Biology: CBSE Sample Question Paper- 2 | Sample Papers for Class 12 Medical and Non-Medical PDF Download

 Page 1


d o n e Biology - Sample Paper-2
1) Where are sperms stored in the male?
Answer:
Sperms stored in the epididymis and undergo physiological maturation in it.
2) Name the two vitamins produced by microbial fermentation.
Answer:
Vitamin  (Cobalamine) and Vitamin  (Riboflavin).
3) Name the enzyme which is used for dissolving fungal cell wall.
Answer:
Chitinase.
4) Name the popular recent technique which is used for detecting the presence of pathogen/virus in an organism.
Answer:
ELISA- Enzyme Linked Immuno Sorbent Assay.
5) What do you understand by the term diapause?
Answer:
Diapause is a period of suspended growth occurring in many insects and other invertebrates in which metabolism is decreased.
6)
(i) What are the symptoms of malaria?
(ii) Name the commonly used hormones present in contraceptive pills.
OR
State any two differences between spermatogenesis and oogenesis.
Answer:
(i)  Malaria is protozoan disease caused by Plasmodium. Symptoms of malaria are chill, shivering, recurring fever every 3rd or 4th day, increase in
pulse and respiration rate, sweating and anaemia.
(ii) Progesterone and estrogen.
OR
Differences between spermatogenesis and oogenesis:
Spermatogenesis Oogenesis
(i) It is the process of formation of sperms in testis. (i) It is the process of formation of ova in ovary.
(ii) One primary spermatocyte produces four sperms. (ii) One primary oocyte produces one ovum.
7) Give a brief account of biochemical evidences of evolution.
Answer:
Living beings exhibit a large degree of similarity in chemical constitution and biochemical reactions. Similarities in proteins and
genes performing a given function among diverse organisms give a clue to common ancestry. These biochemical similarities
point to the common ancestry and evolution of different groups of organisms.                                  
8) Differentiate between Repetitive DNA and Satellite DNA.
Answer:
DNA fingerprinting involves identifying differences in some specific regions in DNA sequence. These are referred as Repetitive
  
Page 2


d o n e Biology - Sample Paper-2
1) Where are sperms stored in the male?
Answer:
Sperms stored in the epididymis and undergo physiological maturation in it.
2) Name the two vitamins produced by microbial fermentation.
Answer:
Vitamin  (Cobalamine) and Vitamin  (Riboflavin).
3) Name the enzyme which is used for dissolving fungal cell wall.
Answer:
Chitinase.
4) Name the popular recent technique which is used for detecting the presence of pathogen/virus in an organism.
Answer:
ELISA- Enzyme Linked Immuno Sorbent Assay.
5) What do you understand by the term diapause?
Answer:
Diapause is a period of suspended growth occurring in many insects and other invertebrates in which metabolism is decreased.
6)
(i) What are the symptoms of malaria?
(ii) Name the commonly used hormones present in contraceptive pills.
OR
State any two differences between spermatogenesis and oogenesis.
Answer:
(i)  Malaria is protozoan disease caused by Plasmodium. Symptoms of malaria are chill, shivering, recurring fever every 3rd or 4th day, increase in
pulse and respiration rate, sweating and anaemia.
(ii) Progesterone and estrogen.
OR
Differences between spermatogenesis and oogenesis:
Spermatogenesis Oogenesis
(i) It is the process of formation of sperms in testis. (i) It is the process of formation of ova in ovary.
(ii) One primary spermatocyte produces four sperms. (ii) One primary oocyte produces one ovum.
7) Give a brief account of biochemical evidences of evolution.
Answer:
Living beings exhibit a large degree of similarity in chemical constitution and biochemical reactions. Similarities in proteins and
genes performing a given function among diverse organisms give a clue to common ancestry. These biochemical similarities
point to the common ancestry and evolution of different groups of organisms.                                  
8) Differentiate between Repetitive DNA and Satellite DNA.
Answer:
DNA fingerprinting involves identifying differences in some specific regions in DNA sequence. These are referred as Repetitive
  
DNA as in these sequences, a small stretch of DNA is repeated many times. The repetitive DNA when separate from bulk DNA
during density gradient centrifugation are known as Satellite DNA.
9) How is DNA isolated in purified form from a bacterial cell?
Answer:
The bacterial cells are treated with lysozyme to break the cells open and release macromolecules. Purified form of DNA is
obtained by removing RNA by treatment with ribonuclease, proteins by treatment with protease and other molecules by
appropriate treatments. Purified DNA is precipitated out by addition of chilled ethanol.
10) How is thermoregulation energetically expensive for small animals?
Answer:
Small animals have a larger surface area relative to their volume. They tend to lose body heat very fast when it is cold outside and
they have to expend much energy to generate body heat through metabolism.
11) What is gametogenesis? Differentiate between isogamy and anisogamy.
Answer:
Gametogenesis is the formation of two types of gametes - male and female which are haploid cells. The main difference
between isogamy and an isogamy are as follows:
Isogamy Anisogamy
(a) Isogamy is the fusion of two gametes which are similar in
appearance, of gametes.
Anisogamy is the fusion of two morphologically dissimilar types
(b) The gametes are so similar that it is very difficult to differentiate
male and female gametes.
Gametes can easily differentiated into male and female gametes.
(c) Such gametes are called isogametes or homogametes. Such gametes are called heterogametes Oran isogametes.
(d) Example: Monocystis, Chlamydomonas. Example: Humans and frogs.
12) What are the different methods of gamete transfer in different organisms?
Answer:
In most of the organisms the male gametes are motile and the female gamete is stationary. The motile male gametes need a
medium for movement. In algae, bryophytes and pteridophytes water is the medium for transfer of male gametes. In seed plants
male gametes are carried by pollen grains.
13) Draw a well- labelled diagram of longitudinal section of a mature anatropous ovule.
Answer:
 Fig: Longitudinal section of a mature anatropous ovule
14) What is Satellite DNA?s? Explain in brief.
Answer:
Highly repetitive, non-transcribed DNA regions in eukaryotic chromosomes are commonly known as satellite DNAs. Depending
on base composition, length of segment and number of repetitive units, the satellite DNA is classified into many categories such
Page 3


d o n e Biology - Sample Paper-2
1) Where are sperms stored in the male?
Answer:
Sperms stored in the epididymis and undergo physiological maturation in it.
2) Name the two vitamins produced by microbial fermentation.
Answer:
Vitamin  (Cobalamine) and Vitamin  (Riboflavin).
3) Name the enzyme which is used for dissolving fungal cell wall.
Answer:
Chitinase.
4) Name the popular recent technique which is used for detecting the presence of pathogen/virus in an organism.
Answer:
ELISA- Enzyme Linked Immuno Sorbent Assay.
5) What do you understand by the term diapause?
Answer:
Diapause is a period of suspended growth occurring in many insects and other invertebrates in which metabolism is decreased.
6)
(i) What are the symptoms of malaria?
(ii) Name the commonly used hormones present in contraceptive pills.
OR
State any two differences between spermatogenesis and oogenesis.
Answer:
(i)  Malaria is protozoan disease caused by Plasmodium. Symptoms of malaria are chill, shivering, recurring fever every 3rd or 4th day, increase in
pulse and respiration rate, sweating and anaemia.
(ii) Progesterone and estrogen.
OR
Differences between spermatogenesis and oogenesis:
Spermatogenesis Oogenesis
(i) It is the process of formation of sperms in testis. (i) It is the process of formation of ova in ovary.
(ii) One primary spermatocyte produces four sperms. (ii) One primary oocyte produces one ovum.
7) Give a brief account of biochemical evidences of evolution.
Answer:
Living beings exhibit a large degree of similarity in chemical constitution and biochemical reactions. Similarities in proteins and
genes performing a given function among diverse organisms give a clue to common ancestry. These biochemical similarities
point to the common ancestry and evolution of different groups of organisms.                                  
8) Differentiate between Repetitive DNA and Satellite DNA.
Answer:
DNA fingerprinting involves identifying differences in some specific regions in DNA sequence. These are referred as Repetitive
  
DNA as in these sequences, a small stretch of DNA is repeated many times. The repetitive DNA when separate from bulk DNA
during density gradient centrifugation are known as Satellite DNA.
9) How is DNA isolated in purified form from a bacterial cell?
Answer:
The bacterial cells are treated with lysozyme to break the cells open and release macromolecules. Purified form of DNA is
obtained by removing RNA by treatment with ribonuclease, proteins by treatment with protease and other molecules by
appropriate treatments. Purified DNA is precipitated out by addition of chilled ethanol.
10) How is thermoregulation energetically expensive for small animals?
Answer:
Small animals have a larger surface area relative to their volume. They tend to lose body heat very fast when it is cold outside and
they have to expend much energy to generate body heat through metabolism.
11) What is gametogenesis? Differentiate between isogamy and anisogamy.
Answer:
Gametogenesis is the formation of two types of gametes - male and female which are haploid cells. The main difference
between isogamy and an isogamy are as follows:
Isogamy Anisogamy
(a) Isogamy is the fusion of two gametes which are similar in
appearance, of gametes.
Anisogamy is the fusion of two morphologically dissimilar types
(b) The gametes are so similar that it is very difficult to differentiate
male and female gametes.
Gametes can easily differentiated into male and female gametes.
(c) Such gametes are called isogametes or homogametes. Such gametes are called heterogametes Oran isogametes.
(d) Example: Monocystis, Chlamydomonas. Example: Humans and frogs.
12) What are the different methods of gamete transfer in different organisms?
Answer:
In most of the organisms the male gametes are motile and the female gamete is stationary. The motile male gametes need a
medium for movement. In algae, bryophytes and pteridophytes water is the medium for transfer of male gametes. In seed plants
male gametes are carried by pollen grains.
13) Draw a well- labelled diagram of longitudinal section of a mature anatropous ovule.
Answer:
 Fig: Longitudinal section of a mature anatropous ovule
14) What is Satellite DNA?s? Explain in brief.
Answer:
Highly repetitive, non-transcribed DNA regions in eukaryotic chromosomes are commonly known as satellite DNAs. Depending
on base composition, length of segment and number of repetitive units, the satellite DNA is classified into many categories such
as micro satellite, mini satellite etc. These sequences usually do not code for any proteins, but they form a large portion of
human genome. These sequences show high degree of polymorphism and form the bases of DNA fingerprinting.
15)
Write the various causes of genetic disorders in humans.
OR
Mention the salient features of Hugo de Vries theory of mutation. How Hugo de Vries theory do differs
from Darwinism?
Answer:
Human beings suffer from various genetic disorders which occur due to:
(a) Numerical changes in chromosomes - These changes some time occur in the number of autosomes
such as trisomy in the 21 chromosomes causes Down's Syndrome. Changes may occur in sex-
chromosomes. Turner's Syndrome due to lack of an X-chromosome in female (44A + XO) = 45
chromosomes.
(b) By gene mutation in chromosomes - Gene mutation in sex- chromosomes causes Haemophilia, red-
green colour blindness, muscular distrophy, etc. While gene mutation in autosomes causes sickle-cell
anaemia, phenylketonuria, and alkaptonuria and albinism genetics disorders.
(c) Genetic disorders are also caused due to incompatibility of genes e.g., Rh- factor, blood groups, etc.
OR
According to Hugo de Vries new species arise from the pre- existing ones in a single generation by a
sudden appearance of marked differences called mutations.
He believed that it is mutation which caused evolution and not the minor variations that Darwin talked
about. Darwinian variations are small and directional. Evolution for Darwin is gradual while de Vries
believed mutation caused speciation and hence called saltation.
16) Hemophilia victims are mostly men. Very rarely women are affected by this disorder. Explain, why is it so.
Answer:
Haemophilia is genetic disorder caused by the presence of a recessive sex-linked gene (h) carried by X-chromosome. This is a
defect of blood which prevents its clotting due to absence of anti-haemophiliac globulin. Hemophiliac recessive gene is located
in the X-chromosome and controls the synthesis of a protein needed for the clotting of blood. This gene loses its ability for
producing the coagulant due to mutation. A female becomes haemophilic only when both its X-chromosomes carry defective
genes While in case of human males, a single gene for the haemophoilia defect is able to express itself as the
Y-chromosome is devoid of any corresponding allele.
17)
(i) For which variety of Indian rice, patent was filed by a USA Company?
(ii) What are biofertilisers?
(iii) What would have happened if antibiotics were not discovered?
Answer:
(i)  Indian Basmati was crossed with semi-dwarf variety and was claimed as a new variety for which the
patent was filed by a USA company.
(ii) Biofertilisers are organisms that enrich the nutrients in the soil.
(iii) If antibiotics were not discovered bacterial and fungal diseases would not have been controllable.
18) Write the names of two vector-borne diseases. Name their vectors and causative organisms.
Answer:
Filariasis and malaria are vector-borne diseases. Vector of filariasis is Culex mosquito and vector of malaria is female Anopheles
mosquito. Causative organism of filariasis is Wuchereria and that of malaria is Plasmodium.
19) What do you understand by the terms - (i) Callus, (ii) Micropropagation, (iii) Plant tissue culture
Answer:
Page 4


d o n e Biology - Sample Paper-2
1) Where are sperms stored in the male?
Answer:
Sperms stored in the epididymis and undergo physiological maturation in it.
2) Name the two vitamins produced by microbial fermentation.
Answer:
Vitamin  (Cobalamine) and Vitamin  (Riboflavin).
3) Name the enzyme which is used for dissolving fungal cell wall.
Answer:
Chitinase.
4) Name the popular recent technique which is used for detecting the presence of pathogen/virus in an organism.
Answer:
ELISA- Enzyme Linked Immuno Sorbent Assay.
5) What do you understand by the term diapause?
Answer:
Diapause is a period of suspended growth occurring in many insects and other invertebrates in which metabolism is decreased.
6)
(i) What are the symptoms of malaria?
(ii) Name the commonly used hormones present in contraceptive pills.
OR
State any two differences between spermatogenesis and oogenesis.
Answer:
(i)  Malaria is protozoan disease caused by Plasmodium. Symptoms of malaria are chill, shivering, recurring fever every 3rd or 4th day, increase in
pulse and respiration rate, sweating and anaemia.
(ii) Progesterone and estrogen.
OR
Differences between spermatogenesis and oogenesis:
Spermatogenesis Oogenesis
(i) It is the process of formation of sperms in testis. (i) It is the process of formation of ova in ovary.
(ii) One primary spermatocyte produces four sperms. (ii) One primary oocyte produces one ovum.
7) Give a brief account of biochemical evidences of evolution.
Answer:
Living beings exhibit a large degree of similarity in chemical constitution and biochemical reactions. Similarities in proteins and
genes performing a given function among diverse organisms give a clue to common ancestry. These biochemical similarities
point to the common ancestry and evolution of different groups of organisms.                                  
8) Differentiate between Repetitive DNA and Satellite DNA.
Answer:
DNA fingerprinting involves identifying differences in some specific regions in DNA sequence. These are referred as Repetitive
  
DNA as in these sequences, a small stretch of DNA is repeated many times. The repetitive DNA when separate from bulk DNA
during density gradient centrifugation are known as Satellite DNA.
9) How is DNA isolated in purified form from a bacterial cell?
Answer:
The bacterial cells are treated with lysozyme to break the cells open and release macromolecules. Purified form of DNA is
obtained by removing RNA by treatment with ribonuclease, proteins by treatment with protease and other molecules by
appropriate treatments. Purified DNA is precipitated out by addition of chilled ethanol.
10) How is thermoregulation energetically expensive for small animals?
Answer:
Small animals have a larger surface area relative to their volume. They tend to lose body heat very fast when it is cold outside and
they have to expend much energy to generate body heat through metabolism.
11) What is gametogenesis? Differentiate between isogamy and anisogamy.
Answer:
Gametogenesis is the formation of two types of gametes - male and female which are haploid cells. The main difference
between isogamy and an isogamy are as follows:
Isogamy Anisogamy
(a) Isogamy is the fusion of two gametes which are similar in
appearance, of gametes.
Anisogamy is the fusion of two morphologically dissimilar types
(b) The gametes are so similar that it is very difficult to differentiate
male and female gametes.
Gametes can easily differentiated into male and female gametes.
(c) Such gametes are called isogametes or homogametes. Such gametes are called heterogametes Oran isogametes.
(d) Example: Monocystis, Chlamydomonas. Example: Humans and frogs.
12) What are the different methods of gamete transfer in different organisms?
Answer:
In most of the organisms the male gametes are motile and the female gamete is stationary. The motile male gametes need a
medium for movement. In algae, bryophytes and pteridophytes water is the medium for transfer of male gametes. In seed plants
male gametes are carried by pollen grains.
13) Draw a well- labelled diagram of longitudinal section of a mature anatropous ovule.
Answer:
 Fig: Longitudinal section of a mature anatropous ovule
14) What is Satellite DNA?s? Explain in brief.
Answer:
Highly repetitive, non-transcribed DNA regions in eukaryotic chromosomes are commonly known as satellite DNAs. Depending
on base composition, length of segment and number of repetitive units, the satellite DNA is classified into many categories such
as micro satellite, mini satellite etc. These sequences usually do not code for any proteins, but they form a large portion of
human genome. These sequences show high degree of polymorphism and form the bases of DNA fingerprinting.
15)
Write the various causes of genetic disorders in humans.
OR
Mention the salient features of Hugo de Vries theory of mutation. How Hugo de Vries theory do differs
from Darwinism?
Answer:
Human beings suffer from various genetic disorders which occur due to:
(a) Numerical changes in chromosomes - These changes some time occur in the number of autosomes
such as trisomy in the 21 chromosomes causes Down's Syndrome. Changes may occur in sex-
chromosomes. Turner's Syndrome due to lack of an X-chromosome in female (44A + XO) = 45
chromosomes.
(b) By gene mutation in chromosomes - Gene mutation in sex- chromosomes causes Haemophilia, red-
green colour blindness, muscular distrophy, etc. While gene mutation in autosomes causes sickle-cell
anaemia, phenylketonuria, and alkaptonuria and albinism genetics disorders.
(c) Genetic disorders are also caused due to incompatibility of genes e.g., Rh- factor, blood groups, etc.
OR
According to Hugo de Vries new species arise from the pre- existing ones in a single generation by a
sudden appearance of marked differences called mutations.
He believed that it is mutation which caused evolution and not the minor variations that Darwin talked
about. Darwinian variations are small and directional. Evolution for Darwin is gradual while de Vries
believed mutation caused speciation and hence called saltation.
16) Hemophilia victims are mostly men. Very rarely women are affected by this disorder. Explain, why is it so.
Answer:
Haemophilia is genetic disorder caused by the presence of a recessive sex-linked gene (h) carried by X-chromosome. This is a
defect of blood which prevents its clotting due to absence of anti-haemophiliac globulin. Hemophiliac recessive gene is located
in the X-chromosome and controls the synthesis of a protein needed for the clotting of blood. This gene loses its ability for
producing the coagulant due to mutation. A female becomes haemophilic only when both its X-chromosomes carry defective
genes While in case of human males, a single gene for the haemophoilia defect is able to express itself as the
Y-chromosome is devoid of any corresponding allele.
17)
(i) For which variety of Indian rice, patent was filed by a USA Company?
(ii) What are biofertilisers?
(iii) What would have happened if antibiotics were not discovered?
Answer:
(i)  Indian Basmati was crossed with semi-dwarf variety and was claimed as a new variety for which the
patent was filed by a USA company.
(ii) Biofertilisers are organisms that enrich the nutrients in the soil.
(iii) If antibiotics were not discovered bacterial and fungal diseases would not have been controllable.
18) Write the names of two vector-borne diseases. Name their vectors and causative organisms.
Answer:
Filariasis and malaria are vector-borne diseases. Vector of filariasis is Culex mosquito and vector of malaria is female Anopheles
mosquito. Causative organism of filariasis is Wuchereria and that of malaria is Plasmodium.
19) What do you understand by the terms - (i) Callus, (ii) Micropropagation, (iii) Plant tissue culture
Answer:
(i)  Callus: The culturing of explant on a suitable nutrient media. The cultured tissues proliferate to
produce an unorganized mass of tissue is known as Callus.
(ii) Micro propagation: It is a technique which produces large quantities of plantlets. Each of these
planets will be genetically identical to the original plant from which they are originated
(iii) Plant tissue culture: It is a technique of growing plant cells, tissue, organ in an artifical prepared
nutrient medium in suitable container under controlled environmental conditions.
20)
(i) What essential features must be present in a cloning vehicle?
(ii) Give each an example of vectors for cloning genes in plants and animals
Answer:
(i)  An ideal cloning vehicle must possess the following features:
(a) It should contain an origin of replication (Ori).
(b) It should incorporate a selective marker, which helps in identifying and eliminating non-
transformants.
(c) The vector must also have atleast one unique restriction endonuclease recognition site.
(ii) The tumour inducing plasmid of Agrobacterium tumefaciens have been modified into a cloning vector
which is not pathogenic to plants. However it is still able to use the procedure to deliver genes of our
interest into various plants.
Similarly, retroviruses have also been disarmed and are now-used to deliver desirable genes into animal
cells.
21) Write a brief account of genetically engineered insulin.
Answer:
Insulin is an important lifesaving drug for diabetic patients. Each insulin molecule consists of 51 amino acids arranged in two
chains - A and B chains containing 21 and 30 amino acids respectively. These two chains are linked together by disulphide
bridges. Insulin, in humans, is synthesised as a prohormone which contains an extra stretch called C-peptide. This C-peptide is
absent in mature insulin and hence it is removed during maturation into insulin. In 1983, Eli Lily an American company, prepared
insulin by using recombinant DNA technology. They prepared two DNA sequences corresponding to chains A and B of human
insulin and introduced them in the plasmid of E.coli to produce insulin chains. These chains - A and B were produced separately,
extracted and combined by creating disulphide (S-S) bonds to form human insulin.
22) Define ecological pyramids and describe with examples, pyramids of number.
Answer:
An ecological pyramid is a graphic representation of an ecological parameter, like number of individuals present in various
trophic levels of a food chain with producers forming the base and top carnivores at the tip. Pyramid of numbers: Pyramid of
numbers can have both erect and inverted shapes. In a grassland ecosystem, number of grasses are maximum. The herbivores
feeding on them are less in numbers. Carnivores like tiger, wolf, etc., are still fewer. In this way, pyramid is erect. On the other
hand, in a forest ecosystem, the pyramid is inverted. The number of trees occurs at the base. Birds and other arboreal animals
are far more than the number of trees. The insects and other small animals occurring as parasites on herbivores is far more than
the herbivores. In this way, the pyramid becomes inverted. 
23)
Write notes on the following:
(i) Food web
(ii) Xerarch
Page 5


d o n e Biology - Sample Paper-2
1) Where are sperms stored in the male?
Answer:
Sperms stored in the epididymis and undergo physiological maturation in it.
2) Name the two vitamins produced by microbial fermentation.
Answer:
Vitamin  (Cobalamine) and Vitamin  (Riboflavin).
3) Name the enzyme which is used for dissolving fungal cell wall.
Answer:
Chitinase.
4) Name the popular recent technique which is used for detecting the presence of pathogen/virus in an organism.
Answer:
ELISA- Enzyme Linked Immuno Sorbent Assay.
5) What do you understand by the term diapause?
Answer:
Diapause is a period of suspended growth occurring in many insects and other invertebrates in which metabolism is decreased.
6)
(i) What are the symptoms of malaria?
(ii) Name the commonly used hormones present in contraceptive pills.
OR
State any two differences between spermatogenesis and oogenesis.
Answer:
(i)  Malaria is protozoan disease caused by Plasmodium. Symptoms of malaria are chill, shivering, recurring fever every 3rd or 4th day, increase in
pulse and respiration rate, sweating and anaemia.
(ii) Progesterone and estrogen.
OR
Differences between spermatogenesis and oogenesis:
Spermatogenesis Oogenesis
(i) It is the process of formation of sperms in testis. (i) It is the process of formation of ova in ovary.
(ii) One primary spermatocyte produces four sperms. (ii) One primary oocyte produces one ovum.
7) Give a brief account of biochemical evidences of evolution.
Answer:
Living beings exhibit a large degree of similarity in chemical constitution and biochemical reactions. Similarities in proteins and
genes performing a given function among diverse organisms give a clue to common ancestry. These biochemical similarities
point to the common ancestry and evolution of different groups of organisms.                                  
8) Differentiate between Repetitive DNA and Satellite DNA.
Answer:
DNA fingerprinting involves identifying differences in some specific regions in DNA sequence. These are referred as Repetitive
  
DNA as in these sequences, a small stretch of DNA is repeated many times. The repetitive DNA when separate from bulk DNA
during density gradient centrifugation are known as Satellite DNA.
9) How is DNA isolated in purified form from a bacterial cell?
Answer:
The bacterial cells are treated with lysozyme to break the cells open and release macromolecules. Purified form of DNA is
obtained by removing RNA by treatment with ribonuclease, proteins by treatment with protease and other molecules by
appropriate treatments. Purified DNA is precipitated out by addition of chilled ethanol.
10) How is thermoregulation energetically expensive for small animals?
Answer:
Small animals have a larger surface area relative to their volume. They tend to lose body heat very fast when it is cold outside and
they have to expend much energy to generate body heat through metabolism.
11) What is gametogenesis? Differentiate between isogamy and anisogamy.
Answer:
Gametogenesis is the formation of two types of gametes - male and female which are haploid cells. The main difference
between isogamy and an isogamy are as follows:
Isogamy Anisogamy
(a) Isogamy is the fusion of two gametes which are similar in
appearance, of gametes.
Anisogamy is the fusion of two morphologically dissimilar types
(b) The gametes are so similar that it is very difficult to differentiate
male and female gametes.
Gametes can easily differentiated into male and female gametes.
(c) Such gametes are called isogametes or homogametes. Such gametes are called heterogametes Oran isogametes.
(d) Example: Monocystis, Chlamydomonas. Example: Humans and frogs.
12) What are the different methods of gamete transfer in different organisms?
Answer:
In most of the organisms the male gametes are motile and the female gamete is stationary. The motile male gametes need a
medium for movement. In algae, bryophytes and pteridophytes water is the medium for transfer of male gametes. In seed plants
male gametes are carried by pollen grains.
13) Draw a well- labelled diagram of longitudinal section of a mature anatropous ovule.
Answer:
 Fig: Longitudinal section of a mature anatropous ovule
14) What is Satellite DNA?s? Explain in brief.
Answer:
Highly repetitive, non-transcribed DNA regions in eukaryotic chromosomes are commonly known as satellite DNAs. Depending
on base composition, length of segment and number of repetitive units, the satellite DNA is classified into many categories such
as micro satellite, mini satellite etc. These sequences usually do not code for any proteins, but they form a large portion of
human genome. These sequences show high degree of polymorphism and form the bases of DNA fingerprinting.
15)
Write the various causes of genetic disorders in humans.
OR
Mention the salient features of Hugo de Vries theory of mutation. How Hugo de Vries theory do differs
from Darwinism?
Answer:
Human beings suffer from various genetic disorders which occur due to:
(a) Numerical changes in chromosomes - These changes some time occur in the number of autosomes
such as trisomy in the 21 chromosomes causes Down's Syndrome. Changes may occur in sex-
chromosomes. Turner's Syndrome due to lack of an X-chromosome in female (44A + XO) = 45
chromosomes.
(b) By gene mutation in chromosomes - Gene mutation in sex- chromosomes causes Haemophilia, red-
green colour blindness, muscular distrophy, etc. While gene mutation in autosomes causes sickle-cell
anaemia, phenylketonuria, and alkaptonuria and albinism genetics disorders.
(c) Genetic disorders are also caused due to incompatibility of genes e.g., Rh- factor, blood groups, etc.
OR
According to Hugo de Vries new species arise from the pre- existing ones in a single generation by a
sudden appearance of marked differences called mutations.
He believed that it is mutation which caused evolution and not the minor variations that Darwin talked
about. Darwinian variations are small and directional. Evolution for Darwin is gradual while de Vries
believed mutation caused speciation and hence called saltation.
16) Hemophilia victims are mostly men. Very rarely women are affected by this disorder. Explain, why is it so.
Answer:
Haemophilia is genetic disorder caused by the presence of a recessive sex-linked gene (h) carried by X-chromosome. This is a
defect of blood which prevents its clotting due to absence of anti-haemophiliac globulin. Hemophiliac recessive gene is located
in the X-chromosome and controls the synthesis of a protein needed for the clotting of blood. This gene loses its ability for
producing the coagulant due to mutation. A female becomes haemophilic only when both its X-chromosomes carry defective
genes While in case of human males, a single gene for the haemophoilia defect is able to express itself as the
Y-chromosome is devoid of any corresponding allele.
17)
(i) For which variety of Indian rice, patent was filed by a USA Company?
(ii) What are biofertilisers?
(iii) What would have happened if antibiotics were not discovered?
Answer:
(i)  Indian Basmati was crossed with semi-dwarf variety and was claimed as a new variety for which the
patent was filed by a USA company.
(ii) Biofertilisers are organisms that enrich the nutrients in the soil.
(iii) If antibiotics were not discovered bacterial and fungal diseases would not have been controllable.
18) Write the names of two vector-borne diseases. Name their vectors and causative organisms.
Answer:
Filariasis and malaria are vector-borne diseases. Vector of filariasis is Culex mosquito and vector of malaria is female Anopheles
mosquito. Causative organism of filariasis is Wuchereria and that of malaria is Plasmodium.
19) What do you understand by the terms - (i) Callus, (ii) Micropropagation, (iii) Plant tissue culture
Answer:
(i)  Callus: The culturing of explant on a suitable nutrient media. The cultured tissues proliferate to
produce an unorganized mass of tissue is known as Callus.
(ii) Micro propagation: It is a technique which produces large quantities of plantlets. Each of these
planets will be genetically identical to the original plant from which they are originated
(iii) Plant tissue culture: It is a technique of growing plant cells, tissue, organ in an artifical prepared
nutrient medium in suitable container under controlled environmental conditions.
20)
(i) What essential features must be present in a cloning vehicle?
(ii) Give each an example of vectors for cloning genes in plants and animals
Answer:
(i)  An ideal cloning vehicle must possess the following features:
(a) It should contain an origin of replication (Ori).
(b) It should incorporate a selective marker, which helps in identifying and eliminating non-
transformants.
(c) The vector must also have atleast one unique restriction endonuclease recognition site.
(ii) The tumour inducing plasmid of Agrobacterium tumefaciens have been modified into a cloning vector
which is not pathogenic to plants. However it is still able to use the procedure to deliver genes of our
interest into various plants.
Similarly, retroviruses have also been disarmed and are now-used to deliver desirable genes into animal
cells.
21) Write a brief account of genetically engineered insulin.
Answer:
Insulin is an important lifesaving drug for diabetic patients. Each insulin molecule consists of 51 amino acids arranged in two
chains - A and B chains containing 21 and 30 amino acids respectively. These two chains are linked together by disulphide
bridges. Insulin, in humans, is synthesised as a prohormone which contains an extra stretch called C-peptide. This C-peptide is
absent in mature insulin and hence it is removed during maturation into insulin. In 1983, Eli Lily an American company, prepared
insulin by using recombinant DNA technology. They prepared two DNA sequences corresponding to chains A and B of human
insulin and introduced them in the plasmid of E.coli to produce insulin chains. These chains - A and B were produced separately,
extracted and combined by creating disulphide (S-S) bonds to form human insulin.
22) Define ecological pyramids and describe with examples, pyramids of number.
Answer:
An ecological pyramid is a graphic representation of an ecological parameter, like number of individuals present in various
trophic levels of a food chain with producers forming the base and top carnivores at the tip. Pyramid of numbers: Pyramid of
numbers can have both erect and inverted shapes. In a grassland ecosystem, number of grasses are maximum. The herbivores
feeding on them are less in numbers. Carnivores like tiger, wolf, etc., are still fewer. In this way, pyramid is erect. On the other
hand, in a forest ecosystem, the pyramid is inverted. The number of trees occurs at the base. Birds and other arboreal animals
are far more than the number of trees. The insects and other small animals occurring as parasites on herbivores is far more than
the herbivores. In this way, the pyramid becomes inverted. 
23)
Write notes on the following:
(i) Food web
(ii) Xerarch
Answer:
(i)  Food web: Food chains are not strictly linear. They may have many branches that may link one food
chain with another. The various interlinked food chains in a community constitute a food web.
There can be 3 types of food chains in a food web:
(a) Predator chains that begin with plants and proceed from small to large animals.
(b) Parasitic chains which proceed from large to small organisms.
(c) Saprophytic chains that proceed from dead animals to microorganisms.
(ii) Xerarch (succession on a barren rock): Lichens are pioneers on any barren rock. They secrete some
acids which breakdown the rock Also, lichen thalli die and decompose forming a soil which is just good for
the growth of mosses. So, lichens and mosses form a pioneer community. As further soil accumulation
occurs, seeds of some herbs can gemmate in It As the litter and soil accumulates further, herbs give rise
to shrubs. After the successful growth of shrubs "soil layer becomes deeper and gradually trees make
their appearance. In a time of hundreds of years, a climax vegetation is reached which is in harmony with
the environment.
24) Ankit was one of the best student in the class and loves to play hockey and also selected as captain of the school team for
the district level tournament. He also does social work. He attended a blood donation camp to donate blood and come to know
that he is HIV positive. He lost interest in games and refused to play or study. He went into mental depression and remained
absent from school for a long time to avoid spreading AIDS to others. The Biology teacher visited his home and counselled him.
Ankit was back at school and also played and won the tournament. Ankit then celebrated his victory with team-mates joyfully.
(i) What sense of responsibility did the Biology teacher exhibit?
(ii) A person detected to be HIV positive should be isolated in the society. Do you agree? Why or Why
not?
(iii) How is AIDS not spread?
Answer:
(i) The teacher shows social and moral responsibility along with his commitment to service as a
professional teacher2.mar
(ii) No. AIDS is not a contagious disease and does not spread until a blood/body fluid contact is
established
(iii) AIDS is not spread by:
(a) body contact in crowded place.
(b) hand shaking.
(c) sharing td ephon e, meal, utensil or clothings.
(d) light kissing.
(e) using same toilet seat or even swimming pool.
(f) it is not transmitted by blood sucking vectors or by coughing and sneezing.
25)
Hybrid varieties of several of our food and vegetable crops are being extensively cultivated. However,
plant breeders face a serious problem about their seeds. What is that and how it can be possible to solve
this problem?
OR
Describe the changes in the following organs in the different phases of the menstrual cycle
(i) Ovaries
(ii) Oviducts
(iii) Uterus.
Answer: