Tag: human influences on the environment

Questions Related to human influences on the environment

At DO below $4$ mg/$l$, water at normal temperature is considered as

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

  1. Heavily polluted

  2. Moderately polluted

  3. Little polluted

  4. Nearly pure

Show answer
Correct Option: A
Explanation:

Dissolved oxygen (DO) refers to the amount of oxygen dissolved in the water. It depends on the following factors:

1. Temperature- colder the temperature, more will be the DO.
2. Pressure- greater the pressure, more will be the DO.
3. Salinity- lower the salinity, more will be the DO.
The levels of DO below 5mg/l is considered to be hazardous to the aquatic lives. At normal temperature, any water body showing less DO than 5mg/l will be highly polluted.
Hence, the correct answer is 'Heavily Polluted'

Fish die in water bodies polluted by sewage due to

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

  1. Pathogens

  2. Clogging of gills by silt

  3. Reduction in oxygen

  4. Foul smell

Show answer
Correct Option: C
Explanation:

 Oxygen enters the water through diffusion and water has the highest potential to hold oxygen. The high temperature, untreated sewage having biotoxins, hazardous waste can reduce the oxygen to an alarming level leading to the hypoxia in fishes, whereafter enduring at the maximum level they die resultantly. This occurs because the untreated sewage is rich in organic matter and microbes utilize the dissolved oxygen for the decomposition called biological oxygen demand (BOD). The more the value of BOD, the lesser will be the oxygen in the water.

Hence, the correct answer is 'Reduction in oxygen'.

Phosphate pollution is caused by _______.

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

  1. Weathering of phosphate rocks only

  2. Agriculture fertilizers

  3. Phosphate rocks and sewage

  4. Sewage and agricultural fertilizers

Show answer
Correct Option: D
Explanation:

Phosphate pollution in the water is directly related to the release of the untreated sewage and agriculture fertilizers into the water body. This results in excessive algal bloom that forms a thick layer on the surface of the water and prevents the sunlight and oxygen from getting into the water. As a result, the underlying aquatic animals and plants suffocate and die. When this algal bloom dies, it further enhances the eutrophication process, greatly decreasing the dissolved oxygen in the water.

Hence, the correct answer is 'Sewage and agricultural fertilizers'.

B.O.D. is connected with

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

  1. Organic matter

  2. Microbes

  3. Microbes and organic matter

  4. None of the above

Show answer
Correct Option: C
Explanation:

BOD refers to the biological oxygen demand by the microbes to decompose the organic matter present in the water body. Oxygen enters the water through diffusion and water has the highest potential to hold oxygen. The high temperature, untreated sewage having biotoxins, hazardous waste can reduce the oxygen to an alarming level leading to the hypoxia in fishes, whereafter enduring at the maximum level they die resultantly. This occurs because the untreated sewage is rich in organic matter and microbes utilize the dissolved oxygen for the decomposition.

So, the correct answer is 'Microbes and organic matter'

Measurement of rate of oxygen utilisation by a unit volume of water over a period of time is to measure

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

  1. Fermentation

  2. Biogas generation

  3. Biosynthetic pathway

  4. Biological oxygen demand

Show answer
Correct Option: D
Explanation:

Biological Oxygen Demand (BOD) in simple terms is the amount of oxygen that would be used by the decomposing bacteria to decompose or break down the organic compounds in the water body. The increase in the BOD reflects that the concentration of the organic mass is tremendous and so a large amount of oxygen would be claimed by the bacteria. This results in the deficiency of the dissolved oxygen in the water and adversely affects the aquatic life due to hypoxia. So, the BOD can be defined as the measurement of the rate of oxygen utilization by a unit volume of water over a period of time.

Hence, the correct answer is 'Biological oxygen demand'.

Continuous sewage flow into a stream would lead to

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

  1. Eutrophication

  2. Algal bloom

  3. Depletion of oxygen

  4. Increase in temperature

Show answer
Correct Option: C
Explanation:

Discharge of untreated sewage into streams which contains high quantity of nutrients induce the disproportionate growth of algae causing eutrophication which results into depletion of dissolved oxygen in the water. The continuous flow of sewage reduces the self-purification capacity of the water body. The condition of hypoxia arises due to depletion of oxygen. Increase in temperature favours the eutrophication and algal bloom is the cause of eutrophication. Depletion of oxygen is the adverse effect of the eutrophication.

Hence, the correct answer is 'Depletion of oxygen'.

A water body has high BOD indicating that water is

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

  1. Being contaminated with sewage

  2. Being aerated

  3. Receiving minerals

  4. Atrophic

Show answer
Correct Option: A
Explanation:

Biological Oxygen Demand indicates the increase in presence of organic matter in the water body. High BOD indicates the great amount of organic matter. The dissolved oxygen in water is consumed by bacteria to decompose the organic matter of sewage or other discharges thereby depleting the oxygen of the water body. The decrease in oxygen can kill the aquatic life in water body.

Hence, the correct answer is 'Being contaminated with sewage'.

BOD is measure of.

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

  1. Industrial waste being poured in water body

  2. Extent of pollution with organic compounds

  3. CO combined with haemoglobin

  4. $O _2$ required by green plants during night

Show answer
Correct Option: B
Explanation:

The microorganisms in polluted bodies use dissolved oxygen to metabolise organic matter in polluted waters. This is called biochemicalical oxygen demand. The more organic matter in sewage and polluted bodies, greater the BOD and hence less oxygen is left availble tor higher animals like fishes.

Which is the correct ascending arrangement of BOD of sewage(S) distillery effluent(DE), paper mill effluent(PE) and sugar mill effluent(SE)?

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

  1. SE$<$PE$<$S$<$DE

  2. PE$<$S$<$SE$<$DE

  3. S$<$DE$<$PE$<$SE

  4. SE$<$S<$PE$<$DE

Show answer
Correct Option: B
Explanation:
  • BOD is the Biological Oxygen Demand that is created when there is an excessive quantity of the organic matter in the water body and its decomposition is initiated by the decomposing bacteria. More the amount of organic waste, the higher will be the BOD and so more will be pollution in the water body. 
  • This causes an extreme reduction in the dissolved oxygen and suffocates the aquatic animals. 
  • Distillery effluent is rich in organic waste left from alcoholic fermentation and it has the highest BOD. 
Sugar mill effluent follows the distillery effluent in the concentration of organic content. The sewage water contains the excreta and detergents mixed with it. 
  • Papermill effluent has the lowest concentration of the organic mass.

Hence, the correct answer is 'PE< S< SE< DE'.

Arrange according to ascending order of BOD.
(a) Highly polluted pond water
(b) Unpolluted pond water
(c) Distilled water

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

  1. b-c-a

  2. c-b-a

  3. c-a-b

  4. a-c-b

Show answer
Correct Option: B
Explanation:

The concentration of the organic waste and its subsequent decomposition determines the BOD of the water. If the organic concentration is high, there will be high BOD because more dissolved oxygen will be used to breakdown the organic mass by the bacteria. So, high BOD marks high pollution. Distilled water has no content of the organic substances as it has been treated and filtered. Unpolluted water pond will not have polluted source of organic mass but the existing organisms die and their dead bodies contribute to a little raised BOD. Highly polluted water will show a very high value of BOD as it will take a lot of dissolved oxygen to breakdown the organic mass in water body. So, distilled water is least polluted, followed by unpolluted pond water and then highly polluted pond water.

Hence, the correct answer is 'c - b - a'.