CBSE Biology Past year paper Delhi (Set - 3) Solutions - 2013, Class 12 | Additional Study Material for NEET PDF Download

 Page 1


  
 
CBSE XII  |  Biology 
Board Paper 2013 – Delhi – Set 3 (Solution) 
 
     
CBSE 
Class XII Biology (Theory) 
Board Paper 2013 – Delhi (Set 3) 
SOLUTION 
Time: 3 hrs Total Marks: 70 
 
SECTION A 
1. Ans. Cellulase enzyme is needed for isolating genetic material from plant cells 
and not from animal cells because it breaks down the plant cell wall made of 
cellulose. Animal cells do not have a cell wall. 
2. Ans. MOET stands for multiple ovulation embryo transfer technology which is 
a programme for herd improvement. The importance of MOET is to increase 
herd size in a short time.  
3. Ans. An anther with malfunctioning tapetum often fails to produce viable 
gametophytes because the tapetum provides nutritive materials to the 
dividing microsporocytes. 
4. Ans. Sharing of injection needles between two individuals is not 
recommended because it causes fatal and incurable diseases such as AIDS and 
hepatitis. 
5. Ans. DNA-dependent DNA polymerase is the enzyme which polymerises the 
DNA strand in the 5' to 3' direction resulting in continuous and discontinuous 
replication. 
6. Ans. Sweet potato tubers and potato tubers are the result of convergent 
evolution. It is because the basic structure of the sweet potato tuber and 
potato tuber is different, but their function is similar. Both of them are meant 
for storage of food and vegetative reproduction. 
7. Ans. The equation of net primary productivity of an ecosystem is 
       NPP = GPP - R 
              where NPP = net primary productivity 
         GPP = gross primary productivity 
         R = respiratory rate 
8. Ans.  
(a) 50,000 different strains of rice: Genetic diversity 
(b) Estuarine and alpine meadows: Ecological diversity 
 
 
 
 
 
 
 
Page 2


  
 
CBSE XII  |  Biology 
Board Paper 2013 – Delhi – Set 3 (Solution) 
 
     
CBSE 
Class XII Biology (Theory) 
Board Paper 2013 – Delhi (Set 3) 
SOLUTION 
Time: 3 hrs Total Marks: 70 
 
SECTION A 
1. Ans. Cellulase enzyme is needed for isolating genetic material from plant cells 
and not from animal cells because it breaks down the plant cell wall made of 
cellulose. Animal cells do not have a cell wall. 
2. Ans. MOET stands for multiple ovulation embryo transfer technology which is 
a programme for herd improvement. The importance of MOET is to increase 
herd size in a short time.  
3. Ans. An anther with malfunctioning tapetum often fails to produce viable 
gametophytes because the tapetum provides nutritive materials to the 
dividing microsporocytes. 
4. Ans. Sharing of injection needles between two individuals is not 
recommended because it causes fatal and incurable diseases such as AIDS and 
hepatitis. 
5. Ans. DNA-dependent DNA polymerase is the enzyme which polymerises the 
DNA strand in the 5' to 3' direction resulting in continuous and discontinuous 
replication. 
6. Ans. Sweet potato tubers and potato tubers are the result of convergent 
evolution. It is because the basic structure of the sweet potato tuber and 
potato tuber is different, but their function is similar. Both of them are meant 
for storage of food and vegetative reproduction. 
7. Ans. The equation of net primary productivity of an ecosystem is 
       NPP = GPP - R 
              where NPP = net primary productivity 
         GPP = gross primary productivity 
         R = respiratory rate 
8. Ans.  
(a) 50,000 different strains of rice: Genetic diversity 
(b) Estuarine and alpine meadows: Ecological diversity 
 
 
 
 
 
 
 
  
 
CBSE XII  |  Biology 
Board Paper 2013 – Delhi – Set 3 (Solution) 
 
     
SECTION B 
 
9. Ans. Small animals are cold-blooded organisms. They do not have constant 
body temperature and need to spend energy to generate heat through 
metabolism. So, they are rarely found in the polar regions. 
 
10.  Ans. The pyramid of energy is a graphical representation of the amount of 
accumulated energy per unit area in different trophic levels of a food chain. 
An energy pyramid is always upright because there is a gradual decrease in 
energy at successive trophic levels. This happens because according to the 
10% law of energy transfer—only 10% of the total energy is transferred from 
one trophic level to another.   
 
11.   Ans. 
(i) PCR: Polymerase chain reaction  
Application of PCR: It is useful to detect genetic disease in the foetus 
before birth. 
(ii) ELISA: Enzyme-linked immunosorbent assay  
Application of ELISA: It is useful in the early diagnosis of diseases using 
antigen–antibody interactions.  
OR 
(a) Exonucleases remove nucleotides from the ends of the DNA, whereas 
endonucleases make cuts at specific positions within the DNA. 
(b) Each restriction endonuclease inspects the DNA molecule in search of a 
specific recognition sequence. When it gets its specific recognition 
sequence, it binds to the site and cuts each of the two strands of the double 
helix at specific points by hydrolysing the phosphodiester backbones. 
 
12. Ans.  
Two sources of e-wastes are 
(i) Parts of computers and television sets 
(ii) Smartphones and parts of air conditioners and refrigerators 
Two ways for disposal of e-wastes are 
(i) Recycling of e-wastes 
(ii) Incineration of e-wastes, i.e. burning e-wastes completely into ashes 
 
13. Ans.  The autogamous flowers are open and can be subjected to cross-
pollination. Various agents which help in cross-pollination are wind, insects 
and birds. However, the steps which ensure cross-pollination in an 
autogamous flower involve artificial hybridisation techniques called 
emasculation and bagging. Removal of stamens or anthers of a bisexual flower 
without affecting the female reproductive organs is called emasculation. The 
Page 3


  
 
CBSE XII  |  Biology 
Board Paper 2013 – Delhi – Set 3 (Solution) 
 
     
CBSE 
Class XII Biology (Theory) 
Board Paper 2013 – Delhi (Set 3) 
SOLUTION 
Time: 3 hrs Total Marks: 70 
 
SECTION A 
1. Ans. Cellulase enzyme is needed for isolating genetic material from plant cells 
and not from animal cells because it breaks down the plant cell wall made of 
cellulose. Animal cells do not have a cell wall. 
2. Ans. MOET stands for multiple ovulation embryo transfer technology which is 
a programme for herd improvement. The importance of MOET is to increase 
herd size in a short time.  
3. Ans. An anther with malfunctioning tapetum often fails to produce viable 
gametophytes because the tapetum provides nutritive materials to the 
dividing microsporocytes. 
4. Ans. Sharing of injection needles between two individuals is not 
recommended because it causes fatal and incurable diseases such as AIDS and 
hepatitis. 
5. Ans. DNA-dependent DNA polymerase is the enzyme which polymerises the 
DNA strand in the 5' to 3' direction resulting in continuous and discontinuous 
replication. 
6. Ans. Sweet potato tubers and potato tubers are the result of convergent 
evolution. It is because the basic structure of the sweet potato tuber and 
potato tuber is different, but their function is similar. Both of them are meant 
for storage of food and vegetative reproduction. 
7. Ans. The equation of net primary productivity of an ecosystem is 
       NPP = GPP - R 
              where NPP = net primary productivity 
         GPP = gross primary productivity 
         R = respiratory rate 
8. Ans.  
(a) 50,000 different strains of rice: Genetic diversity 
(b) Estuarine and alpine meadows: Ecological diversity 
 
 
 
 
 
 
 
  
 
CBSE XII  |  Biology 
Board Paper 2013 – Delhi – Set 3 (Solution) 
 
     
SECTION B 
 
9. Ans. Small animals are cold-blooded organisms. They do not have constant 
body temperature and need to spend energy to generate heat through 
metabolism. So, they are rarely found in the polar regions. 
 
10.  Ans. The pyramid of energy is a graphical representation of the amount of 
accumulated energy per unit area in different trophic levels of a food chain. 
An energy pyramid is always upright because there is a gradual decrease in 
energy at successive trophic levels. This happens because according to the 
10% law of energy transfer—only 10% of the total energy is transferred from 
one trophic level to another.   
 
11.   Ans. 
(i) PCR: Polymerase chain reaction  
Application of PCR: It is useful to detect genetic disease in the foetus 
before birth. 
(ii) ELISA: Enzyme-linked immunosorbent assay  
Application of ELISA: It is useful in the early diagnosis of diseases using 
antigen–antibody interactions.  
OR 
(a) Exonucleases remove nucleotides from the ends of the DNA, whereas 
endonucleases make cuts at specific positions within the DNA. 
(b) Each restriction endonuclease inspects the DNA molecule in search of a 
specific recognition sequence. When it gets its specific recognition 
sequence, it binds to the site and cuts each of the two strands of the double 
helix at specific points by hydrolysing the phosphodiester backbones. 
 
12. Ans.  
Two sources of e-wastes are 
(i) Parts of computers and television sets 
(ii) Smartphones and parts of air conditioners and refrigerators 
Two ways for disposal of e-wastes are 
(i) Recycling of e-wastes 
(ii) Incineration of e-wastes, i.e. burning e-wastes completely into ashes 
 
13. Ans.  The autogamous flowers are open and can be subjected to cross-
pollination. Various agents which help in cross-pollination are wind, insects 
and birds. However, the steps which ensure cross-pollination in an 
autogamous flower involve artificial hybridisation techniques called 
emasculation and bagging. Removal of stamens or anthers of a bisexual flower 
without affecting the female reproductive organs is called emasculation. The 
  
 
CBSE XII  |  Biology 
Board Paper 2013 – Delhi – Set 3 (Solution) 
 
     
emasculated flower is immediately enclosed in a bag to avoid pollination by 
any unwanted pollen. This process is called bagging.  
Emasculation is applied only when artificial pollination is carried out in a 
bisexual flower. It is not required in unisexual flowers. During artificial 
pollination, the mature and viable pollen grains are collected from the anther 
of the male parent and are dusted on the stigma of the female parent.  
  
14.  Ans. Chorionic villi are finger-like projections which arise from the 
trophoblast layer and develops in the zygote after it has undergone 
implantation. 
Functions of chorionic villi: 
(a) It takes part in the formation of placenta, which is the connecting link 
between the mother and the foetus. 
(b) It supplies oxygen and nutrients to the growing embryo. 
 
15.  Ans. In a cross between two tall pea plants, some offspring produced were 
dwarf which ensures that both parents are heterozygous (Tt). 
 
 
Phenotypic ratio: 3:1 
Genotypic ratio: 1:2:1 
 
16.  Ans. 
(a) An allergy is the hypersensitivity of the body to certain foreign substances 
called allergens. It is related with the immune system of the body.  
(b)  
(i) The immune system shows specificity to a particular allergen. 
(ii) It exhibits memory, i.e. first exposure to allergen causes primary 
response but does not cause allergy. When an allergen enters the body 
the second time, it causes a second immune response reaction and 
causes allergy and produces antibodies. 
 
17. Ans. Because DNA is a hydrophilic molecule, it can pass through the 
membranes, so the bacterial cells must be made capable to take up DNA. This 
is done by treating them with a specific concentration of a divalent cation, 
Page 4


  
 
CBSE XII  |  Biology 
Board Paper 2013 – Delhi – Set 3 (Solution) 
 
     
CBSE 
Class XII Biology (Theory) 
Board Paper 2013 – Delhi (Set 3) 
SOLUTION 
Time: 3 hrs Total Marks: 70 
 
SECTION A 
1. Ans. Cellulase enzyme is needed for isolating genetic material from plant cells 
and not from animal cells because it breaks down the plant cell wall made of 
cellulose. Animal cells do not have a cell wall. 
2. Ans. MOET stands for multiple ovulation embryo transfer technology which is 
a programme for herd improvement. The importance of MOET is to increase 
herd size in a short time.  
3. Ans. An anther with malfunctioning tapetum often fails to produce viable 
gametophytes because the tapetum provides nutritive materials to the 
dividing microsporocytes. 
4. Ans. Sharing of injection needles between two individuals is not 
recommended because it causes fatal and incurable diseases such as AIDS and 
hepatitis. 
5. Ans. DNA-dependent DNA polymerase is the enzyme which polymerises the 
DNA strand in the 5' to 3' direction resulting in continuous and discontinuous 
replication. 
6. Ans. Sweet potato tubers and potato tubers are the result of convergent 
evolution. It is because the basic structure of the sweet potato tuber and 
potato tuber is different, but their function is similar. Both of them are meant 
for storage of food and vegetative reproduction. 
7. Ans. The equation of net primary productivity of an ecosystem is 
       NPP = GPP - R 
              where NPP = net primary productivity 
         GPP = gross primary productivity 
         R = respiratory rate 
8. Ans.  
(a) 50,000 different strains of rice: Genetic diversity 
(b) Estuarine and alpine meadows: Ecological diversity 
 
 
 
 
 
 
 
  
 
CBSE XII  |  Biology 
Board Paper 2013 – Delhi – Set 3 (Solution) 
 
     
SECTION B 
 
9. Ans. Small animals are cold-blooded organisms. They do not have constant 
body temperature and need to spend energy to generate heat through 
metabolism. So, they are rarely found in the polar regions. 
 
10.  Ans. The pyramid of energy is a graphical representation of the amount of 
accumulated energy per unit area in different trophic levels of a food chain. 
An energy pyramid is always upright because there is a gradual decrease in 
energy at successive trophic levels. This happens because according to the 
10% law of energy transfer—only 10% of the total energy is transferred from 
one trophic level to another.   
 
11.   Ans. 
(i) PCR: Polymerase chain reaction  
Application of PCR: It is useful to detect genetic disease in the foetus 
before birth. 
(ii) ELISA: Enzyme-linked immunosorbent assay  
Application of ELISA: It is useful in the early diagnosis of diseases using 
antigen–antibody interactions.  
OR 
(a) Exonucleases remove nucleotides from the ends of the DNA, whereas 
endonucleases make cuts at specific positions within the DNA. 
(b) Each restriction endonuclease inspects the DNA molecule in search of a 
specific recognition sequence. When it gets its specific recognition 
sequence, it binds to the site and cuts each of the two strands of the double 
helix at specific points by hydrolysing the phosphodiester backbones. 
 
12. Ans.  
Two sources of e-wastes are 
(i) Parts of computers and television sets 
(ii) Smartphones and parts of air conditioners and refrigerators 
Two ways for disposal of e-wastes are 
(i) Recycling of e-wastes 
(ii) Incineration of e-wastes, i.e. burning e-wastes completely into ashes 
 
13. Ans.  The autogamous flowers are open and can be subjected to cross-
pollination. Various agents which help in cross-pollination are wind, insects 
and birds. However, the steps which ensure cross-pollination in an 
autogamous flower involve artificial hybridisation techniques called 
emasculation and bagging. Removal of stamens or anthers of a bisexual flower 
without affecting the female reproductive organs is called emasculation. The 
  
 
CBSE XII  |  Biology 
Board Paper 2013 – Delhi – Set 3 (Solution) 
 
     
emasculated flower is immediately enclosed in a bag to avoid pollination by 
any unwanted pollen. This process is called bagging.  
Emasculation is applied only when artificial pollination is carried out in a 
bisexual flower. It is not required in unisexual flowers. During artificial 
pollination, the mature and viable pollen grains are collected from the anther 
of the male parent and are dusted on the stigma of the female parent.  
  
14.  Ans. Chorionic villi are finger-like projections which arise from the 
trophoblast layer and develops in the zygote after it has undergone 
implantation. 
Functions of chorionic villi: 
(a) It takes part in the formation of placenta, which is the connecting link 
between the mother and the foetus. 
(b) It supplies oxygen and nutrients to the growing embryo. 
 
15.  Ans. In a cross between two tall pea plants, some offspring produced were 
dwarf which ensures that both parents are heterozygous (Tt). 
 
 
Phenotypic ratio: 3:1 
Genotypic ratio: 1:2:1 
 
16.  Ans. 
(a) An allergy is the hypersensitivity of the body to certain foreign substances 
called allergens. It is related with the immune system of the body.  
(b)  
(i) The immune system shows specificity to a particular allergen. 
(ii) It exhibits memory, i.e. first exposure to allergen causes primary 
response but does not cause allergy. When an allergen enters the body 
the second time, it causes a second immune response reaction and 
causes allergy and produces antibodies. 
 
17. Ans. Because DNA is a hydrophilic molecule, it can pass through the 
membranes, so the bacterial cells must be made capable to take up DNA. This 
is done by treating them with a specific concentration of a divalent cation, 
  
 
CBSE XII  |  Biology 
Board Paper 2013 – Delhi – Set 3 (Solution) 
 
     
such as calcium which makes the cell wall permeable. Recombinant DNA can 
be forced into such cells by incubating the cells with recombinant DNA on ice, 
followed by placing them at 42°C (heat shock) and then putting them back on 
ice. This enables the bacteria to take up the recombinant DNA. 
 
18.  Ans.  
(a) The first clinical gene therapy was given in1990 to a 4-year-old girl with 
adenosine deaminase (ADA) deficiency. 
(b) The patient has defective gene for the enzyme adenosine deaminase (ADA) 
which causes severe combined immune deficiency (SCID). 
It can be cured by gene therapy treatment.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Page 5


  
 
CBSE XII  |  Biology 
Board Paper 2013 – Delhi – Set 3 (Solution) 
 
     
CBSE 
Class XII Biology (Theory) 
Board Paper 2013 – Delhi (Set 3) 
SOLUTION 
Time: 3 hrs Total Marks: 70 
 
SECTION A 
1. Ans. Cellulase enzyme is needed for isolating genetic material from plant cells 
and not from animal cells because it breaks down the plant cell wall made of 
cellulose. Animal cells do not have a cell wall. 
2. Ans. MOET stands for multiple ovulation embryo transfer technology which is 
a programme for herd improvement. The importance of MOET is to increase 
herd size in a short time.  
3. Ans. An anther with malfunctioning tapetum often fails to produce viable 
gametophytes because the tapetum provides nutritive materials to the 
dividing microsporocytes. 
4. Ans. Sharing of injection needles between two individuals is not 
recommended because it causes fatal and incurable diseases such as AIDS and 
hepatitis. 
5. Ans. DNA-dependent DNA polymerase is the enzyme which polymerises the 
DNA strand in the 5' to 3' direction resulting in continuous and discontinuous 
replication. 
6. Ans. Sweet potato tubers and potato tubers are the result of convergent 
evolution. It is because the basic structure of the sweet potato tuber and 
potato tuber is different, but their function is similar. Both of them are meant 
for storage of food and vegetative reproduction. 
7. Ans. The equation of net primary productivity of an ecosystem is 
       NPP = GPP - R 
              where NPP = net primary productivity 
         GPP = gross primary productivity 
         R = respiratory rate 
8. Ans.  
(a) 50,000 different strains of rice: Genetic diversity 
(b) Estuarine and alpine meadows: Ecological diversity 
 
 
 
 
 
 
 
  
 
CBSE XII  |  Biology 
Board Paper 2013 – Delhi – Set 3 (Solution) 
 
     
SECTION B 
 
9. Ans. Small animals are cold-blooded organisms. They do not have constant 
body temperature and need to spend energy to generate heat through 
metabolism. So, they are rarely found in the polar regions. 
 
10.  Ans. The pyramid of energy is a graphical representation of the amount of 
accumulated energy per unit area in different trophic levels of a food chain. 
An energy pyramid is always upright because there is a gradual decrease in 
energy at successive trophic levels. This happens because according to the 
10% law of energy transfer—only 10% of the total energy is transferred from 
one trophic level to another.   
 
11.   Ans. 
(i) PCR: Polymerase chain reaction  
Application of PCR: It is useful to detect genetic disease in the foetus 
before birth. 
(ii) ELISA: Enzyme-linked immunosorbent assay  
Application of ELISA: It is useful in the early diagnosis of diseases using 
antigen–antibody interactions.  
OR 
(a) Exonucleases remove nucleotides from the ends of the DNA, whereas 
endonucleases make cuts at specific positions within the DNA. 
(b) Each restriction endonuclease inspects the DNA molecule in search of a 
specific recognition sequence. When it gets its specific recognition 
sequence, it binds to the site and cuts each of the two strands of the double 
helix at specific points by hydrolysing the phosphodiester backbones. 
 
12. Ans.  
Two sources of e-wastes are 
(i) Parts of computers and television sets 
(ii) Smartphones and parts of air conditioners and refrigerators 
Two ways for disposal of e-wastes are 
(i) Recycling of e-wastes 
(ii) Incineration of e-wastes, i.e. burning e-wastes completely into ashes 
 
13. Ans.  The autogamous flowers are open and can be subjected to cross-
pollination. Various agents which help in cross-pollination are wind, insects 
and birds. However, the steps which ensure cross-pollination in an 
autogamous flower involve artificial hybridisation techniques called 
emasculation and bagging. Removal of stamens or anthers of a bisexual flower 
without affecting the female reproductive organs is called emasculation. The 
  
 
CBSE XII  |  Biology 
Board Paper 2013 – Delhi – Set 3 (Solution) 
 
     
emasculated flower is immediately enclosed in a bag to avoid pollination by 
any unwanted pollen. This process is called bagging.  
Emasculation is applied only when artificial pollination is carried out in a 
bisexual flower. It is not required in unisexual flowers. During artificial 
pollination, the mature and viable pollen grains are collected from the anther 
of the male parent and are dusted on the stigma of the female parent.  
  
14.  Ans. Chorionic villi are finger-like projections which arise from the 
trophoblast layer and develops in the zygote after it has undergone 
implantation. 
Functions of chorionic villi: 
(a) It takes part in the formation of placenta, which is the connecting link 
between the mother and the foetus. 
(b) It supplies oxygen and nutrients to the growing embryo. 
 
15.  Ans. In a cross between two tall pea plants, some offspring produced were 
dwarf which ensures that both parents are heterozygous (Tt). 
 
 
Phenotypic ratio: 3:1 
Genotypic ratio: 1:2:1 
 
16.  Ans. 
(a) An allergy is the hypersensitivity of the body to certain foreign substances 
called allergens. It is related with the immune system of the body.  
(b)  
(i) The immune system shows specificity to a particular allergen. 
(ii) It exhibits memory, i.e. first exposure to allergen causes primary 
response but does not cause allergy. When an allergen enters the body 
the second time, it causes a second immune response reaction and 
causes allergy and produces antibodies. 
 
17. Ans. Because DNA is a hydrophilic molecule, it can pass through the 
membranes, so the bacterial cells must be made capable to take up DNA. This 
is done by treating them with a specific concentration of a divalent cation, 
  
 
CBSE XII  |  Biology 
Board Paper 2013 – Delhi – Set 3 (Solution) 
 
     
such as calcium which makes the cell wall permeable. Recombinant DNA can 
be forced into such cells by incubating the cells with recombinant DNA on ice, 
followed by placing them at 42°C (heat shock) and then putting them back on 
ice. This enables the bacteria to take up the recombinant DNA. 
 
18.  Ans.  
(a) The first clinical gene therapy was given in1990 to a 4-year-old girl with 
adenosine deaminase (ADA) deficiency. 
(b) The patient has defective gene for the enzyme adenosine deaminase (ADA) 
which causes severe combined immune deficiency (SCID). 
It can be cured by gene therapy treatment.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
 
CBSE XII  |  Biology 
Board Paper 2013 – Delhi – Set 3 (Solution) 
 
     
SECTION C 
19.  Ans. 
(a) In multiple allelism, a character is controlled by three or more alleles. 
Because the ABO blood group has three alleles—i, I
A
 and I
B
, it is 
considered a good example of multiple alleles.   
(b) Genotype of mother: I
A
I
A
; Genotype of father: I
B
I
B
 
Parents:         I
A
I
A
       ×      I
B
I
B
 
                                       Gametes:  I
A
                      I
B
 
 
 
F 1 progeny                I
A
 I
B
 
The blood group of the child will be AB. This is due to co-dominance where 
allele I
A
 for the A-type blood group is co-dominant with its allele I
B 
for the B-
type blood group. 
 
20. Ans.  RNA molecule is a single chain polynucleotide. Each nucleotide is 
composed of three main components—a nitrogenous base, a 5-carbon ribose 
sugar and a phosphate group. 
(i) The axis or backbone of a polynucleotide chain is formed of alternate 
residues of phosphate and ribose sugar. 
(ii) Phosphate combines with carbon of its sugar and carbon 3' of the next 
sugar. 
(iii) Nitrogenous bases are purines (adenine and guanine) and pyrimidines 
(cytosine and uracil). Nitrogenous base is linked to the ribose sugar 
through N-glycosidic linkages.