CBSE Board Paper 2020 (Marking Scheme and Solutions) | Biology Class 12 - NEET PDF Download

 Page 1


General Instructions: - 
 
1. You are aware that evaluation is the most important process in the actual and correct 
assessment of the candidates. A small mistake in evaluation may lead to serious 
problems which may affect the future of the candidates, education system and teaching 
profession. To avoid mistakes, it is requested that before starting evaluation, you must 
read and understand the spot evaluation guidelines carefully.Evaluation is a 10-12 
days mission for all of us. Hence, it is necessary that you put in your best efforts 
in this process. 
2. Evaluation is to be done as per instructions provided in the Marking Scheme. It should 
3. The Head-Examiner must go through the first five answer books evaluated by each 
evaluator on the first day, to ensure that evaluation has been carried out as per the 
instructions given in the Marking Scheme. The remaining answer books meant for 
evaluation shall be given only after ensuring that there is no significant variation in the 
marking of individual evaluators. 
4. Evaluators will mark( v ) wherever answer is correct.  For wrong answer ‘X”be marked.  
Evaluators will not put right kind of mark while evaluating which gives an impression that 
5. If a question has parts, please award marks on the right-hand side for each part. Marks 
awarded for different parts of the question should then be totaled up and written in the 
left-hand margin and encircled.  This may be followed strictly. 
6. If a question does not have any parts, marks must be awarded in the left-hand margin 
and encircled. This may also be followed strictly. 
7. If a student has attempted an extra question, answer of the question deserving more 
marks should be retained and the other answer scored out. 
8. No marks to be deducted for the cumulative effect of an error. It should be penalized 
only once. 
10. Every examiner has to necessarily do evaluation work for full working hours i.e. 8 hours 
every day and evaluate 20 answer books per day in main subjects and 25 answer books 
per day in other subjects (Details are given in Spot Guidelines). 
11. Ensure that you do not make the following common types of errors committed by the 
Examiner in the past:- 
? Leaving answer or part thereof unassessed in an answer book. 
? Giving more marks for an answer than assigned to it. 
? Wrong totaling of marks awarded on a reply. 
not be done according to one’s own interpretation or any other consideration. Marking 
Scheme should be strictly adhered to and religiously followed. However, while 
evaluating, answers which are based on latest information or knowledge and/or 
are innovative, they may be assessed for their correctness otherwise and marks 
be awarded to them. 
answer is correct and no marks are awarded.  This is most common mistake which 
evaluators are committing. 
Strictly Confidential: (For Internal and Restricted use only) 
Senior School Certificate Examination-2020 
Marking Scheme – BIOLOGY (SUBJECT CODE - 044) 
(PAPER CODE – 57/1/1,2,3) 
9. A full scale of marks 0-70 has to be used. Please do not hesitate to award full marks if 
the answer deserves it. 
Page 2


General Instructions: - 
 
1. You are aware that evaluation is the most important process in the actual and correct 
assessment of the candidates. A small mistake in evaluation may lead to serious 
problems which may affect the future of the candidates, education system and teaching 
profession. To avoid mistakes, it is requested that before starting evaluation, you must 
read and understand the spot evaluation guidelines carefully.Evaluation is a 10-12 
days mission for all of us. Hence, it is necessary that you put in your best efforts 
in this process. 
2. Evaluation is to be done as per instructions provided in the Marking Scheme. It should 
3. The Head-Examiner must go through the first five answer books evaluated by each 
evaluator on the first day, to ensure that evaluation has been carried out as per the 
instructions given in the Marking Scheme. The remaining answer books meant for 
evaluation shall be given only after ensuring that there is no significant variation in the 
marking of individual evaluators. 
4. Evaluators will mark( v ) wherever answer is correct.  For wrong answer ‘X”be marked.  
Evaluators will not put right kind of mark while evaluating which gives an impression that 
5. If a question has parts, please award marks on the right-hand side for each part. Marks 
awarded for different parts of the question should then be totaled up and written in the 
left-hand margin and encircled.  This may be followed strictly. 
6. If a question does not have any parts, marks must be awarded in the left-hand margin 
and encircled. This may also be followed strictly. 
7. If a student has attempted an extra question, answer of the question deserving more 
marks should be retained and the other answer scored out. 
8. No marks to be deducted for the cumulative effect of an error. It should be penalized 
only once. 
10. Every examiner has to necessarily do evaluation work for full working hours i.e. 8 hours 
every day and evaluate 20 answer books per day in main subjects and 25 answer books 
per day in other subjects (Details are given in Spot Guidelines). 
11. Ensure that you do not make the following common types of errors committed by the 
Examiner in the past:- 
? Leaving answer or part thereof unassessed in an answer book. 
? Giving more marks for an answer than assigned to it. 
? Wrong totaling of marks awarded on a reply. 
not be done according to one’s own interpretation or any other consideration. Marking 
Scheme should be strictly adhered to and religiously followed. However, while 
evaluating, answers which are based on latest information or knowledge and/or 
are innovative, they may be assessed for their correctness otherwise and marks 
be awarded to them. 
answer is correct and no marks are awarded.  This is most common mistake which 
evaluators are committing. 
Strictly Confidential: (For Internal and Restricted use only) 
Senior School Certificate Examination-2020 
Marking Scheme – BIOLOGY (SUBJECT CODE - 044) 
(PAPER CODE – 57/1/1,2,3) 
9. A full scale of marks 0-70 has to be used. Please do not hesitate to award full marks if 
the answer deserves it. 
? Wrong transfer of marks from the inside pages of the answer book to the title page. 
? Wrong question wise totaling on the title page. 
? Wrong totaling of marks of the two columns on the title page. 
? Wrong grand total. 
? Marks in words and figures not tallying. 
? Wrong transfer of marks from the answer book to online award list. 
? Answers marked as correct, but marks not awarded. (Ensure that the right tick mark 
is correctly and clearly indicated. It should merely be a line. Same is with the X for 
incorrect answer.) 
? Half or a part of answer marked correct and the rest as wrong, but no marks 
awarded.  
 
12. While evaluating the answer books if the answer is found to be totally incorrect, it should 
be marked as cross (X) and awarded zero (0)Marks. 
  
13. Any unassessed portion, non-carrying over of marks to the title page, or totaling error 
detected by the candidate shall damage the prestige of all the personnel engaged in the 
evaluation work as also of the Board. Hence, in order to uphold the prestige of all 
concerned, it is again reiterated that the instructions be followed meticulously and 
judiciously. 
 
14. The Examiners should acquaint themselves with the guidelines given in the Guidelines 
for spot Evaluation before starting the actual evaluation. 
 
15. Every Examiner shall also ensure that all the answers are evaluated, marks carried over 
to the title page, correctly totaled and written in figures and words. 
 
16. The Board permits candidates to obtain photocopy of the Answer Book on request in an 
RTI application and also separately as a part of the re-evaluation process on payment of 
the processing charges 
  
Page 3


General Instructions: - 
 
1. You are aware that evaluation is the most important process in the actual and correct 
assessment of the candidates. A small mistake in evaluation may lead to serious 
problems which may affect the future of the candidates, education system and teaching 
profession. To avoid mistakes, it is requested that before starting evaluation, you must 
read and understand the spot evaluation guidelines carefully.Evaluation is a 10-12 
days mission for all of us. Hence, it is necessary that you put in your best efforts 
in this process. 
2. Evaluation is to be done as per instructions provided in the Marking Scheme. It should 
3. The Head-Examiner must go through the first five answer books evaluated by each 
evaluator on the first day, to ensure that evaluation has been carried out as per the 
instructions given in the Marking Scheme. The remaining answer books meant for 
evaluation shall be given only after ensuring that there is no significant variation in the 
marking of individual evaluators. 
4. Evaluators will mark( v ) wherever answer is correct.  For wrong answer ‘X”be marked.  
Evaluators will not put right kind of mark while evaluating which gives an impression that 
5. If a question has parts, please award marks on the right-hand side for each part. Marks 
awarded for different parts of the question should then be totaled up and written in the 
left-hand margin and encircled.  This may be followed strictly. 
6. If a question does not have any parts, marks must be awarded in the left-hand margin 
and encircled. This may also be followed strictly. 
7. If a student has attempted an extra question, answer of the question deserving more 
marks should be retained and the other answer scored out. 
8. No marks to be deducted for the cumulative effect of an error. It should be penalized 
only once. 
10. Every examiner has to necessarily do evaluation work for full working hours i.e. 8 hours 
every day and evaluate 20 answer books per day in main subjects and 25 answer books 
per day in other subjects (Details are given in Spot Guidelines). 
11. Ensure that you do not make the following common types of errors committed by the 
Examiner in the past:- 
? Leaving answer or part thereof unassessed in an answer book. 
? Giving more marks for an answer than assigned to it. 
? Wrong totaling of marks awarded on a reply. 
not be done according to one’s own interpretation or any other consideration. Marking 
Scheme should be strictly adhered to and religiously followed. However, while 
evaluating, answers which are based on latest information or knowledge and/or 
are innovative, they may be assessed for their correctness otherwise and marks 
be awarded to them. 
answer is correct and no marks are awarded.  This is most common mistake which 
evaluators are committing. 
Strictly Confidential: (For Internal and Restricted use only) 
Senior School Certificate Examination-2020 
Marking Scheme – BIOLOGY (SUBJECT CODE - 044) 
(PAPER CODE – 57/1/1,2,3) 
9. A full scale of marks 0-70 has to be used. Please do not hesitate to award full marks if 
the answer deserves it. 
? Wrong transfer of marks from the inside pages of the answer book to the title page. 
? Wrong question wise totaling on the title page. 
? Wrong totaling of marks of the two columns on the title page. 
? Wrong grand total. 
? Marks in words and figures not tallying. 
? Wrong transfer of marks from the answer book to online award list. 
? Answers marked as correct, but marks not awarded. (Ensure that the right tick mark 
is correctly and clearly indicated. It should merely be a line. Same is with the X for 
incorrect answer.) 
? Half or a part of answer marked correct and the rest as wrong, but no marks 
awarded.  
 
12. While evaluating the answer books if the answer is found to be totally incorrect, it should 
be marked as cross (X) and awarded zero (0)Marks. 
  
13. Any unassessed portion, non-carrying over of marks to the title page, or totaling error 
detected by the candidate shall damage the prestige of all the personnel engaged in the 
evaluation work as also of the Board. Hence, in order to uphold the prestige of all 
concerned, it is again reiterated that the instructions be followed meticulously and 
judiciously. 
 
14. The Examiners should acquaint themselves with the guidelines given in the Guidelines 
for spot Evaluation before starting the actual evaluation. 
 
15. Every Examiner shall also ensure that all the answers are evaluated, marks carried over 
to the title page, correctly totaled and written in figures and words. 
 
16. The Board permits candidates to obtain photocopy of the Answer Book on request in an 
RTI application and also separately as a part of the re-evaluation process on payment of 
the processing charges 
  
3
Question Paper Code 57/1/1
SECTION – A
1. Meselson and Stahl carried out centrifugation in CsCl
2
 density gradient to separate :
(A) DNA from RNA
(B) DNA from protein
(C) The normal DNA from 
15
N-DNA
(D) DNA from tRNA
Ans C / The normal  DNA from 
15
N-DNA
[1 Mark]
2. Self-pollination is fully ensured if
(A) the flower is bisexual.
(B) the style is longer than the filament.
(C) the flower is cleistogamous.
(D) the time of pistil and anther maturity is different.
Ans C / Flower is Cleistogamous
OR
Zoospores are the reproductive units to carry asexual reproduction in
(A) Chlamydomonas
(B) Spirogyra
(C) Yeast
(D) Rhizopus
Ans A / Chlamydomonas
[1 Mark]
3. Micropropagation can be achieved by
(A) Self-pollination
(B) Asexual reproduction
(C) Tissue culture
(D) Vegetative propagation
Ans C  / Tissue Culture
OR
The microbes commonly used in kitchens are
(A) Lactobacillus and Yeast
Page 4


General Instructions: - 
 
1. You are aware that evaluation is the most important process in the actual and correct 
assessment of the candidates. A small mistake in evaluation may lead to serious 
problems which may affect the future of the candidates, education system and teaching 
profession. To avoid mistakes, it is requested that before starting evaluation, you must 
read and understand the spot evaluation guidelines carefully.Evaluation is a 10-12 
days mission for all of us. Hence, it is necessary that you put in your best efforts 
in this process. 
2. Evaluation is to be done as per instructions provided in the Marking Scheme. It should 
3. The Head-Examiner must go through the first five answer books evaluated by each 
evaluator on the first day, to ensure that evaluation has been carried out as per the 
instructions given in the Marking Scheme. The remaining answer books meant for 
evaluation shall be given only after ensuring that there is no significant variation in the 
marking of individual evaluators. 
4. Evaluators will mark( v ) wherever answer is correct.  For wrong answer ‘X”be marked.  
Evaluators will not put right kind of mark while evaluating which gives an impression that 
5. If a question has parts, please award marks on the right-hand side for each part. Marks 
awarded for different parts of the question should then be totaled up and written in the 
left-hand margin and encircled.  This may be followed strictly. 
6. If a question does not have any parts, marks must be awarded in the left-hand margin 
and encircled. This may also be followed strictly. 
7. If a student has attempted an extra question, answer of the question deserving more 
marks should be retained and the other answer scored out. 
8. No marks to be deducted for the cumulative effect of an error. It should be penalized 
only once. 
10. Every examiner has to necessarily do evaluation work for full working hours i.e. 8 hours 
every day and evaluate 20 answer books per day in main subjects and 25 answer books 
per day in other subjects (Details are given in Spot Guidelines). 
11. Ensure that you do not make the following common types of errors committed by the 
Examiner in the past:- 
? Leaving answer or part thereof unassessed in an answer book. 
? Giving more marks for an answer than assigned to it. 
? Wrong totaling of marks awarded on a reply. 
not be done according to one’s own interpretation or any other consideration. Marking 
Scheme should be strictly adhered to and religiously followed. However, while 
evaluating, answers which are based on latest information or knowledge and/or 
are innovative, they may be assessed for their correctness otherwise and marks 
be awarded to them. 
answer is correct and no marks are awarded.  This is most common mistake which 
evaluators are committing. 
Strictly Confidential: (For Internal and Restricted use only) 
Senior School Certificate Examination-2020 
Marking Scheme – BIOLOGY (SUBJECT CODE - 044) 
(PAPER CODE – 57/1/1,2,3) 
9. A full scale of marks 0-70 has to be used. Please do not hesitate to award full marks if 
the answer deserves it. 
? Wrong transfer of marks from the inside pages of the answer book to the title page. 
? Wrong question wise totaling on the title page. 
? Wrong totaling of marks of the two columns on the title page. 
? Wrong grand total. 
? Marks in words and figures not tallying. 
? Wrong transfer of marks from the answer book to online award list. 
? Answers marked as correct, but marks not awarded. (Ensure that the right tick mark 
is correctly and clearly indicated. It should merely be a line. Same is with the X for 
incorrect answer.) 
? Half or a part of answer marked correct and the rest as wrong, but no marks 
awarded.  
 
12. While evaluating the answer books if the answer is found to be totally incorrect, it should 
be marked as cross (X) and awarded zero (0)Marks. 
  
13. Any unassessed portion, non-carrying over of marks to the title page, or totaling error 
detected by the candidate shall damage the prestige of all the personnel engaged in the 
evaluation work as also of the Board. Hence, in order to uphold the prestige of all 
concerned, it is again reiterated that the instructions be followed meticulously and 
judiciously. 
 
14. The Examiners should acquaint themselves with the guidelines given in the Guidelines 
for spot Evaluation before starting the actual evaluation. 
 
15. Every Examiner shall also ensure that all the answers are evaluated, marks carried over 
to the title page, correctly totaled and written in figures and words. 
 
16. The Board permits candidates to obtain photocopy of the Answer Book on request in an 
RTI application and also separately as a part of the re-evaluation process on payment of 
the processing charges 
  
3
Question Paper Code 57/1/1
SECTION – A
1. Meselson and Stahl carried out centrifugation in CsCl
2
 density gradient to separate :
(A) DNA from RNA
(B) DNA from protein
(C) The normal DNA from 
15
N-DNA
(D) DNA from tRNA
Ans C / The normal  DNA from 
15
N-DNA
[1 Mark]
2. Self-pollination is fully ensured if
(A) the flower is bisexual.
(B) the style is longer than the filament.
(C) the flower is cleistogamous.
(D) the time of pistil and anther maturity is different.
Ans C / Flower is Cleistogamous
OR
Zoospores are the reproductive units to carry asexual reproduction in
(A) Chlamydomonas
(B) Spirogyra
(C) Yeast
(D) Rhizopus
Ans A / Chlamydomonas
[1 Mark]
3. Micropropagation can be achieved by
(A) Self-pollination
(B) Asexual reproduction
(C) Tissue culture
(D) Vegetative propagation
Ans C  / Tissue Culture
OR
The microbes commonly used in kitchens are
(A) Lactobacillus and Yeast
(B) Penicillium and Yeast
(C) Microspora and E. coli
(D) Rhizopus and Lactobacillus
Ans A  / Lactobacillus and Yeast
[1 Mark]
4. The main barrier that prevents the entry of micro-organisms into our body is
(A) Antibodies
(B) Macrophages
(C) Monocytes
(D) Skin
Ans D / Skin
[1 Mark]
5. Nematode specific genes were introduced into the tobacco host plant using a vector
(A) pBR 322
(B) Plasmid
(C) Bacteriophage
(D) Agrobacterium
Ans D  / Agrobacterium
[1 Mark]
SECTION – B
6. Given below is one of the strands of a DNA segment :
(a) Write its complementary strand.
(b) Write a possible RNA strand that can be transcribed from the above
DNA molecule formed.
Ans (a) 5'  
? ? ? ? ? ? ? ? ? ? ? ? ?
GCATGC ATGCATGCAT
 3'        (polarity =½ , nucleotide sequence =½)
(b) 5'   
? ? ? ? ? ? ? ? ? ? ? ? ?
GCAUGC AUGCAUGCAU
  3' (polarity =½ , nucleotide sequence =½)
 [1 + 1 = 2 Marks]
7. Wings of birds and wings of butterflies contribute to locomotion. Explain the type of
evolution such organs are a result of.
Ans They are not anatomically similar in structure but perform same function , hence these are
analogous structure = ½ + ½
type of evolution is convergent evolution =1
Page 5


General Instructions: - 
 
1. You are aware that evaluation is the most important process in the actual and correct 
assessment of the candidates. A small mistake in evaluation may lead to serious 
problems which may affect the future of the candidates, education system and teaching 
profession. To avoid mistakes, it is requested that before starting evaluation, you must 
read and understand the spot evaluation guidelines carefully.Evaluation is a 10-12 
days mission for all of us. Hence, it is necessary that you put in your best efforts 
in this process. 
2. Evaluation is to be done as per instructions provided in the Marking Scheme. It should 
3. The Head-Examiner must go through the first five answer books evaluated by each 
evaluator on the first day, to ensure that evaluation has been carried out as per the 
instructions given in the Marking Scheme. The remaining answer books meant for 
evaluation shall be given only after ensuring that there is no significant variation in the 
marking of individual evaluators. 
4. Evaluators will mark( v ) wherever answer is correct.  For wrong answer ‘X”be marked.  
Evaluators will not put right kind of mark while evaluating which gives an impression that 
5. If a question has parts, please award marks on the right-hand side for each part. Marks 
awarded for different parts of the question should then be totaled up and written in the 
left-hand margin and encircled.  This may be followed strictly. 
6. If a question does not have any parts, marks must be awarded in the left-hand margin 
and encircled. This may also be followed strictly. 
7. If a student has attempted an extra question, answer of the question deserving more 
marks should be retained and the other answer scored out. 
8. No marks to be deducted for the cumulative effect of an error. It should be penalized 
only once. 
10. Every examiner has to necessarily do evaluation work for full working hours i.e. 8 hours 
every day and evaluate 20 answer books per day in main subjects and 25 answer books 
per day in other subjects (Details are given in Spot Guidelines). 
11. Ensure that you do not make the following common types of errors committed by the 
Examiner in the past:- 
? Leaving answer or part thereof unassessed in an answer book. 
? Giving more marks for an answer than assigned to it. 
? Wrong totaling of marks awarded on a reply. 
not be done according to one’s own interpretation or any other consideration. Marking 
Scheme should be strictly adhered to and religiously followed. However, while 
evaluating, answers which are based on latest information or knowledge and/or 
are innovative, they may be assessed for their correctness otherwise and marks 
be awarded to them. 
answer is correct and no marks are awarded.  This is most common mistake which 
evaluators are committing. 
Strictly Confidential: (For Internal and Restricted use only) 
Senior School Certificate Examination-2020 
Marking Scheme – BIOLOGY (SUBJECT CODE - 044) 
(PAPER CODE – 57/1/1,2,3) 
9. A full scale of marks 0-70 has to be used. Please do not hesitate to award full marks if 
the answer deserves it. 
? Wrong transfer of marks from the inside pages of the answer book to the title page. 
? Wrong question wise totaling on the title page. 
? Wrong totaling of marks of the two columns on the title page. 
? Wrong grand total. 
? Marks in words and figures not tallying. 
? Wrong transfer of marks from the answer book to online award list. 
? Answers marked as correct, but marks not awarded. (Ensure that the right tick mark 
is correctly and clearly indicated. It should merely be a line. Same is with the X for 
incorrect answer.) 
? Half or a part of answer marked correct and the rest as wrong, but no marks 
awarded.  
 
12. While evaluating the answer books if the answer is found to be totally incorrect, it should 
be marked as cross (X) and awarded zero (0)Marks. 
  
13. Any unassessed portion, non-carrying over of marks to the title page, or totaling error 
detected by the candidate shall damage the prestige of all the personnel engaged in the 
evaluation work as also of the Board. Hence, in order to uphold the prestige of all 
concerned, it is again reiterated that the instructions be followed meticulously and 
judiciously. 
 
14. The Examiners should acquaint themselves with the guidelines given in the Guidelines 
for spot Evaluation before starting the actual evaluation. 
 
15. Every Examiner shall also ensure that all the answers are evaluated, marks carried over 
to the title page, correctly totaled and written in figures and words. 
 
16. The Board permits candidates to obtain photocopy of the Answer Book on request in an 
RTI application and also separately as a part of the re-evaluation process on payment of 
the processing charges 
  
3
Question Paper Code 57/1/1
SECTION – A
1. Meselson and Stahl carried out centrifugation in CsCl
2
 density gradient to separate :
(A) DNA from RNA
(B) DNA from protein
(C) The normal DNA from 
15
N-DNA
(D) DNA from tRNA
Ans C / The normal  DNA from 
15
N-DNA
[1 Mark]
2. Self-pollination is fully ensured if
(A) the flower is bisexual.
(B) the style is longer than the filament.
(C) the flower is cleistogamous.
(D) the time of pistil and anther maturity is different.
Ans C / Flower is Cleistogamous
OR
Zoospores are the reproductive units to carry asexual reproduction in
(A) Chlamydomonas
(B) Spirogyra
(C) Yeast
(D) Rhizopus
Ans A / Chlamydomonas
[1 Mark]
3. Micropropagation can be achieved by
(A) Self-pollination
(B) Asexual reproduction
(C) Tissue culture
(D) Vegetative propagation
Ans C  / Tissue Culture
OR
The microbes commonly used in kitchens are
(A) Lactobacillus and Yeast
(B) Penicillium and Yeast
(C) Microspora and E. coli
(D) Rhizopus and Lactobacillus
Ans A  / Lactobacillus and Yeast
[1 Mark]
4. The main barrier that prevents the entry of micro-organisms into our body is
(A) Antibodies
(B) Macrophages
(C) Monocytes
(D) Skin
Ans D / Skin
[1 Mark]
5. Nematode specific genes were introduced into the tobacco host plant using a vector
(A) pBR 322
(B) Plasmid
(C) Bacteriophage
(D) Agrobacterium
Ans D  / Agrobacterium
[1 Mark]
SECTION – B
6. Given below is one of the strands of a DNA segment :
(a) Write its complementary strand.
(b) Write a possible RNA strand that can be transcribed from the above
DNA molecule formed.
Ans (a) 5'  
? ? ? ? ? ? ? ? ? ? ? ? ?
GCATGC ATGCATGCAT
 3'        (polarity =½ , nucleotide sequence =½)
(b) 5'   
? ? ? ? ? ? ? ? ? ? ? ? ?
GCAUGC AUGCAUGCAU
  3' (polarity =½ , nucleotide sequence =½)
 [1 + 1 = 2 Marks]
7. Wings of birds and wings of butterflies contribute to locomotion. Explain the type of
evolution such organs are a result of.
Ans They are not anatomically similar in structure but perform same function , hence these are
analogous structure = ½ + ½
type of evolution is convergent evolution =1
//
similar habitat of birds and butterflies has resulted in selection of similar adaptive features
(wings) in different groups of organisms , but towards the same function  = ½ + ½
convergent evolution = 1
[2 Marks]
8. It is often observed that the chances of a person suffering from measles in his or her
lifetime are low if he or she has suffered from the disease in their early childhood. Justify
the statement.
Ans Memory cells develop during measles in early childhood , subsequent encounters with the
same pathogen elicits a highly intensified secondary / anamnestic response  = 1+1
[2 Marks]
9. List the three hormones produced in women only during pregnancy. What happens to
the levels of estrogen and progesterone during pregnancy ?
Ans
- Human chorionic gonadotropin / hCG ,
- Human placental lactogen  / hPL ,
- Relaxin ,
       (The level of progesterone & estrogen) increases =½×4
[2 Marks]
10. A student on a field trip suddenly felt breathlessness and started to sneeze very badly.
Name this response and explain what it is due to.
Ans Allergy = 1
Allergens ( dust / pollen / mites etc.), due to release of chemicals like histamine/serotonin (
from mast cells)
=½+½
[2 Marks]
11. With the help of a suitable example, explain how cross-breeding is carried out in
developing a new breed in animals.
Ans Mating of superior male of one breed with superior female of another breed. =1
Hisardale , is a new breed of sheep ( developed in punjab) by crossing Bikaneri Ewes and
Marino Rams.
= ½+½
[2 Marks]
12. Name the genus of baculovirus that acts as a biological control agent in
spite of being a pathogen. Justify by giving three reasons that make it an excellent
candidate for the job.
Ans Genus -Nucleopolyhedrovirus, species-specific , Narrow spectrum , No negative impact on
(plants /mammals/ birds /fish ) non-target organisms  =  ½ ×4 =2