Past Year Paper - Solutions, Biology (Set - 1), Delhi, 2016, Class 12, Biology | Additional Study Material for NEET PDF Download

 Page 1


Question Paper Code  57/1
SECTION A
1. Name the part of the flower which the tassels of the corn-cob represent.
Ans. Style = ½ ,  stigma  = ½
[1 mark]
2. Mention any two contrasting traits with respect to seeds in pea plant that were studied
by Mendel.
Ans. Round/Wrinkled = ½, Yellow/ Green = ½
[1 mark]
3. Why is secondary immune response more intense than the primary immune response in
humans?
Ans. Body will have memory of the First Encounter / Presence of antibodies developed during primary
immune response.
[1 mark]
4. Why is it not possible for an alien DNA to become part of a chromosome anywhere
along its length and replicate normally?
Ans. Alien DNA must be linked to ori / origin of replication / site to start replication.
[1 mark]
5. State the role of C-peptide in human insulin.
Ans. C-peptide (extra stretch of polypeptide) which makes the insulin inactive / proinsulin is inactive
because it contain C-peptide.
[1 mark]
6. Name the enzymes that are used for the isolation of DNA from bacterial and fungal cells
for recombinant DNA technology.
Ans. Bacteria: lysozyme = ½, fungi: chitinase  = ½
[1 mark]
7. State Gause's Competitive Exclusion Principle.
Ans. Two closely related species competing for same resources, cannot coexist indefinitely (the inferior
will be eliminated).
[1 mark]
8. Name the type of association that the genus Glomus exhibits with higher plants.
Ans. Symbiosis / Mycorrhizae / Mutualism.
[1 mark]
SECTION B
9. Why are the human testes located outside the abdominal cavity? Name the pouch in
which they are present.
Ans. Needs lower temperature (2 - 2.5°C) less than the body temperature for the formation of
sperms/ for spermatogenesis. = 1
Scrotal sac / Scrotum = 1
[2 marks]
Page 2


Question Paper Code  57/1
SECTION A
1. Name the part of the flower which the tassels of the corn-cob represent.
Ans. Style = ½ ,  stigma  = ½
[1 mark]
2. Mention any two contrasting traits with respect to seeds in pea plant that were studied
by Mendel.
Ans. Round/Wrinkled = ½, Yellow/ Green = ½
[1 mark]
3. Why is secondary immune response more intense than the primary immune response in
humans?
Ans. Body will have memory of the First Encounter / Presence of antibodies developed during primary
immune response.
[1 mark]
4. Why is it not possible for an alien DNA to become part of a chromosome anywhere
along its length and replicate normally?
Ans. Alien DNA must be linked to ori / origin of replication / site to start replication.
[1 mark]
5. State the role of C-peptide in human insulin.
Ans. C-peptide (extra stretch of polypeptide) which makes the insulin inactive / proinsulin is inactive
because it contain C-peptide.
[1 mark]
6. Name the enzymes that are used for the isolation of DNA from bacterial and fungal cells
for recombinant DNA technology.
Ans. Bacteria: lysozyme = ½, fungi: chitinase  = ½
[1 mark]
7. State Gause's Competitive Exclusion Principle.
Ans. Two closely related species competing for same resources, cannot coexist indefinitely (the inferior
will be eliminated).
[1 mark]
8. Name the type of association that the genus Glomus exhibits with higher plants.
Ans. Symbiosis / Mycorrhizae / Mutualism.
[1 mark]
SECTION B
9. Why are the human testes located outside the abdominal cavity? Name the pouch in
which they are present.
Ans. Needs lower temperature (2 - 2.5°C) less than the body temperature for the formation of
sperms/ for spermatogenesis. = 1
Scrotal sac / Scrotum = 1
[2 marks]
10. In Snapdragon, A cross between true breeding red flower (RR) plants and true breeding
white flower (rr) plants showed a Progeny of plants with all pink flowers.
(a) The appearance of pink flowers is not known as blending. Why?
(b) What is the phenomenon known as?
Ans. (a) R (dominant allele red colour) is not completely dominant over r (recessive allele white
colour) / r maintains its originality and reappear in F
2
 generation. = 1
(b) Incomplete dominance = 1
[2 marks]
11. With the help of one example, explain the phenomena of co-dominance and multiple
allelism in human population.
Ans. ABO blood group in human being is an example of multiple allelism = ½
Three alleles for the gene I i.e. I
A
, I
B
, i = ½
When I
A
 and I
B
 are present together the blood group is AB. = ½
Both A and B are expressed and is called codominance. = ½
[2 marks]
12. Write the scientific name of the fruit-fly. Why did Morgan prefer to work with fruit-flies
for his experiments? State any three reasons.
Ans. Drosophila  melanogaster = ½
Grown in simple synthetic medium, complete the life cycle in two weeks / short life cycle, single
mating produce more progeny , dimorphism, many heritable variations / easy to handle.
(any three) = 1½
[2 marks]
OR
Linkage or crossing-over of genes are alternatives of each other. Justify with the help
of an example.
Ans. In Drosophila a yellow bodied white eyed female was crossed with brown bodied red eyed male,
F
1
 progeny produced and intercrossed the F
2
 phenotypic ratio of Drosophila deviated
significantly from Mendel’s 9:3:3:1, the genes for eye colour & body colour are closely located
on the ‘X’ chromosome showing linkage & therefore inherited together, recombinants were
formed due to crossing over but at low percentage. = ½×4
[2 marks]
13. List the symptoms of Ascariasis. How does a healthy person acquire this infection?
Ans. Internal bleeding, muscular pain, anaemia, blockage of intestinal passage.
(any three) = 1½
Intake of water, vegetables / fruits / foods contaminated with eggs of the parasite. = ½
[2 marks]
14. Explain the significant role of the genus Nucleopolyhedrovirus in an ecological sensitive
area.
Ans. Species specific,  narrow  spectrum , insecticidal application (IPM), no negative impact on plants
/ mammals / birds / fish / even non target insects. = ½×4
[2 marks]
15. How does a restriction nuclease function? Explain.
Ans. Restriction nuclease cut DNA at specific sites = 1
Page 3


Question Paper Code  57/1
SECTION A
1. Name the part of the flower which the tassels of the corn-cob represent.
Ans. Style = ½ ,  stigma  = ½
[1 mark]
2. Mention any two contrasting traits with respect to seeds in pea plant that were studied
by Mendel.
Ans. Round/Wrinkled = ½, Yellow/ Green = ½
[1 mark]
3. Why is secondary immune response more intense than the primary immune response in
humans?
Ans. Body will have memory of the First Encounter / Presence of antibodies developed during primary
immune response.
[1 mark]
4. Why is it not possible for an alien DNA to become part of a chromosome anywhere
along its length and replicate normally?
Ans. Alien DNA must be linked to ori / origin of replication / site to start replication.
[1 mark]
5. State the role of C-peptide in human insulin.
Ans. C-peptide (extra stretch of polypeptide) which makes the insulin inactive / proinsulin is inactive
because it contain C-peptide.
[1 mark]
6. Name the enzymes that are used for the isolation of DNA from bacterial and fungal cells
for recombinant DNA technology.
Ans. Bacteria: lysozyme = ½, fungi: chitinase  = ½
[1 mark]
7. State Gause's Competitive Exclusion Principle.
Ans. Two closely related species competing for same resources, cannot coexist indefinitely (the inferior
will be eliminated).
[1 mark]
8. Name the type of association that the genus Glomus exhibits with higher plants.
Ans. Symbiosis / Mycorrhizae / Mutualism.
[1 mark]
SECTION B
9. Why are the human testes located outside the abdominal cavity? Name the pouch in
which they are present.
Ans. Needs lower temperature (2 - 2.5°C) less than the body temperature for the formation of
sperms/ for spermatogenesis. = 1
Scrotal sac / Scrotum = 1
[2 marks]
10. In Snapdragon, A cross between true breeding red flower (RR) plants and true breeding
white flower (rr) plants showed a Progeny of plants with all pink flowers.
(a) The appearance of pink flowers is not known as blending. Why?
(b) What is the phenomenon known as?
Ans. (a) R (dominant allele red colour) is not completely dominant over r (recessive allele white
colour) / r maintains its originality and reappear in F
2
 generation. = 1
(b) Incomplete dominance = 1
[2 marks]
11. With the help of one example, explain the phenomena of co-dominance and multiple
allelism in human population.
Ans. ABO blood group in human being is an example of multiple allelism = ½
Three alleles for the gene I i.e. I
A
, I
B
, i = ½
When I
A
 and I
B
 are present together the blood group is AB. = ½
Both A and B are expressed and is called codominance. = ½
[2 marks]
12. Write the scientific name of the fruit-fly. Why did Morgan prefer to work with fruit-flies
for his experiments? State any three reasons.
Ans. Drosophila  melanogaster = ½
Grown in simple synthetic medium, complete the life cycle in two weeks / short life cycle, single
mating produce more progeny , dimorphism, many heritable variations / easy to handle.
(any three) = 1½
[2 marks]
OR
Linkage or crossing-over of genes are alternatives of each other. Justify with the help
of an example.
Ans. In Drosophila a yellow bodied white eyed female was crossed with brown bodied red eyed male,
F
1
 progeny produced and intercrossed the F
2
 phenotypic ratio of Drosophila deviated
significantly from Mendel’s 9:3:3:1, the genes for eye colour & body colour are closely located
on the ‘X’ chromosome showing linkage & therefore inherited together, recombinants were
formed due to crossing over but at low percentage. = ½×4
[2 marks]
13. List the symptoms of Ascariasis. How does a healthy person acquire this infection?
Ans. Internal bleeding, muscular pain, anaemia, blockage of intestinal passage.
(any three) = 1½
Intake of water, vegetables / fruits / foods contaminated with eggs of the parasite. = ½
[2 marks]
14. Explain the significant role of the genus Nucleopolyhedrovirus in an ecological sensitive
area.
Ans. Species specific,  narrow  spectrum , insecticidal application (IPM), no negative impact on plants
/ mammals / birds / fish / even non target insects. = ½×4
[2 marks]
15. How does a restriction nuclease function? Explain.
Ans. Restriction nuclease cut DNA at specific sites = 1
exonuclease cuts DNA at the ends, endonuclease cuts at specific position within DNA. /
Restriction endonuclease cuts the DNA at specific pallindromic sequence. = ½+½
[2 marks]
16. How have transgenic animals proved to be beneficial in:
(a) Production of biological products
(b) Chemical safety testing
Ans. a) (Rosie - transgenic cow) produced human protein / alpha lactalbumin enriched  milk, alpha-
1 antitrypsin used to treat emphysema. = ½+½
b) (Toxicity Testing) - more sensitive to toxic substances, results obtained in less time. = ½+½
[2 marks]
17. Describe the mutual relationship between fig tree and wasp and comment on the
phenomenon that operates in their relationship.
Ans. Wasp - helps in pollination / pollinator (specific)
Oviposition / seeds and ovules  used for nourishing larva.
(any two) = ½+½
Co evolution exists between their close specific tight relationship. = 1
[2 marks]
18. Construct an age pyramid which reflects an expanding growth status of human
population.
Ans.
Post-reproductive (½)
Reproductive (½)
Pre-reproductive 
(½)
Expanding
Construction of Pyramid = ½
[2 marks]
SECTION C
19. Make a list of any three out breeding devices that flowering plants have developed and
explain how they help to encourage cross-pollination.
Ans. (i) Time of pollen release and stigma receptivity are different (not synchronized), self
pollination prevented.
(ii) Anther & stigma are placed at different positions, so the pollen can not come in contact
with the stigma of the same flower.
(iii) Self incompatibility, genetic mechanism  (prevent the pollen germination on the stigma of the
same flower)
(iv) Production of unisexual flowers / dioecious plants, cross pollination ensured.
(any three) = (½ x 6)
[3 marks]
OR
Why are angiosperm anthers called dithecous? Describe the structure of its
microsporangium.
Page 4


Question Paper Code  57/1
SECTION A
1. Name the part of the flower which the tassels of the corn-cob represent.
Ans. Style = ½ ,  stigma  = ½
[1 mark]
2. Mention any two contrasting traits with respect to seeds in pea plant that were studied
by Mendel.
Ans. Round/Wrinkled = ½, Yellow/ Green = ½
[1 mark]
3. Why is secondary immune response more intense than the primary immune response in
humans?
Ans. Body will have memory of the First Encounter / Presence of antibodies developed during primary
immune response.
[1 mark]
4. Why is it not possible for an alien DNA to become part of a chromosome anywhere
along its length and replicate normally?
Ans. Alien DNA must be linked to ori / origin of replication / site to start replication.
[1 mark]
5. State the role of C-peptide in human insulin.
Ans. C-peptide (extra stretch of polypeptide) which makes the insulin inactive / proinsulin is inactive
because it contain C-peptide.
[1 mark]
6. Name the enzymes that are used for the isolation of DNA from bacterial and fungal cells
for recombinant DNA technology.
Ans. Bacteria: lysozyme = ½, fungi: chitinase  = ½
[1 mark]
7. State Gause's Competitive Exclusion Principle.
Ans. Two closely related species competing for same resources, cannot coexist indefinitely (the inferior
will be eliminated).
[1 mark]
8. Name the type of association that the genus Glomus exhibits with higher plants.
Ans. Symbiosis / Mycorrhizae / Mutualism.
[1 mark]
SECTION B
9. Why are the human testes located outside the abdominal cavity? Name the pouch in
which they are present.
Ans. Needs lower temperature (2 - 2.5°C) less than the body temperature for the formation of
sperms/ for spermatogenesis. = 1
Scrotal sac / Scrotum = 1
[2 marks]
10. In Snapdragon, A cross between true breeding red flower (RR) plants and true breeding
white flower (rr) plants showed a Progeny of plants with all pink flowers.
(a) The appearance of pink flowers is not known as blending. Why?
(b) What is the phenomenon known as?
Ans. (a) R (dominant allele red colour) is not completely dominant over r (recessive allele white
colour) / r maintains its originality and reappear in F
2
 generation. = 1
(b) Incomplete dominance = 1
[2 marks]
11. With the help of one example, explain the phenomena of co-dominance and multiple
allelism in human population.
Ans. ABO blood group in human being is an example of multiple allelism = ½
Three alleles for the gene I i.e. I
A
, I
B
, i = ½
When I
A
 and I
B
 are present together the blood group is AB. = ½
Both A and B are expressed and is called codominance. = ½
[2 marks]
12. Write the scientific name of the fruit-fly. Why did Morgan prefer to work with fruit-flies
for his experiments? State any three reasons.
Ans. Drosophila  melanogaster = ½
Grown in simple synthetic medium, complete the life cycle in two weeks / short life cycle, single
mating produce more progeny , dimorphism, many heritable variations / easy to handle.
(any three) = 1½
[2 marks]
OR
Linkage or crossing-over of genes are alternatives of each other. Justify with the help
of an example.
Ans. In Drosophila a yellow bodied white eyed female was crossed with brown bodied red eyed male,
F
1
 progeny produced and intercrossed the F
2
 phenotypic ratio of Drosophila deviated
significantly from Mendel’s 9:3:3:1, the genes for eye colour & body colour are closely located
on the ‘X’ chromosome showing linkage & therefore inherited together, recombinants were
formed due to crossing over but at low percentage. = ½×4
[2 marks]
13. List the symptoms of Ascariasis. How does a healthy person acquire this infection?
Ans. Internal bleeding, muscular pain, anaemia, blockage of intestinal passage.
(any three) = 1½
Intake of water, vegetables / fruits / foods contaminated with eggs of the parasite. = ½
[2 marks]
14. Explain the significant role of the genus Nucleopolyhedrovirus in an ecological sensitive
area.
Ans. Species specific,  narrow  spectrum , insecticidal application (IPM), no negative impact on plants
/ mammals / birds / fish / even non target insects. = ½×4
[2 marks]
15. How does a restriction nuclease function? Explain.
Ans. Restriction nuclease cut DNA at specific sites = 1
exonuclease cuts DNA at the ends, endonuclease cuts at specific position within DNA. /
Restriction endonuclease cuts the DNA at specific pallindromic sequence. = ½+½
[2 marks]
16. How have transgenic animals proved to be beneficial in:
(a) Production of biological products
(b) Chemical safety testing
Ans. a) (Rosie - transgenic cow) produced human protein / alpha lactalbumin enriched  milk, alpha-
1 antitrypsin used to treat emphysema. = ½+½
b) (Toxicity Testing) - more sensitive to toxic substances, results obtained in less time. = ½+½
[2 marks]
17. Describe the mutual relationship between fig tree and wasp and comment on the
phenomenon that operates in their relationship.
Ans. Wasp - helps in pollination / pollinator (specific)
Oviposition / seeds and ovules  used for nourishing larva.
(any two) = ½+½
Co evolution exists between their close specific tight relationship. = 1
[2 marks]
18. Construct an age pyramid which reflects an expanding growth status of human
population.
Ans.
Post-reproductive (½)
Reproductive (½)
Pre-reproductive 
(½)
Expanding
Construction of Pyramid = ½
[2 marks]
SECTION C
19. Make a list of any three out breeding devices that flowering plants have developed and
explain how they help to encourage cross-pollination.
Ans. (i) Time of pollen release and stigma receptivity are different (not synchronized), self
pollination prevented.
(ii) Anther & stigma are placed at different positions, so the pollen can not come in contact
with the stigma of the same flower.
(iii) Self incompatibility, genetic mechanism  (prevent the pollen germination on the stigma of the
same flower)
(iv) Production of unisexual flowers / dioecious plants, cross pollination ensured.
(any three) = (½ x 6)
[3 marks]
OR
Why are angiosperm anthers called dithecous? Describe the structure of its
microsporangium.
Ans. • Anther bilobed, each lobe of anther has two theca. = ½+½
• Microsporangium surrounded by four wall layers named as epidermis, endothecium, middle
layer and tapetum. = 1
• In young anther a group of compactly arranged homogenous cells called sporogenous
tissue occupies the centre of each microsporangium which produce microspores / pollen
grains.  = 1
[3 marks]
20. If implementation of better techniques and new strategies are required to provide more
efficient care and assistance to people, then why is there a statutory ban on
amniocentesis? Write the use of this technique and give reason to justify.
Ans. To legally check female foeticide / Misuse of sex determination technique = 1
To detect the abnormal chromosomes / genetic disorder = 1
Justify : Prevent (female foeticide) change in sex ratio of the population. = 1
[3 marks]
21. Why is pedigree analysis done in the study of human genetics? State the conclusions
that can be drawn from it.
Ans. (i) Control crosses are not possible in case of humans beings. = 1
(ii) Analysis of traits in several generations of a family / To trace pattern of inheritance /
Whether the trait is dominant or recessive / sex linked or not.
(any two) = 1+1
[3 marks]
22. Identify 'a', 'b', 'c', 'd', 'e' and 'f' in the table given below :
No. Syndrome  Cause Characreristics 
of affected 
individual  
Sex  
Male/Female/Both 
1 Down’s Trisomy  
 of 21  
‘a’   (i) 
       (ii) 
‘b’ 
2 ‘c’ XXY Overall 
masculine 
development 
‘d’ 
3 Turner’s 45 with 
OX 
‘e’    (i) 
        (ii) 
‘f’ 
 
Ans. a. short statured / small round head / furrowed tongue / partially open mouth / palm is broad
/ physical development retarded / psychomotor development retarded / mental
development retarded .
(any two) = ½
b. both  / male and female = ½
c. klinefelter's syndrome = ½
d. male = ½
e. sterile ovaries / rudimentary ovaries, lack of secondary sexual characters. = ½
f. female= ½
[½×6= 3 marks]
Page 5


Question Paper Code  57/1
SECTION A
1. Name the part of the flower which the tassels of the corn-cob represent.
Ans. Style = ½ ,  stigma  = ½
[1 mark]
2. Mention any two contrasting traits with respect to seeds in pea plant that were studied
by Mendel.
Ans. Round/Wrinkled = ½, Yellow/ Green = ½
[1 mark]
3. Why is secondary immune response more intense than the primary immune response in
humans?
Ans. Body will have memory of the First Encounter / Presence of antibodies developed during primary
immune response.
[1 mark]
4. Why is it not possible for an alien DNA to become part of a chromosome anywhere
along its length and replicate normally?
Ans. Alien DNA must be linked to ori / origin of replication / site to start replication.
[1 mark]
5. State the role of C-peptide in human insulin.
Ans. C-peptide (extra stretch of polypeptide) which makes the insulin inactive / proinsulin is inactive
because it contain C-peptide.
[1 mark]
6. Name the enzymes that are used for the isolation of DNA from bacterial and fungal cells
for recombinant DNA technology.
Ans. Bacteria: lysozyme = ½, fungi: chitinase  = ½
[1 mark]
7. State Gause's Competitive Exclusion Principle.
Ans. Two closely related species competing for same resources, cannot coexist indefinitely (the inferior
will be eliminated).
[1 mark]
8. Name the type of association that the genus Glomus exhibits with higher plants.
Ans. Symbiosis / Mycorrhizae / Mutualism.
[1 mark]
SECTION B
9. Why are the human testes located outside the abdominal cavity? Name the pouch in
which they are present.
Ans. Needs lower temperature (2 - 2.5°C) less than the body temperature for the formation of
sperms/ for spermatogenesis. = 1
Scrotal sac / Scrotum = 1
[2 marks]
10. In Snapdragon, A cross between true breeding red flower (RR) plants and true breeding
white flower (rr) plants showed a Progeny of plants with all pink flowers.
(a) The appearance of pink flowers is not known as blending. Why?
(b) What is the phenomenon known as?
Ans. (a) R (dominant allele red colour) is not completely dominant over r (recessive allele white
colour) / r maintains its originality and reappear in F
2
 generation. = 1
(b) Incomplete dominance = 1
[2 marks]
11. With the help of one example, explain the phenomena of co-dominance and multiple
allelism in human population.
Ans. ABO blood group in human being is an example of multiple allelism = ½
Three alleles for the gene I i.e. I
A
, I
B
, i = ½
When I
A
 and I
B
 are present together the blood group is AB. = ½
Both A and B are expressed and is called codominance. = ½
[2 marks]
12. Write the scientific name of the fruit-fly. Why did Morgan prefer to work with fruit-flies
for his experiments? State any three reasons.
Ans. Drosophila  melanogaster = ½
Grown in simple synthetic medium, complete the life cycle in two weeks / short life cycle, single
mating produce more progeny , dimorphism, many heritable variations / easy to handle.
(any three) = 1½
[2 marks]
OR
Linkage or crossing-over of genes are alternatives of each other. Justify with the help
of an example.
Ans. In Drosophila a yellow bodied white eyed female was crossed with brown bodied red eyed male,
F
1
 progeny produced and intercrossed the F
2
 phenotypic ratio of Drosophila deviated
significantly from Mendel’s 9:3:3:1, the genes for eye colour & body colour are closely located
on the ‘X’ chromosome showing linkage & therefore inherited together, recombinants were
formed due to crossing over but at low percentage. = ½×4
[2 marks]
13. List the symptoms of Ascariasis. How does a healthy person acquire this infection?
Ans. Internal bleeding, muscular pain, anaemia, blockage of intestinal passage.
(any three) = 1½
Intake of water, vegetables / fruits / foods contaminated with eggs of the parasite. = ½
[2 marks]
14. Explain the significant role of the genus Nucleopolyhedrovirus in an ecological sensitive
area.
Ans. Species specific,  narrow  spectrum , insecticidal application (IPM), no negative impact on plants
/ mammals / birds / fish / even non target insects. = ½×4
[2 marks]
15. How does a restriction nuclease function? Explain.
Ans. Restriction nuclease cut DNA at specific sites = 1
exonuclease cuts DNA at the ends, endonuclease cuts at specific position within DNA. /
Restriction endonuclease cuts the DNA at specific pallindromic sequence. = ½+½
[2 marks]
16. How have transgenic animals proved to be beneficial in:
(a) Production of biological products
(b) Chemical safety testing
Ans. a) (Rosie - transgenic cow) produced human protein / alpha lactalbumin enriched  milk, alpha-
1 antitrypsin used to treat emphysema. = ½+½
b) (Toxicity Testing) - more sensitive to toxic substances, results obtained in less time. = ½+½
[2 marks]
17. Describe the mutual relationship between fig tree and wasp and comment on the
phenomenon that operates in their relationship.
Ans. Wasp - helps in pollination / pollinator (specific)
Oviposition / seeds and ovules  used for nourishing larva.
(any two) = ½+½
Co evolution exists between their close specific tight relationship. = 1
[2 marks]
18. Construct an age pyramid which reflects an expanding growth status of human
population.
Ans.
Post-reproductive (½)
Reproductive (½)
Pre-reproductive 
(½)
Expanding
Construction of Pyramid = ½
[2 marks]
SECTION C
19. Make a list of any three out breeding devices that flowering plants have developed and
explain how they help to encourage cross-pollination.
Ans. (i) Time of pollen release and stigma receptivity are different (not synchronized), self
pollination prevented.
(ii) Anther & stigma are placed at different positions, so the pollen can not come in contact
with the stigma of the same flower.
(iii) Self incompatibility, genetic mechanism  (prevent the pollen germination on the stigma of the
same flower)
(iv) Production of unisexual flowers / dioecious plants, cross pollination ensured.
(any three) = (½ x 6)
[3 marks]
OR
Why are angiosperm anthers called dithecous? Describe the structure of its
microsporangium.
Ans. • Anther bilobed, each lobe of anther has two theca. = ½+½
• Microsporangium surrounded by four wall layers named as epidermis, endothecium, middle
layer and tapetum. = 1
• In young anther a group of compactly arranged homogenous cells called sporogenous
tissue occupies the centre of each microsporangium which produce microspores / pollen
grains.  = 1
[3 marks]
20. If implementation of better techniques and new strategies are required to provide more
efficient care and assistance to people, then why is there a statutory ban on
amniocentesis? Write the use of this technique and give reason to justify.
Ans. To legally check female foeticide / Misuse of sex determination technique = 1
To detect the abnormal chromosomes / genetic disorder = 1
Justify : Prevent (female foeticide) change in sex ratio of the population. = 1
[3 marks]
21. Why is pedigree analysis done in the study of human genetics? State the conclusions
that can be drawn from it.
Ans. (i) Control crosses are not possible in case of humans beings. = 1
(ii) Analysis of traits in several generations of a family / To trace pattern of inheritance /
Whether the trait is dominant or recessive / sex linked or not.
(any two) = 1+1
[3 marks]
22. Identify 'a', 'b', 'c', 'd', 'e' and 'f' in the table given below :
No. Syndrome  Cause Characreristics 
of affected 
individual  
Sex  
Male/Female/Both 
1 Down’s Trisomy  
 of 21  
‘a’   (i) 
       (ii) 
‘b’ 
2 ‘c’ XXY Overall 
masculine 
development 
‘d’ 
3 Turner’s 45 with 
OX 
‘e’    (i) 
        (ii) 
‘f’ 
 
Ans. a. short statured / small round head / furrowed tongue / partially open mouth / palm is broad
/ physical development retarded / psychomotor development retarded / mental
development retarded .
(any two) = ½
b. both  / male and female = ½
c. klinefelter's syndrome = ½
d. male = ½
e. sterile ovaries / rudimentary ovaries, lack of secondary sexual characters. = ½
f. female= ½
[½×6= 3 marks]
23. Community Service department of your school plans a visit to a slum area near the
school with an objective to educate the slum dwellers with respect to health and hygiene.
(a) Why is there a need to organize such visits?
(b) Write the steps you will highlight, as a member of this department, in your
interaction with them to enable them to lead a healthy life.
Ans. (i) To create awareness about disease and their effects on the body / about immunization /
health and hygiene. = 1
(ii) Disposal of waste
Control of V ectors
Hygienic food and water / fresh drinking water /
Balanced diet / Regular exercise / Yoga
(any four) = ½×4=2 [1+2=3 marks]
24. The following graph shows the species-area relationship. Answer the following question
as directed.
Species richness
log-log scale
‘a’
‘b’
Area
(a) Name the naturalist who studied the kind of relationship shown in the graph. Write
the observation made by him.
(b) Write the situations as discovered by the ecologists when the value of 'Z' (slope
of the line) lies
(i) 0.1 and 0.2
(ii) 0.6 and 1.2
What does 'Z' stand for?
(c) When would the slope of the line 'b' become steeper?
Ans. a) Alexander V on Humboldt. = ½
Within a region species richness increased with increasing explored area but only up to a
limit. = ½
b) i. the slopes of regression lines are similar / unaffected distribution in an area / normal
range = ½
ii. the slope of regression is steeper when we analyse the species area relationship
among very large areas like entire continent = ½