Tag: biology

• Water conservation is a very important practice which helps to maintain water balance in a natural resource. 
• The water which has been used for one type of work can be used for varied purposes. 
• The water which is used for washing the fruits and vegetables should not be thrown away. 
• The water can be used for watering the plants or for other purposes. 
• Thus, the correct answer is option D. 

Disinfectants are the antimicrobial agents which is mainly used to stop the growth of pathogen on the non-living organism. It may affect the substances on which it is applied. Phenyl is a disinfectant which cannot be used for purification of drinking water because it will kill the pathogens of the bacteria but the quality of the water will  degrade as it is poisonous for the living organisms. It has a pungent odour. All the other options are used as disinfectant because they do not have an adverse effect on the quality of water.

The Ministry of Environment and Forests has. initiated Ganga Action Plan and Yamuna Action Plan, to save these major rivers of our country from pollution. Under these plans, it is proposed to build a large number of sewage treatment plants so that only treated water may be discharged in the rivers.

Eichhornia crassipes, commonly known as common water hyacinth, is an aquatic plant native to the Amazon basin, and is often a highly problematic invasive species outside its native range. Water hyacinth is a free-floating perennial aquatic plant (or hydrophyte) native to tropical and subtropical South America. With broad, thick, glossy, ovate leaves, water hyacinth may rise above the surface of the water as much as 1 meter in height. One of the fastest growing plants known, water hyacinth reproduces primarily by way of runners or stolons, which eventually form daughter plants. Each plant additionally can produce thousands of seeds each year, and these seeds can remain viable for more than 28 years. It was introduced in Bengal in India because of its beautiful flowers and shapes of leaves, but turned out to be an invasive weed draining oxygen from the water bodies and resulted in death of many fish. Fish is a supplement food in Bengal, and because of the fish scarcity in Bengal caused by Eichhornia, the water hyacinth is also called "Terror of Bengal".

BOD is a chemical procedure for determining the amount of dissolved $O _2$, needed by aerobic biological organisms in a body of water to break down organic material present in a given water sample at a certain temperature over a specific time period.

A bioindicator is a living organism that gives us an idea of the health of an ecosystem. Some organisms are very sensitive to pollution in their environment, so if pollutants are present, the organism may change its behaviour, or it could even die. Sewage fungus is a thick growth of fungi that develops on stagnant water contaminated with sewage effluents. The filamentous fungus indicates that the sewage has not had secondary treatment. Adult stoneflies are always found near freshwater only as aquatic larvae. As water temperature increases, the larvae dies. As BOD increases in polluted water, there occurs an increase in haemoglobin possessing blood and sludge worms. Hence, the correct answer is option E.

Water hyacinth( Eichhornia crassipes) is known as the terror of bengal because it is an exotic shrub which strongly competes with the native species and has also eliminated many of them. It is a water-based plant that flourishes in the hot and humid climate of Bengal. Fish is a supplement food in Bengal. Water hyacinth is efficient in utilizing aquatic nutrients and solar energy for profuse biomass production and results in decline in number of fishes and because of the fish scarcity in Bengal caused by Eichhornia, the water hyacinth is also called "Terror of Bengal". 

Autotrophs of greatest significance in sanitary engineering are the nitrifying, sulfur, and iron. Because these bacteria use CO$ _2$ as the carbon source and oxidize inorganic compounds for energy. 

Indicator organisms are organisms used as a sign of quality or hygienic status in food, dietary supplements, water or the environment for example algal bloom is an indicator of eutrophication. The presence of E.coli is an indicator for water pollution.