Question

Which of the following is called an indicator species for polluted water?
A. Tubifex
B. Phytoplanktons
C. Zooplanktons
D. Prawns

Answer 1

Hint: When harmful substances like chemicals, plastic wastes or microbes contaminate a water body like the sea, river, ocean it is known as water pollution. The water from these bodies are known as polluted water.

Complete answer:
In simple words, water pollution can be defined as the process by which water bodies are contaminated. The sources of water pollution are as follows,
- Industrial effluents
- Use of detergents and fertilizers
- Social and religious practices
- Deforestation
- Throwing of waste materials like plastics wastes, household wastes, etc directly into the water body

Option A: Oligochaetes are commonly used as water quality indicators. Tubifex is an example of aquatic oligochaete. It is commonly used as a water quality indicator as it has the ability to tolerate presence of heavy metals in water, low oxygen conditions, and various other environmental conditions.

Option B: Phytoplanktons are commonly seen in water which are rich in ammonia. They absorb nutrients from water and use it for their growth and they also remove ammonia concentration from the water. They are not helpful in determining the water quality.

Option C: Zooplanktons are small microscopic to large species which are found in large water bodies. They are a type of heterotrophic plankton. They are an important element of the aquatic food chain.

Option D: Prawns are an example of crustaceans which are found in aquatic bodies. They have no role in determining the water quality. They are generally used in cooking food.

Thus, the correct option is A) Tubifex.

Note: Water pollution can be controlled by the following methods,
- Not throwing wastes like plastic wastes, food wastes, etc into the water body directly.
- Instead of releasing the sewage wastes into the water bodies, the waste must be first treated and then discharged.
- Growing water hyacinth in water bodies can help in reducing the amount of toxic chemicals like cadmium, etc as the plant has the ability to absorb them.
- Using different methods like reverse osmosis, ion exchange methods, recycling water, etc to purify the water.