Environmental Issues VBQs Class 12 Biology

VBQs for Class 12

VBQs Environmental Issues Class 12 Biology with solutions has been provided below for standard students. We have provided chapter wise VBQ for Class 12 Biology with solutions. The following Environmental Issues Class 12 Biology value based questions with answers will come in your exams. Students should understand the concepts and learn the solved cased based VBQs provided below. This will help you to get better marks in class 12 examinations.

Environmental Issues VBQs Class 12 Biology

Very Short Answer Type Questions

Question. Mention two advantages for preferring CNG over diesel as an automobile fuel.
Answer :
Advantages of CNG :
(i) Burns efficiently/less unburnt residues.
(ii) Cheaper than petrol/diesel.
(iii) Causes less pollution.
(iv) Cannot be adulterated.
(v) Cannot be siphoned by thieves. 

Question. List two advantages of the use of unleaded petrol in automobiles as fuel.
Answer : The advantages are as follows :
(i) Unleaded petrol does not release lead compounds from exhaust fumes into the atmosphere and causes less pollution.
(ii) It does not emit harmful compounds, it helps in preventing health diseases like bronchitis, asthma and lung diseases.
(iii) It allows catalytic converter to remain active.

Question. Inspite of being non-polluting why are there great apprehensions in using nuclear energy for generating electricity ?
Answer : Accidental leakages, safe disposal of radioactive waste. 

Question. An electrostatic precipitator in a thermal power plant is not able to generate high voltage of several thousands.
Write ecological implication because of it. 
Answer :
Air Pollution // Particulate matter //dust particles released in the air. 

Question. State the cause of Accelerated Eutrophication.
Answer :
Pollutants from human activities / effluents from industries / effluents from home / sewage / agricultural (chemical) wastes radically accelerate the ageing process. 

Question. BOD of two samples of water A & B were 120 mg/l and 400 mg/L respectively. Which sample is more polluted ?
Answer :
Sample B is more polluted than Sample A.

Short Answer Type Questions

Question. How e-wastes are being handled in our country?
Write the correct solution for treating this waste.
Answer :
E-wastes are being buried in landfills, or incinerated (manually). Recycling this waste in the environment friendly manner is the right solution. 

Question. How did Ahmed Khan, plastic sacks manufacturer from Bangalore, solve the ever-increasing problem of accumulating plastic waste ?
Answer :
Collected plastic wastes-recycled-powdered-to form polyblend, blended with bitumen, used in road laying, increased road life by a factor of three / more durable. 
Detailed Answer :
He collected plastic wastes and recycled them.
He powdered plastic to form polyblend, which is blended with bitumen. Polyblend was used in road laying, which increased road life by a factor of three, making it more durable.

Question. What is polyblend ? Why did the plastic manufacturers think of producing it ? Write its usefulness.
Answer :
Polyblend : It is a fine powder of recycled modified plastic developed by a Bangalore-based company.
This mixture is mixed with the bitumen that is used to lay roads.
The plastic sack manufacturer in Bangalore has managed to find the ideal solution to the everincreasing problem of accumulating plastic waste.
Polyblend and bitumen, when used to lay roads, enhanced the bitumen—water repellant properties and helped to increase the road life by a factor of three. 

Question. Mention how e-waste is produced and disposed off. Write the solution for its treatment.
Answer :
Irreparable computers and other electronic goods are known as electronic wastes (e-wastes).
E-wastes are buried in landfills or incinerated.
The e-wastes generated in the developed world are exported to developing countries, mainly to China, India, and Pakistan, where metals like copper, iron, silicon, nickel and gold are recovered during the recycling process. Unlike developed countries, recycling of e-wastes, in developing countries often, involves manual participation, thus exposing workers to toxic substances present in e-wastes.
Recycling is the only solution for the treatment of e-waste, provided it is carried out in an environment friendly way. 

Question. Explain accelerated eutrophication. Mention any two consequences of this phenomenon.
Answer :
Accelerated eutrophication occurs due to the passage of sewage and run-off from fertilized fields into ponds, lakes and other water bodies. Nutrients present in sewage and fertilizers causes dense growth of plants and planktonic algae.
Consequences of accelerated eutrophication :
(i) Eutrophic water bodies support excessive growth of floating plants, e.g., water hyacinth is one such plant that sometimes chokes ponds, lakes and rivers.
(ii) Due to increase of algal blooms, there is drastic decrease in oxygen replenishment inside water that kills aquatic animals. 

Question. Why lichens are regarded as pollution indicators ? 
Answer :
Lichens are very sensitive to air pollution particularly caused by SO2. Air pollution due to SO2 destroy lichen population. They do not grow in such a polluted area. Therefore, they are regarded as indicators of pollution. 

Question. Why is Eichhornia crassipes nicknamed as ‘‘Terror of Bengal’’. 
Answer :
Eichhornia crassipes is nicknamed as ‘Terror of Bengal’ because it grows luxuriantly in eutrophic water bodies. Its excessive growth causes blockage in our water ways, thereby leading to an imbalance in the ecosystem dynamics of water body. Its rate of excessive growth is higher than the rate of its removal. ‘‘Terror of Bengal’’ is the title given to this aquatic weed because initially it was introduced in water bodies of Bengal for its flowers and shape of leaves but however it turned out to be highly invasive water weed that not only spread in water bodies of Bengal but also throughout India. 

Question. Our farmers still use DDT. How is this affecting the local bird population ?
Answer :
As a result of biomagnification, through an aquatic food chain, high concentration of DDT disturbs calcium metabolism in birds, which causes thinning of egg shell, and premature breaking, eventually leading to decline in bird population. 

Question. Explain how biomagnification of DDT occurs in an aquatic food chain.
With the help of a flowchart, show the phenomenon of biomagnification of DDT in an aquatic food chain. 
Answer :
DDT in water taken up by an organism cannot be metabolised or excreted and thus passed on to successive trophic level in higher concentration.
Water (0.003 ppm)→ Zooplankton (0.04 ppm) → Small fish (0.5 ppm) → Large fish (2 ppm) → Fish eating birds (25 ppm)
Detailed Answer:
Biomagnification is the increase in the concentration of a toxin at successive trophic levels. The toxin gets accumulated in the body of an organism and is passed on to the next trophic level.
For example, DDT (dichlorodiphenyl trichloroethane) and other heavy metals such as mercury and calcium are the toxins that cause biomagnification.

Environmental Issues VBQs Class 12 Biology

Question. Presently, air quality of Delhi has significantly improved in comparison to what existed before 1997. This is the result of conscious human efforts.
You are being asked to conduct an awareness programme in your locality wherein you will comment on the steps taken by Delhi Government to improve the air quality.
(i) Write any two of your comments.
(ii) List any two ways that you would include in your programme so as to ensure the maintenance of good quality of air.
(iii) State any two values your programme will inculcate in the people of your locality.
Answer :
(i) (a) Use of CNG as fuel encouraged in vehicles.
(b) Improved public transport system like new fleet of DTC buses, Introduced Metro.
(c) Pollution check of vehicles was made mandatory.
(d) Availability of sulphur free fuel (Euro II norms). (Any other suitable value)
(ii) (a) Car pool essential
(b) Use of bicycle
(c) Get your car pollution checked regularly
(iii) (a) Consciousness about the environment increase plantation activity
(b) Concern for others
(c) Improving social skills
(d) Leadership quality 

Question. Why should the spraying of DDT as an insecticide on vegetable crops be banned ?
Answer :
DDT is insoluble in water but soluble in fats.
Due to low efficient transfer of energy from one trophic level to other, herbivores eat more DDT–polluted vegetables. Similarly, carnivores eat many herbivores. A predator stores much quantity of DDT with its prey continuously. This process continues for several years by which a significant concentration of DDT accumulates in top carnivores. DDT causes thinning of eggshells and their premature breaking, eventually causing decline in bird populations. 

Question. How does algal bloom destroy the quality of a fresh water body ? Explain.
Answer :
The excessive growth of planktonic (free-floating) algae is called algal bloom. Nutrients present in sewage and fertilizers cause dense growth of plants and planktonic algae. Soon planktonic algae increase in number and impart a characteristic colouration to water. Algal bloom is toxic to animals and humans. It blocks light for submerged plants.
There is a drastic decrease in oxygen due to which animals die. 

Question. Looking at the deteriorating air quality because of air pollution in many cities of the country, the citizens are very much worried and concerned about their health. The doctors have declared health emergency in the cities where the air quality is very severely poor.
(a) Mention any two major causes of air pollution 
(b) Write any two harmful effects of air pollution to plants and humans.
(c) As a captain of your school Eco-club, suggest any two programmes you would plan to organize in the school so as to bring awareness among the students on how to check air pollution in and around the school.
Answer :
(a) Vehicular discharge / smoke from industries / burning of agricultural wastes / smoke from incinerator / dust / smoke from thermal plants or any other correct cause.
(b) Reduces growth of plants / reduces yields of crops / premature death of plants / respiratory problems / acid rain / any other relevant point.
(Any two – one from plant and one from human)
(c) Plantation drive / awareness programmes through posters / nukkad natak / film show / rallies / debates or any other.

Question. Particulate and gaseous pollutants alongwith harmless gases are released from the thermal power plants.
(i) Name any two harmless gases released.
(ii) Name the most widely used device for removing
particulate pollutants from the air. Explain how the device is used ?
Answer :
(i) CO2 & N2.
(ii) The most widely used device for removing particulate pollutant from air is the electrostatic precipitator. It has electrode wires and a stage of collecting plates connected electrically with earth. The particles occurring in polluted air are charged electrically. These charged particles are passed over collecting plates. These particles settle down after losing their charge. 

Question. A young sperm whale, 33-foot long was found dead off the coast. It had a large amount of human trash like trash bags, polypropylene sacks, ropes, net segments etc. amounting to 29 kilograms in its digestive system. The whale died because of inflammation of the abdominal lining. Analyze the possible reasons for such mishaps and suggest measures that can be taken to reduce such incidents.
Answer :
Due to cheap and quick production, durability and usefulness in several applications, plastic has become desired material for creating objects like trash bags, polypropylene sacks, ropes, net segments. But plastic is non-biodegradable product and extremely harmful. These plastic products get transported to nearby rivers and to oceans. These products are swallowed by marine animals mistaken it to be a food. Thus, plastic, once ingested, cannot be digested or passed by an animal so it stays in the gut leading to their death.
Measures that could be taken to reduce such mishaps are:
(a) We can support government’s initiative across the country for reducing the use of plastics and use of eco-friendly packaging.
(b) We can do our bit by carrying cloth or other natural fibre carry-bags when we go for shopping and by refusing to take the polythene bags from shopkeepers.
(c) It is important that all garbage generated is sorted. The biodegradable materials can be put into deep pits in the ground and be left for natural breakdown. It leaves only the non-biodegradable to be disposed of, the quantity of which should be minimized.
The need to reduce our garbage generation should be a prime goal.

Long Answer Type Questions

Question. (i) Public transport in Delhi uses CNG since 2002. List the advantages of this fuel policy.
(ii) BOD was measured in two different places A and B of a river in the direction of its flow. BOD value was higher at A than B. What do you infer from this observation and why ?
Answer :
(i) Delhi Government shifted to CNG (Compressed Natural Gas) because :
(a) It burns more efficiently, unlike petrol or diesel, in automobiles and very little of it is left unburnt.
(b) CNG is cheaper than petrol and diesel.
(c) It cannot be siphoned off by thieves.
(d) It cannot be adulterated like petrol or diesel.
(ii) Biochemical oxygen demand (BOD) refers to the amount of the oxygen that would be consumed if all the organic matter in one liter of water were oxidized by bacteria.
As the BOD value is higher at A, therefore, the amount of dissolved oxygen is lower in that place.
Excessive growth of algae, plants and animals in water bodies due to the nutrient enrichment, particularly with nitrogen and phosphorus, and discharge of domestic sewage into a river results in the rise of BOD. However, as the organic matter is decomposed, there is a gradual rise in the amount of dissolved oxygen downstream.