CBSE Class 12 Biology Value Based Questions All Chapters Set A

Value Based Questions

1. Tarun was one of the best boys in the class. In spite of his efforts he was not doing well in class XI. His father wanted him to qualify for medical sciences. He got frustrated with his results and resorted to drugs. He started misbehaving with parents and friends in school. His friends started neglecting him. The school authorities counselled Tarun but to no effect. His parents were upset and took him to a rehabilitation center. After a few months he came back recovered.

Question. What values did the Principal reflect through his initiative?
Answer: The Principal showed his social liability and responsibility.

Question. What is drug abuse?
Answer: Intake of drugs for a non- medical purpose in the dose, strength, frequency and the way of taking which impairs mental and physical functions of human being is drug abuse.

Question. Name some commonly abused drugs and their source.
Answer: i) Opium: from plant Papaver somniferum- its derivatives includes morphine, codeine, heroin, smack i.e brown sugar etc.
ii) Cocaine: from Erythroxylon coca, crack - a cocaine derivative, caffeine from Thea sinensis, Coffea Arabica, Theobroma cacao
iii) LSD: from fungus Claviceps purpurea
iv) Any other may be included

Question. What should be the attitude of his parents after his return? 
Answer: Parents should be compassionate and more caring towards the child and behave normally

2. Joy loves to play football and was 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 came to know that he was HIV positive. He lost interest in games and refused to play or study. He started counting his days. He remained absent from school for a long time. The Biology teacher visited his house and counselled him. Joy was back at school and also played the tournament.

Question. What sense of responsibility did the Biology teacher exhibit?
Answer: The teacher shows social and moral responsibility along with his commitment to service as a professional teacher.

Question. A person detected to be HIV positive should be isolated in the society? Do you agree? Why/ Why not?
Answer: No. AIDS is not a contagious disease and does not spread until a blood/ body fluid contact is established.

Question. How is AIDS not spread?
Answer: AIDS is not spread by: body contact in crowded place, hand shaking, sharing telephone, meal, utensil or clothings, light kissing, using same toilet seat or even swimming pool. It is not transmitted by blood sucking vectors or by coughing and sneezing.

3. Ratan lives in a remote village. Suddenly he comes to know that his father has arranged the marriage of his younger sister, who is only 14 years old, to a well- to -do middle aged man living in a nearby village. Ratan objected to his father’s act. Ratan was not convinced by his father’s idea that a better groom might not be available later. Ratan complained to the village head and got the problem solved.

Question. Did Ratan act properly by approaching the village head? Why/ Why not?
Answer: Yes, it was necessary to stop the act since as per the government order, the minimum marriageable age of a girl is 18 years.

Question. What biological considerations made Ratan object to his father’s decision?
Answer: Ratan thought of the following Disadvantages of ealy marriage: (Any two)

            Forced sexual relation and denial of freedom with restriction to family bindings.

            Domestic violence

            Denial of education

            Reproductive health problems

            Teenage pregnancy

            Child birth associated trauma

            High postnatal mortality

            Population pressure, health costs, human development loss

           Health costs

           Early widowhood,

Question. What values and responsibilities did Ratan show?
Answer: Sense of responsibility and consciousness for his family and respect of government laws. He expressed his views boldly for the right cause.

4. During a visit to Kedarnath, Mohun came across a young couple staying in the adjacent room in the hotel. He learnt that the couple had been visiting different temples and performing rituals to get a child. Mohun was astonished and explained to them about ART which he had recently studied in Biology. The couple were happy and understood their wrong approach and thanked Mohun.

Question. Identify the values which Mohun has shown.
Answer: Sympathetic attitude with alertness and practical approach.

Question. What is ART? What are the various method included in ART?
Answer: Assisted Reproductive Technology
Methods are: i) test tube baby programme which includes IVF and Zygote or embryo transfer b) gamete intra fallopian transfer iii) Intra cytoplasmic sperm injection iv) artificial insemination methods.

Question. What are the limitations for which ART is not commonly accepted?
Answer: 1. These techniques require extremely high precision handling by specialized professionals and expensive instrumentation. Therefore, these facilities are presently available only in a very few centres in the country.

2. Emotional, religious and social factors are also deterrents in the adoption of these methods.

5. A teenage girl accidently became pregnant. She stopped coming to college and also preferred to remain isolated. She was scared to inform her parents. One of her friends Sweta met her and came to know about the problem. She took her to a doctor and got her aborted. She convinced the parents and kept the matter concealed.

Question. Did Sweta take the correct decision? What values did she show?
Answer: Yes. Sweta expressed her helpful attitude and true friendship. She had social commitment and sensitivity to act as per the situation.

Question. What is the medical term for abortion? What is the period which is considered safe for abortion?
Answer: Medical termination of pregnancy (MTP) or Induced abortion.
It is safe up to the first trimester of pregnancy (12 weeks)

Question. What prevention may be taken to avoid pregnancy?
Answer: i) Abstinence

           ii) Contraceptive methods

          iii) Any other

6. On world population day Rohit and his friends arranged an awareness campaign programme in their locality. Some elderly people rebuked the children and asked them not to talk on such things in public. The children convinced the elders about the need for the programme and on understanding their point of view, they also joined the campaign.

Question. What values did the elderly people and Rohit show on the occasion?
Answer: Rohit and his friends show understanding of population explosion, team work and motivational capacity. 

Question. Why is such awareness programme necessary?
Answer: To understand the problem faced by the family and the nation due to increasing population, simultaneously the benefits of having a small family. 

Question. What role has the government played in controlling population explosion?
Answer: i) Public awareness through mass media

           ii) Education at all levels

          iii) Family planning 

          iv) Increasing marriageable age (18 for girls, 21 for boys)

          v) Any other

7. Some parents wrote a complaint letter to the local municipality to remove all hoardings in the city advertising the use of condoms and matters relating to AIDS prevention. The children of these parents came to know about the matter and raised their voice against removal of those hoardings. The parents were convinced by the awareness level of their children and withdrew the complaint.

Question. Parents considered the hoarding as sight pollution. Why do you disagree?
Answer: Since the awareness among our people has not reached to that extent that forceful and constant reminding is not required. Our country is overpopulated and number of AIDS is increasing too fast.

Question. What value is promoted by the children protesting against their parents?
Answer: Sense of understanding AIDS and application in life, National responsibility and commitment towards society.

Question. What are the methods by which AIDS spreads?
Answer: i) Unprotected sexual contact

          ii) Use of contaminated needles and syringes

         iii) Use of contaminated razors or other instruments used for piercing body parts e.g. pinna

         iv) Transfusion of infected blood or blood products

         v) Organ transplant

        vi) Parturition

        vii) Any other

8. Rita and her parents were watching a TV serial in the evening. During a commercial break, an advertisement flashed on the screen which was promoting use of sanitary napkins. Rita was still watching the TV. The parents got embarrassed and changed the channel. Rita objected to her parents’ behaviour and explained the need for these advertisements.

Question. What values did the parents show?
Answer: The parents were traditional but understood the need for such advertisements. 

They showed maturity and openness later.

Question. Briefly describe the phases of a menstrual cycle.

9. Anita was happy when she gave birth to her first child. Her in- laws were dissatisfied at her not giving birth to a male child and blamed Anita. Anita tried to convince her in laws that she had no role in the child’s gender. They understood the biological reason but were yet to be satisfied. Anita’s husband took up the matter and convinced the parents.

Question. What values did Anita’s husband show in the above situation?
Answer: Strong and determined personality with responsibility towards the family and respect for elders.

Question. What governs sex determination in humans? How is it different from birds?
Answer: Sex chromosomes. In human males it is XY and in female it is XX In birds, male is ZZ while female is ZW.

Question. Why can’t Anita be blamed for not giving birth to a male child?
Answer: Human females are homogametic i.e. produces only one type of gametes containing 22+X chromosomes only. Males are heterogametic and produce two types of gametes 22+X and 22+Y. It is the type of male gamete which determines the sex of the foetus. If X chromosome containing sperm fuses with the egg, it produces a female child whereas if Y chromosome containing sperm fuses with the egg, it produces a male child.

10. Mrs. Kavita was eager to know the sex of the foetus which her daughter- in- law was carrying. She was so anxious that she could pay any amount for that. The doctor refused to disclose the result of the test.

Question. What value do you learn from the doctor’s act?
Answer: The doctor is devoted to his duties and has professional ethics.

Question. How can one know the sex of the foetus? How is it done? 
Answer: By amniocentesis 

           The process – step wise

Question. Why is disclosing the sex of the foetus banned in our country?
Answer: In the past there have been numerous cases where the female foetus has been aborted. This anti -feeling for the girl child is considered a crime. The number of females to males is thereby reduced.

11. Ravi was rushed to a nearby hospital after an accident which caused a lot of blood loss. The hospital failed to supply O negative blood for transfusion. Rahman who was attending a patient learned about the situation and agreed to donate blood being of the same blood group. Ravi’s mother initially refused but was later convinced by her daughter.

Question. What values do you find in Ravi’s sister and Rahman?
Answer: Humanity is above all religion. Ravi’s sister shows understanding of science. Rahman believes in helping a person in need without thinking about which religion or caste he belongs to.

Question. Why can’t O positive blood be transfused into Ravi’s body?
Answer: O+ blood group contains antigen for Rh factor. Rh negative blood lacks the antigen. So if the two bloods mix it shall cause clotting resulting in death of the patient.

Question. What is the genetic basis of blood group inheritance?
Answer: Human blood groups are A, B, AB and O. The four phenotypes are expressed by paired combination of three alleles (IA, IB and i). IA and IB are dominant alleles for blood groups A and B respectively. O blood group is due to lack of any dominant gene. Its genotype is ii. Alleles IAIB expresses both dominant traits and the blood group is AB.

12. While finalising an alliance between his son and Rita, Mr. Ram was curious to know what was Rita’s blood group. Nobody was interested in their blood groups since their horoscopes matched. Mr. Ram was adamant in wanting to know the blood groups before finalising. The senior people got annoyed. Then Rita stood up and gave the reasons. Mr. Ram was happy and the marriage date was finalised.

Question. Mr. Ram’s refusal to accept only horoscopes shows certain values. What are they? 
Answer: Mr. Ram was not orthodox, he had a modern and scientific outlook.

Question. What effect on the foetus may be expected if the father has A⁺ and the mother O⁺ blood groups? 
Answer: If the mother carries a foetus having A blood group, it acts as antigen to mother’s blood. The mother accordingly develops antibodies against the foetus. Severity is observed in the subsequent issue where the child may be born with anaemia and jaundice.

Question. What is the possible remedy in case of an Rh factor incompatibility between the foetus and mother’s blood?
Answer: Today, when a woman with the potential to develop Rh incompatibility is pregnant, doctors administer a series of two Rh immune-globulin shots during her first pregnancy. The first shot is given around the 28th week of pregnancy and the second within 72 hours after giving birth. Rh immune-globulin acts like a vaccine, preventing the mother's body from producing any potentially dangerous Rh antibodies that can cause serious complications in the newborn or complicate any future pregnancies.

13. Sonam is a bright, fair girl. Her parents are dark complexioned. Her friends in college regularly passed remarks asking her how she was so fair or what treatment she had undergone to become fair. Sonam got irritated at their repeated embarrassing questions. Her friend Srijita came to her support and invited the friends to the Biology lab where she explained the inheritance of body colour. The friends realised their mistake and stopped teasing Sonam.

Question. What good values did Srijita reflect from her deeds? 
Answer: Humanity and responsibility towards a friend. She also used her knowledge to educate her friends.

Question. What is the name of the inheritance pattern discussed?
Answer: Polygenic inheritance or quantitative inheritance

Question. Which other characters in human follow the same pattern?
Answer: Height, weight, skin colour, hair colour, size of some organs, face form, intelligence etc of human beings are examples of quantitative inheritance.

Question. Explain how Sonam could be fairer than her parents. 
Answer: Since each dominant allele synthesises equivalent amount of melanin pigment (to give skin colour), the skin colour is directly proportionately to the number of dominant alleles inherited. If the sum of recessive alleles inherited by the offspring be more than or equal to that of the parents, the child is expected to be fairer than the parents. E.g. if the parents are heterozygous for all alleles (3 dominant and 3 recessive) then they are intermediate in colour. If the child inherits 4 recessive alleles from the parents, the expression shall be fairer than the parents.

14. During Primary art classes the teacher asked Parthiv to mix green and yellow paint and report on the combined colour formed. Parthiv could not find green colour in his box and was scolded by the teacher who found it lying right in front. Suddenly Vijay realised that Parthiv was not able to identify red colour and reported the matter to the teacher who was of the opinion that he lacked colour concept. After school was over, Vijay reported this matter to Parthiv’s parents.

Question. What values did Vijay possess? 
Answer: Vijay was alert, curious, clever and a responsible child.

Question. Did Parthiv lack knowledge of colours ? If not give the biological reason for the same.
Answer: According to the teacher Parthiv lacks the concept of colours. But when he could not identify red colour, it proved to be a case of colour blindness. It is a sex linked inherited disorder.

Question. Give the technical term for this type of inheritance. Explain with a typical example. 
Answer: This is a human disease which causes the loss of ability to differentiate between red colour and green colour. The gene for this red-green colour blindness is present on X chromosome. Colour blindness is recessive to normal vision.

If a colour blind man (XcY) marries a girl with normal vision (XX), the daughters would have normal vision but would be carrier, while sons would also be normal Cross (a)

If the carrier girl (heterozygous for colour blindness, XcX) now marries a colour blind man XcY the offspring would show 50% females and 50% males. Of the females, 50% would be carrier for colour blindness and the rest 50% would be colour blind. Of the males, 50% would have normal vision and the 50% would be colour blind

15. A Couple quarrelled with the hospital authority on suspicion that their child had been exchanged after birth. The couple based their argument on the fact that their child is O blood group whereas they are A and B blood groups respectively. The doctor smiled and explained.

Question. What values of the doctor is reflected here? 
Answer: The doctor was assertive, patient and pragmatic.​​​​​​​

Question. How can the child be O blood group as explained by the doctor? 
Answer: It is possible if the parents are hererozygotes, i.e.

Ai x Bi. If the child receives i from both the parents, it becomes ii, and expresses O blood group. 

See the chart below.

Question. Which test method can be considered authentic to identify the biological parents of the child? 
Answer: DNA finger printing 

Question. Name the other blood group(s) which the child could have inherited. 
Answer: A or B or AB

16. Brijmohan angrily says to his daughter not to marry Rajiv since their family is known to inherit Haemophilia. The daughter objected to her father’s order. Brijmohan was adamant and threatened Rajiv also. Brijmohan’s daughter explained the biological interpretation of his fear and convinced her father. 

Question. Rajiv was not haemophilic. Why was Brijmohan so worried?  
Answer: Brijmohan was not aware of the inheritance pattern for haemophilia. He thought that the disease shall be expressed among his grandchildren.  

Question. What values do you identify from the role played by Brijmohan’s daughter?
Answer: Scientific attitude, deep understanding and practical application of the subject. She was focussed having convincing ability. 

Question. What explanation must have convinced Brijmohan?
Answer: Haemophilia is a sex linked recessive inherited disease. The gene is located on the X chromosome. Human male has only one sex chromosome (44A + XY). Rajiv is not haemophilic since he does not have the gene on his X chromosome. There remains no chance for him to pass on any haemophilic gene to the next generation. 

Question. Is there any fear of haemophilia if Brijmohan’s daughter marries Rajiv?  
Answer: No there remains no fear if they are married, provided the girl is not a carrier of haemophilia. If the girl is a carrier, then the chance for the son to be haemophilic is 50%.

17. The Biology teacher asked the students to verify the experiment on Transformation principle in bacteria to establish DNA as genetic material. The class was divided into two groups. The teacher asked them to submit the reports. Group 2 did not use mouse and did not repeat Griffith’s experiment. The teacher praised them. 

Question. What values did Group 2 exhibit? 
Answer: Scientific attitude, awareness and love for animals and respect towards government policies. 

Question. Which experiment did they perform? Explain in brief. 
Answer: The students repeated the experiment performed by Oswald Avery, Colin MacLeod and Maclyn McCarty (1933-44), who worked to determine the biochemical nature of ‘transforming principle’ in Griffith's experiment. 

They purified biochemicals (proteins, DNA, RNA, etc.) from the heat-killed S cells to see which ones could transform live R cells into S cells. They discovered that DNA alone from S bacteria caused R bacteria to become transformed. They also discovered that protein-digesting enzymes (proteases) and RNA-digesting enzymes (RNases) did not affect transformation, so the transforming substance was not a protein or RNA. Digestion with DNase did inhibit transformation, suggesting that the DNA caused the transformation. 

Follow the diagram below.

18. Ratan was a known sportsman in his school. While returning home he found some unknown miscreants beating a young fellow. He tried to drive them off but by that time the fellow died of injury. The police arrested Ratan and he was put on trial. The judge being convinced by Ratan’s plea, ordered for DNA finger printing reports.

Question. Ratan’s fingerprints on the dead body were sufficient to convict him but the judge asked for authentic proof? What values can be observed? 
Answer: The judge showed wisdom and intention to search for the truth.

Question. What is the basis of DNA finger printing? 
Answer: 1. DNA fingerprinting involves identifying differences in some specific regions in DNA sequence called as repetitive DNA.

2. Depending on base composition (A: T rich or G:C rich), length of segment, and number of repetitive units, the satellite DNA is classified into many categories,(Micro-satellites, mini-satellites etc).

3. These sequences normally do not code for any proteins, but they form a large portion of human genome. These sequence show high degree of polymorphism and form the basis of DNA fingerprinting.

Question. Explain the steps in DNA finger printing.
Answer: (i) isolation of DNA,

(ii) digestion of DNA by restriction endonucleases,

(iii) separation of DNA fragments by electrophoresis,

(iv) transferring (blotting) of separated DNA fragments to synthetic membranes, such as nitrocellulose or nylon,

(v) hybridisation using labelled VNTR probe, and 

(vi) detection of hybridised DNA fragments by autoradiography.

19. During an excursion to a botanical garden, the teacher shows an old tree which was on the verge of extinction. As soon as the teacher advanced with the students, some enthusiastic students climbed up the tree and started cutting the branches, collecting its leaves as precious collection. Rajesh instead took photographs of the tree from various angles. The boys mocked at Rajesh while the teacher appreciated him.

Question. What values did Rajesh possess?
Answer: Respect for nature, scientific attitude with a vision of the future

Question. Why should we conserve biodiversity?
Answer: We should conserve Biodiversity since it provides us

           • Main source of food

           • Source of economically important fibers (cotton, flax, hemp, jute etc)

           • Plant products (gum, resin, dye, fragrance, waxes, wool, leather, honey, lac, pearl, ivory, silk, horns)

           • Drugs and medicine

           • Sports and recreation

           • Aesthetic value

           • Cultural value

           • Scientific research

          • Eco system services 

(More points may be added)

Question. How can be biodiversity be conserved?

20. A snake charmer came to the house and smelled the presence of a cobra which the residents had never seen in the last 10 years. The landlord agreed to allow the man to search, catch and take away with him the snake. Little Jazman disagreed and drove the man away.

Question. Did Jazman do the right thing? What values did he show?
Answer: Scientific attitude, obligation to maintain the biodiversity of nature. 

Question. What importance do snakes have in nature?
Answer: Important member in food chain (web), see picture below.

Question. Draw a food web showing the place of snakes.

21. Seeing a crowd of students in one corner of the school, the Principal rushed to see the matter and found some children beating and chasing a small monitor lizard. On seeing the Principal, all the children fled to their classes except Alok who requested the Principal to arrange for some medical assistance for the injured animal. The Principal rewarded the student.

Question. Was Alok an indisciplined boy who did not run to the class on seeing the Principal? What values does the act promote? 
Answer: No. Alok was a brave and courteous boy. He expressed his love for animals, commitment towards natural resource conservation.

Question. How do endangered species differ from vulnerable species? 
Answer: Endangered species (when population of a species reduces to a level which poses immediate danger of extinction, e.g. one horn rhinoceros, great Indian bustard, musk deer etc).
Vulnerable species (species whose population have greatly reduced and may be endangered species in future if the causative factors continue to operate. E.g Asiatic wild ass, black buck, spotted deer, golden langur etc).

Question. Mention the factors resulting in loss of biodiversity / extinction. 
Answer: (i) Habitat loss and fragmentation

           (ii) Over exploitation

           (iii) Alien species invasion

           (iv) Co-extinction

22. During a visit to a government office with his father, young Pratap saw dirty spittoons in every corner of the building. Some people were spitting paan and gutka through the window grills. As soon as he objected to their action, Pratap was scolded by some persons and the quarrel between the two parties became a matter of concern. The very next week Pratap was amazed to see the walls cleaned, no spittoons and a notification hung to maintain cleanliness and hygiene inside the office. The officer appreciated Pratap.

Question. What values are promoted through the incident?
Answer: Self Awareness, boldness, insight and commitment towards community health

Question. Which diseases are transmitted through droplets and air?

Question. How does chewing paan or gutka cause health hazard? 
Answer: Gutka contains heavy amounts of magnesium as well as calcium carbonate which are very toxic chemicals. High amounts of magnesium carbonate in the human body can cause respiratory and cardiac depression, while calcium carbonate or lime damages the mucosa, causing chronic mucosal injuries and ulcers in the mouth.

Apart from this, gutka can also cause hypertension and cause reproductive health dysfunction.

Possible problems: Hypertension and cardiovascular diseases, nervous system disorders, liver and kidney diseases, reproductive health dysfunctions, oro-dental problems, metabolic disorders including diabetes and obesity, and psychological disorders including addiction, can be caused by excessive consumption of gutka.

23. Raj’s mother wondered why the mosquitos were not responding to the mosquito repellent which she had been using for several years. Raj asked his mother to change the brand they were using. When it worked, she opined that the quality of the brand she had been using might have degraded over the time. Raj objected and explained to his mother the reality.

Question. What values are reflected in the above case? 
Answer: Raj’s mother was too judgemental while Raj had a Scientific attitude, approach and sense of exploration.

Question. Why did the mosquitoes not respond to the repellent? Explain on the basis of Natural Selection. 
Answer: Sensitive ones died leaving behind the resistant strains which multiplied to increase their population.

Question. Cite any two examples of natural selection which we often come across. 
Answer: i) Bacteria developing resistance towards antibiotics
ii) Pesticide resistance (DDT resistant mosquitoes)

24. One Sunday morning Ratan and his friend emptied all the overhead tanks belonging to flat owners who were not residing in their apartments for the last few months. On their return, the owners complained about their empty tanks and created unrest in the campus.

Some elderly people spoke against Ratan and his friends. Ratan humbly apologized for the inconvenience caused but explained why they had done so. The people were happy and appreciated the boys.

Question. What was the objective behind Ratan’s act? 
Answer: The water in the tanks had become stagnant and become a breeding ground for mosquitoes.

Question. What values did he promote? 
Answer: Social responsibility, commitment towards community health and respect towards elders. 

Question. Explain in brief the stages of life cycle of a malarial parasite in human body. 
Answer: Life cycle of malaria parasite

25. Samir planned to introduce MOET in his farm. He purchased one high milk yielding exotic breed of cow. Within a few years he earned lot of money by selling calves but the mother cow met with a premature death. Raghavan objected to Samir earning money by this way.

Question. What values in life did Raghavan possess? 
Answer: Raghavan was bold, having love for animals. He had ethics and prudence.​​​​​​​

Question. Expand MOET. 
Answer: Multiple Ovulation Embryo Transfer Technology

Question. Briefly describe the process. 
Answer: • The cow is administered hormones, with FSH-like activity, to induce Follicular maturation and super ovulation (instead of one egg, which they normally yield per cycle, they produce 6-8 eggs).

           • The animal is either mated with an elite bull or artificially inseminated.

           • The fertilised eggs at 8–32 cells stages, are recovered non-surgically and transferred to surrogate mothers.

           • The genetic mother is available for another round of super ovulation.

        • This technology has been demonstrated for cattle, sheep, rabbits, buffaloes, mares, etc. High milk-yielding breeds of females and high quality (lean meat with less lipid) meat-yielding bulls have been bred successfully to increase the herd size within a short span of time.

26. Jeevan was waiting at a bus stop. Many passengers along with their kids were on their way to school. A bus came and painted the children with black smoke ejected from the exhaust pipe. Jeevan immediately stopped the bus and called the conductor and driver to show what they had done. Passengers waiting in the bus stop supported Jeevan while those on board became restless for being delayed.

Question. What values did Jeevan promote through his action? 
Answer: Jeevan shows alertness, responsibility and firmness in tackling a problem. He expresses boldness towards environment consciousness.

Question. Why are children more affected by vehicle exhausts? 
Answer: Height of the smoke emitted from exhaust pipe is closer to the height of the children.

Question. Cars are seen with Bharat stage IV stickers. What does it imply? 
Answer: It indicates that the vehicles comply with the new auto fuel policy. At present vehicles complying Euro-IV or equivalent BS-IV norms are to ply in the identified 11 cities, rest of the country to follow Euro III / BS-III norms.

Question. How do catalytic convertors reduce vehicular gas emission? 
Answer: In these devices, platinum - palladium and Rhodium are used as catalysts. As the exhaust passes through the convertor, unburnt hydrocarbons are converted into CO₂ and H₂O. Carbon monoxide and nitric oxide are changed into CO₂ and N₂ gas respectively. Vehicles fitted with such equipment should run on unleaded petrol only since lead in petrol inactivates the catalysts

27. Saptarshi entered into a quarrel with some farmers who were spraying DDT in their field.
Many people gathered at the spot to see and enjoy the incident. The angry mob demanded that Saptarshi should not interfere in the farmers’ job. Saptarshi tried to explain his point and finally succeeded. The farmers gave up spraying DDT.

Question. What did Saptarshi explain to the farmers?
Answer: Saptarshi explained the health hazard on self and others due to DDT spraying.

• That DDT was a Non Biodegradable substance

• That DDT could enter into the food chain and in course of time everyone associated would be affected due to its accumulation in the blood.

Question. What is Biomagnification? Explain with an example.

Question. What values did Saptarshi promote?
Answer: Health awareness, eco friendly nature, sympathy and boldness for the right cause

28. Sanjeev lives in a remote village where electricity has not reached every home. He discovered that people keep their kerosene oil lamp lit in their rooms while sleeping. Next day he called a meeting of all the residents and explained the ill effects of the smoke. They met the village head and requested for electrification of their village at the earliest.

Question. What values did Sanjeev show here? 
Answer: Health Consciousness, , kindness for humanity and leadership quality

Question. What could be the ill effect of the oil lamp?
 

Answer: Carbon monoxide is produced by common household appliances. When not properly ventilated, carbon monoxide emitted by these appliances is accumulated.

Carbon monoxide is an odorless, tasteless, and colorless gas and is known as the "silent killer."

Early symptoms of carbon monoxide poisoning such as headaches, nausea, fatigue, Dizziness, Weakness, Nausea, Vomiting, Chest pain. Prolonged exposure can lead to brain damage and even death.

29. During her tour to a renowned forest, Sakshi saw a highway being constructed which passes through the middle of the forest. She was unhappy. On return she contacted the local eco club and approached the concerned department to stop the work.

Question. What values did Sakshi reflect here? 
Answer: Love for nature and environmental consciousness. She was brave, focussed having vision to see the disaster in the future.

Question. What would be the effect on Biodiversity if the highway is constructed? 
Answer: Continuity of the habitat (here forest) is disrupted. Animals get confined to smaller area.

Fragmentation characteristically reduces species richness and taxon diversity, and may reduce the efficacy of ecosystem functioning. Fragmentation not only reduces the amount of functional habitat, but it may isolate a species population into subpopulations, that may be sufficiently near the minimum viable population size to risk local extinction from successive demographic processes or catastrophic events.

30. Richa was walking through a village. She saw a group of women quarrelling near a well. 
She moved forward to know what was going on and came to know that the quarrel was on fetching water. She immediately solved the problem by telling them a story on how birds also solved their problem.

Question. What values of Richa can be observed here?
Answer: Richa shows brilliance and cheerfulness through her Problem solving ability. She has a helping attitude.

Question. Give a scientific interpretation of sharing a common resource by animals.
Answer: Resource Partitioning

Question. Provide an example from your text.

Please refer to the link below for CBSE Class 12 Biology Value Based Questions All Chapters.