lines are evaluated for their yield and other agronomic traits of quality, disease resistance, etc. This evaluation is done by growing these in the research fields and recording their performance under ideal fertilizer application, irrigation, and other crop management practices. The evaluation in research fields is followed by testing the materials in farmers’ fields:, for at least three growing seasons at several locations in the country, representing all the agro climatic zones where the crop is usually grown. The material is evaluated in comparison to the best available local crop cultivar a check or reference cultivar.

2. (a) The shift from grain to meat diets creates more demands for cereals. Why? (b) A250 kg cow produces 200 g of protein per day but 250 g of Methylophillus methylotrophus can produce 25 tonnes of protein. Name this emerging area of research. Explain its benefits.
Answer. (a) It takes 3-10 kg of grain to produce 1 kg of meat using animal farming. That is why cereals demand increases.
(b) Production of single cell proteins (SCP) by microbes. Microbes are being grown on an Industrial scale. Spirulina can be easily grown on starch, molasses etc., and can make food which is rich in proteins, minerals, fats, carbohydrates and vitamins. This could be a good alternative for dealing with the problem of malnutrition.

3. What are the advantages of tissue culture methods over conventional method of plant breeding in crop improvement programmes?
Answer. The advantages of tissue culture methods are:
By application of these methods it is possible to achieve propagation of a large number ofplants in very short durations. This method of producing thousands of plants through tissue culture is called micro-propagation. Each of these plants will be genetically identical to the original plant from which they were grown, i.e., they are somaclones. Many important food plants like tonjato, banana, apple, etc., have been produced on commercial scale using this method. Try to visit a tissue culture laboratory with your teacher to better understand and . appreciate the process. Another important application of the method is the recovery of healthy plants from diseased plants. Although the plant is infected with a virus, the meristem (apical and axillary) is free of virus. Hence, one can remove the meristem and grow it in vitro to obtain virus-free plants. Scientists have succeeded in culturing meristems of banana, sugarcane, potato, etc.

4. ‘Modem methods of breeding animals and plants can alleviate the global food shortage’. Comment on the statement and give suitable examples.-
Answer. The main steps in breeding a new genetic variety of a crop are:
(i) Collection of variability: Genetic variability is the root of any breeding programme. In many crops pre-existing genetic variability is available from wild relatives of the crop. Collection and preservation of all the different wild varieties, species and relatives of the cultivated species (followed by their evaluation for their characteristics) is a pre-requisite for effective exploitation of natural genes available in the populations. The entire collection (of plants/seeds) having all the diverse alleles for all genes in a given crop is called germplasm collection.
(ii) Evaluation and selection of parents: The germplasm is evaluated so as
to identify plants with desirable combination of characters. The selected plants are multiplied and used in the process of hybridisation. Pure lines are created wherever desirable and possible. ‘
(iii) Cross hybridisation among the selected parents: The desired characters have very often to be combined from two different plants (parents), for example high protein quality of one parent may need to be combined with disease resistance from another parent. This is possible by cross hybridising the two parents to produce hybrids that genetically combine the desired characters in one plant. This is a very time-consuming and tedious process since the pollen grains from the desirable plant chosen as male parent have to be collected and placed on the stigma of the flowers selected as female parent (In chapter 2 details on how to make crosses have been described). Also, it is not necessary that the hybrids do combine the desirable characters; usually only one in few hundred to a thousand crosses shows the desirable combination.
(iv) Selection and testing of superior, recombinants: This step consists of selecting, among the progeny of the hybrids, those plants that have the desired character combination. The selection process is crucial to the success of the breeding objective and requires careful scientific evaluation of the progeny. This step yields plants that are superior to both of the parents (very often more than one superior progeny plant may become available). These are self-pollinated for several generations till they reach a state of uniformity (homozygosity), so that the characters will not segregate in the progeny.
(v) Testing, release and commercialisation of new cultivars: The newly selected lines are evaluated for their yield and other agronomic traits of quality, disease resistance, etc. This evaluation is done by growing these in the research fields and recording their performance under ideal fertilizer application, irrigation, and other crop management practices. The evaluation in research fields is followed by testing the materials in farmers’ fields:, for at least three growing seasons at several locations in the country, representing all the agro climatic zones where the crop is usually grown. The material is evaluated in comparison to the best available local crop cultivar a check or reference cultivar.
(a) It takes 3-10 kg of grain to produce 1 kg of meat using animal farming. That is why cereals demand increases.
(b) Production of single cell proteins (SCP) by microbes. Microbes are being grown on an Industrial scale. Spirulina can be easily grown on starch, molasses etc., and can make food which is rich in proteins, minerals, fats, carbohydrates and vitamins. This could be a good alternative for dealing with the problem of malnutrition.
The advantages of tissue culture methods are:
By application of these methods it is possible to achieve propagation of a large number ofplants in very short durations. This method of producing thousands of plants through tissue culture is called micro-propagation. Each of these plants will be genetically identical to the original plant from which they were grown, i.e., they are somaclones. Many important food plants like tonjato, banana, apple, etc., have been produced on commercial scale using this method. Try to visit a tissue culture laboratory with your teacher to better understand and . appreciate the process. Another important application of the method is the recovery of healthy plants from diseased plants. Although the plant is infected with a virus, the meristem (apical and axillary) is free of virus. Hence, one can remove the meristem and grow it in vitro to obtain virus-free plants. Scientists have succeeded in culturing meristems of banana, sugarcane, potato, etc.

5. Does apiculture offer multiple advantages to farmers? List its advantages if it is located near a place of commercial flower Cultivation.
Answer. Bee-keeping or apiculture is the maintenance of hives of honeybees for the production of honey, ft has been an age-old cottage industry. Honey is a food of high nutritive value and also find its use in the indigenous systems of medicine. Honeybee also produces beeswax, which finds many uses in industry, such as in the preparation of cosmetics and polishes of various kinds. The increased demand of honey has led to large-scale beekeeping practices; it has become an established income generating industry, whether practiced on a small or on a large scale.
Bees are the pollinators of many of our crop species such as sunflower, Brass tea, apple and pear. Keeping beehives in crop fields during flowering period increases pollination efficiency and improves the yield-beneficial both from the point of view of crop yield and honey yield.

6. (a) Mutations are beneficial for plant breeding. Taking an example, justify the statement.
(b) Discuss briefly the technology that made us self-sufficient in food production.
Answer. (a) Mutation is the process by which genetic variations are created through changes, in the base sequence within genes resulting in the creation of a new character or trait not found in the parental type. It is possible to induce mutations artificially through use of chemicals or radiations (like gamma radiations), and selecting and using the plants that have the desirable character as a source in breeding. This process is called mutation breeding. In mung bean, resistance to yellow mosaic virus and powdery mildew were induced by mutations.
(b) Plant breeding is the purposeful manipulation of plant species in order to create desired plant types that are better suited for cultivation, give better yields and are disease resistant. With advancements in genetics, molecular biology and tissue culture, plant breeding is now increasingly being carried out by using molecular genetic tools.

7. Discuss how the property of plant cell totipotency has been utilised for plant propagation and improvement
Answer. The capacity to generate a whole plant from any cell/explant is called totipotency. By application of these methods it is possible to achieve propagation of a large number of plants in very short durations. This method of producing thousands of plants through tissue culture is called micro propagation. Each of these plants will be genetically identical to the original plant from which they were grown, i.e., they are somaclones. Many important food plants like tomato, banana, apple, etc., have been produced on a commercial scale using this method. Try to visit a tissue culture laboratory with your teacher to better understand and appreciate the process.
Another important application ef the method is the recovery of healthy plants from diseased plants. Although the plant is infected with a virus, the meristem (apical and axillary) is free of virus. Hence, one can remove the meristem and grow it in vitro to obtain virus-free plants. Scientists have succeeded in culturing meristems of banana, sugarcane, potato, etc.

8. What are three options to increase food production? Discuss each giving the salient features, merits and demerits.
Answer. With ever increasing population of the world, enhancement of food production is a major necessity. Biological principles as applied to animal husbandry (See Ans 1 of short answer type questions) and plant breeding (See Ans 1) have a major role in our efforts to increase food production. Several new techniques like embryo transfer technology and tissue culture tecbniques(See Ans 7) are going to play a pivotal role in further enhancing food production.

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