CBSE Biology All India Past year paper (Set - 3) Solutions - 2015, Class 12 | Additional Study Material for NEET PDF Download

 Page 1


  
 
CBSE XII  |  Biology 
Board Paper – 2015 – All India – Set 3 (Solution) 
 
     
CBSE 
Class XII Biology 
Board Paper – 2015 – All India (Set 3)  
SOLUTION 
  
                                                                                  SECTION A 
 
1. A cistron is a segment of DNA which codes for a polypeptide. 
 
2. Drones of honey bee possess 16 chromosomes. The sperms in honey bee are produced 
by mitosis.  
 
3. Advantages of unleaded petrol in automobiles as fuel: 
i. Automobiles equipped with a catalytic converter should use unleaded petrol 
because lead in the petrol inactivates the catalysts of the converter. 
ii. Use of unleaded petrol prevents the release of poisonous gases such as nitrous oxide 
in the environment. 
 
4. Retroviruses have RNA as genetic material. After the entrance of the virus into the body 
of the host, the virus enters macrophages where its RNA genome replicates to form 
viral DNA with the help of the reverse transcriptase enzyme.      
 
5. Adenosine deaminase deficiency can be cured by enzyme replacement therapy and 
bone marrow transplantation. 
       
SECTION B 
 
6. The combinations having divergent evolution are 
i. Forelimbs of cheetah and mammals 
ii. Forelimbs of whales and mammals 
These two pairs exhibit divergent evolution because they have the same basic 
structural plan but are different in function. 
 
7. A liverwort is a bryophyte which is unable to complete its life cycle in a dry 
environment because 
i. The fertilisation of male and female gametes takes place in water. 
ii. Male gametes, antherozoids, swim in water to reach the eggs for sexual 
reproduction to take place. 
  
Page 2


  
 
CBSE XII  |  Biology 
Board Paper – 2015 – All India – Set 3 (Solution) 
 
     
CBSE 
Class XII Biology 
Board Paper – 2015 – All India (Set 3)  
SOLUTION 
  
                                                                                  SECTION A 
 
1. A cistron is a segment of DNA which codes for a polypeptide. 
 
2. Drones of honey bee possess 16 chromosomes. The sperms in honey bee are produced 
by mitosis.  
 
3. Advantages of unleaded petrol in automobiles as fuel: 
i. Automobiles equipped with a catalytic converter should use unleaded petrol 
because lead in the petrol inactivates the catalysts of the converter. 
ii. Use of unleaded petrol prevents the release of poisonous gases such as nitrous oxide 
in the environment. 
 
4. Retroviruses have RNA as genetic material. After the entrance of the virus into the body 
of the host, the virus enters macrophages where its RNA genome replicates to form 
viral DNA with the help of the reverse transcriptase enzyme.      
 
5. Adenosine deaminase deficiency can be cured by enzyme replacement therapy and 
bone marrow transplantation. 
       
SECTION B 
 
6. The combinations having divergent evolution are 
i. Forelimbs of cheetah and mammals 
ii. Forelimbs of whales and mammals 
These two pairs exhibit divergent evolution because they have the same basic 
structural plan but are different in function. 
 
7. A liverwort is a bryophyte which is unable to complete its life cycle in a dry 
environment because 
i. The fertilisation of male and female gametes takes place in water. 
ii. Male gametes, antherozoids, swim in water to reach the eggs for sexual 
reproduction to take place. 
  
  
 
CBSE XII  |  Biology 
Board Paper – 2015 – All India – Set 3 (Solution) 
 
     
8. Mutualism is the relationship between two organisms where both are benefited either 
with food or shelter or substratum for attachment. 
Examples: 
i. Mycorrhizae are the mutualistic relationship between fungi and roots of higher 
plants. The fungus helps in mineral nutrition of the plant with which it is associated 
and obtains, in turn, carbohydrates from the plant. 
ii. Nitrogen-fixing bacteria, Rhizobium, live in the root nodules of legumes where the 
bacterium derives nutrition from the host plant but fixes the atmospheric nitrogen 
and makes it available to the plants.  
OR 
Ex situ conservation is the conservation of selected rare plants or animals in places 
outside their natural homes. Ex situ conservation of biodiversity has been employed in 
i. Gene banks: These are institutes which maintain stocks of viable seeds, live growing 
plants, tissue culture and frozen germplasm with the whole range of genetic 
variability. 
ii. Cryopreservation: Cryopreservation can maintain tissue culture, embryos, gametes, 
animal cells or tissues. Endangered organisms are being cryopreserved so that they 
can be revived to help in conservation. 
iii. Orchards: Plants with recalcitrant seeds are grown in orchards where all possible 
strains and varieties are maintained. 
iv. Tissue culture: It is carried out through callus formation, embryoids, pollen grain 
culture and shoot tip culture for plants which are either seedless, have recalcitrant 
seeds, variable seed progeny or where clone is to be maintained. 
 
9.    
(a) Plants raised through micropropagation are termed somaclones because they are 
genetically identical to the original plant from which they are grown. 
(b) Advantages of micropropagation: 
i. A large number of plants can be raised from a single individual plant within a 
relatively short period and limited space. 
ii. Virus-free healthy plants can be produced from the shoot apical meristem. 
 
10. An anaerobic sludge digester is a large tank where the anaerobic bacteria digest the 
bacteria and fungi in the sludge and produce a mixture of gases such as methane, H 2S 
and CO 2. 
 
 
  
Page 3


  
 
CBSE XII  |  Biology 
Board Paper – 2015 – All India – Set 3 (Solution) 
 
     
CBSE 
Class XII Biology 
Board Paper – 2015 – All India (Set 3)  
SOLUTION 
  
                                                                                  SECTION A 
 
1. A cistron is a segment of DNA which codes for a polypeptide. 
 
2. Drones of honey bee possess 16 chromosomes. The sperms in honey bee are produced 
by mitosis.  
 
3. Advantages of unleaded petrol in automobiles as fuel: 
i. Automobiles equipped with a catalytic converter should use unleaded petrol 
because lead in the petrol inactivates the catalysts of the converter. 
ii. Use of unleaded petrol prevents the release of poisonous gases such as nitrous oxide 
in the environment. 
 
4. Retroviruses have RNA as genetic material. After the entrance of the virus into the body 
of the host, the virus enters macrophages where its RNA genome replicates to form 
viral DNA with the help of the reverse transcriptase enzyme.      
 
5. Adenosine deaminase deficiency can be cured by enzyme replacement therapy and 
bone marrow transplantation. 
       
SECTION B 
 
6. The combinations having divergent evolution are 
i. Forelimbs of cheetah and mammals 
ii. Forelimbs of whales and mammals 
These two pairs exhibit divergent evolution because they have the same basic 
structural plan but are different in function. 
 
7. A liverwort is a bryophyte which is unable to complete its life cycle in a dry 
environment because 
i. The fertilisation of male and female gametes takes place in water. 
ii. Male gametes, antherozoids, swim in water to reach the eggs for sexual 
reproduction to take place. 
  
  
 
CBSE XII  |  Biology 
Board Paper – 2015 – All India – Set 3 (Solution) 
 
     
8. Mutualism is the relationship between two organisms where both are benefited either 
with food or shelter or substratum for attachment. 
Examples: 
i. Mycorrhizae are the mutualistic relationship between fungi and roots of higher 
plants. The fungus helps in mineral nutrition of the plant with which it is associated 
and obtains, in turn, carbohydrates from the plant. 
ii. Nitrogen-fixing bacteria, Rhizobium, live in the root nodules of legumes where the 
bacterium derives nutrition from the host plant but fixes the atmospheric nitrogen 
and makes it available to the plants.  
OR 
Ex situ conservation is the conservation of selected rare plants or animals in places 
outside their natural homes. Ex situ conservation of biodiversity has been employed in 
i. Gene banks: These are institutes which maintain stocks of viable seeds, live growing 
plants, tissue culture and frozen germplasm with the whole range of genetic 
variability. 
ii. Cryopreservation: Cryopreservation can maintain tissue culture, embryos, gametes, 
animal cells or tissues. Endangered organisms are being cryopreserved so that they 
can be revived to help in conservation. 
iii. Orchards: Plants with recalcitrant seeds are grown in orchards where all possible 
strains and varieties are maintained. 
iv. Tissue culture: It is carried out through callus formation, embryoids, pollen grain 
culture and shoot tip culture for plants which are either seedless, have recalcitrant 
seeds, variable seed progeny or where clone is to be maintained. 
 
9.    
(a) Plants raised through micropropagation are termed somaclones because they are 
genetically identical to the original plant from which they are grown. 
(b) Advantages of micropropagation: 
i. A large number of plants can be raised from a single individual plant within a 
relatively short period and limited space. 
ii. Virus-free healthy plants can be produced from the shoot apical meristem. 
 
10. An anaerobic sludge digester is a large tank where the anaerobic bacteria digest the 
bacteria and fungi in the sludge and produce a mixture of gases such as methane, H 2S 
and CO 2. 
 
 
  
  
 
CBSE XII  |  Biology 
Board Paper – 2015 – All India – Set 3 (Solution) 
 
     
SECTION C 
 
11. Monohybrid cross is a cross where two forms of a single trait are hybridised. Mendel 
crossed a pure tall pea plant with a pure dwarf pea plant and obtained all tall plants in 
the first filial generation. The character which appeared in the F 1 generation is called 
the dominant character, whereas the character which is not expressed in the F 1 
generation is called the recessive character. After intercrossing the hybrids of the F 1 
generation, he obtained the tall and the dwarf progeny in the ratio 3:1 (phenotypic 
ratio), but the genetic ratio was 1:2:1 which is TT, Tt and tt. 
 
 
 
12. The seeds produced without fertilisation are called apomictic seeds. 
Advantages: 
The embryos produced through apomixis are generally free from infection. 
Disadvantages: 
An apomictic embryo develops to produce several embryos inside a seed, a condition 
called polyembryony, which may require a stimulus in pollination. 
 
13.  
(a) The doctor injects the preformed antitoxin into the patient’s body. 
(b) The vaccine stimulates the production of antibodies against the antigen for inducing 
active acquired immunity. 
(c) The injection was given to prevent tetanus. It provides acquired immunity. 
 
14. A very small sample of tissue or even a drop of blood can help determine paternity by 
DNA fingerprinting. The DNA is extracted from the nuclei of cells or blood cell. The DNA 
molecules are first broken with the help of an enzyme restriction endonuclease which 
cuts them into fragments which contain variable number tandem repeats (VNTRs). The 
fragments are separated according to size by gel electrophoresis and are multiplied by 
the polymerase chain reaction (PCR) technique. They are then treated with alkaline 
chemicals to split them into single-stranded DNAs and are transferred onto a nylon 
membrane. An X-ray film is exposed to the nylon membrane on which the dark bands 
represent the DNA fingerprints. 
Page 4


  
 
CBSE XII  |  Biology 
Board Paper – 2015 – All India – Set 3 (Solution) 
 
     
CBSE 
Class XII Biology 
Board Paper – 2015 – All India (Set 3)  
SOLUTION 
  
                                                                                  SECTION A 
 
1. A cistron is a segment of DNA which codes for a polypeptide. 
 
2. Drones of honey bee possess 16 chromosomes. The sperms in honey bee are produced 
by mitosis.  
 
3. Advantages of unleaded petrol in automobiles as fuel: 
i. Automobiles equipped with a catalytic converter should use unleaded petrol 
because lead in the petrol inactivates the catalysts of the converter. 
ii. Use of unleaded petrol prevents the release of poisonous gases such as nitrous oxide 
in the environment. 
 
4. Retroviruses have RNA as genetic material. After the entrance of the virus into the body 
of the host, the virus enters macrophages where its RNA genome replicates to form 
viral DNA with the help of the reverse transcriptase enzyme.      
 
5. Adenosine deaminase deficiency can be cured by enzyme replacement therapy and 
bone marrow transplantation. 
       
SECTION B 
 
6. The combinations having divergent evolution are 
i. Forelimbs of cheetah and mammals 
ii. Forelimbs of whales and mammals 
These two pairs exhibit divergent evolution because they have the same basic 
structural plan but are different in function. 
 
7. A liverwort is a bryophyte which is unable to complete its life cycle in a dry 
environment because 
i. The fertilisation of male and female gametes takes place in water. 
ii. Male gametes, antherozoids, swim in water to reach the eggs for sexual 
reproduction to take place. 
  
  
 
CBSE XII  |  Biology 
Board Paper – 2015 – All India – Set 3 (Solution) 
 
     
8. Mutualism is the relationship between two organisms where both are benefited either 
with food or shelter or substratum for attachment. 
Examples: 
i. Mycorrhizae are the mutualistic relationship between fungi and roots of higher 
plants. The fungus helps in mineral nutrition of the plant with which it is associated 
and obtains, in turn, carbohydrates from the plant. 
ii. Nitrogen-fixing bacteria, Rhizobium, live in the root nodules of legumes where the 
bacterium derives nutrition from the host plant but fixes the atmospheric nitrogen 
and makes it available to the plants.  
OR 
Ex situ conservation is the conservation of selected rare plants or animals in places 
outside their natural homes. Ex situ conservation of biodiversity has been employed in 
i. Gene banks: These are institutes which maintain stocks of viable seeds, live growing 
plants, tissue culture and frozen germplasm with the whole range of genetic 
variability. 
ii. Cryopreservation: Cryopreservation can maintain tissue culture, embryos, gametes, 
animal cells or tissues. Endangered organisms are being cryopreserved so that they 
can be revived to help in conservation. 
iii. Orchards: Plants with recalcitrant seeds are grown in orchards where all possible 
strains and varieties are maintained. 
iv. Tissue culture: It is carried out through callus formation, embryoids, pollen grain 
culture and shoot tip culture for plants which are either seedless, have recalcitrant 
seeds, variable seed progeny or where clone is to be maintained. 
 
9.    
(a) Plants raised through micropropagation are termed somaclones because they are 
genetically identical to the original plant from which they are grown. 
(b) Advantages of micropropagation: 
i. A large number of plants can be raised from a single individual plant within a 
relatively short period and limited space. 
ii. Virus-free healthy plants can be produced from the shoot apical meristem. 
 
10. An anaerobic sludge digester is a large tank where the anaerobic bacteria digest the 
bacteria and fungi in the sludge and produce a mixture of gases such as methane, H 2S 
and CO 2. 
 
 
  
  
 
CBSE XII  |  Biology 
Board Paper – 2015 – All India – Set 3 (Solution) 
 
     
SECTION C 
 
11. Monohybrid cross is a cross where two forms of a single trait are hybridised. Mendel 
crossed a pure tall pea plant with a pure dwarf pea plant and obtained all tall plants in 
the first filial generation. The character which appeared in the F 1 generation is called 
the dominant character, whereas the character which is not expressed in the F 1 
generation is called the recessive character. After intercrossing the hybrids of the F 1 
generation, he obtained the tall and the dwarf progeny in the ratio 3:1 (phenotypic 
ratio), but the genetic ratio was 1:2:1 which is TT, Tt and tt. 
 
 
 
12. The seeds produced without fertilisation are called apomictic seeds. 
Advantages: 
The embryos produced through apomixis are generally free from infection. 
Disadvantages: 
An apomictic embryo develops to produce several embryos inside a seed, a condition 
called polyembryony, which may require a stimulus in pollination. 
 
13.  
(a) The doctor injects the preformed antitoxin into the patient’s body. 
(b) The vaccine stimulates the production of antibodies against the antigen for inducing 
active acquired immunity. 
(c) The injection was given to prevent tetanus. It provides acquired immunity. 
 
14. A very small sample of tissue or even a drop of blood can help determine paternity by 
DNA fingerprinting. The DNA is extracted from the nuclei of cells or blood cell. The DNA 
molecules are first broken with the help of an enzyme restriction endonuclease which 
cuts them into fragments which contain variable number tandem repeats (VNTRs). The 
fragments are separated according to size by gel electrophoresis and are multiplied by 
the polymerase chain reaction (PCR) technique. They are then treated with alkaline 
chemicals to split them into single-stranded DNAs and are transferred onto a nylon 
membrane. An X-ray film is exposed to the nylon membrane on which the dark bands 
represent the DNA fingerprints. 
  
 
CBSE XII  |  Biology 
Board Paper – 2015 – All India – Set 3 (Solution) 
 
     
15. The given equation represents the gene frequency of the total population according to 
Hardy–Weinberg law. In this equation, suppose a gene has two alleles A and a and p is 
the frequency of occurrence of the dominant allele A and q is the frequency of 
occurrence of the recessive allele a in the parental generation. 
Then according to the equation   
p
2
 + 2pq + q
2
 = 1, 
where p
2
  = frequency of occurrence of individuals with homozygous dominant alleles 
(AA) 
2pq = frequency of occurrence of heterozygous individuals (Aa) 
q
2
 = frequency of occurrence of individuals with homozygous recessive alleles (aa) 
 
16. Potential applications of genetically modified plants: 
i. GMO crops are more tolerant to abiotic stresses. 
ii. They have reduced the dependency on chemical pesticides. 
iii. They have enhanced the nutritional value of food such as vitamin A-enriched rice. 
 
17. The structure of insulin consists of two short polypeptide chains – chain A and chain B 
linked together by disulphide bridges. In mammals, including human beings, insulin is 
synthesised as a pro-hormone which contains an extra stretch called the C peptide that 
is removed during maturation to insulin. The rDNA technique was for assembling of 
insulin into the mature form.  
In 1983, Eli Lily, an American company, prepared two DNA sequences corresponding to 
the A and B chains of human insulin and introduced them in the plasmids of E. coli to 
produce insulin chains. Chains A and B were produced separately, extracted and 
combined by creating disulphide bonds to form human insulin.  
 
 
 
 
Page 5


  
 
CBSE XII  |  Biology 
Board Paper – 2015 – All India – Set 3 (Solution) 
 
     
CBSE 
Class XII Biology 
Board Paper – 2015 – All India (Set 3)  
SOLUTION 
  
                                                                                  SECTION A 
 
1. A cistron is a segment of DNA which codes for a polypeptide. 
 
2. Drones of honey bee possess 16 chromosomes. The sperms in honey bee are produced 
by mitosis.  
 
3. Advantages of unleaded petrol in automobiles as fuel: 
i. Automobiles equipped with a catalytic converter should use unleaded petrol 
because lead in the petrol inactivates the catalysts of the converter. 
ii. Use of unleaded petrol prevents the release of poisonous gases such as nitrous oxide 
in the environment. 
 
4. Retroviruses have RNA as genetic material. After the entrance of the virus into the body 
of the host, the virus enters macrophages where its RNA genome replicates to form 
viral DNA with the help of the reverse transcriptase enzyme.      
 
5. Adenosine deaminase deficiency can be cured by enzyme replacement therapy and 
bone marrow transplantation. 
       
SECTION B 
 
6. The combinations having divergent evolution are 
i. Forelimbs of cheetah and mammals 
ii. Forelimbs of whales and mammals 
These two pairs exhibit divergent evolution because they have the same basic 
structural plan but are different in function. 
 
7. A liverwort is a bryophyte which is unable to complete its life cycle in a dry 
environment because 
i. The fertilisation of male and female gametes takes place in water. 
ii. Male gametes, antherozoids, swim in water to reach the eggs for sexual 
reproduction to take place. 
  
  
 
CBSE XII  |  Biology 
Board Paper – 2015 – All India – Set 3 (Solution) 
 
     
8. Mutualism is the relationship between two organisms where both are benefited either 
with food or shelter or substratum for attachment. 
Examples: 
i. Mycorrhizae are the mutualistic relationship between fungi and roots of higher 
plants. The fungus helps in mineral nutrition of the plant with which it is associated 
and obtains, in turn, carbohydrates from the plant. 
ii. Nitrogen-fixing bacteria, Rhizobium, live in the root nodules of legumes where the 
bacterium derives nutrition from the host plant but fixes the atmospheric nitrogen 
and makes it available to the plants.  
OR 
Ex situ conservation is the conservation of selected rare plants or animals in places 
outside their natural homes. Ex situ conservation of biodiversity has been employed in 
i. Gene banks: These are institutes which maintain stocks of viable seeds, live growing 
plants, tissue culture and frozen germplasm with the whole range of genetic 
variability. 
ii. Cryopreservation: Cryopreservation can maintain tissue culture, embryos, gametes, 
animal cells or tissues. Endangered organisms are being cryopreserved so that they 
can be revived to help in conservation. 
iii. Orchards: Plants with recalcitrant seeds are grown in orchards where all possible 
strains and varieties are maintained. 
iv. Tissue culture: It is carried out through callus formation, embryoids, pollen grain 
culture and shoot tip culture for plants which are either seedless, have recalcitrant 
seeds, variable seed progeny or where clone is to be maintained. 
 
9.    
(a) Plants raised through micropropagation are termed somaclones because they are 
genetically identical to the original plant from which they are grown. 
(b) Advantages of micropropagation: 
i. A large number of plants can be raised from a single individual plant within a 
relatively short period and limited space. 
ii. Virus-free healthy plants can be produced from the shoot apical meristem. 
 
10. An anaerobic sludge digester is a large tank where the anaerobic bacteria digest the 
bacteria and fungi in the sludge and produce a mixture of gases such as methane, H 2S 
and CO 2. 
 
 
  
  
 
CBSE XII  |  Biology 
Board Paper – 2015 – All India – Set 3 (Solution) 
 
     
SECTION C 
 
11. Monohybrid cross is a cross where two forms of a single trait are hybridised. Mendel 
crossed a pure tall pea plant with a pure dwarf pea plant and obtained all tall plants in 
the first filial generation. The character which appeared in the F 1 generation is called 
the dominant character, whereas the character which is not expressed in the F 1 
generation is called the recessive character. After intercrossing the hybrids of the F 1 
generation, he obtained the tall and the dwarf progeny in the ratio 3:1 (phenotypic 
ratio), but the genetic ratio was 1:2:1 which is TT, Tt and tt. 
 
 
 
12. The seeds produced without fertilisation are called apomictic seeds. 
Advantages: 
The embryos produced through apomixis are generally free from infection. 
Disadvantages: 
An apomictic embryo develops to produce several embryos inside a seed, a condition 
called polyembryony, which may require a stimulus in pollination. 
 
13.  
(a) The doctor injects the preformed antitoxin into the patient’s body. 
(b) The vaccine stimulates the production of antibodies against the antigen for inducing 
active acquired immunity. 
(c) The injection was given to prevent tetanus. It provides acquired immunity. 
 
14. A very small sample of tissue or even a drop of blood can help determine paternity by 
DNA fingerprinting. The DNA is extracted from the nuclei of cells or blood cell. The DNA 
molecules are first broken with the help of an enzyme restriction endonuclease which 
cuts them into fragments which contain variable number tandem repeats (VNTRs). The 
fragments are separated according to size by gel electrophoresis and are multiplied by 
the polymerase chain reaction (PCR) technique. They are then treated with alkaline 
chemicals to split them into single-stranded DNAs and are transferred onto a nylon 
membrane. An X-ray film is exposed to the nylon membrane on which the dark bands 
represent the DNA fingerprints. 
  
 
CBSE XII  |  Biology 
Board Paper – 2015 – All India – Set 3 (Solution) 
 
     
15. The given equation represents the gene frequency of the total population according to 
Hardy–Weinberg law. In this equation, suppose a gene has two alleles A and a and p is 
the frequency of occurrence of the dominant allele A and q is the frequency of 
occurrence of the recessive allele a in the parental generation. 
Then according to the equation   
p
2
 + 2pq + q
2
 = 1, 
where p
2
  = frequency of occurrence of individuals with homozygous dominant alleles 
(AA) 
2pq = frequency of occurrence of heterozygous individuals (Aa) 
q
2
 = frequency of occurrence of individuals with homozygous recessive alleles (aa) 
 
16. Potential applications of genetically modified plants: 
i. GMO crops are more tolerant to abiotic stresses. 
ii. They have reduced the dependency on chemical pesticides. 
iii. They have enhanced the nutritional value of food such as vitamin A-enriched rice. 
 
17. The structure of insulin consists of two short polypeptide chains – chain A and chain B 
linked together by disulphide bridges. In mammals, including human beings, insulin is 
synthesised as a pro-hormone which contains an extra stretch called the C peptide that 
is removed during maturation to insulin. The rDNA technique was for assembling of 
insulin into the mature form.  
In 1983, Eli Lily, an American company, prepared two DNA sequences corresponding to 
the A and B chains of human insulin and introduced them in the plasmids of E. coli to 
produce insulin chains. Chains A and B were produced separately, extracted and 
combined by creating disulphide bonds to form human insulin.  
 
 
 
 
  
 
CBSE XII  |  Biology 
Board Paper – 2015 – All India – Set 3 (Solution) 
 
     
18. Adaptations in unfavourable conditions in the following organisms: 
i. Snails: Snails undergo aestivation to avoid summer-related problems such as heat 
and desiccation. 
ii. Seeds: The seeds undergo dormancy to tide over adverse environmental conditions. 
They reduce their metabolic activity and remain quiescent till the suitable 
environmental conditions return. 
iii. Bears: They undergo hibernation during winters to escape harsh winter conditions. 
iv. Zooplankton: Under unfavourable conditions, zooplankton species in lakes and 
ponds enter diapause which is a stage of suspended development.  
v. Fungi: In fungi, various kinds of thick-walled spores are formed which help them to 
survive in unfavourable conditions. The spores germinate on return of favourable 
conditions. 
vi. Bacteria: Bacteria form thick spores which help them to survive under unfavourable 
conditions. 
 
19. Essentials of good, effective dairy farm management practices are 
i. Good breeds of dairy farm animals should be selected. 
ii. Suitable environmental conditions such as adequate ventilation, suitable 
temperature, sufficient light, water, air and well-drained housing accommodation 
should be provided. 
iii. Each animal should be fed on a balanced ration. 
iv. Hygiene and proper cleanliness of animals should be included in the guidelines for 
housing of animals. 
v. Animals should be vaccinated at regular time intervals in order to protect them 
from diseases. 
vi. Regular visits by a veterinary doctor are a must.