Power plants- thermal and nuclear, chemical and other industries use lot of water (about 30% of all abstracted water) for cooling purposes and the used hot water is discharged into rivers, streams or oceans. The waste heat from the boilers and heating processes increases the temperature of the cooling water. Discharge of hot water may increase the temperature of the receiving water by 10 to 15°C above the ambient water temperature. This is thermal pollution. Increase in water temperature decreases dissolved oxygen in water which adversely affects aquatic life. Unlike terrestrial ecosystems, the temperature of water bodies remain steady and does not change very much. Accordingly, aquatic organisms are adopted to a uniform steady temperature of environment and any fluctuation in water temperature severely affects aquatic plants and animals. Hence discharge of hot water from power plants adversely affects aquatic organisms. Aquatic plants and animals in the warm tropical water live dangerously close to their upper limit of temperature, particularly during the warm summer months. It requires only a slight deviation from this limit to cause a thermal stress to these organisms.
Discharge of hot water in water body affects feeding in fishes, increases their metabolism and affects their growth. Their swimming efficiently declines. Running away from predators or chasing prey becomes difficult. Their resistance to diseases and parasites decreases. Due to thermal pollution biological diversity is reduced. One of the best methods of reducing thermal pollution is to store the hot water in cooling ponds, allow the water to cool before releasing into any receiving water body.
Select the word which means - 'Connected with planet earth'.
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Terrestrial
Terrestrial means of or living on the earth or on land, as opposed to water or the sky. The passage contrasts terrestrial ecosystems with water bodies.
Example: Lions and elephants are terrestrial animals.
Why the Other Options are Incorrect?
Option 1: Aquatic — Incorrect. Aquatic means living or growing in water, the opposite of terrestrial.
Example: Lotus is an aquatic plant.
Option 2: Organisms — Incorrect. Organisms are living things such as plants, animals and bacteria; the word says nothing about the earth.
Example: A drop of pond water contains many tiny organisms.
Option 3: Metabolism — Incorrect. Metabolism is the chemical process by which a body turns food into energy.
Example: Regular exercise speeds up your metabolism.