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CBSE 12th Term-2 2022 : Biology Most Important 2 Marks Questions with Solution
Given below is the set of important 2 marks questions which are suggested by the experts to practice for the CBSE Class 12 Biology Term 2 Exam 2022 that is going to be conducted on 30 May. These questions are best for last-minute revision and fine-tune your preparations for the exam.
Q1. Write the events that take place when a vaccine for any disease is introduced into the human body.
Ans : Vaccine is an antigen protein of pathogens or inactivated or weakened pathogens or their toxin. When it is introduced into the body of a person who is required to be made immune it stimulates the production of antibody and memory cell which is called primary response. It does not cause harm when this pathogen enters second time. These memory cells show rapid and massive responses so body become immune to this pathogen.
Q2. Why is a person with cuts and bruises following an accident administered tetanus antitoxin? Give reason.
Ans : Vaccine is an antigen protein of pathogens or inactivated or weakened pathogens or their toxin. When it is introduced into the body of a person who is required to be made immune it stimulates the production of antibody and memory cell which is called primary response. It does not cause harm when this pathogen enters second time. These memory cells show rapid and massive responses so body become immune to this pathogen.
Q3. Write the source and effect on the human body of the following drugs.
1. Cocaine
2. Morphine
Ans : 1. Cocaine is obtained from coca plant Erythroxylum coca. It interferes with the transmit of the neurotransmitter, dopamine.
2. Morphine is obtained from poppy plant Papaver somniferum. It binds to specific opioid receptors present in central nervous system and gastrointestinal tract.
Q4. Differentiate between innate immunity and acquired immunity.
Ans : Innate immunity is the immunity by the virtue of genetic constitutional makeup, i.e. it is inherited from parents. It is present in the body without any external stimulation or a previous infection, whereas acquired immunity is the resistance to a disease which an individual acquires during a lifetime. It may be the result of either a previous infection or from readymade antibodies supplied from outside.
Q5. How are morphine and heroin related? Mention the effect each one of them has on the human body?
Ans : Heroin is obtained as a result of acctvlation of morphine. Morphine is used as an effective pain-killer & sedative while heroin is a depressant & slows down the functions of the body.
Q6. Name the microbes which are used for the industrial production of the following.
a.Citric acid
b. Acetic acid
c. Butyric acid
Ans : (a) Citric acid - Citric acid is produced by Aspergillus niger.
(b) Acetic Acid - Acetic Acid is produced by the bacterium Acetobacter acetic.
(c) Butyric acid - Butyric acidand butyric acid are produced by the bacterium Clostridium butylicum.
Q7. Organ-transplant patients need a medicine called cyclosporine. How is it useful for the patient? Name the source of this medicine.
Ans : Cyclosporine is used to prevent organ rejection in people who have received a liver, kidney, or heart transplant. It is usually used along with other medications to allow your new organ to function normally. Cyclosporine belongs to a class of drugs known as immunosuppressants.
Q8. Bottled fruit juices brought from the market are clearer as compared to those made at home. Why?
Ans : The bottled fruit juices that are brought are tested by treating them with enzymes - pectinases and proteases.so, they are clearer as compare to those made at home.
Q9. What is the key difference between primary and secondary sewage treatment?
Ans : Primary sewage treatment is a physical process that removes large impurities while secondary sewage treatment is a biological process that removes organic matter of sewage through the action of microbes.
Q10. Identify the recognition sites in the given sequences at which E. coli will cut and make sticky ends.
5 ́GAATTC 3 ́
3 ́CTTAAG5 ́
Ans : It will cut between the GA sequence
5' G AATTC 3'
3' CTTAA G 5'
Q11. What is the role of Ori for cloning vector?
Ans : Ori: It is a genetic sequence that acts as the initiation site for replication of DNA. Any fragment of DNA, when linked to the ori region, can be initiated to replicate.
Q12. Study the linking of DNA fragments shown above
(i) Name “a” DNA and “b” DNA
(ii) Name the restriction enzymes that recognizes this palindrome
(iii) Name the enzyme that can link these two DNA fragments
Ans : (i) (a) – vector DNA
(b) – foreign DNA
(ii) EcoRI
(iii) DNA ligase
Q13. Make a list of tools of recombinant DNA technology
Ans : The key tools used in recombinant DNA technology are
1.Isolation of DNA
2.Fragmentation of DNA by restriction endonucleases
3.Isolation of the desired DNA fragment.
4.Amplification of the gene of interest.
5.Ligation of the DNA fragment into a vector using DNA ligase.
6.Transfer of recombination DNA into the host and many more.
Q14. Why is it not possible for an alien DNA to become part of chromosome anywhere along its length and replicate?
Ans : Alien DNA cannot become part of the chromosome anywhere along its length and replicate normally because in order to ligate itself to the host chromosome alien DNA requires specific recognition sequences. The sequence should also be close to the origin of replication or Ori where DNA replication starts. This site is necessary for the binding of the DNA polymerase to start replication.
Q15. What are transgenic animals? How was the first transgenic cow found to be more useful than the normal cow, for humans?
Ans : Those animals which go under the DNA manipulation to express an extra gene in them. The first transgenic cow was Rosie, and these were its features:
- produced human protein-enriched milk
- 2.4 gm protein per litre which contained human alpha-lactalbumin
- milk was nutritionally more balanced for human babies than natural cow milk
Q16. How does silencing of specific mRNA in RNA interference prevent parasitic infestation?
Ans : In the process of silencing of mRNA, a eukaryotic cell produces a strand of RNA which is complimentary to the mRNA of the parasite, thus making it's RNA double stranded. This inhibits the parasite to translate it's RNA to any kind of protein and thus it prevents infection.
Q17. Write the function of adenosine deaminase enzyme. State the cause of ADA deficiency in humans.
Ans : Adenosine deaminase enzyme is a very important enzyme which is for the functioning of immune system.
Cause: ADA deficiency is due to deletion of the gene for adenosine deaminase.
Q18. List any four ways by which GMOs have been useful for enhanced crop output.
Ans : 1. GMO's have genetic modifications outcomes of these genetic modifications include increased food production.
2. Genetically modified crops are stress tolerant to extreme conditions like cold, heat, drought, etc.
3. Some crops are made pest resistant by genetic modification which cuts down the use of pesticides and hence becomes economically and ecologically beneficial.
4. Helps in increasing the efficiency of mineral usage by plants which maintains the mineral content of the soil and keeps it fertile for longer duration.
Q19. Suggest any two possible treatments that can be given to a patient exhibiting adenosine deaminase deficiency.
Ans : i. Enzymes replacement therapy (in which functional ADA is injected)
ii. Bone marrow transplantation
iii. Gene therapy/Culturing the lymphocytes followed by introduction of functional ADA cDNA into it and returning it into the patient’s body.
Q20. Draw labelled diagrams of stable and declining age pyramids of human population.
Ans : Stable and declining age pyramids of human Population.
Q21. Shark is eurythermal while polar bear is stenothermal. What is the advantage the former has and what is the constraint the later has?
Ans : The advantage that shark is eurythermal is that they can tolerate the wide range of the temperatures, while polar bear has constraints that they can cope with only a narrow range of the temperature hence they have restricted habitat.
Q22. How do mammals living in colder regions and seals living in polar regions able to reduce the loss of their body heat?
Ans : Mammals from colder climates generally have shorter ears and limbs which minimize heat loss (Allen's rule).
In polar region seals have thick layer of fat (blubber) below their skin that acts as insulator and reduce loss of body heat.
Q23. How do kangaroo rats and desert plants adapt themselves to survive in their extreme habitat? Explain.
Ans : Kangaroo and rats use their internal fat oxidation where water is a byproduct and excretes concentrated urine.
Desert Plants dapt themselves to survive in their extreme habitat via thick cuticle, sunken stomata,leaves reduced to spines, deep roots, Special photosynthetic pathway, CAM.
Q24. Identify the areas labelled i, ii, iii and iv in the pie chart given below representing the biodiversity of plants showing their proportionate number of species of major taxa.
Ans : (i) Litchen
(ii) Algae
(iii) Fungi
(iv) Masses
Q25. Suggest two practices giving one example of each, that help protect rare or threatened species.
Ans : (i) Ex-situ conservation : The threatened animals and plants are taken out from the natural habitats and are placed in special settings where they can be protected and given special care. Zoological parks, botanical gardens, wildlife safari parks serve as ex-situ conservation.
(ii) In-situ conservation : It is the conservation of genetic resources within natural or human-made ecosystems in which they occur. e.g. Protected areas such as National Parks, Sanctuaries, Sacred Forests, Hotspots
Q26. Suggest four advanced ex-situ methods to conserve threatened biodiversity.
Ans : Techniques for plants:-
1.Cryopreservation
2.Seed banking
3.Tissue culture (storage and propagation)
4.Field gene banking
5.Cultivation collections
6.Inter situ
Q27. ‘‘India has greater ecosystem diversity than Norway.’’ Do you agree with the statement? Give reasons in support of your answer.
Ans : Ecological diversity refers to the different types of habitats. It includes various biological zones, like lake, desert, coast, estuaries, wetlands, mangroves, coral reefs etc. A geographical region having different ecosystems will have more ecologically diverse organisms. At the ecosystem level, India, for instance, with its deserts, rainforests, mangroves, coral reefs, wetlands, estuaries, and alpine meadows has a greater ecosystem diversity than a Scandinavian country like Norway. Although India has only 2.4 percent of the world’s land area, its share of the global species diversity is an impressive 8.1 percent. That is what makes India one of the 12 megadiversity countries of the world. Nearly 45,000 species of plants and twice as many of animals have been recorded from India.
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