CBSE Biology Past year paper Delhi (Set - 1) Solutions - 2012, Class 12 | Additional Study Material for NEET PDF Download

 Page 1


  
 
CBSE XII  |  Biology 
Board Paper 2012 – Delhi – Set 1 (Solution) 
 
     
CBSE 
Class XII Biology (Theory) 
Board Paper 2012 – Delhi (Set 1) 
SOLUTION 
Time: 3 hrs Total Marks: 70 
 
SECTION A 
1. Ans. Neelakurinji (Strobilanthes kunthiana) is a shrub which grows in the 
grasslands of the Western Ghats in South India. The main phenomenon of this 
flowering plant is that it produces flowers after a gap of 12 years. 
 
2. Ans. Smoking of tobacco releases carbon monoxide in the body, thereby 
depleting the oxygen content which is bound to haemoglobin. 
 
3.  Ans. Inflated yellow seeds are dominant over constricted green seeds. 
4. Ans. Eichhornia crassipes is called ‘Terror of Bengal’ because it grows very fast in 
the water body. It increases the oxygen demand in low quantity of light, thereby 
causing the death of aquatic organisms. 
 
5. Ans. Sertoli cells are located in the germinal epithelium of seminiferous tubules. 
They provide nourishment for the growing spermatozoa. 
 
6. Ans. 
(a) Sonalika is the semi-dwarf variety of wheat which is high-yielding and 
disease resistant. 
(b) Zonkey is an interspecific hybrid mammal which is a cross between zebra 
and donkey. 
 
7. Ans. Bat wings and butterfly wings are analogous to each other because both are 
structurally different but functionally same. They perform similar functions. 
Evolutionary relationships can be inferred from the above reference.  
 
8. Ans. Phytophagous insects feed on plant sap and other parts of plants. 
  
Page 2


  
 
CBSE XII  |  Biology 
Board Paper 2012 – Delhi – Set 1 (Solution) 
 
     
CBSE 
Class XII Biology (Theory) 
Board Paper 2012 – Delhi (Set 1) 
SOLUTION 
Time: 3 hrs Total Marks: 70 
 
SECTION A 
1. Ans. Neelakurinji (Strobilanthes kunthiana) is a shrub which grows in the 
grasslands of the Western Ghats in South India. The main phenomenon of this 
flowering plant is that it produces flowers after a gap of 12 years. 
 
2. Ans. Smoking of tobacco releases carbon monoxide in the body, thereby 
depleting the oxygen content which is bound to haemoglobin. 
 
3.  Ans. Inflated yellow seeds are dominant over constricted green seeds. 
4. Ans. Eichhornia crassipes is called ‘Terror of Bengal’ because it grows very fast in 
the water body. It increases the oxygen demand in low quantity of light, thereby 
causing the death of aquatic organisms. 
 
5. Ans. Sertoli cells are located in the germinal epithelium of seminiferous tubules. 
They provide nourishment for the growing spermatozoa. 
 
6. Ans. 
(a) Sonalika is the semi-dwarf variety of wheat which is high-yielding and 
disease resistant. 
(b) Zonkey is an interspecific hybrid mammal which is a cross between zebra 
and donkey. 
 
7. Ans. Bat wings and butterfly wings are analogous to each other because both are 
structurally different but functionally same. They perform similar functions. 
Evolutionary relationships can be inferred from the above reference.  
 
8. Ans. Phytophagous insects feed on plant sap and other parts of plants. 
  
  
 
CBSE XII  |  Biology 
Board Paper 2012 – Delhi – Set 1 (Solution) 
 
     
SECTION B 
9. Ans.                                           
 
 
10. 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. 
 
11. 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 have entered the host 
cells. Helper T-cells stimulate B-cells to produce antibodies, and killer T-cells 
migrate to the site of infection. 
 
12. Ans.  In 1972, Stanley Cohen and Herbert Boyer invented the technique of DNA 
cloning,   which allowed genes to be transplanted between different biological 
species. It was the beginning of genetic modification techniques. Cohen worked 
on the ways to isolate genes using plasmids and clone them into E. coli bacteria. 
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.   
 
13. 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 3


  
 
CBSE XII  |  Biology 
Board Paper 2012 – Delhi – Set 1 (Solution) 
 
     
CBSE 
Class XII Biology (Theory) 
Board Paper 2012 – Delhi (Set 1) 
SOLUTION 
Time: 3 hrs Total Marks: 70 
 
SECTION A 
1. Ans. Neelakurinji (Strobilanthes kunthiana) is a shrub which grows in the 
grasslands of the Western Ghats in South India. The main phenomenon of this 
flowering plant is that it produces flowers after a gap of 12 years. 
 
2. Ans. Smoking of tobacco releases carbon monoxide in the body, thereby 
depleting the oxygen content which is bound to haemoglobin. 
 
3.  Ans. Inflated yellow seeds are dominant over constricted green seeds. 
4. Ans. Eichhornia crassipes is called ‘Terror of Bengal’ because it grows very fast in 
the water body. It increases the oxygen demand in low quantity of light, thereby 
causing the death of aquatic organisms. 
 
5. Ans. Sertoli cells are located in the germinal epithelium of seminiferous tubules. 
They provide nourishment for the growing spermatozoa. 
 
6. Ans. 
(a) Sonalika is the semi-dwarf variety of wheat which is high-yielding and 
disease resistant. 
(b) Zonkey is an interspecific hybrid mammal which is a cross between zebra 
and donkey. 
 
7. Ans. Bat wings and butterfly wings are analogous to each other because both are 
structurally different but functionally same. They perform similar functions. 
Evolutionary relationships can be inferred from the above reference.  
 
8. Ans. Phytophagous insects feed on plant sap and other parts of plants. 
  
  
 
CBSE XII  |  Biology 
Board Paper 2012 – Delhi – Set 1 (Solution) 
 
     
SECTION B 
9. Ans.                                           
 
 
10. 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. 
 
11. 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 have entered the host 
cells. Helper T-cells stimulate B-cells to produce antibodies, and killer T-cells 
migrate to the site of infection. 
 
12. Ans.  In 1972, Stanley Cohen and Herbert Boyer invented the technique of DNA 
cloning,   which allowed genes to be transplanted between different biological 
species. It was the beginning of genetic modification techniques. Cohen worked 
on the ways to isolate genes using plasmids and clone them into E. coli bacteria. 
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.   
 
13. 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 1 (Solution) 
 
     
 
14. Ans. 
(a) The chromosome number is haploid in gametes, whereas there is a diploid 
set of chromosomes in the meiocyte (gamete mother cell). 
(b) Whiptail lizard is said to be parthenogenetic because the female gamete 
undergoes development to form new organisms without fertilisation. 
 
15. Ans. Smack is popularly called ‘Heroine’. It is derived from the latex of the poppy 
plant Papaver somniferum. It is a stronger analgesic than morphine. It reduces 
heartbeat, blood pressure and increases blood sugar.  
OR 
Rhizobium lives in the root nodules of leguminous plants. This association is 
mutually beneficial, so Rhizobium is called symbiotic bacteria. Rhizobium gets 
food and shelter from the leguminous plant and the leguminous plant gets 
nitrogen in return. Because Rhizobium can fix atmospheric nitrogen, it acts as a 
biofertiliser. 
 
16. 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. 
 
17. 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 4


  
 
CBSE XII  |  Biology 
Board Paper 2012 – Delhi – Set 1 (Solution) 
 
     
CBSE 
Class XII Biology (Theory) 
Board Paper 2012 – Delhi (Set 1) 
SOLUTION 
Time: 3 hrs Total Marks: 70 
 
SECTION A 
1. Ans. Neelakurinji (Strobilanthes kunthiana) is a shrub which grows in the 
grasslands of the Western Ghats in South India. The main phenomenon of this 
flowering plant is that it produces flowers after a gap of 12 years. 
 
2. Ans. Smoking of tobacco releases carbon monoxide in the body, thereby 
depleting the oxygen content which is bound to haemoglobin. 
 
3.  Ans. Inflated yellow seeds are dominant over constricted green seeds. 
4. Ans. Eichhornia crassipes is called ‘Terror of Bengal’ because it grows very fast in 
the water body. It increases the oxygen demand in low quantity of light, thereby 
causing the death of aquatic organisms. 
 
5. Ans. Sertoli cells are located in the germinal epithelium of seminiferous tubules. 
They provide nourishment for the growing spermatozoa. 
 
6. Ans. 
(a) Sonalika is the semi-dwarf variety of wheat which is high-yielding and 
disease resistant. 
(b) Zonkey is an interspecific hybrid mammal which is a cross between zebra 
and donkey. 
 
7. Ans. Bat wings and butterfly wings are analogous to each other because both are 
structurally different but functionally same. They perform similar functions. 
Evolutionary relationships can be inferred from the above reference.  
 
8. Ans. Phytophagous insects feed on plant sap and other parts of plants. 
  
  
 
CBSE XII  |  Biology 
Board Paper 2012 – Delhi – Set 1 (Solution) 
 
     
SECTION B 
9. Ans.                                           
 
 
10. 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. 
 
11. 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 have entered the host 
cells. Helper T-cells stimulate B-cells to produce antibodies, and killer T-cells 
migrate to the site of infection. 
 
12. Ans.  In 1972, Stanley Cohen and Herbert Boyer invented the technique of DNA 
cloning,   which allowed genes to be transplanted between different biological 
species. It was the beginning of genetic modification techniques. Cohen worked 
on the ways to isolate genes using plasmids and clone them into E. coli bacteria. 
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.   
 
13. 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 1 (Solution) 
 
     
 
14. Ans. 
(a) The chromosome number is haploid in gametes, whereas there is a diploid 
set of chromosomes in the meiocyte (gamete mother cell). 
(b) Whiptail lizard is said to be parthenogenetic because the female gamete 
undergoes development to form new organisms without fertilisation. 
 
15. Ans. Smack is popularly called ‘Heroine’. It is derived from the latex of the poppy 
plant Papaver somniferum. It is a stronger analgesic than morphine. It reduces 
heartbeat, blood pressure and increases blood sugar.  
OR 
Rhizobium lives in the root nodules of leguminous plants. This association is 
mutually beneficial, so Rhizobium is called symbiotic bacteria. Rhizobium gets 
food and shelter from the leguminous plant and the leguminous plant gets 
nitrogen in return. Because Rhizobium can fix atmospheric nitrogen, it acts as a 
biofertiliser. 
 
16. 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. 
 
17. 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 1 (Solution) 
 
     
 
18.  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.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Page 5


  
 
CBSE XII  |  Biology 
Board Paper 2012 – Delhi – Set 1 (Solution) 
 
     
CBSE 
Class XII Biology (Theory) 
Board Paper 2012 – Delhi (Set 1) 
SOLUTION 
Time: 3 hrs Total Marks: 70 
 
SECTION A 
1. Ans. Neelakurinji (Strobilanthes kunthiana) is a shrub which grows in the 
grasslands of the Western Ghats in South India. The main phenomenon of this 
flowering plant is that it produces flowers after a gap of 12 years. 
 
2. Ans. Smoking of tobacco releases carbon monoxide in the body, thereby 
depleting the oxygen content which is bound to haemoglobin. 
 
3.  Ans. Inflated yellow seeds are dominant over constricted green seeds. 
4. Ans. Eichhornia crassipes is called ‘Terror of Bengal’ because it grows very fast in 
the water body. It increases the oxygen demand in low quantity of light, thereby 
causing the death of aquatic organisms. 
 
5. Ans. Sertoli cells are located in the germinal epithelium of seminiferous tubules. 
They provide nourishment for the growing spermatozoa. 
 
6. Ans. 
(a) Sonalika is the semi-dwarf variety of wheat which is high-yielding and 
disease resistant. 
(b) Zonkey is an interspecific hybrid mammal which is a cross between zebra 
and donkey. 
 
7. Ans. Bat wings and butterfly wings are analogous to each other because both are 
structurally different but functionally same. They perform similar functions. 
Evolutionary relationships can be inferred from the above reference.  
 
8. Ans. Phytophagous insects feed on plant sap and other parts of plants. 
  
  
 
CBSE XII  |  Biology 
Board Paper 2012 – Delhi – Set 1 (Solution) 
 
     
SECTION B 
9. Ans.                                           
 
 
10. 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. 
 
11. 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 have entered the host 
cells. Helper T-cells stimulate B-cells to produce antibodies, and killer T-cells 
migrate to the site of infection. 
 
12. Ans.  In 1972, Stanley Cohen and Herbert Boyer invented the technique of DNA 
cloning,   which allowed genes to be transplanted between different biological 
species. It was the beginning of genetic modification techniques. Cohen worked 
on the ways to isolate genes using plasmids and clone them into E. coli bacteria. 
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.   
 
13. 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 1 (Solution) 
 
     
 
14. Ans. 
(a) The chromosome number is haploid in gametes, whereas there is a diploid 
set of chromosomes in the meiocyte (gamete mother cell). 
(b) Whiptail lizard is said to be parthenogenetic because the female gamete 
undergoes development to form new organisms without fertilisation. 
 
15. Ans. Smack is popularly called ‘Heroine’. It is derived from the latex of the poppy 
plant Papaver somniferum. It is a stronger analgesic than morphine. It reduces 
heartbeat, blood pressure and increases blood sugar.  
OR 
Rhizobium lives in the root nodules of leguminous plants. This association is 
mutually beneficial, so Rhizobium is called symbiotic bacteria. Rhizobium gets 
food and shelter from the leguminous plant and the leguminous plant gets 
nitrogen in return. Because Rhizobium can fix atmospheric nitrogen, it acts as a 
biofertiliser. 
 
16. 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. 
 
17. 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 1 (Solution) 
 
     
 
18.  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.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
 
CBSE XII  |  Biology 
Board Paper 2012 – Delhi – Set 1 (Solution) 
 
     
 
SECTION C 
 
19. Ans. RNA is the first genetic material because 
(i) RNA can store genetic information like DNA and acts as an enzyme to 
catalyse reactions. 
(ii) RNA is involved in metabolism, genetic translation and transcription. 
(iii) RNA is capable of self-replication. 
OR 
(a) RNA polymerase in prokaryotes and RNA polymerase III in eukaryotes are 
responsible for transcription of tRNA. Initiator tRNA gets linked with 
formulated methionine in prokaryotes and methionine in eukaryotes. 
(b) Initiator tRNA combines with methionine in the presence of amino acyl-tRNA 
enzyme resulting in the formation of charged tRNA. This initiator tRNA 
combines with two subunits of ribosomes and mRNA forming a translation 
initiation complex. First, mRNA attaches to a small subunit of ribosome and 
charged initiator tRNA. The initiator tRNA joins the initiation codon AUG and 
signals the start of translation. Now, the large subunit of ribosome combines 
with the small subunit. Initiator tRNA lies at the P site of the ribosome. 
 
20. Ans. The theory of biogenesis was proposed by Louis Pasteur. He proposed that 
all living things arise from pre-existing life. These cells further originated from 
organic compounds. So life could have come from non-living matter and these 
were formed from inorganic constituents. 
Urey and Miller in 1953 demonstrated that the electrical discharges or heat 
energy can form complex organic substances from the mixture of water (H 2O), 
methane (CH 4), ammonia (NH 3) and hydrogen (H 2). The chemicals were all 
sealed inside a sterile array of glass flasks and flasks connected in a loop, with 
one flask half-full of liquid water and another flask containing a pair of 
electrodes. The liquid water was heated to induce evaporation. Sparks were 
fired between the electrodes to simulate lightning through the atmosphere and 
water vapour, and then the atmosphere was cooled again so that the water could 
condense and trickle back into the first flask in a continuous cycle. They 
observed the production of acetic acid, urea, fatty acids, lactic acid and amino 
acids like glycine, alanine and aspartic acid. Other investigators observed the 
formation of sugars and nitrogen bases by using UV light. Hence, this experiment 
supported that life has evolved from pre-existing non-living organic molecules.