Read the passage given below and then answer the questions given below the passage. Some words may be highlighted for your attention. Read carefully. Water pollution occurs from sewage and poorly managed solid waste in urban areas when it enters the aquatic ecosystem of lakes and rivers. Sewage lea
Read the passage given below and then answer the questions given below the passage. Some words may be highlighted for your attention. Read carefully.
Water pollution occurs from sewage and poorly managed solid waste in urban areas when it enters the aquatic ecosystem of lakes and rivers. Sewage leads to a process called eutrophication, which destroys life in the water as the oxygen content is severely reduced. Fish and crustacea cannot breath and are killed. A foul odour is produced. Gradually the natural flora and fauna of the aquatic ecosystem is destroyed. In rural areas the excessive use of fertilisers causes an increase in nutrients, which leads to eutrophication. Pesticides used in adjacent fields pollute water and kills off its aquatic animals. Chemical pollution from industry kills a large number of life forms in adjacent aquatic ecosystems. Contamination by heavy metals and other toxic chemicals affects the health of people who live near areas as they depend on this water.
For sustainable use of an aquatic ecosystem, water pollution must be prevented. It does not make sense to allow water to be polluted and then try to clean it up. Changing the nature of the aquatic ecosystem from a flowing water ecosystem to a static ecosystem destroys its natural biological diversity. Thus, dams across rivers decrease the population of species that require running water, while favouring those that need standing water.
Which of the following are the effects of constructing dams on rivers?
A. It adversely affects those species that require flowing water.
B. It restricts the river system to a flowing ecosystem.
C. It leads to pollution that leads to eutrophication.
1). Only A
2). Only B
3). Only C
4). Both A & B
1 answers
Correct option - 1
On looking at above mentioned passage, we observe that it is based on harmful effects of water pollution. It is discussed that construction of dams across rivers decreases the population of species that require running water i.e. flowing water which is available in rivers.
Thus, correct option is 1.
However, on the other hand, 2nd statement doesn't justify the question asked as it is nowhere mentioned in the passage that water pollution restricts the river system to a flowing ecosystem.
3rd statement doesn't clearly establish the relation between eutrophication and water pollution. Eutrophication is actually caused by fertilisers used on the crops to protect them from harmful organisms.