Science Past Year Paper SA-2 Solution(Set -3) - 2015, Class 10, CBSE Notes | EduRev

Science Class 10

Created by: Manju Sen

Class 10 : Science Past Year Paper SA-2 Solution(Set -3) - 2015, Class 10, CBSE Notes | EduRev

 Page 1


Outside Delhi – 31/3 Page 1 
 
Strictly Confidential- (For Internal and Restricted Use Only) Secondary School Examination 
SUMMATIVE ASSESSMENT - II 
March 2015 
 
Marking Scheme – Science (Outside Delhi) 31/3 
 
 
1. The Marking Scheme provides general guidelines to reduce subjectivity in the marking. It carries 
only suggested value points for the answer. These are only guidelines and do not constitute the 
complete answer. Any other individual response with suitable justification should also be 
accepted even if there is no reference to the text. 
 
2. Evaluation is to be done as per instructions provided in the Marking Scheme. It should not be 
done according to one's own interpretation or any other consideration. Marking Scheme should 
be strictly adhered to and religiously followed. 
 
3. If a question has parts, please award marks in the right hand side for each part. Marks awarded 
for different parts of the question should then be totalled up and written in the left hand margin. 
 
4. If a question does not have any parts, marks be awarded in the left hand side margin. 
 
5. If a candidate has attempted an extra question, marks obtained in the question attempted first 
should be retained and the other answer should be scored out. 
 
6. Wherever only two/three of a 'given' number of examples/factors/points are expected only the 
first two/three or expected number should be read. The rest are irrelevant and should not be 
examined. 
 
7. There should be no effort at 'moderation' of the marks by the evaluating teachers. The actual 
total marks obtained by the candidate may be of no concern of the evaluators. 
 
8. All the Head Examiners / Examiners are instructed that while evaluating the answer scripts, if the 
answer is found to be totally incorrect, the (X) should be marked on the incorrect answer and 
awarded ‘0’ marks. 
  
9. ½ mark may be deducted if a candidate either does not write units or writes wrong units in the 
final answer of a numerical problem. 
 
10. A full scale of mark 0 to 100 has to be used. Please do not hesitate to award full marks if the 
answer deserves it. 
 
11. As per orders of the Hon’ble Supreme Court the candidates would now be permitted to obtain 
photocopy of the Answer Book on request on payment of the prescribed fee. All Examiners/Head 
Examiners are once again reminded that they must ensure that evaluation is carried out strictly 
as per value points given in the marking scheme. 
 
 
 
 
Page 2


Outside Delhi – 31/3 Page 1 
 
Strictly Confidential- (For Internal and Restricted Use Only) Secondary School Examination 
SUMMATIVE ASSESSMENT - II 
March 2015 
 
Marking Scheme – Science (Outside Delhi) 31/3 
 
 
1. The Marking Scheme provides general guidelines to reduce subjectivity in the marking. It carries 
only suggested value points for the answer. These are only guidelines and do not constitute the 
complete answer. Any other individual response with suitable justification should also be 
accepted even if there is no reference to the text. 
 
2. Evaluation is to be done as per instructions provided in the Marking Scheme. It should not be 
done according to one's own interpretation or any other consideration. Marking Scheme should 
be strictly adhered to and religiously followed. 
 
3. If a question has parts, please award marks in the right hand side for each part. Marks awarded 
for different parts of the question should then be totalled up and written in the left hand margin. 
 
4. If a question does not have any parts, marks be awarded in the left hand side margin. 
 
5. If a candidate has attempted an extra question, marks obtained in the question attempted first 
should be retained and the other answer should be scored out. 
 
6. Wherever only two/three of a 'given' number of examples/factors/points are expected only the 
first two/three or expected number should be read. The rest are irrelevant and should not be 
examined. 
 
7. There should be no effort at 'moderation' of the marks by the evaluating teachers. The actual 
total marks obtained by the candidate may be of no concern of the evaluators. 
 
8. All the Head Examiners / Examiners are instructed that while evaluating the answer scripts, if the 
answer is found to be totally incorrect, the (X) should be marked on the incorrect answer and 
awarded ‘0’ marks. 
  
9. ½ mark may be deducted if a candidate either does not write units or writes wrong units in the 
final answer of a numerical problem. 
 
10. A full scale of mark 0 to 100 has to be used. Please do not hesitate to award full marks if the 
answer deserves it. 
 
11. As per orders of the Hon’ble Supreme Court the candidates would now be permitted to obtain 
photocopy of the Answer Book on request on payment of the prescribed fee. All Examiners/Head 
Examiners are once again reminded that they must ensure that evaluation is carried out strictly 
as per value points given in the marking scheme. 
 
 
 
 
Outside Delhi – 31/3 Page 2 
 
MARKING SCHEME 
CLASS X – OUTSIDE DELHI 
Code No. 31/3 
 
 
 
 Expected Answer/ Value point Marks Total 
 SECTION – A   
    
Q1. Thirteen 
1 1 
    
Q2. Planaria / hydra / earthworm (any two) ½, ½ 1 
    
Q3. Herbivores 1 1 
    
Q4. 
                            
Diagram 1 
 
 Marking of angles  ½ × 2 2 
    
Q5. Management of natural resources –  
 To sustain the resources for future generation and current basic needs of 
the population. 
 
 Reuse is a better practice because it can be done at household level with 
no expense of energy. 
 Reuse does not cause pollution. 
 Eco friendly  
(any one) 
1 
 
 
 
 
 
 
1 2 
    
Q6. Biodiversity is the range and number of species of living organisms in a 
given area. 
 
Two advantages-  
 Maintains ecological balance. 
 Helps in maintaining rainfall. 
 Prevent soil erosion. 
(any two) 
1 
 
 
 
 
 
 
½ , ½  2 
    
Q7. Alkene,  C
n
H
2n 
  
           Or   
 Alkyne,  C
n
H
2n-2
 ½ , ½  
    
 Presence of Ni / Pd / Pt as catalyst ½  
Page 3


Outside Delhi – 31/3 Page 1 
 
Strictly Confidential- (For Internal and Restricted Use Only) Secondary School Examination 
SUMMATIVE ASSESSMENT - II 
March 2015 
 
Marking Scheme – Science (Outside Delhi) 31/3 
 
 
1. The Marking Scheme provides general guidelines to reduce subjectivity in the marking. It carries 
only suggested value points for the answer. These are only guidelines and do not constitute the 
complete answer. Any other individual response with suitable justification should also be 
accepted even if there is no reference to the text. 
 
2. Evaluation is to be done as per instructions provided in the Marking Scheme. It should not be 
done according to one's own interpretation or any other consideration. Marking Scheme should 
be strictly adhered to and religiously followed. 
 
3. If a question has parts, please award marks in the right hand side for each part. Marks awarded 
for different parts of the question should then be totalled up and written in the left hand margin. 
 
4. If a question does not have any parts, marks be awarded in the left hand side margin. 
 
5. If a candidate has attempted an extra question, marks obtained in the question attempted first 
should be retained and the other answer should be scored out. 
 
6. Wherever only two/three of a 'given' number of examples/factors/points are expected only the 
first two/three or expected number should be read. The rest are irrelevant and should not be 
examined. 
 
7. There should be no effort at 'moderation' of the marks by the evaluating teachers. The actual 
total marks obtained by the candidate may be of no concern of the evaluators. 
 
8. All the Head Examiners / Examiners are instructed that while evaluating the answer scripts, if the 
answer is found to be totally incorrect, the (X) should be marked on the incorrect answer and 
awarded ‘0’ marks. 
  
9. ½ mark may be deducted if a candidate either does not write units or writes wrong units in the 
final answer of a numerical problem. 
 
10. A full scale of mark 0 to 100 has to be used. Please do not hesitate to award full marks if the 
answer deserves it. 
 
11. As per orders of the Hon’ble Supreme Court the candidates would now be permitted to obtain 
photocopy of the Answer Book on request on payment of the prescribed fee. All Examiners/Head 
Examiners are once again reminded that they must ensure that evaluation is carried out strictly 
as per value points given in the marking scheme. 
 
 
 
 
Outside Delhi – 31/3 Page 2 
 
MARKING SCHEME 
CLASS X – OUTSIDE DELHI 
Code No. 31/3 
 
 
 
 Expected Answer/ Value point Marks Total 
 SECTION – A   
    
Q1. Thirteen 
1 1 
    
Q2. Planaria / hydra / earthworm (any two) ½, ½ 1 
    
Q3. Herbivores 1 1 
    
Q4. 
                            
Diagram 1 
 
 Marking of angles  ½ × 2 2 
    
Q5. Management of natural resources –  
 To sustain the resources for future generation and current basic needs of 
the population. 
 
 Reuse is a better practice because it can be done at household level with 
no expense of energy. 
 Reuse does not cause pollution. 
 Eco friendly  
(any one) 
1 
 
 
 
 
 
 
1 2 
    
Q6. Biodiversity is the range and number of species of living organisms in a 
given area. 
 
Two advantages-  
 Maintains ecological balance. 
 Helps in maintaining rainfall. 
 Prevent soil erosion. 
(any two) 
1 
 
 
 
 
 
 
½ , ½  2 
    
Q7. Alkene,  C
n
H
2n 
  
           Or   
 Alkyne,  C
n
H
2n-2
 ½ , ½  
    
 Presence of Ni / Pd / Pt as catalyst ½  
Outside Delhi – 31/3 Page 3 
 
 
 
½  
            Alkene                                           Alkane  ½ , ½  
    
 Or   any other hydrogenation reaction.  3 
    
Q8. ? Test 1 (Litmus Test) ½  
 Take two strips of blue litmus paper. Place a drop each of the alcohol and 
carboxylic acid on these strips separately. The blue litmus paper turns red in the 
case of carboxylic acid and remains unaffected in the case of alcohol. 1 
 
 ? Test 2 (Sodium hydrogen carbonate test / sodium carbonate test) ½  
 A pinch of sodium hydrogen carbonate or sodium carbonate is added, to both 
separately. If brisk effervescence with the evolution of a colorless gas is 
observed, it indicates the presence of carboxylic acid. 
If no change is observed then it confirms the presence of the alcohol. 1 
 
 ? Test 3 – Ester test  or any other suitable test                   (any two)  3 
    
Q9. a) D,           2, 8, 8, 1 ½ , ½  
 b) A and E belong to the same group as both have the same no. of valence 
electrons / same no. of electrons (2) in the outermost shell. ½ , ½  
 c) A and B  / D and E. ½  
  A has a bigger  atomic radius than B. or D has a  bigger atomic radius than 
E. ½ 3 
    
Q10. Electronic configuration of element with atomic no. 16 is 2,8,6. 1  
 Since it has 3 shells, the period no. will be 3. ½  
 Since the no. of valence electrons is 6, the group no. will be 10 + 6 = 16. ½  
 Valency of the element will be 8- valence electrons  ie  8 – 6 = 2. 1 3 
    
Q11. A – Stigma 
 
B – Pollen tube 
 
C – Ovule / germ cell / egg cell 
1 
 
1 
 
1 3 
    
Q12. Four categories of contraceptive methods –  
1. Barrier method (Condoms) 
2. Surgical method or its name 
3. Withdrawal method 
4. Calendar method 
5. Hormonal method 
6. IUCD/ Copper T/ Loop 
(any four) 
 
Two advantages –  
1. Helps in maintaining health of women. 
½ x 4 
 
 
 
 
 
 
 
   
Page 4


Outside Delhi – 31/3 Page 1 
 
Strictly Confidential- (For Internal and Restricted Use Only) Secondary School Examination 
SUMMATIVE ASSESSMENT - II 
March 2015 
 
Marking Scheme – Science (Outside Delhi) 31/3 
 
 
1. The Marking Scheme provides general guidelines to reduce subjectivity in the marking. It carries 
only suggested value points for the answer. These are only guidelines and do not constitute the 
complete answer. Any other individual response with suitable justification should also be 
accepted even if there is no reference to the text. 
 
2. Evaluation is to be done as per instructions provided in the Marking Scheme. It should not be 
done according to one's own interpretation or any other consideration. Marking Scheme should 
be strictly adhered to and religiously followed. 
 
3. If a question has parts, please award marks in the right hand side for each part. Marks awarded 
for different parts of the question should then be totalled up and written in the left hand margin. 
 
4. If a question does not have any parts, marks be awarded in the left hand side margin. 
 
5. If a candidate has attempted an extra question, marks obtained in the question attempted first 
should be retained and the other answer should be scored out. 
 
6. Wherever only two/three of a 'given' number of examples/factors/points are expected only the 
first two/three or expected number should be read. The rest are irrelevant and should not be 
examined. 
 
7. There should be no effort at 'moderation' of the marks by the evaluating teachers. The actual 
total marks obtained by the candidate may be of no concern of the evaluators. 
 
8. All the Head Examiners / Examiners are instructed that while evaluating the answer scripts, if the 
answer is found to be totally incorrect, the (X) should be marked on the incorrect answer and 
awarded ‘0’ marks. 
  
9. ½ mark may be deducted if a candidate either does not write units or writes wrong units in the 
final answer of a numerical problem. 
 
10. A full scale of mark 0 to 100 has to be used. Please do not hesitate to award full marks if the 
answer deserves it. 
 
11. As per orders of the Hon’ble Supreme Court the candidates would now be permitted to obtain 
photocopy of the Answer Book on request on payment of the prescribed fee. All Examiners/Head 
Examiners are once again reminded that they must ensure that evaluation is carried out strictly 
as per value points given in the marking scheme. 
 
 
 
 
Outside Delhi – 31/3 Page 2 
 
MARKING SCHEME 
CLASS X – OUTSIDE DELHI 
Code No. 31/3 
 
 
 
 Expected Answer/ Value point Marks Total 
 SECTION – A   
    
Q1. Thirteen 
1 1 
    
Q2. Planaria / hydra / earthworm (any two) ½, ½ 1 
    
Q3. Herbivores 1 1 
    
Q4. 
                            
Diagram 1 
 
 Marking of angles  ½ × 2 2 
    
Q5. Management of natural resources –  
 To sustain the resources for future generation and current basic needs of 
the population. 
 
 Reuse is a better practice because it can be done at household level with 
no expense of energy. 
 Reuse does not cause pollution. 
 Eco friendly  
(any one) 
1 
 
 
 
 
 
 
1 2 
    
Q6. Biodiversity is the range and number of species of living organisms in a 
given area. 
 
Two advantages-  
 Maintains ecological balance. 
 Helps in maintaining rainfall. 
 Prevent soil erosion. 
(any two) 
1 
 
 
 
 
 
 
½ , ½  2 
    
Q7. Alkene,  C
n
H
2n 
  
           Or   
 Alkyne,  C
n
H
2n-2
 ½ , ½  
    
 Presence of Ni / Pd / Pt as catalyst ½  
Outside Delhi – 31/3 Page 3 
 
 
 
½  
            Alkene                                           Alkane  ½ , ½  
    
 Or   any other hydrogenation reaction.  3 
    
Q8. ? Test 1 (Litmus Test) ½  
 Take two strips of blue litmus paper. Place a drop each of the alcohol and 
carboxylic acid on these strips separately. The blue litmus paper turns red in the 
case of carboxylic acid and remains unaffected in the case of alcohol. 1 
 
 ? Test 2 (Sodium hydrogen carbonate test / sodium carbonate test) ½  
 A pinch of sodium hydrogen carbonate or sodium carbonate is added, to both 
separately. If brisk effervescence with the evolution of a colorless gas is 
observed, it indicates the presence of carboxylic acid. 
If no change is observed then it confirms the presence of the alcohol. 1 
 
 ? Test 3 – Ester test  or any other suitable test                   (any two)  3 
    
Q9. a) D,           2, 8, 8, 1 ½ , ½  
 b) A and E belong to the same group as both have the same no. of valence 
electrons / same no. of electrons (2) in the outermost shell. ½ , ½  
 c) A and B  / D and E. ½  
  A has a bigger  atomic radius than B. or D has a  bigger atomic radius than 
E. ½ 3 
    
Q10. Electronic configuration of element with atomic no. 16 is 2,8,6. 1  
 Since it has 3 shells, the period no. will be 3. ½  
 Since the no. of valence electrons is 6, the group no. will be 10 + 6 = 16. ½  
 Valency of the element will be 8- valence electrons  ie  8 – 6 = 2. 1 3 
    
Q11. A – Stigma 
 
B – Pollen tube 
 
C – Ovule / germ cell / egg cell 
1 
 
1 
 
1 3 
    
Q12. Four categories of contraceptive methods –  
1. Barrier method (Condoms) 
2. Surgical method or its name 
3. Withdrawal method 
4. Calendar method 
5. Hormonal method 
6. IUCD/ Copper T/ Loop 
(any four) 
 
Two advantages –  
1. Helps in maintaining health of women. 
½ x 4 
 
 
 
 
 
 
 
   
Outside Delhi – 31/3 Page 4 
 
2. Helps in preventing STDs especially AIDS 
3. Helps in birth control 
 (any two) ½, ½ 3 
    
Q13. Chromosomes – thread like structures made up of DNA found in the 
nucleus. 1  
 The original number of chromosomes becomes half during gamete 
formation.  
Hence, when the gametes combine, the original number of chromosomes 
gets restored in the progeny. (or same thing explained in the form of  a 
flow chart). 1,1 3 
    
Q14. ? Speciation – evolution of a new species from pre-existing species 
? Occurring due to accumulation of variations 
? By processes like genetic drift / geographical barriers like mountains, 
rivers etc., leading to incapability to reproduce amongst themselves in 
the population. ½ × 3  
    
 Natural selection – 
? Change in frequency of some genes in a population 
? Which give survival advantage to a species from elimination. 
? Ex. – in a population of beetles, a new variation (green colour) get 
survival benefit / advantage to green beetles whereas other (red) 
perishes. ½ × 3 3 
    
Q15. Homologous organs – study of homologous organs suggests that the 
organs having same structure but performing different functions have 
evolved from a common ancestor. 
Ex. - forelimbs of a frog, lizard, bird and man. 
½ 
 
 
½   
    
 Analogous organs – show adoption of organs for common use. 
Ex. – wings of butterfly and wings of bat. 
½ 
½   
    
 Fossils – provide the missing links between two species. 
Ex. – Archeopteryx / fossils of some dinosaurs with feathers. 
½ 
½  3 
    
Q16. The Sun appears reddish at Sunrise as well as at the Sunset and appears 
white at noon when it is overhead. 1  
 At Sunrise/Sunset the blue light of shorter wave lengths, get scattered 
away while passing through the thicker layer of air/ large distance through 
air, and red light of longer wave length reach our eye. 1  
 At noon, the Sun is overhead and the light of the Sun travels relatively 
shorter distance to our eyes and little of blue and violet colors are 
scattered, and white light reaches our eye. 1 3 
    
Q17. ? h = +5 cm    f = -10 cm u = - 20 cm v = ? h ? = ?   
 
u v f
1 1 1
? ? 
½  
Page 5


Outside Delhi – 31/3 Page 1 
 
Strictly Confidential- (For Internal and Restricted Use Only) Secondary School Examination 
SUMMATIVE ASSESSMENT - II 
March 2015 
 
Marking Scheme – Science (Outside Delhi) 31/3 
 
 
1. The Marking Scheme provides general guidelines to reduce subjectivity in the marking. It carries 
only suggested value points for the answer. These are only guidelines and do not constitute the 
complete answer. Any other individual response with suitable justification should also be 
accepted even if there is no reference to the text. 
 
2. Evaluation is to be done as per instructions provided in the Marking Scheme. It should not be 
done according to one's own interpretation or any other consideration. Marking Scheme should 
be strictly adhered to and religiously followed. 
 
3. If a question has parts, please award marks in the right hand side for each part. Marks awarded 
for different parts of the question should then be totalled up and written in the left hand margin. 
 
4. If a question does not have any parts, marks be awarded in the left hand side margin. 
 
5. If a candidate has attempted an extra question, marks obtained in the question attempted first 
should be retained and the other answer should be scored out. 
 
6. Wherever only two/three of a 'given' number of examples/factors/points are expected only the 
first two/three or expected number should be read. The rest are irrelevant and should not be 
examined. 
 
7. There should be no effort at 'moderation' of the marks by the evaluating teachers. The actual 
total marks obtained by the candidate may be of no concern of the evaluators. 
 
8. All the Head Examiners / Examiners are instructed that while evaluating the answer scripts, if the 
answer is found to be totally incorrect, the (X) should be marked on the incorrect answer and 
awarded ‘0’ marks. 
  
9. ½ mark may be deducted if a candidate either does not write units or writes wrong units in the 
final answer of a numerical problem. 
 
10. A full scale of mark 0 to 100 has to be used. Please do not hesitate to award full marks if the 
answer deserves it. 
 
11. As per orders of the Hon’ble Supreme Court the candidates would now be permitted to obtain 
photocopy of the Answer Book on request on payment of the prescribed fee. All Examiners/Head 
Examiners are once again reminded that they must ensure that evaluation is carried out strictly 
as per value points given in the marking scheme. 
 
 
 
 
Outside Delhi – 31/3 Page 2 
 
MARKING SCHEME 
CLASS X – OUTSIDE DELHI 
Code No. 31/3 
 
 
 
 Expected Answer/ Value point Marks Total 
 SECTION – A   
    
Q1. Thirteen 
1 1 
    
Q2. Planaria / hydra / earthworm (any two) ½, ½ 1 
    
Q3. Herbivores 1 1 
    
Q4. 
                            
Diagram 1 
 
 Marking of angles  ½ × 2 2 
    
Q5. Management of natural resources –  
 To sustain the resources for future generation and current basic needs of 
the population. 
 
 Reuse is a better practice because it can be done at household level with 
no expense of energy. 
 Reuse does not cause pollution. 
 Eco friendly  
(any one) 
1 
 
 
 
 
 
 
1 2 
    
Q6. Biodiversity is the range and number of species of living organisms in a 
given area. 
 
Two advantages-  
 Maintains ecological balance. 
 Helps in maintaining rainfall. 
 Prevent soil erosion. 
(any two) 
1 
 
 
 
 
 
 
½ , ½  2 
    
Q7. Alkene,  C
n
H
2n 
  
           Or   
 Alkyne,  C
n
H
2n-2
 ½ , ½  
    
 Presence of Ni / Pd / Pt as catalyst ½  
Outside Delhi – 31/3 Page 3 
 
 
 
½  
            Alkene                                           Alkane  ½ , ½  
    
 Or   any other hydrogenation reaction.  3 
    
Q8. ? Test 1 (Litmus Test) ½  
 Take two strips of blue litmus paper. Place a drop each of the alcohol and 
carboxylic acid on these strips separately. The blue litmus paper turns red in the 
case of carboxylic acid and remains unaffected in the case of alcohol. 1 
 
 ? Test 2 (Sodium hydrogen carbonate test / sodium carbonate test) ½  
 A pinch of sodium hydrogen carbonate or sodium carbonate is added, to both 
separately. If brisk effervescence with the evolution of a colorless gas is 
observed, it indicates the presence of carboxylic acid. 
If no change is observed then it confirms the presence of the alcohol. 1 
 
 ? Test 3 – Ester test  or any other suitable test                   (any two)  3 
    
Q9. a) D,           2, 8, 8, 1 ½ , ½  
 b) A and E belong to the same group as both have the same no. of valence 
electrons / same no. of electrons (2) in the outermost shell. ½ , ½  
 c) A and B  / D and E. ½  
  A has a bigger  atomic radius than B. or D has a  bigger atomic radius than 
E. ½ 3 
    
Q10. Electronic configuration of element with atomic no. 16 is 2,8,6. 1  
 Since it has 3 shells, the period no. will be 3. ½  
 Since the no. of valence electrons is 6, the group no. will be 10 + 6 = 16. ½  
 Valency of the element will be 8- valence electrons  ie  8 – 6 = 2. 1 3 
    
Q11. A – Stigma 
 
B – Pollen tube 
 
C – Ovule / germ cell / egg cell 
1 
 
1 
 
1 3 
    
Q12. Four categories of contraceptive methods –  
1. Barrier method (Condoms) 
2. Surgical method or its name 
3. Withdrawal method 
4. Calendar method 
5. Hormonal method 
6. IUCD/ Copper T/ Loop 
(any four) 
 
Two advantages –  
1. Helps in maintaining health of women. 
½ x 4 
 
 
 
 
 
 
 
   
Outside Delhi – 31/3 Page 4 
 
2. Helps in preventing STDs especially AIDS 
3. Helps in birth control 
 (any two) ½, ½ 3 
    
Q13. Chromosomes – thread like structures made up of DNA found in the 
nucleus. 1  
 The original number of chromosomes becomes half during gamete 
formation.  
Hence, when the gametes combine, the original number of chromosomes 
gets restored in the progeny. (or same thing explained in the form of  a 
flow chart). 1,1 3 
    
Q14. ? Speciation – evolution of a new species from pre-existing species 
? Occurring due to accumulation of variations 
? By processes like genetic drift / geographical barriers like mountains, 
rivers etc., leading to incapability to reproduce amongst themselves in 
the population. ½ × 3  
    
 Natural selection – 
? Change in frequency of some genes in a population 
? Which give survival advantage to a species from elimination. 
? Ex. – in a population of beetles, a new variation (green colour) get 
survival benefit / advantage to green beetles whereas other (red) 
perishes. ½ × 3 3 
    
Q15. Homologous organs – study of homologous organs suggests that the 
organs having same structure but performing different functions have 
evolved from a common ancestor. 
Ex. - forelimbs of a frog, lizard, bird and man. 
½ 
 
 
½   
    
 Analogous organs – show adoption of organs for common use. 
Ex. – wings of butterfly and wings of bat. 
½ 
½   
    
 Fossils – provide the missing links between two species. 
Ex. – Archeopteryx / fossils of some dinosaurs with feathers. 
½ 
½  3 
    
Q16. The Sun appears reddish at Sunrise as well as at the Sunset and appears 
white at noon when it is overhead. 1  
 At Sunrise/Sunset the blue light of shorter wave lengths, get scattered 
away while passing through the thicker layer of air/ large distance through 
air, and red light of longer wave length reach our eye. 1  
 At noon, the Sun is overhead and the light of the Sun travels relatively 
shorter distance to our eyes and little of blue and violet colors are 
scattered, and white light reaches our eye. 1 3 
    
Q17. ? h = +5 cm    f = -10 cm u = - 20 cm v = ? h ? = ?   
 
u v f
1 1 1
? ? 
½  
Outside Delhi – 31/3 Page 5 
 
 
? 
u f v
1 1 1
? ? = 
) 20 (
1
) 10 (
1
?
?
?
 = 
20
1 2 ? ?
  =  
20
3 ?
 
  
 
? cm
3
20
? ? v 
1  
 Nature – Virtual, erect ½  
 
cm
3
5
cm 5
20
1
3
20
? ? ?
?
?
?
?
?
?
?
?
?
? ? ? ? h
u
v
h 
1 3 
    
Q18. Biodegradable substances – can be broken down into simpler substances 
by nature / decomposers/ bacteria/ saprophytes/ saprobionts. 
Ex. – Human Excreta/ Vegetable peels, etc. (any one) 
½ 
 
½   
 Non-biodegradable substances – can’t be broken down into simpler 
substances by nature / decomposers. 
Ex. – Plastic/ glass (or any other)                                        (any one) 
½ 
 
½   
 Habits: 
- Use of separate dustbins for biodegradable and non 
biodegradable waste, 
- Reuse of things such as poly-bags, etc., 
- Recycle of waste 
- Use of cotton /jute bags for carrying vegetables etc. 
                                                                                                 (any two) ½ x 2 3 
    
Q19. ? Ciliary muscles modify the curvature of the eye lens to enable the eye 
to focus objects at varying distances/ help in adjusting the focal length 
of the eye lens 1  
 ? Presbyopia ½  
 ? Bifocal lens ½  
 (a) Defect – Myopia/ Nearsightedness ½  
 Corrective lens – Concave/ Diverging lens ½  
 (b) Values – Concerned, Caring etc. (one value of teacher, one value of 
Salman) ½, ½  
 (c) By thanking the teacher and Salman 1 5 
    
Q20. ? Power of lens:- Ability of a lens to converge or diverge the light rays 
falling on it/ The degree of convergence or divergence of light rays 
achieved by a lens/ Reciprocal of focal length of the lens. 1  
 ? 1 dioptre – It is the power of a lens whose focal length is 1 metre. ½  
 
? m 1 . 0 cm 10 ? ? ?
A
f 
  
 Converging/ Convex lens ½  
 
D 10
m 1 . 0
1 1
P ? ?
?
? ?
A
A
f
 
½  
 m 1 . 0 cm 10 ? ? ? ?
B
f 
  
 Diverging/ Concave lens ½  
 
D 10
m 1 . 0
1 1
P ? ?
?
? ?
B
B
f
 
½  
 ? In this case the object will be between the optical centre and principal ½  
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