CBSE Sample Question Paper Biology - 1 | Additional Study Material for NEET PDF Download

 Page 1


d o n e Biology - Sample Paper-1
1) Mention the sites where syngamy occurs in amphibians and reptiles.
Answer:
In amphibians, syngamy occurs in water outside the body of the organism (external fertilization and external development). In
reptiles, it occurs inside the body of female (internal fertilization and external development).
2) State the role of microbes in sewage treatment.
Answer:
Microbes clean sewage water and make it possible for us to use this water again. They effectively use up unwanted nutrients in
the system, by metabolizing the solid waste that passes through the treatment plant.
3) Mention two factors responsible for reduction in biodiversity at high altitudes!
Answer:
(a) Drop in temperature   
(b) Greater seasonal variability                                                                 
4) What is plasmid?
Answer:
Plasmid is an autonomously replicating circular extrachromosomal DNA used as cloning vector.
5) What are alleles?
Answer:
The alternative forms of a gene are called alleles.                                                                                 
6)
How does endosperm of angiosperms become triploid
OR
What is emasculation? Explain its importance in hybridisation.
Answer:
Endosperm of angiosperms develops from the central cell of embryo sac where two polar nuclei fuse to
form a secondary nucleus. This diploid nucleus of central cell fuses with one of the two male gametes. The
two polar nuclei and one male gamete ruse to form a triploid primary endosperm nucleus (3n). Thus, the
endosperm is formed from this triploid nucleus and becomes triploid.                 
                                                                          
OR
Emasculation is the practice of removal of anthers/stamens from the flower bud before the anther
dehisces in a bisexual female flower.                                                                                                                                  
It prevents contamination of stigmas with unwanted pollen grains that can be easily deposited on stigmas.
7) Name the pioneer and the climax species in a water body. Mention the changes observed in the biomass and the biodiversity
of the successive seral communities developing in the water body.
Answer:
(i) Pioneer species in a water body are autotrophic phytoplanktons such as diatoms, unicellular or
filamentous algae, flagellates and cyanobacteria.                                                                                  
Climax species in a water body are trees.                                                                
(ii) Biomass and the biodiversity goes on increasing in the successive seral communities developing in
the water body.
 
Page 2


d o n e Biology - Sample Paper-1
1) Mention the sites where syngamy occurs in amphibians and reptiles.
Answer:
In amphibians, syngamy occurs in water outside the body of the organism (external fertilization and external development). In
reptiles, it occurs inside the body of female (internal fertilization and external development).
2) State the role of microbes in sewage treatment.
Answer:
Microbes clean sewage water and make it possible for us to use this water again. They effectively use up unwanted nutrients in
the system, by metabolizing the solid waste that passes through the treatment plant.
3) Mention two factors responsible for reduction in biodiversity at high altitudes!
Answer:
(a) Drop in temperature   
(b) Greater seasonal variability                                                                 
4) What is plasmid?
Answer:
Plasmid is an autonomously replicating circular extrachromosomal DNA used as cloning vector.
5) What are alleles?
Answer:
The alternative forms of a gene are called alleles.                                                                                 
6)
How does endosperm of angiosperms become triploid
OR
What is emasculation? Explain its importance in hybridisation.
Answer:
Endosperm of angiosperms develops from the central cell of embryo sac where two polar nuclei fuse to
form a secondary nucleus. This diploid nucleus of central cell fuses with one of the two male gametes. The
two polar nuclei and one male gamete ruse to form a triploid primary endosperm nucleus (3n). Thus, the
endosperm is formed from this triploid nucleus and becomes triploid.                 
                                                                          
OR
Emasculation is the practice of removal of anthers/stamens from the flower bud before the anther
dehisces in a bisexual female flower.                                                                                                                                  
It prevents contamination of stigmas with unwanted pollen grains that can be easily deposited on stigmas.
7) Name the pioneer and the climax species in a water body. Mention the changes observed in the biomass and the biodiversity
of the successive seral communities developing in the water body.
Answer:
(i) Pioneer species in a water body are autotrophic phytoplanktons such as diatoms, unicellular or
filamentous algae, flagellates and cyanobacteria.                                                                                  
Climax species in a water body are trees.                                                                
(ii) Biomass and the biodiversity goes on increasing in the successive seral communities developing in
the water body.
 
8) What is BOD? What does it mean if a water sample has more BOD?
Answer:
BOD means the biochemical oxygen demand which represents the amount of dissolved oxygen that would
be consumed if all the organic matter in one litre of water were oxidised by microorganisms.                            
More value of BOD means the water sample is polluted by organic matter.                                                 
9) Mention the effects of nicotine on human body.
Answer:
Nicotine stimulates adrenal glands to release adrenaline and nor-adrenaline into blood circulation, both of which increase blood
pressure and heart beat rate. This lead to increased risk of heart disease.                            
10) If a double stranded DNA has 20 per cent of cytosine, calculate the per cent of adenine in the DNA.
Answer:
Cytosine = 20%, therefore Guanine = 20%                                                                                      According to Chargaffs rule, A+T=100 -
(G+C) A + T = 100 - 40. Since both adenine and thymine are in equal amounts,                                                    Thymine =
Adenine                                                                              
11) Write a short note on dairy farm management.
Answer:
Farm management includes the management of animals which provide milk and their products for human consumption. The
common dairy animals are cows, buffaloes, sheep and goats. For a good dairy farm management, the animals should be of good
breeds which may increase the milk yield and improve the quality of milk. The good quality breeds must be maintained, housed
well and fed properly. Their area must be free from accumulation of manure and dirt. The person concerned with milking and
handling of milk must follow the sanitary techniques.                                                                                                                
12) What is the difference between homothallic and heterothallic plants?
Answer:
When both male and female reproductive structures are present on the same plant they are called bisexual or homothallic but
when male and female reproductive structures are present on different plants they are called unisexual or heterothallic.
13) Red flowered (RR) plant is crossed with white flowered (rr) plants. The offspring was pink flowered. Explain the
genetic phenomenon.
Answer:
The resultant offspring is of pink flowered plants by using red flowered (RR) with white flowered (rr) plants. It means
that neither the red flower colour is dominant over the white flower colour nor the white flower is dominant over red. The 
heterozygous (Rr) plants were pink coloured. Hence, it indicates the phenomenon of incomplete dominance.      
                                                                                                                            
                                                     
14) What is meant by semi-conservative mode of DNA replication?
Answer:
A unique property of DNA is that it governs its own synthesis. The copying process of DNA to produce additional DNA molecules
is called replication.                                                                                                   The two strands of DNA would separate and each
Page 3


d o n e Biology - Sample Paper-1
1) Mention the sites where syngamy occurs in amphibians and reptiles.
Answer:
In amphibians, syngamy occurs in water outside the body of the organism (external fertilization and external development). In
reptiles, it occurs inside the body of female (internal fertilization and external development).
2) State the role of microbes in sewage treatment.
Answer:
Microbes clean sewage water and make it possible for us to use this water again. They effectively use up unwanted nutrients in
the system, by metabolizing the solid waste that passes through the treatment plant.
3) Mention two factors responsible for reduction in biodiversity at high altitudes!
Answer:
(a) Drop in temperature   
(b) Greater seasonal variability                                                                 
4) What is plasmid?
Answer:
Plasmid is an autonomously replicating circular extrachromosomal DNA used as cloning vector.
5) What are alleles?
Answer:
The alternative forms of a gene are called alleles.                                                                                 
6)
How does endosperm of angiosperms become triploid
OR
What is emasculation? Explain its importance in hybridisation.
Answer:
Endosperm of angiosperms develops from the central cell of embryo sac where two polar nuclei fuse to
form a secondary nucleus. This diploid nucleus of central cell fuses with one of the two male gametes. The
two polar nuclei and one male gamete ruse to form a triploid primary endosperm nucleus (3n). Thus, the
endosperm is formed from this triploid nucleus and becomes triploid.                 
                                                                          
OR
Emasculation is the practice of removal of anthers/stamens from the flower bud before the anther
dehisces in a bisexual female flower.                                                                                                                                  
It prevents contamination of stigmas with unwanted pollen grains that can be easily deposited on stigmas.
7) Name the pioneer and the climax species in a water body. Mention the changes observed in the biomass and the biodiversity
of the successive seral communities developing in the water body.
Answer:
(i) Pioneer species in a water body are autotrophic phytoplanktons such as diatoms, unicellular or
filamentous algae, flagellates and cyanobacteria.                                                                                  
Climax species in a water body are trees.                                                                
(ii) Biomass and the biodiversity goes on increasing in the successive seral communities developing in
the water body.
 
8) What is BOD? What does it mean if a water sample has more BOD?
Answer:
BOD means the biochemical oxygen demand which represents the amount of dissolved oxygen that would
be consumed if all the organic matter in one litre of water were oxidised by microorganisms.                            
More value of BOD means the water sample is polluted by organic matter.                                                 
9) Mention the effects of nicotine on human body.
Answer:
Nicotine stimulates adrenal glands to release adrenaline and nor-adrenaline into blood circulation, both of which increase blood
pressure and heart beat rate. This lead to increased risk of heart disease.                            
10) If a double stranded DNA has 20 per cent of cytosine, calculate the per cent of adenine in the DNA.
Answer:
Cytosine = 20%, therefore Guanine = 20%                                                                                      According to Chargaffs rule, A+T=100 -
(G+C) A + T = 100 - 40. Since both adenine and thymine are in equal amounts,                                                    Thymine =
Adenine                                                                              
11) Write a short note on dairy farm management.
Answer:
Farm management includes the management of animals which provide milk and their products for human consumption. The
common dairy animals are cows, buffaloes, sheep and goats. For a good dairy farm management, the animals should be of good
breeds which may increase the milk yield and improve the quality of milk. The good quality breeds must be maintained, housed
well and fed properly. Their area must be free from accumulation of manure and dirt. The person concerned with milking and
handling of milk must follow the sanitary techniques.                                                                                                                
12) What is the difference between homothallic and heterothallic plants?
Answer:
When both male and female reproductive structures are present on the same plant they are called bisexual or homothallic but
when male and female reproductive structures are present on different plants they are called unisexual or heterothallic.
13) Red flowered (RR) plant is crossed with white flowered (rr) plants. The offspring was pink flowered. Explain the
genetic phenomenon.
Answer:
The resultant offspring is of pink flowered plants by using red flowered (RR) with white flowered (rr) plants. It means
that neither the red flower colour is dominant over the white flower colour nor the white flower is dominant over red. The 
heterozygous (Rr) plants were pink coloured. Hence, it indicates the phenomenon of incomplete dominance.      
                                                                                                                            
                                                     
14) What is meant by semi-conservative mode of DNA replication?
Answer:
A unique property of DNA is that it governs its own synthesis. The copying process of DNA to produce additional DNA molecules
is called replication.                                                                                                   The two strands of DNA would separate and each
strand acts as a template for the synthesis of new complementary strand alongside it. After the completion of replication each
DNA daughter molecule would have one parental and one newly synthesized strand and the two daughter DNA molecules are
identical to the parent molecule. In each daughter DNA molecule only one parent strand is conserved. This mode of replication is
said to be semiconservative.  
15)
(i) For producing a recombinant protein (for therapeutic purpose) in large scale, which vector would you
choose-a low copy number or hight copy number?
(ii) Would you like to choose an exonuclease enzyme while producing a recombinant DNA molecule?
Answer:
(i) We choose a high-copy number, because higher the copy number, higher will be the formation of
recombinant protein. 
(ii) 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.                                                               
16)
(i) What is seminal plasma? What are its components?
(ii) Where do sperms mature and become motile?
Answer:
(i)  The accessory glands of a male reproductive system secrete a fluid mixture called seminal plasma. It is
rich in fructose, calcium and certian enzymes.
(ii) The sperms mature in epididymis. The mature spermatozoa from epididymis pass into the vas deferens.
Here, they partly swim and are mainly moved by muscular action of the vas deferens.
17) Name three incurable sexually transmitted diseases and their causative organisms.
Answer:
Sexually transmitted disease Causal agent
(a) Hepatitis-B Hepatitis-B virus                                             
(b) Genital herpes Herpes simplex virus
(c) AIDS HTV (Human immunodeficiency Virus)                   
18) What are the advantages of using biofertilisers in agriculture?
Answer:
Following are the advantages of using biofertilisers in agriculture:
(a) Biofertilisers do not cause any pollution.
(b) These are cheap and economical.
(c) Some of them act as biopesticides also.
(d) In ill-irrigated conditions few biofertilisers can enhance the crop yield.
(e) They improve soil structure and function.
(f) They make available vitamins and other growth promoting biochemicals.  
19)
(i) Name the substance used as a medium/matrix in gel electrophoresis.
(ii) Why does DNA move towards the anode in gel electrophoresis?
(iii) Name the compound used for staining the isolated DNA in the gel electrophoresis.
Answer:
(i) Agarose.                                                                                                                                     
Page 4


d o n e Biology - Sample Paper-1
1) Mention the sites where syngamy occurs in amphibians and reptiles.
Answer:
In amphibians, syngamy occurs in water outside the body of the organism (external fertilization and external development). In
reptiles, it occurs inside the body of female (internal fertilization and external development).
2) State the role of microbes in sewage treatment.
Answer:
Microbes clean sewage water and make it possible for us to use this water again. They effectively use up unwanted nutrients in
the system, by metabolizing the solid waste that passes through the treatment plant.
3) Mention two factors responsible for reduction in biodiversity at high altitudes!
Answer:
(a) Drop in temperature   
(b) Greater seasonal variability                                                                 
4) What is plasmid?
Answer:
Plasmid is an autonomously replicating circular extrachromosomal DNA used as cloning vector.
5) What are alleles?
Answer:
The alternative forms of a gene are called alleles.                                                                                 
6)
How does endosperm of angiosperms become triploid
OR
What is emasculation? Explain its importance in hybridisation.
Answer:
Endosperm of angiosperms develops from the central cell of embryo sac where two polar nuclei fuse to
form a secondary nucleus. This diploid nucleus of central cell fuses with one of the two male gametes. The
two polar nuclei and one male gamete ruse to form a triploid primary endosperm nucleus (3n). Thus, the
endosperm is formed from this triploid nucleus and becomes triploid.                 
                                                                          
OR
Emasculation is the practice of removal of anthers/stamens from the flower bud before the anther
dehisces in a bisexual female flower.                                                                                                                                  
It prevents contamination of stigmas with unwanted pollen grains that can be easily deposited on stigmas.
7) Name the pioneer and the climax species in a water body. Mention the changes observed in the biomass and the biodiversity
of the successive seral communities developing in the water body.
Answer:
(i) Pioneer species in a water body are autotrophic phytoplanktons such as diatoms, unicellular or
filamentous algae, flagellates and cyanobacteria.                                                                                  
Climax species in a water body are trees.                                                                
(ii) Biomass and the biodiversity goes on increasing in the successive seral communities developing in
the water body.
 
8) What is BOD? What does it mean if a water sample has more BOD?
Answer:
BOD means the biochemical oxygen demand which represents the amount of dissolved oxygen that would
be consumed if all the organic matter in one litre of water were oxidised by microorganisms.                            
More value of BOD means the water sample is polluted by organic matter.                                                 
9) Mention the effects of nicotine on human body.
Answer:
Nicotine stimulates adrenal glands to release adrenaline and nor-adrenaline into blood circulation, both of which increase blood
pressure and heart beat rate. This lead to increased risk of heart disease.                            
10) If a double stranded DNA has 20 per cent of cytosine, calculate the per cent of adenine in the DNA.
Answer:
Cytosine = 20%, therefore Guanine = 20%                                                                                      According to Chargaffs rule, A+T=100 -
(G+C) A + T = 100 - 40. Since both adenine and thymine are in equal amounts,                                                    Thymine =
Adenine                                                                              
11) Write a short note on dairy farm management.
Answer:
Farm management includes the management of animals which provide milk and their products for human consumption. The
common dairy animals are cows, buffaloes, sheep and goats. For a good dairy farm management, the animals should be of good
breeds which may increase the milk yield and improve the quality of milk. The good quality breeds must be maintained, housed
well and fed properly. Their area must be free from accumulation of manure and dirt. The person concerned with milking and
handling of milk must follow the sanitary techniques.                                                                                                                
12) What is the difference between homothallic and heterothallic plants?
Answer:
When both male and female reproductive structures are present on the same plant they are called bisexual or homothallic but
when male and female reproductive structures are present on different plants they are called unisexual or heterothallic.
13) Red flowered (RR) plant is crossed with white flowered (rr) plants. The offspring was pink flowered. Explain the
genetic phenomenon.
Answer:
The resultant offspring is of pink flowered plants by using red flowered (RR) with white flowered (rr) plants. It means
that neither the red flower colour is dominant over the white flower colour nor the white flower is dominant over red. The 
heterozygous (Rr) plants were pink coloured. Hence, it indicates the phenomenon of incomplete dominance.      
                                                                                                                            
                                                     
14) What is meant by semi-conservative mode of DNA replication?
Answer:
A unique property of DNA is that it governs its own synthesis. The copying process of DNA to produce additional DNA molecules
is called replication.                                                                                                   The two strands of DNA would separate and each
strand acts as a template for the synthesis of new complementary strand alongside it. After the completion of replication each
DNA daughter molecule would have one parental and one newly synthesized strand and the two daughter DNA molecules are
identical to the parent molecule. In each daughter DNA molecule only one parent strand is conserved. This mode of replication is
said to be semiconservative.  
15)
(i) For producing a recombinant protein (for therapeutic purpose) in large scale, which vector would you
choose-a low copy number or hight copy number?
(ii) Would you like to choose an exonuclease enzyme while producing a recombinant DNA molecule?
Answer:
(i) We choose a high-copy number, because higher the copy number, higher will be the formation of
recombinant protein. 
(ii) 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.                                                               
16)
(i) What is seminal plasma? What are its components?
(ii) Where do sperms mature and become motile?
Answer:
(i)  The accessory glands of a male reproductive system secrete a fluid mixture called seminal plasma. It is
rich in fructose, calcium and certian enzymes.
(ii) The sperms mature in epididymis. The mature spermatozoa from epididymis pass into the vas deferens.
Here, they partly swim and are mainly moved by muscular action of the vas deferens.
17) Name three incurable sexually transmitted diseases and their causative organisms.
Answer:
Sexually transmitted disease Causal agent
(a) Hepatitis-B Hepatitis-B virus                                             
(b) Genital herpes Herpes simplex virus
(c) AIDS HTV (Human immunodeficiency Virus)                   
18) What are the advantages of using biofertilisers in agriculture?
Answer:
Following are the advantages of using biofertilisers in agriculture:
(a) Biofertilisers do not cause any pollution.
(b) These are cheap and economical.
(c) Some of them act as biopesticides also.
(d) In ill-irrigated conditions few biofertilisers can enhance the crop yield.
(e) They improve soil structure and function.
(f) They make available vitamins and other growth promoting biochemicals.  
19)
(i) Name the substance used as a medium/matrix in gel electrophoresis.
(ii) Why does DNA move towards the anode in gel electrophoresis?
(iii) Name the compound used for staining the isolated DNA in the gel electrophoresis.
Answer:
(i) Agarose.                                                                                                                                     
(ii) The DNA fragments are negatively charged so they move towards the positively charged
anode.            
(iii) Ethidium bromide.                                                                                                                                  
20)
(i) What is cloning vector?
(ii) Explain any two methods of vectorless gene transfer.
Answer:
(i)  Cloning vectors are carriers or vehicles of desired DNA fragments which can replicate independently
to increase copies of desired genes in the host cell, e.g., plasmids, bacteriophages.                                           
(ii) The two methods of vectorless gene transfer are:
(a) Micro-injection: The technique of introducing foreign gene in a target cell by injecting the DNA
directly into the nucleus by micro-needle is called micro-injection.
(b) Electroporation: The process in which transient holes are produced in the plasma membrane of the
target cell to incorporate foreign DNA.                                                                                           
21)
(i) Give the scientific name of the soil bacterium which produces crystal (Cry) proteins.
(ii) How are these proteins useful in agriculture?
(iii) What do the differently written terms 'Cry' and ? ? represent respectively?
Answer:
(i)                                                                                                                
(ii) These Cry proteins are toxic to certain larvae of insects and thus provide resistance from them. The
gene encoding Cry proteins are used in several crop plants (Bt toxin). Such a crop plant is resistant to the
particular insect pest. 
(iii) Cry represents crystal protein while cry refers to the gene encoding the Cry protein.                           
22) What is meant by the term 'hotspots9 in biodiversity? List two criteria used for determining a ?hot spot?. Name two hot
spots of India.
Answer:
A hot spot is an area having endangered endemic species with very high levels of species richness.              
Criteria used for determining a hot spot:
(i) Number of endemic species, i.e., species which are not found anywhere else.
(ii) Degree of threat which is measured in terms of habitat loss.
Western Ghats and Eastern Himalayas are two hot spots in India.
23)
What is eutrophication? Explain its consequence on the life of plants and animals in such water
bodies.
OR
What is biological magnification? How does DDT as a water pollutant undergo biological
magnification?
Answer:
Eutrophication is excessive growth of algae, plants and animals in water bodies due to the nutrient
enrichment, particularly with nitrogen and phosphorus.                                                                                               
Consequences ofeutrophication on the life of plants and animals in such water bodies are as follows:
(a) Presence of large amount of nutrient in such water bodies causes excessive growth of planktonic (free-
floating) algae leading to algal bloom. Algal bloom caused deterioration of water quality and fish mortality.
Some of them are toxic to human being and animals.
(b) Growth of water hyacinth (aquatic weed) lead to an imbalance in the aquatic ecosystem.                   
OR
Page 5


d o n e Biology - Sample Paper-1
1) Mention the sites where syngamy occurs in amphibians and reptiles.
Answer:
In amphibians, syngamy occurs in water outside the body of the organism (external fertilization and external development). In
reptiles, it occurs inside the body of female (internal fertilization and external development).
2) State the role of microbes in sewage treatment.
Answer:
Microbes clean sewage water and make it possible for us to use this water again. They effectively use up unwanted nutrients in
the system, by metabolizing the solid waste that passes through the treatment plant.
3) Mention two factors responsible for reduction in biodiversity at high altitudes!
Answer:
(a) Drop in temperature   
(b) Greater seasonal variability                                                                 
4) What is plasmid?
Answer:
Plasmid is an autonomously replicating circular extrachromosomal DNA used as cloning vector.
5) What are alleles?
Answer:
The alternative forms of a gene are called alleles.                                                                                 
6)
How does endosperm of angiosperms become triploid
OR
What is emasculation? Explain its importance in hybridisation.
Answer:
Endosperm of angiosperms develops from the central cell of embryo sac where two polar nuclei fuse to
form a secondary nucleus. This diploid nucleus of central cell fuses with one of the two male gametes. The
two polar nuclei and one male gamete ruse to form a triploid primary endosperm nucleus (3n). Thus, the
endosperm is formed from this triploid nucleus and becomes triploid.                 
                                                                          
OR
Emasculation is the practice of removal of anthers/stamens from the flower bud before the anther
dehisces in a bisexual female flower.                                                                                                                                  
It prevents contamination of stigmas with unwanted pollen grains that can be easily deposited on stigmas.
7) Name the pioneer and the climax species in a water body. Mention the changes observed in the biomass and the biodiversity
of the successive seral communities developing in the water body.
Answer:
(i) Pioneer species in a water body are autotrophic phytoplanktons such as diatoms, unicellular or
filamentous algae, flagellates and cyanobacteria.                                                                                  
Climax species in a water body are trees.                                                                
(ii) Biomass and the biodiversity goes on increasing in the successive seral communities developing in
the water body.
 
8) What is BOD? What does it mean if a water sample has more BOD?
Answer:
BOD means the biochemical oxygen demand which represents the amount of dissolved oxygen that would
be consumed if all the organic matter in one litre of water were oxidised by microorganisms.                            
More value of BOD means the water sample is polluted by organic matter.                                                 
9) Mention the effects of nicotine on human body.
Answer:
Nicotine stimulates adrenal glands to release adrenaline and nor-adrenaline into blood circulation, both of which increase blood
pressure and heart beat rate. This lead to increased risk of heart disease.                            
10) If a double stranded DNA has 20 per cent of cytosine, calculate the per cent of adenine in the DNA.
Answer:
Cytosine = 20%, therefore Guanine = 20%                                                                                      According to Chargaffs rule, A+T=100 -
(G+C) A + T = 100 - 40. Since both adenine and thymine are in equal amounts,                                                    Thymine =
Adenine                                                                              
11) Write a short note on dairy farm management.
Answer:
Farm management includes the management of animals which provide milk and their products for human consumption. The
common dairy animals are cows, buffaloes, sheep and goats. For a good dairy farm management, the animals should be of good
breeds which may increase the milk yield and improve the quality of milk. The good quality breeds must be maintained, housed
well and fed properly. Their area must be free from accumulation of manure and dirt. The person concerned with milking and
handling of milk must follow the sanitary techniques.                                                                                                                
12) What is the difference between homothallic and heterothallic plants?
Answer:
When both male and female reproductive structures are present on the same plant they are called bisexual or homothallic but
when male and female reproductive structures are present on different plants they are called unisexual or heterothallic.
13) Red flowered (RR) plant is crossed with white flowered (rr) plants. The offspring was pink flowered. Explain the
genetic phenomenon.
Answer:
The resultant offspring is of pink flowered plants by using red flowered (RR) with white flowered (rr) plants. It means
that neither the red flower colour is dominant over the white flower colour nor the white flower is dominant over red. The 
heterozygous (Rr) plants were pink coloured. Hence, it indicates the phenomenon of incomplete dominance.      
                                                                                                                            
                                                     
14) What is meant by semi-conservative mode of DNA replication?
Answer:
A unique property of DNA is that it governs its own synthesis. The copying process of DNA to produce additional DNA molecules
is called replication.                                                                                                   The two strands of DNA would separate and each
strand acts as a template for the synthesis of new complementary strand alongside it. After the completion of replication each
DNA daughter molecule would have one parental and one newly synthesized strand and the two daughter DNA molecules are
identical to the parent molecule. In each daughter DNA molecule only one parent strand is conserved. This mode of replication is
said to be semiconservative.  
15)
(i) For producing a recombinant protein (for therapeutic purpose) in large scale, which vector would you
choose-a low copy number or hight copy number?
(ii) Would you like to choose an exonuclease enzyme while producing a recombinant DNA molecule?
Answer:
(i) We choose a high-copy number, because higher the copy number, higher will be the formation of
recombinant protein. 
(ii) 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.                                                               
16)
(i) What is seminal plasma? What are its components?
(ii) Where do sperms mature and become motile?
Answer:
(i)  The accessory glands of a male reproductive system secrete a fluid mixture called seminal plasma. It is
rich in fructose, calcium and certian enzymes.
(ii) The sperms mature in epididymis. The mature spermatozoa from epididymis pass into the vas deferens.
Here, they partly swim and are mainly moved by muscular action of the vas deferens.
17) Name three incurable sexually transmitted diseases and their causative organisms.
Answer:
Sexually transmitted disease Causal agent
(a) Hepatitis-B Hepatitis-B virus                                             
(b) Genital herpes Herpes simplex virus
(c) AIDS HTV (Human immunodeficiency Virus)                   
18) What are the advantages of using biofertilisers in agriculture?
Answer:
Following are the advantages of using biofertilisers in agriculture:
(a) Biofertilisers do not cause any pollution.
(b) These are cheap and economical.
(c) Some of them act as biopesticides also.
(d) In ill-irrigated conditions few biofertilisers can enhance the crop yield.
(e) They improve soil structure and function.
(f) They make available vitamins and other growth promoting biochemicals.  
19)
(i) Name the substance used as a medium/matrix in gel electrophoresis.
(ii) Why does DNA move towards the anode in gel electrophoresis?
(iii) Name the compound used for staining the isolated DNA in the gel electrophoresis.
Answer:
(i) Agarose.                                                                                                                                     
(ii) The DNA fragments are negatively charged so they move towards the positively charged
anode.            
(iii) Ethidium bromide.                                                                                                                                  
20)
(i) What is cloning vector?
(ii) Explain any two methods of vectorless gene transfer.
Answer:
(i)  Cloning vectors are carriers or vehicles of desired DNA fragments which can replicate independently
to increase copies of desired genes in the host cell, e.g., plasmids, bacteriophages.                                           
(ii) The two methods of vectorless gene transfer are:
(a) Micro-injection: The technique of introducing foreign gene in a target cell by injecting the DNA
directly into the nucleus by micro-needle is called micro-injection.
(b) Electroporation: The process in which transient holes are produced in the plasma membrane of the
target cell to incorporate foreign DNA.                                                                                           
21)
(i) Give the scientific name of the soil bacterium which produces crystal (Cry) proteins.
(ii) How are these proteins useful in agriculture?
(iii) What do the differently written terms 'Cry' and ? ? represent respectively?
Answer:
(i)                                                                                                                
(ii) These Cry proteins are toxic to certain larvae of insects and thus provide resistance from them. The
gene encoding Cry proteins are used in several crop plants (Bt toxin). Such a crop plant is resistant to the
particular insect pest. 
(iii) Cry represents crystal protein while cry refers to the gene encoding the Cry protein.                           
22) What is meant by the term 'hotspots9 in biodiversity? List two criteria used for determining a ?hot spot?. Name two hot
spots of India.
Answer:
A hot spot is an area having endangered endemic species with very high levels of species richness.              
Criteria used for determining a hot spot:
(i) Number of endemic species, i.e., species which are not found anywhere else.
(ii) Degree of threat which is measured in terms of habitat loss.
Western Ghats and Eastern Himalayas are two hot spots in India.
23)
What is eutrophication? Explain its consequence on the life of plants and animals in such water
bodies.
OR
What is biological magnification? How does DDT as a water pollutant undergo biological
magnification?
Answer:
Eutrophication is excessive growth of algae, plants and animals in water bodies due to the nutrient
enrichment, particularly with nitrogen and phosphorus.                                                                                               
Consequences ofeutrophication on the life of plants and animals in such water bodies are as follows:
(a) Presence of large amount of nutrient in such water bodies causes excessive growth of planktonic (free-
floating) algae leading to algal bloom. Algal bloom caused deterioration of water quality and fish mortality.
Some of them are toxic to human being and animals.
(b) Growth of water hyacinth (aquatic weed) lead to an imbalance in the aquatic ecosystem.                   
OR
Biological magnification or biomagnification is the increase in concentration of toxic materials like heavy
metals and pesticides at each trophic level of a food chain due to their
accumulation.                                                
When DDT was used to control mosquitoes in a lake of USA, 800 times more DDT was found in the
phytoplanktons than in the water of the lake. Zooplanktons had about 13 times more DDT than
phytoplanktons. It was also observed that the fishes population had 9-40 times more DDT than
zooplanktons and fish eating birds had 25 times more DDT than fish.
24) Kavita was very happy when she gave birth to her first child. But her in-laws were unhappy and blamed on Kavita to give a
female child. Kavita tried to conyince them that she had no role in the child's gender. Then Kavita's husband took up the matter
and convinced the parents.
(i) What values did Kavita's husband show in the above situation?
(ii) What governs sex determination in humans?
(iii) Why can't Kavita be blamed for not giving birth to a male child?
Answer:
(i)  Strong and determined personality with lesponsibility towards the family and respect for
elders.            
(ii) Sex chromosomes. In human males it is XY and female it is XX.                                                      
Human females are homogametic i.e. produces only one type of gamete containing 22+X
chromosomes only. Males are heterogametic and produce two types of gametes 22+X and 22 + Y. It is
the type of male gamete which determines the sex of the foetus. If X chromosome containing sperm
fuses with the egg, it produces a female child whereas if Y chromosome containing sperm fuses with
the egg, it produces a male child.
25)
Drawa labelled diagram of the sectional view of a mature pollen grain in angiosperms. Explain the
functions of its different parts.
OR
(i) What is the role of cervix of the human female system in reproduction?
(ii) Distinguish between spermatogenesis and oogenesis.
Answer:
Functions of the parts of Pollen grains: A mature pollen grain has two layered wall-the outer exine and the inner intine. The wall encloses a large
vegetative cell containing vegetative nucleus and a lenticular generative cell.
Their functions are as follows:
Exine: The outer thick exine layer is made up of sporopollenin which is resistant to physical and biological decomposition. It provides protection
during the hazardous journey of pollen from anther to the stigma. There are one or many germpores on the pollen surface which are directly or
indirectly associated with its germination.
Intine: The intine is pecto-cellulosic in nature. It is associated with the formation of pollen tube.
Vegetative cell: The vegetative cell is large and contains abundant food reserve. It has a large vegetative nucleus. The function of vegetative cell is
to provide the medium for the movement of male gametes in pollen tube.