Biology

Environmental Issues- Competency-Based Questions

Class 12 Biology Competency-Based Questions Chapter 16

1 Mark Questions

1. Two statements are given below – one labelled Assertion (A) and the other labelled Reason (R).

Assertion (A): Waste material from hospitals is hazardous and is incinerated.
Reason (R): Incineration reduces the risk of the spread of pathogens by killing them.

Which of the following is correct?

A. Both A and R are true, and R is the correct explanation for A.

B. Both A and R are true, but R is not the correct explanation for A.

C. A is true, but R is false.

D. A is false, but R is true.

Ans: A. Both A and R are true, and R is the correct explanation for A.

2. A research group aims to study the adverse effects of aromatic polyhydrocarbons (PAHs), a class of unsaturated hydrocarbons, on the organ systems of marine organisms.

Which of the following is LIKELY to be the most suitable environment for the study?

A. Middle of an ocean where vessels transfer oil between each other

B. Region in the Arctic Ocean with minimal pollution

C. River with frequent temperature fluctuations

D. Lake in the middle of dense rainforest

Ans: A. Middle of an ocean where vessels transfer oil between each other

3. Two statements are given below- one labelled Assertion (A) and the other labelled Reason (R).

Assertion (A): Nuclear waste is an extremely dangerous pollutant.
Reason (R): Nuclear waste has the shortest half-life as compared to that of the other types of pollutants.

Which of the following is correct?

A. Both A and R are true, and R is the correct explanation for A.

B. Both A and R are true, but R is not the correct explanation for A.

C. A is true, but R is false.

D. A is false, but R is true.

Ans: C. A is true, but R is false.

4. What happens to the BOD of a water body with REMOVAL of effluents from it?

A. Increases

B. Decreases

C. Remains the same

D. Increases and then stagnates

Ans: B. Decreases

5. Which of the following statements are CORRECT about the process of eutrophication?

(P) Increase in nutrient levels

(Q) Increase in water clarity

(R) Decrease in dissolved oxygen

(S) Decrease in penetration of sunlight into water

(T) Decrease in the growth of algae and aquatic plants

A. Only (P) and (R)

B. Only (P), (R), and (S)

C. Only (Q), (R), and (T)

D. All – (P), (Q), (R), (S), and (T)

Ans: B. Only (P), (R), and (S)

2 Marks Questions

6. In a research paper titled “Ecological Risk of DDT: A Case Study of Biomagnification Causing Extinction Risk of Herring Gull in Long Island” (Nakamaru et al, 2001), it was cited that the use of DDT causes immense risks of extinction of a bird named Herring Gull. There are severe implications of this.

(a) The Herring Gull is a top predator in the food pyramid of the area. How will its extinction impact the food chain?

(b) State ONE reason how bio-magnification can cause extinction of birds like the Herring Gull?

Ans:

(a)
- Increase in other predators, carnivores, and herbivores in the area
- Imbalance in the availability of food
(b)
- Decrease in fertility
- Early breakage of eggshells
- Thinning of eggshells

7. (a) Recycling of e-waste is one of the most popular methods of e-waste management in developing countries. It benefits a sizable proportion of the population by providing employment in such countries. What can be one of the biggest disadvantages of these recycling efforts?

(b) Incineration, as a process of e-waste management, can destroy organic constituents in e-waste. What is the main advantage of using incineration in a landfill?

Ans:

(a) Exposes workers to hazardous and toxic substances during manual participation

(b) Reduces the volume of the waste

8. Brominated Flame Retardants (BFRs) are extensively used in the manufacturing of electronics, furniture, textiles, vehicles, and other products. However, the release of these chemicals into water bodies is a known source of pollution. In water, BFRs are known to enter various food chains, and one such food chain is as follows:

(a) In this food chain, at which organismal level would you expect the concentration of BFR to be the highest, and why?

(b) Which phenomenon is being exemplified in the above description?

Ans:

(a)
- In this food chain, the highest concentration can be found at the ‘humans’ level.
- Reason – The non-degradable pollutants accumulate and result in higher concentrations in organisms with each successive level in a food chain.
(b) The above description is an example of a phenomenon called biomagnification.

3 Marks Questions

9. Impurities in domestic sewage account for 0.1% of the total wastewater. Such impurities include:

A: suspended solids like sand, silt, and clay

B: colloidal material like faecal matter, bacteria

C: dissolved materials like nutrients (nitrates, ammonia, phosphate, sodium, calcium, etc).

As a project manager for the treatment of domestic sewage in a town, Shivam thought of recycling the sewage water into other processes in the area.

(a) How can Shivam remove the suspended solids from the sewage water?

(b) How can the colloidal impurities be used in any other process in the town?

(c) If domestic sewage is allowed to enter a pond or a lake without being treated, what can be ONE impact it has on the quality of water in the water body?

Ans:

(a)
- Sedimentation
- Filtration
(b) In agricultural fields, as organic manure
(c)
- Increase in BOD
- Eutrophication

10. The paper industry releases SO₂ as an effluent, resulting in air pollution in the city.

(a) Mention any TWO potential negative effects of this SO₂ release.

(b) Suggest an instrument that can be used to reduce this kind of pollution, and explain its working principle.

Ans:

(a)
- SO₂ pollution can cause respiratory problems such as asthma, bronchitis, etc., in humans and animals.
- SO₂ reacts with other components of air and causes acid rain that harms animals, plants, and infrastructure.
- It can lead to the acidification of soil and water and affect the survival of the resident organisms.
- SO2 adversely affects the ability of leaves to photosynthesise and results in reduced growth in plants.
(b)
- In order to control the SO₂ release, instruments called scrubbers can be used.
- Working principle of scrubbers – Lime or water is sprayed onto an exhaust stream containing the pollutant, leading to the gaseous pollutant being removed and collected as sludge.

In order to control the SO₂ release, instruments called electrostatic precipitators can be used.
Working principle of electrostatic precipitators – An external attachment of charge to the stream of pollutant molecules happens, leading to their movement toward one of the charged electrodes kept across the stream, thereby removing them from the stream.