CBSE Biology Past year paper Delhi (Set - 3) Solutions - 2010, Class 12 | Additional Study Material for NEET PDF Download

 Page 1


  
 
CBSE XII  |  Biology 
Board Paper – 2010 – Delhi – Set 3 (Solution) 
 
     
CBSE 
Class XII Biology (Theory) 
Board Paper 2010 – Delhi (Set 3) 
SOLUTION 
Time: 3 hrs Total Marks: 70 
 
SECTION A 
1. Ans. Positive application of amniocentesis: 
Amniocentesis helps find genetic and metabolic disorders of the foetus. 
Negative application of amniocentesis: 
It is used to kill the normal female foetus. 
 
2. Ans. Animals like fish and snails avoid summer-related unfavourable conditions like 
heat and desiccation by the process called aestivation or summer sleep and become 
inactive during summer. 
 
3. Ans. The birth rate of population per capita would be 
        40/200 = 0.2 offspring per frog per year 
 
4. Ans. AUG has dual function. 
(i) It codes for Methionine (Met). 
(ii) It also acts as initiator codon. 
 
5. Ans. Different viral and bacterial DNA in a host body can be detected by polymerase 
chain reaction (PCR). PCR can detect very low amounts of DNA. PCR is now usually 
used to detect HIV in suspected AIDS patients. It is a good technique to identify 
many other genetic disorders. 
 
6. Ans. Louis Pasteur disproved the spontaneous generation theory. According to this 
theory, life originated repeatedly from non-living materials spontaneously. 
However, according to Louis Pasteur, life originated from pre-existing organisms of 
their own kind. 
 
7. Ans. On exposure to antigens or vaccines, the antibodies produced in the body 
neutralise the pathogenic agent during infection. The vaccines generate memory B 
cells and T cells during primary response. When the vaccinated person is attacked 
by the same pathogen, the existing memory T or B cells recognise the antigen 
quickly and attack the invaders with a massive production of lymphocytes and 
antibodies. 
 
Page 2


  
 
CBSE XII  |  Biology 
Board Paper – 2010 – Delhi – Set 3 (Solution) 
 
     
CBSE 
Class XII Biology (Theory) 
Board Paper 2010 – Delhi (Set 3) 
SOLUTION 
Time: 3 hrs Total Marks: 70 
 
SECTION A 
1. Ans. Positive application of amniocentesis: 
Amniocentesis helps find genetic and metabolic disorders of the foetus. 
Negative application of amniocentesis: 
It is used to kill the normal female foetus. 
 
2. Ans. Animals like fish and snails avoid summer-related unfavourable conditions like 
heat and desiccation by the process called aestivation or summer sleep and become 
inactive during summer. 
 
3. Ans. The birth rate of population per capita would be 
        40/200 = 0.2 offspring per frog per year 
 
4. Ans. AUG has dual function. 
(i) It codes for Methionine (Met). 
(ii) It also acts as initiator codon. 
 
5. Ans. Different viral and bacterial DNA in a host body can be detected by polymerase 
chain reaction (PCR). PCR can detect very low amounts of DNA. PCR is now usually 
used to detect HIV in suspected AIDS patients. It is a good technique to identify 
many other genetic disorders. 
 
6. Ans. Louis Pasteur disproved the spontaneous generation theory. According to this 
theory, life originated repeatedly from non-living materials spontaneously. 
However, according to Louis Pasteur, life originated from pre-existing organisms of 
their own kind. 
 
7. Ans. On exposure to antigens or vaccines, the antibodies produced in the body 
neutralise the pathogenic agent during infection. The vaccines generate memory B 
cells and T cells during primary response. When the vaccinated person is attacked 
by the same pathogen, the existing memory T or B cells recognise the antigen 
quickly and attack the invaders with a massive production of lymphocytes and 
antibodies. 
 
  
 
CBSE XII  |  Biology 
Board Paper – 2010 – Delhi – Set 3 (Solution) 
 
     
SECTION B 
 
9. Ans. Triple fusion occurs inside the embryo sac (female gametophyte) of 
angiosperms.  
It is called so because one male gamete fuses with two polar nuclei (secondary 
nucleus) to form a triploid primary endosperm nucleus. 
Significance of triple fusion: 
Endosperm is a highly nutritive tissue formed as a result of triple fusion and 
provides nourishment to the developing embryo. 
  
10. Ans. Certain regions have been declared as biodiversity ‘hotspots’ by 
environmentalists of the world because these areas are of high endemism and high 
level of species richness. In India, biodiversity hotspots are the Western Ghats and 
the Himalayas. 
 
11. Ans. The eggs are located in the archegonium in moss. For fertilisation to take place, 
antherozoids swim in water to reach the eggs. Moss produces a large number of 
antherozoids to increase the chance of fertilisation.  
  
12. Ans. Adenosine deaminase deficiency can be cured by enzyme replacement therapy, 
but the cure is not permanent even after infusion of genetically engineered 
lymphocytes into a patient as the cells are not immortal. The patient does not have 
functional T-lymphocytes so they cannot provide immune responses against 
invading pathogens.  The patient requires periodic infusion of such genetically 
engineered lymphocytes. However, if the gene isolated from bone marrow cell-
producing ADA is introduced into cells at early embryonic stages, it could prove to 
be a permanent cure. 
 
13. Ans.   
(a) There is a continuous increase in the DDT content in different trophic levels of 
the chain because it accumulates in the fat of the body. 
(b) The phenomenon responsible for the increase in DDT content in different 
trophic levels is called biomagnification. 
 
14. Ans. Bee farms or apiaries are established in an area where abundance of wild 
shrubs, fruit orchards and cultivated crops is available in a 1–2 km radius. 
Availability of flowering plants for the collection of nectar and pollen is called 
pasturage. It plays an important role in the quality and quantity of honey. The 
beehives when kept in the fields of sunflower, Brassica, apple and pear increase the 
pollination efficiency of flowering plants and improve the yields. 
OR 
 
Page 3


  
 
CBSE XII  |  Biology 
Board Paper – 2010 – Delhi – Set 3 (Solution) 
 
     
CBSE 
Class XII Biology (Theory) 
Board Paper 2010 – Delhi (Set 3) 
SOLUTION 
Time: 3 hrs Total Marks: 70 
 
SECTION A 
1. Ans. Positive application of amniocentesis: 
Amniocentesis helps find genetic and metabolic disorders of the foetus. 
Negative application of amniocentesis: 
It is used to kill the normal female foetus. 
 
2. Ans. Animals like fish and snails avoid summer-related unfavourable conditions like 
heat and desiccation by the process called aestivation or summer sleep and become 
inactive during summer. 
 
3. Ans. The birth rate of population per capita would be 
        40/200 = 0.2 offspring per frog per year 
 
4. Ans. AUG has dual function. 
(i) It codes for Methionine (Met). 
(ii) It also acts as initiator codon. 
 
5. Ans. Different viral and bacterial DNA in a host body can be detected by polymerase 
chain reaction (PCR). PCR can detect very low amounts of DNA. PCR is now usually 
used to detect HIV in suspected AIDS patients. It is a good technique to identify 
many other genetic disorders. 
 
6. Ans. Louis Pasteur disproved the spontaneous generation theory. According to this 
theory, life originated repeatedly from non-living materials spontaneously. 
However, according to Louis Pasteur, life originated from pre-existing organisms of 
their own kind. 
 
7. Ans. On exposure to antigens or vaccines, the antibodies produced in the body 
neutralise the pathogenic agent during infection. The vaccines generate memory B 
cells and T cells during primary response. When the vaccinated person is attacked 
by the same pathogen, the existing memory T or B cells recognise the antigen 
quickly and attack the invaders with a massive production of lymphocytes and 
antibodies. 
 
  
 
CBSE XII  |  Biology 
Board Paper – 2010 – Delhi – Set 3 (Solution) 
 
     
SECTION B 
 
9. Ans. Triple fusion occurs inside the embryo sac (female gametophyte) of 
angiosperms.  
It is called so because one male gamete fuses with two polar nuclei (secondary 
nucleus) to form a triploid primary endosperm nucleus. 
Significance of triple fusion: 
Endosperm is a highly nutritive tissue formed as a result of triple fusion and 
provides nourishment to the developing embryo. 
  
10. Ans. Certain regions have been declared as biodiversity ‘hotspots’ by 
environmentalists of the world because these areas are of high endemism and high 
level of species richness. In India, biodiversity hotspots are the Western Ghats and 
the Himalayas. 
 
11. Ans. The eggs are located in the archegonium in moss. For fertilisation to take place, 
antherozoids swim in water to reach the eggs. Moss produces a large number of 
antherozoids to increase the chance of fertilisation.  
  
12. Ans. Adenosine deaminase deficiency can be cured by enzyme replacement therapy, 
but the cure is not permanent even after infusion of genetically engineered 
lymphocytes into a patient as the cells are not immortal. The patient does not have 
functional T-lymphocytes so they cannot provide immune responses against 
invading pathogens.  The patient requires periodic infusion of such genetically 
engineered lymphocytes. However, if the gene isolated from bone marrow cell-
producing ADA is introduced into cells at early embryonic stages, it could prove to 
be a permanent cure. 
 
13. Ans.   
(a) There is a continuous increase in the DDT content in different trophic levels of 
the chain because it accumulates in the fat of the body. 
(b) The phenomenon responsible for the increase in DDT content in different 
trophic levels is called biomagnification. 
 
14. Ans. Bee farms or apiaries are established in an area where abundance of wild 
shrubs, fruit orchards and cultivated crops is available in a 1–2 km radius. 
Availability of flowering plants for the collection of nectar and pollen is called 
pasturage. It plays an important role in the quality and quantity of honey. The 
beehives when kept in the fields of sunflower, Brassica, apple and pear increase the 
pollination efficiency of flowering plants and improve the yields. 
OR 
 
  
 
CBSE XII  |  Biology 
Board Paper – 2010 – Delhi – Set 3 (Solution) 
 
     
When a small amount of curd is added to milk, the fermentation process begins. 
During this process, the lactose sugar of milk is converted to lactic acid which 
acidifies the fermenting medium. The acidic medium helps in coagulating milk 
protein by partially digesting it so that a thick concentrated curd is prepared. 
              Lactic acid bacteria improve its nutritional quality by increasing vitamin B 12. 
 
15. Ans. Aquatic ecosystem: Pond ecosystem 
         Terrestrial ecosystem: Detritus food chain 
 
Aquatic Ecosystem Terrestrial Ecosystem 
It describes the ecosystem in 
water. Example: Pond ecosystem 
 
 
It describes the ecosystem on land. 
Example: Detritus food chain 
 
 
 
16. Ans.  
(a) Formation of gametocytes occurs in the red blood cells of the human host. 
(b) Fertilisation of gametocytes occurs in the mosquito’s stomach. 
 
17. Ans. In Snapdragon, when two types of pure breeding plants bearing red flower and 
white flower are crossed, the F 1 generation plants neither bear red nor white 
flowers. They bear pink flowers exhibiting incomplete dominance.  
On self-breeding, the pink flowers yield a progeny consisting of three types of 
plants—red, pink and white, i.e. 1:2:1, both phenotypically and genotypically.  
So, we conclude that when genotypic and phenotypic ratios are the same, the alleles 
show incomplete dominance. 
Page 4


  
 
CBSE XII  |  Biology 
Board Paper – 2010 – Delhi – Set 3 (Solution) 
 
     
CBSE 
Class XII Biology (Theory) 
Board Paper 2010 – Delhi (Set 3) 
SOLUTION 
Time: 3 hrs Total Marks: 70 
 
SECTION A 
1. Ans. Positive application of amniocentesis: 
Amniocentesis helps find genetic and metabolic disorders of the foetus. 
Negative application of amniocentesis: 
It is used to kill the normal female foetus. 
 
2. Ans. Animals like fish and snails avoid summer-related unfavourable conditions like 
heat and desiccation by the process called aestivation or summer sleep and become 
inactive during summer. 
 
3. Ans. The birth rate of population per capita would be 
        40/200 = 0.2 offspring per frog per year 
 
4. Ans. AUG has dual function. 
(i) It codes for Methionine (Met). 
(ii) It also acts as initiator codon. 
 
5. Ans. Different viral and bacterial DNA in a host body can be detected by polymerase 
chain reaction (PCR). PCR can detect very low amounts of DNA. PCR is now usually 
used to detect HIV in suspected AIDS patients. It is a good technique to identify 
many other genetic disorders. 
 
6. Ans. Louis Pasteur disproved the spontaneous generation theory. According to this 
theory, life originated repeatedly from non-living materials spontaneously. 
However, according to Louis Pasteur, life originated from pre-existing organisms of 
their own kind. 
 
7. Ans. On exposure to antigens or vaccines, the antibodies produced in the body 
neutralise the pathogenic agent during infection. The vaccines generate memory B 
cells and T cells during primary response. When the vaccinated person is attacked 
by the same pathogen, the existing memory T or B cells recognise the antigen 
quickly and attack the invaders with a massive production of lymphocytes and 
antibodies. 
 
  
 
CBSE XII  |  Biology 
Board Paper – 2010 – Delhi – Set 3 (Solution) 
 
     
SECTION B 
 
9. Ans. Triple fusion occurs inside the embryo sac (female gametophyte) of 
angiosperms.  
It is called so because one male gamete fuses with two polar nuclei (secondary 
nucleus) to form a triploid primary endosperm nucleus. 
Significance of triple fusion: 
Endosperm is a highly nutritive tissue formed as a result of triple fusion and 
provides nourishment to the developing embryo. 
  
10. Ans. Certain regions have been declared as biodiversity ‘hotspots’ by 
environmentalists of the world because these areas are of high endemism and high 
level of species richness. In India, biodiversity hotspots are the Western Ghats and 
the Himalayas. 
 
11. Ans. The eggs are located in the archegonium in moss. For fertilisation to take place, 
antherozoids swim in water to reach the eggs. Moss produces a large number of 
antherozoids to increase the chance of fertilisation.  
  
12. Ans. Adenosine deaminase deficiency can be cured by enzyme replacement therapy, 
but the cure is not permanent even after infusion of genetically engineered 
lymphocytes into a patient as the cells are not immortal. The patient does not have 
functional T-lymphocytes so they cannot provide immune responses against 
invading pathogens.  The patient requires periodic infusion of such genetically 
engineered lymphocytes. However, if the gene isolated from bone marrow cell-
producing ADA is introduced into cells at early embryonic stages, it could prove to 
be a permanent cure. 
 
13. Ans.   
(a) There is a continuous increase in the DDT content in different trophic levels of 
the chain because it accumulates in the fat of the body. 
(b) The phenomenon responsible for the increase in DDT content in different 
trophic levels is called biomagnification. 
 
14. Ans. Bee farms or apiaries are established in an area where abundance of wild 
shrubs, fruit orchards and cultivated crops is available in a 1–2 km radius. 
Availability of flowering plants for the collection of nectar and pollen is called 
pasturage. It plays an important role in the quality and quantity of honey. The 
beehives when kept in the fields of sunflower, Brassica, apple and pear increase the 
pollination efficiency of flowering plants and improve the yields. 
OR 
 
  
 
CBSE XII  |  Biology 
Board Paper – 2010 – Delhi – Set 3 (Solution) 
 
     
When a small amount of curd is added to milk, the fermentation process begins. 
During this process, the lactose sugar of milk is converted to lactic acid which 
acidifies the fermenting medium. The acidic medium helps in coagulating milk 
protein by partially digesting it so that a thick concentrated curd is prepared. 
              Lactic acid bacteria improve its nutritional quality by increasing vitamin B 12. 
 
15. Ans. Aquatic ecosystem: Pond ecosystem 
         Terrestrial ecosystem: Detritus food chain 
 
Aquatic Ecosystem Terrestrial Ecosystem 
It describes the ecosystem in 
water. Example: Pond ecosystem 
 
 
It describes the ecosystem on land. 
Example: Detritus food chain 
 
 
 
16. Ans.  
(a) Formation of gametocytes occurs in the red blood cells of the human host. 
(b) Fertilisation of gametocytes occurs in the mosquito’s stomach. 
 
17. Ans. In Snapdragon, when two types of pure breeding plants bearing red flower and 
white flower are crossed, the F 1 generation plants neither bear red nor white 
flowers. They bear pink flowers exhibiting incomplete dominance.  
On self-breeding, the pink flowers yield a progeny consisting of three types of 
plants—red, pink and white, i.e. 1:2:1, both phenotypically and genotypically.  
So, we conclude that when genotypic and phenotypic ratios are the same, the alleles 
show incomplete dominance. 
  
 
CBSE XII  |  Biology 
Board Paper – 2010 – Delhi – Set 3 (Solution) 
 
     
 
 
18. Ans. The Mediterranean orchid Ophrys has a very strange relationship with its 
insect pollinator Colpa aurea (a hairy wasp). The orchid bears flowers which 
resemble the female wasp in colour, odour and appearance. The male wasp matures 
first and leaves the burrow about four weeks before the females come out for open 
air mating. The inexperienced males try to pseudocopulate the orchid flowers 
presuming them as their female partners and bring about pollination.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Page 5


  
 
CBSE XII  |  Biology 
Board Paper – 2010 – Delhi – Set 3 (Solution) 
 
     
CBSE 
Class XII Biology (Theory) 
Board Paper 2010 – Delhi (Set 3) 
SOLUTION 
Time: 3 hrs Total Marks: 70 
 
SECTION A 
1. Ans. Positive application of amniocentesis: 
Amniocentesis helps find genetic and metabolic disorders of the foetus. 
Negative application of amniocentesis: 
It is used to kill the normal female foetus. 
 
2. Ans. Animals like fish and snails avoid summer-related unfavourable conditions like 
heat and desiccation by the process called aestivation or summer sleep and become 
inactive during summer. 
 
3. Ans. The birth rate of population per capita would be 
        40/200 = 0.2 offspring per frog per year 
 
4. Ans. AUG has dual function. 
(i) It codes for Methionine (Met). 
(ii) It also acts as initiator codon. 
 
5. Ans. Different viral and bacterial DNA in a host body can be detected by polymerase 
chain reaction (PCR). PCR can detect very low amounts of DNA. PCR is now usually 
used to detect HIV in suspected AIDS patients. It is a good technique to identify 
many other genetic disorders. 
 
6. Ans. Louis Pasteur disproved the spontaneous generation theory. According to this 
theory, life originated repeatedly from non-living materials spontaneously. 
However, according to Louis Pasteur, life originated from pre-existing organisms of 
their own kind. 
 
7. Ans. On exposure to antigens or vaccines, the antibodies produced in the body 
neutralise the pathogenic agent during infection. The vaccines generate memory B 
cells and T cells during primary response. When the vaccinated person is attacked 
by the same pathogen, the existing memory T or B cells recognise the antigen 
quickly and attack the invaders with a massive production of lymphocytes and 
antibodies. 
 
  
 
CBSE XII  |  Biology 
Board Paper – 2010 – Delhi – Set 3 (Solution) 
 
     
SECTION B 
 
9. Ans. Triple fusion occurs inside the embryo sac (female gametophyte) of 
angiosperms.  
It is called so because one male gamete fuses with two polar nuclei (secondary 
nucleus) to form a triploid primary endosperm nucleus. 
Significance of triple fusion: 
Endosperm is a highly nutritive tissue formed as a result of triple fusion and 
provides nourishment to the developing embryo. 
  
10. Ans. Certain regions have been declared as biodiversity ‘hotspots’ by 
environmentalists of the world because these areas are of high endemism and high 
level of species richness. In India, biodiversity hotspots are the Western Ghats and 
the Himalayas. 
 
11. Ans. The eggs are located in the archegonium in moss. For fertilisation to take place, 
antherozoids swim in water to reach the eggs. Moss produces a large number of 
antherozoids to increase the chance of fertilisation.  
  
12. Ans. Adenosine deaminase deficiency can be cured by enzyme replacement therapy, 
but the cure is not permanent even after infusion of genetically engineered 
lymphocytes into a patient as the cells are not immortal. The patient does not have 
functional T-lymphocytes so they cannot provide immune responses against 
invading pathogens.  The patient requires periodic infusion of such genetically 
engineered lymphocytes. However, if the gene isolated from bone marrow cell-
producing ADA is introduced into cells at early embryonic stages, it could prove to 
be a permanent cure. 
 
13. Ans.   
(a) There is a continuous increase in the DDT content in different trophic levels of 
the chain because it accumulates in the fat of the body. 
(b) The phenomenon responsible for the increase in DDT content in different 
trophic levels is called biomagnification. 
 
14. Ans. Bee farms or apiaries are established in an area where abundance of wild 
shrubs, fruit orchards and cultivated crops is available in a 1–2 km radius. 
Availability of flowering plants for the collection of nectar and pollen is called 
pasturage. It plays an important role in the quality and quantity of honey. The 
beehives when kept in the fields of sunflower, Brassica, apple and pear increase the 
pollination efficiency of flowering plants and improve the yields. 
OR 
 
  
 
CBSE XII  |  Biology 
Board Paper – 2010 – Delhi – Set 3 (Solution) 
 
     
When a small amount of curd is added to milk, the fermentation process begins. 
During this process, the lactose sugar of milk is converted to lactic acid which 
acidifies the fermenting medium. The acidic medium helps in coagulating milk 
protein by partially digesting it so that a thick concentrated curd is prepared. 
              Lactic acid bacteria improve its nutritional quality by increasing vitamin B 12. 
 
15. Ans. Aquatic ecosystem: Pond ecosystem 
         Terrestrial ecosystem: Detritus food chain 
 
Aquatic Ecosystem Terrestrial Ecosystem 
It describes the ecosystem in 
water. Example: Pond ecosystem 
 
 
It describes the ecosystem on land. 
Example: Detritus food chain 
 
 
 
16. Ans.  
(a) Formation of gametocytes occurs in the red blood cells of the human host. 
(b) Fertilisation of gametocytes occurs in the mosquito’s stomach. 
 
17. Ans. In Snapdragon, when two types of pure breeding plants bearing red flower and 
white flower are crossed, the F 1 generation plants neither bear red nor white 
flowers. They bear pink flowers exhibiting incomplete dominance.  
On self-breeding, the pink flowers yield a progeny consisting of three types of 
plants—red, pink and white, i.e. 1:2:1, both phenotypically and genotypically.  
So, we conclude that when genotypic and phenotypic ratios are the same, the alleles 
show incomplete dominance. 
  
 
CBSE XII  |  Biology 
Board Paper – 2010 – Delhi – Set 3 (Solution) 
 
     
 
 
18. Ans. The Mediterranean orchid Ophrys has a very strange relationship with its 
insect pollinator Colpa aurea (a hairy wasp). The orchid bears flowers which 
resemble the female wasp in colour, odour and appearance. The male wasp matures 
first and leaves the burrow about four weeks before the females come out for open 
air mating. The inexperienced males try to pseudocopulate the orchid flowers 
presuming them as their female partners and bring about pollination.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
 
CBSE XII  |  Biology 
Board Paper – 2010 – Delhi – Set 3 (Solution) 
 
     
 
SECTION C 
 
19. Ans. Morgan attributed this to the physical association or linkage of the two genes 
and coined the term linkage to describe the physical association of genes on a 
chromosome and the term recombination to describe the generation of non-
parental gene combinations. Morgan and his co-workers also found that even when 
genes were grouped on the same chromosomes, some genes were very tightly 
linked which showed very low recombination, while others were loosely linked and 
showed higher recombination. For example, he found that genes for white and 
yellow body colour were tightly linked and showed only 1.3% recombination, while 
white and miniature wing showed 37.2% recombination.   
 
20. Ans. Process elongation during transcription remains continued until it reaches the 
terminator sequence in the sense DNA strand (3'–AAAAAAT–5'). At this point, 
another protein particle, the rho (?) factor, forms a complex with RNA polymerase. 
This causes the enzyme to go off the DNA track and thus new mRNA is released. 
 
 
21. Ans. A nematode (Meloidogyne incognita) infects the roots of tobacco plants and 
reduces its yield. A method of cellular defence, RNA interference (RNAi) takes place 
in all eukaryotic organisms which involves silencing of a specific mRNA. 
Agrobacterium vectors were used for introducing nematode-specific genes into the 
host plant. The introduction of DNA produces both sense and antisense RNA in the 
host cells. These two RNAs, being complementary to each other, form a double-
stranded RNA which binds to and prevents translation of mRNA (silencing) of the 
nematode. The parasite does not survive in a transgenic host expressing specific 
interfering RNA. The transgenic plant therefore gets itself protected from the 
parasite.