CBSE Biology Past year paper Delhi (Set - 3) Solutions - 2012, Class 12 | Additional Study Material for NEET PDF Download

 Page 1


  
 
CBSE XII  |  Biology 
Board Paper 2012 – Delhi – Set 3 (solutions) 
 
     
CBSE 
Class XII Biology (Theory) 
Board Paper 2012 – Delhi (Set 3) 
SOLUTION 
Time: 3 hrs Total Marks: 70 
 
SECTION A 
 
1. Ans. Spermiogenesis is the process where spermatids undergo a series of 
complex changes resulting in the development of mature spermatozoa, whereas 
spermiation is the release of sperms from the seminiferous tubules of the testes. 
 
2. Ans. Inflated yellow seeds are dominant over constricted green seeds. 
 
3. Ans. This interaction is called commensalism. 
 
4. Ans.  Jaya and Ratna 
 
5. Ans. Phytophagous insects feed on plant sap and other parts of the plant. 
 
6. Ans. Bamboo plants flower only once after a long time, usually after 50–100 
years. They produce a large number of fruits and then die. 
 
7. Ans. Smoking of tobacco releases carbon monoxide in the body, thereby 
depleting the oxygen content which is bound to the haemoglobin. 
 
8. Ans. Living organisms exhibit a large degree of biochemical similarities which 
provide several evidences of common ancestry and evolution of different groups 
of organisms. 
  
Page 2


  
 
CBSE XII  |  Biology 
Board Paper 2012 – Delhi – Set 3 (solutions) 
 
     
CBSE 
Class XII Biology (Theory) 
Board Paper 2012 – Delhi (Set 3) 
SOLUTION 
Time: 3 hrs Total Marks: 70 
 
SECTION A 
 
1. Ans. Spermiogenesis is the process where spermatids undergo a series of 
complex changes resulting in the development of mature spermatozoa, whereas 
spermiation is the release of sperms from the seminiferous tubules of the testes. 
 
2. Ans. Inflated yellow seeds are dominant over constricted green seeds. 
 
3. Ans. This interaction is called commensalism. 
 
4. Ans.  Jaya and Ratna 
 
5. Ans. Phytophagous insects feed on plant sap and other parts of the plant. 
 
6. Ans. Bamboo plants flower only once after a long time, usually after 50–100 
years. They produce a large number of fruits and then die. 
 
7. Ans. Smoking of tobacco releases carbon monoxide in the body, thereby 
depleting the oxygen content which is bound to the haemoglobin. 
 
8. Ans. Living organisms exhibit a large degree of biochemical similarities which 
provide several evidences of common ancestry and evolution of different groups 
of organisms. 
  
  
 
CBSE XII  |  Biology 
Board Paper 2012 – Delhi – Set 3 (solutions) 
 
     
SECTION B 
 
9. Ans. In 1972, Stanley Cohen and Herbert Boyer introduced a piece of gene containing 
foreign DNA into the plasmid of E. coli. They invented the technique of DNA cloning,   
which allowed genes to be transplanted between different biological species. Boyer had 
discovered a restriction enzyme which cut DNA strands at specific positions, allowing 
them to be connected to other DNA. Combining these techniques allowed them to invent 
genetic engineering, to choose the genes to transplant and to choose the position to clone 
them.                                             
10. Ans. 
(a) The chromosome number is haploid in gametes, whereas there is a diploid 
set of chromosomes in meiocytes (gamete mother cells). 
(b) Whiptail lizard is said to be parthenogenetic because the female gamete 
undergoes development to form new organisms without fertilisation. 
 
11. Ans. 
 
 
12. Ans. 
(i) Cysts formed in bacteria and fungi help them to survive in unfavourable 
conditions and germinate in favourable conditions. 
(ii) Higher plants, seeds and vegetative structures germinate to form new plants 
under favourable temperature and moisture conditions, thereby reducing 
the metabolic activity. 
(iii) Animals stay at favourable conditions by going into hibernation during 
winter and aestivation during summer. For example, bears go into 
hibernation and snails go into aestivation. 
(iv) Many zooplankton are known to enter diapause, a stage of suspended 
development under unfavourable conditions. 
 
 
 
 
 
 
Page 3


  
 
CBSE XII  |  Biology 
Board Paper 2012 – Delhi – Set 3 (solutions) 
 
     
CBSE 
Class XII Biology (Theory) 
Board Paper 2012 – Delhi (Set 3) 
SOLUTION 
Time: 3 hrs Total Marks: 70 
 
SECTION A 
 
1. Ans. Spermiogenesis is the process where spermatids undergo a series of 
complex changes resulting in the development of mature spermatozoa, whereas 
spermiation is the release of sperms from the seminiferous tubules of the testes. 
 
2. Ans. Inflated yellow seeds are dominant over constricted green seeds. 
 
3. Ans. This interaction is called commensalism. 
 
4. Ans.  Jaya and Ratna 
 
5. Ans. Phytophagous insects feed on plant sap and other parts of the plant. 
 
6. Ans. Bamboo plants flower only once after a long time, usually after 50–100 
years. They produce a large number of fruits and then die. 
 
7. Ans. Smoking of tobacco releases carbon monoxide in the body, thereby 
depleting the oxygen content which is bound to the haemoglobin. 
 
8. Ans. Living organisms exhibit a large degree of biochemical similarities which 
provide several evidences of common ancestry and evolution of different groups 
of organisms. 
  
  
 
CBSE XII  |  Biology 
Board Paper 2012 – Delhi – Set 3 (solutions) 
 
     
SECTION B 
 
9. Ans. In 1972, Stanley Cohen and Herbert Boyer introduced a piece of gene containing 
foreign DNA into the plasmid of E. coli. They invented the technique of DNA cloning,   
which allowed genes to be transplanted between different biological species. Boyer had 
discovered a restriction enzyme which cut DNA strands at specific positions, allowing 
them to be connected to other DNA. Combining these techniques allowed them to invent 
genetic engineering, to choose the genes to transplant and to choose the position to clone 
them.                                             
10. Ans. 
(a) The chromosome number is haploid in gametes, whereas there is a diploid 
set of chromosomes in meiocytes (gamete mother cells). 
(b) Whiptail lizard is said to be parthenogenetic because the female gamete 
undergoes development to form new organisms without fertilisation. 
 
11. Ans. 
 
 
12. Ans. 
(i) Cysts formed in bacteria and fungi help them to survive in unfavourable 
conditions and germinate in favourable conditions. 
(ii) Higher plants, seeds and vegetative structures germinate to form new plants 
under favourable temperature and moisture conditions, thereby reducing 
the metabolic activity. 
(iii) Animals stay at favourable conditions by going into hibernation during 
winter and aestivation during summer. For example, bears go into 
hibernation and snails go into aestivation. 
(iv) Many zooplankton are known to enter diapause, a stage of suspended 
development under unfavourable conditions. 
 
 
 
 
 
 
  
 
CBSE XII  |  Biology 
Board Paper 2012 – Delhi – Set 3 (solutions) 
 
     
13. Ans. 
(a) DNA ligase enzyme helps in joining the two ends of fragments, having the 
same kind of sticky ends. 
(b) Meloidogyne incognita is a nematode which infects the roots of tobacco plant. 
If Meloidogyne incognita consumes cells with the RNAi gene, the DNA forms 
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 the translation of the mRNA of the nematode. The parasite 
could not survive in a transgenic host expressing specific interfering RNA and 
dies. The transgenic plant therefore gets protected from the parasite. 
 
14. Ans. Sporopollenin is found in the cell wall of plant spores and the exine of 
pollen grains. It is a complex substance of an oxidative polymer of carotenoids. It 
is the most resistant to biological materials which helps in fossilisation of pollen 
grains. 
 
15. Ans.  
(a) Lactic acid bacteria play a very beneficial role in checking disease-causing 
microbes in the stomach. 
(b) It normalises acidity. 
 
      OR 
Methanogens such as Methanobacterium grow anaerobically on the excreta of 
cattle and produce a large amount of methane gas which is the main component 
of biogas. CO 2 and H 2 are also produced along with methane gas. 
 
16. Ans.   
(a) Entamoeba histolytica causes amoebic dysentery in humans (amoebiasis). 
(b) Two diagnostic symptoms of this disease are 
(i) Constipation and abdominal pain 
(ii) Stools with excessive mucus and blood clots 
(c) Amoebiasis is transmitted through dirty drinking water and food 
contaminated by faecal matter.  
 
17. Ans. 
(a) In the thymus, immature lymphocytes differentiate into antigen-sensitive 
lymphocytes. After maturation in the thymus, they migrate to secondary 
lymphoid organs.   
(b) The cells released from the thymus are called T-lymphocytes. These 
lymphocytes are responsible for cell-mediated immunity which defends the 
body against virus, fungi and some bacteria which enter the host cells. Helper 
T-cells stimulate B-cells to produce antibodies, and killer T-cells migrate to 
the site of infection. 
Page 4


  
 
CBSE XII  |  Biology 
Board Paper 2012 – Delhi – Set 3 (solutions) 
 
     
CBSE 
Class XII Biology (Theory) 
Board Paper 2012 – Delhi (Set 3) 
SOLUTION 
Time: 3 hrs Total Marks: 70 
 
SECTION A 
 
1. Ans. Spermiogenesis is the process where spermatids undergo a series of 
complex changes resulting in the development of mature spermatozoa, whereas 
spermiation is the release of sperms from the seminiferous tubules of the testes. 
 
2. Ans. Inflated yellow seeds are dominant over constricted green seeds. 
 
3. Ans. This interaction is called commensalism. 
 
4. Ans.  Jaya and Ratna 
 
5. Ans. Phytophagous insects feed on plant sap and other parts of the plant. 
 
6. Ans. Bamboo plants flower only once after a long time, usually after 50–100 
years. They produce a large number of fruits and then die. 
 
7. Ans. Smoking of tobacco releases carbon monoxide in the body, thereby 
depleting the oxygen content which is bound to the haemoglobin. 
 
8. Ans. Living organisms exhibit a large degree of biochemical similarities which 
provide several evidences of common ancestry and evolution of different groups 
of organisms. 
  
  
 
CBSE XII  |  Biology 
Board Paper 2012 – Delhi – Set 3 (solutions) 
 
     
SECTION B 
 
9. Ans. In 1972, Stanley Cohen and Herbert Boyer introduced a piece of gene containing 
foreign DNA into the plasmid of E. coli. They invented the technique of DNA cloning,   
which allowed genes to be transplanted between different biological species. Boyer had 
discovered a restriction enzyme which cut DNA strands at specific positions, allowing 
them to be connected to other DNA. Combining these techniques allowed them to invent 
genetic engineering, to choose the genes to transplant and to choose the position to clone 
them.                                             
10. Ans. 
(a) The chromosome number is haploid in gametes, whereas there is a diploid 
set of chromosomes in meiocytes (gamete mother cells). 
(b) Whiptail lizard is said to be parthenogenetic because the female gamete 
undergoes development to form new organisms without fertilisation. 
 
11. Ans. 
 
 
12. Ans. 
(i) Cysts formed in bacteria and fungi help them to survive in unfavourable 
conditions and germinate in favourable conditions. 
(ii) Higher plants, seeds and vegetative structures germinate to form new plants 
under favourable temperature and moisture conditions, thereby reducing 
the metabolic activity. 
(iii) Animals stay at favourable conditions by going into hibernation during 
winter and aestivation during summer. For example, bears go into 
hibernation and snails go into aestivation. 
(iv) Many zooplankton are known to enter diapause, a stage of suspended 
development under unfavourable conditions. 
 
 
 
 
 
 
  
 
CBSE XII  |  Biology 
Board Paper 2012 – Delhi – Set 3 (solutions) 
 
     
13. Ans. 
(a) DNA ligase enzyme helps in joining the two ends of fragments, having the 
same kind of sticky ends. 
(b) Meloidogyne incognita is a nematode which infects the roots of tobacco plant. 
If Meloidogyne incognita consumes cells with the RNAi gene, the DNA forms 
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 the translation of the mRNA of the nematode. The parasite 
could not survive in a transgenic host expressing specific interfering RNA and 
dies. The transgenic plant therefore gets protected from the parasite. 
 
14. Ans. Sporopollenin is found in the cell wall of plant spores and the exine of 
pollen grains. It is a complex substance of an oxidative polymer of carotenoids. It 
is the most resistant to biological materials which helps in fossilisation of pollen 
grains. 
 
15. Ans.  
(a) Lactic acid bacteria play a very beneficial role in checking disease-causing 
microbes in the stomach. 
(b) It normalises acidity. 
 
      OR 
Methanogens such as Methanobacterium grow anaerobically on the excreta of 
cattle and produce a large amount of methane gas which is the main component 
of biogas. CO 2 and H 2 are also produced along with methane gas. 
 
16. Ans.   
(a) Entamoeba histolytica causes amoebic dysentery in humans (amoebiasis). 
(b) Two diagnostic symptoms of this disease are 
(i) Constipation and abdominal pain 
(ii) Stools with excessive mucus and blood clots 
(c) Amoebiasis is transmitted through dirty drinking water and food 
contaminated by faecal matter.  
 
17. Ans. 
(a) In the thymus, immature lymphocytes differentiate into antigen-sensitive 
lymphocytes. After maturation in the thymus, they migrate to secondary 
lymphoid organs.   
(b) The cells released from the thymus are called T-lymphocytes. These 
lymphocytes are responsible for cell-mediated immunity which defends the 
body against virus, fungi and some bacteria which enter the host cells. Helper 
T-cells stimulate B-cells to produce antibodies, and killer T-cells migrate to 
the site of infection. 
  
 
CBSE XII  |  Biology 
Board Paper 2012 – Delhi – Set 3 (solutions) 
 
     
18. Ans. The clown fish protects itself from predators by attaching itself to the body 
of sea anemone which possesses stinging tentacles. The sea anemone does not 
get any benefit from the clown fish. This interaction is called commensalism as 
one species is benefited, whereas the other species is neither harmed nor 
benefited. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Page 5


  
 
CBSE XII  |  Biology 
Board Paper 2012 – Delhi – Set 3 (solutions) 
 
     
CBSE 
Class XII Biology (Theory) 
Board Paper 2012 – Delhi (Set 3) 
SOLUTION 
Time: 3 hrs Total Marks: 70 
 
SECTION A 
 
1. Ans. Spermiogenesis is the process where spermatids undergo a series of 
complex changes resulting in the development of mature spermatozoa, whereas 
spermiation is the release of sperms from the seminiferous tubules of the testes. 
 
2. Ans. Inflated yellow seeds are dominant over constricted green seeds. 
 
3. Ans. This interaction is called commensalism. 
 
4. Ans.  Jaya and Ratna 
 
5. Ans. Phytophagous insects feed on plant sap and other parts of the plant. 
 
6. Ans. Bamboo plants flower only once after a long time, usually after 50–100 
years. They produce a large number of fruits and then die. 
 
7. Ans. Smoking of tobacco releases carbon monoxide in the body, thereby 
depleting the oxygen content which is bound to the haemoglobin. 
 
8. Ans. Living organisms exhibit a large degree of biochemical similarities which 
provide several evidences of common ancestry and evolution of different groups 
of organisms. 
  
  
 
CBSE XII  |  Biology 
Board Paper 2012 – Delhi – Set 3 (solutions) 
 
     
SECTION B 
 
9. Ans. In 1972, Stanley Cohen and Herbert Boyer introduced a piece of gene containing 
foreign DNA into the plasmid of E. coli. They invented the technique of DNA cloning,   
which allowed genes to be transplanted between different biological species. Boyer had 
discovered a restriction enzyme which cut DNA strands at specific positions, allowing 
them to be connected to other DNA. Combining these techniques allowed them to invent 
genetic engineering, to choose the genes to transplant and to choose the position to clone 
them.                                             
10. Ans. 
(a) The chromosome number is haploid in gametes, whereas there is a diploid 
set of chromosomes in meiocytes (gamete mother cells). 
(b) Whiptail lizard is said to be parthenogenetic because the female gamete 
undergoes development to form new organisms without fertilisation. 
 
11. Ans. 
 
 
12. Ans. 
(i) Cysts formed in bacteria and fungi help them to survive in unfavourable 
conditions and germinate in favourable conditions. 
(ii) Higher plants, seeds and vegetative structures germinate to form new plants 
under favourable temperature and moisture conditions, thereby reducing 
the metabolic activity. 
(iii) Animals stay at favourable conditions by going into hibernation during 
winter and aestivation during summer. For example, bears go into 
hibernation and snails go into aestivation. 
(iv) Many zooplankton are known to enter diapause, a stage of suspended 
development under unfavourable conditions. 
 
 
 
 
 
 
  
 
CBSE XII  |  Biology 
Board Paper 2012 – Delhi – Set 3 (solutions) 
 
     
13. Ans. 
(a) DNA ligase enzyme helps in joining the two ends of fragments, having the 
same kind of sticky ends. 
(b) Meloidogyne incognita is a nematode which infects the roots of tobacco plant. 
If Meloidogyne incognita consumes cells with the RNAi gene, the DNA forms 
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 the translation of the mRNA of the nematode. The parasite 
could not survive in a transgenic host expressing specific interfering RNA and 
dies. The transgenic plant therefore gets protected from the parasite. 
 
14. Ans. Sporopollenin is found in the cell wall of plant spores and the exine of 
pollen grains. It is a complex substance of an oxidative polymer of carotenoids. It 
is the most resistant to biological materials which helps in fossilisation of pollen 
grains. 
 
15. Ans.  
(a) Lactic acid bacteria play a very beneficial role in checking disease-causing 
microbes in the stomach. 
(b) It normalises acidity. 
 
      OR 
Methanogens such as Methanobacterium grow anaerobically on the excreta of 
cattle and produce a large amount of methane gas which is the main component 
of biogas. CO 2 and H 2 are also produced along with methane gas. 
 
16. Ans.   
(a) Entamoeba histolytica causes amoebic dysentery in humans (amoebiasis). 
(b) Two diagnostic symptoms of this disease are 
(i) Constipation and abdominal pain 
(ii) Stools with excessive mucus and blood clots 
(c) Amoebiasis is transmitted through dirty drinking water and food 
contaminated by faecal matter.  
 
17. Ans. 
(a) In the thymus, immature lymphocytes differentiate into antigen-sensitive 
lymphocytes. After maturation in the thymus, they migrate to secondary 
lymphoid organs.   
(b) The cells released from the thymus are called T-lymphocytes. These 
lymphocytes are responsible for cell-mediated immunity which defends the 
body against virus, fungi and some bacteria which enter the host cells. Helper 
T-cells stimulate B-cells to produce antibodies, and killer T-cells migrate to 
the site of infection. 
  
 
CBSE XII  |  Biology 
Board Paper 2012 – Delhi – Set 3 (solutions) 
 
     
18. Ans. The clown fish protects itself from predators by attaching itself to the body 
of sea anemone which possesses stinging tentacles. The sea anemone does not 
get any benefit from the clown fish. This interaction is called commensalism as 
one species is benefited, whereas the other species is neither harmed nor 
benefited. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
 
CBSE XII  |  Biology 
Board Paper 2012 – Delhi – Set 3 (solutions) 
 
     
SECTION C 
19. Ans. 
(a)  
 
(b) The RNA strand transcribed from the above transcription unit: 
 
OR 
Lactose acts as an inducer in lac operon. It binds to the repressor and forms a 
complex, inducer–repressor, which remains unable to bind the operator. The 
RNA polymerase now becomes free to join with the promoter and the 
operator is switched on. This initiates the transcription of the structural 
genes, producing the three polypeptides.  
In the absence of lactose, no inactivation of repressor occurs, and hence, the           
repressor binds to the operator region of the operon, thus preventing RNA 
polymerase from transcribing the operon. This inactivates the production of  
structural genes in E. coli.  
 
20. Ans. 
(a) The seminal vesicle constitutes seminal plasma which is rich in fructose, 
calcium and enzymes. It helps facilitate the motility of sperms. 
(b) The scutellum is the cotyledon of the monocot seed and acts as a passage for 
the movement of nutrients from the endosperm to the developing embryo. 
(c) The acrosome of the human sperm contains hydrolytic enzymes which help 
in the penetration of the egg during fertilisation. 
 
21. Ans. 
(a) A represents female Anopheles mosquito which acts as a vector for 
plasmodium. 
(b) Event C represents the process of fertilisation which takes place inside the 
intestine of the mosquito. 
(c) Organ B is the salivary gland of the mosquito and the cells removed are 
sporozoites.