Tag: biology

Questions Related to biology

Water pollination is best assessed by determining.

biology human influences on the environment effects of water pollution effect of water pollution water pollution and its control

  1. DO and BOD

  2. BOD and turbidity

  3. Do and acidity

  4. BOD and alkalinity

Show answer
Correct Option: A
Explanation:

 D.O. is the dissolved gaseous form of oxygen that is essential for respiration of fish and other aquatic organisms. Wastewater from sewage treatment plants often contains organic materials that are decomposed by microorganisms. The amount of oxygen consumed by these organisms in breaking down the waste is known as the biochemical oxygen demand or BOD. BOD directly affects the amount of dissolved oxygen in rivers and streams. The greater the BOD, the more rapidly oxygen is depleted in the stream, thus reducing the oxygen available to higher forms of aquatic life. Pollution, therefore, increases the BOD of a water body. So, the water pollution status of a water body can be assessed by studying the dissolved oxygen (DO) and biological oxygen demand (BOD) of the water body. So, the correct option is 'DO and BOD'.

Two bottles were half filled with water from Ganga ('P') and Kaveri ('Q') and kept under identical airtight conditions for 5 days. The oxygen was determined to be 2% in bottle ('P') and 10% in bottle ('Q'). What could because of this indifference?

biology human influences on the environment effects of water pollution effect of water pollution water pollution and its control

  1. Ganga is more polluted than Kaveri

  2. Both the rivers are equally polluted

  3. Kaveri is more polluted than Ganga

  4. Kaveri has more minerals than Ganga

Show answer
Correct Option: A
Explanation:
Biochemical oxygen demand or BOD is the amount of dissolved oxygen needed by the aerobic bacteria present in water in a given amount of time. Given that 'P' has 2% oxygen and 'Q' has 10% oxygen dissolved after 5 days in an airtight condition. So, one can conclude that the aerobic bacteria present in 'P' is more than 'Q' as BOD of 'P' is much more than 'Q'. So Ganga is more polluted than Kaveri.    

Consider the following statements regarding the ecosystem which helps in reducing the level of pollution in the atmosphere.
$1$. Ecosystems and ecological processes play an important role in maintenance of gaseous composition of the atmosphere, breakdown of wastes and removal of pollutants.
$2$. Some ecosystems, especially wetlands have the ability to breaking down and absorb pollutants.
$3$. Natural and artificial wetlands are being used to filter effluents to remove nutrients, heavy metals, suspended solids; reduce the BOD (Biological Oxygen Demand) and destroy harmful micro-organisms.
Which of the statements given is/are correct?

biology human influences on the environment effects of water pollution effect of water pollution water pollution and its control

  1. $1$ only

  2. $1$ and $2$

  3. $2$ and $3$

  4. All of the above

Show answer
Correct Option: D
Explanation:
Ecosystems and ecological processes play an important role in the maintenance of gaseous composition of the atmosphere, breakdown of wastes and removal of pollutants.  Some ecosystems, especially wetlands have the ability to breaking down and absorb pollutants. Constructed wetlands are a sanitation technology that has not typically been designed for pathogen removal, but instead, have been designed to remove other water quality constituents such as suspended solids, organic matter (BOD/COD) and nutrients (nitrogen and phosphorus). Thus, all of these statements are true.

So the correct option is 'All of the above'.

Multiple Choice Questions
BOD in river water

biology human influences on the environment effects of water pollution effect of water pollution water pollution and its control

  1. Remains unchanged when algal bloom occurs

  2. Increases when sewage gets mixed up with river water

  3. Has no relationship with concentration of oxygen in water

  4. Give a measure for Salmonella in water.

Show answer
Correct Option: B
Explanation:

Biochemical Oxygen Demand or BOD is the amount of dissolved oxygen needed by aerobic microbes to break down organic matter present in a particular water sample at a certain temperature over a specified period of time. Value of BOD increases, given that the organic matter content is high in the water sample. Sewage is rich in organic residues thus it increases BOD of river water upon mixing.

So, the correct answer is option B, increases when sewage gets mixed up with river water.

Multiple Choice Questions
BOD is a measure of

biology human influences on the environment effects of water pollution effect of water pollution water pollution and its control

  1. Industrial wastes passed into water bodies

  2. amount of carbon monoxide combined with haemogloblin

  3. extent of pollution with organic matter

  4. amount of oxygen required by plants during night.

Show answer
Correct Option: C
Explanation:

BOD or Biochemical Oxygen Demand measures the degree of impurity of a water body or sample due to organic matter. BOD is the amount of dissolved oxygen needed by aerobic microbes to breakdown the organic matter present in the water body.

So, the correct answer is extend of pollution with organic matter.

Disposal of sewage and industrial effluents into water bodies, resulting in contamination of

biology human influences on the environment effects of water pollution effect of water pollution water pollution and its control

  1. Soil

  2. Water

  3. Air

  4. Atmosphere

Show answer
Correct Option: B

Limit of B.O.D. prescribed by Central Pollution Control Board for the discharge of industrial and municipal waste waters into natural surface waters, is 

biology human influences on the environment effects of water pollution effect of water pollution water pollution and its control

  1. < 30 ppm

  2. < 3.0 ppm

  3. < 10 ppm

  4. < 100 ppm

Show answer
Correct Option: C
Explanation:

Biochemical oxygen demand (BOD) is the amount of dissolved oxygen needed by aerobic biological organisms to break down organic material present in a given water sample at certain temperature over a specific time period. The central pollution control board prescribed the BOD limit for the discharge of industrial and municipal waste water as < 10ppm

So, the correct answer is '< 10 ppm'

In a survey conducted in Delhi, on the efforts being made to clear the Km patch in Yamuna, it was observed that the BOD in 2003 was 13 mg/litre while it was 18 mg/litre in 2004. 
What inference can you draw from the following data?
biology human influences on the environment effects of water pollution effect of water pollution water pollution and its control

  1. The pollutants in the river has decreased due to efforts by Delhi government.

  2. Despite efforts there are still dissolved minerals in the river.

  3. Although efforts are being made, the pollution is still on an increase in Delhi.

  4. There is an algae in the river.

Show answer
Correct Option: C
Explanation:

Biochemical oxygen demand (BOD) is the amount of dissolved oxygen needed by aerobic biological organisms to break down organic material present in a given water sample at certain temperature over a specific time period. As the level of BOD increases, this shows that efforts are being made to clean Yamuna river but pollution is still on an increase in Delhi. 

Therefore, the correct answer is option C.

Increase of BOD in water leads to

biology human influences on the environment effects of water pollution effect of water pollution water pollution and its control

  1. Increase in the dissolved oxygen concentration

  2. Decrease in the dissolved oxygen concentration

  3. Maintenance of dissolved oxygen concentration at the same level

  4. No effect on dissolved oxygen concentration

Show answer
Correct Option: B
Explanation:

Biochemical oxygen demand (BOD) is the amount of dissolved oxygen needed by aerobic biological organisms in a body of water to break down organic material present in a given water sample at certain temperature over a specific time period. Domestic sewage primarily contains biodegradable organic matter, which readily decomposes by micro-organisms, which can multiply using these organic substances as substrates and hence utilise some of the components of sewage. It is possible to estimate the amount of biodegradable organic matter in sewage water by measuring biochemical oxygen demand (BOD). Micro-organisms involved in biodegradation of organic matter in the receiving water body consume a lot of oxygen, and as a result there is a sharp decline in dissolved oxygen downstream from the point of sewage discharge. This causes mortality of fish and other aquatic creatures. 

Sewage drainage into water bodies is harmful for fishes because

biology human influences on the environment effects of water pollution effect of water pollution water pollution and its control

  1. Excessive CO$ _2$ is added in water.

  2. It gives off a bad smell.

  3. It removes the competition with fishes to dissolved oxygen.

  4. It increase competition of fishes for dissolved oxygen.

Show answer
Correct Option: D
Explanation:

Domestic sewage primarily contains biodegradable organic matter, which readily decomposes by bacteria and other micro-organisms, which can multiply using these organic substances as substrates and hence utilise some of the components of sewage. It is possible to estimate the amount of biodegradable organic matter in sewage water by measuring biochemical oxygen demand (BOD). Micro-organisms involved in biodegradation of organic matter in the receiving water body consume a lot of oxygen, and as a result there is a sharp decline in dissolved oxygen downstream from the point of sewage discharge. This causes mortality of fish and other aquatic creatures.