12th Biology Practical ~ (Part A) 7.Study of water samples collected from different water bodies for their pH, clarity and presence of living organisms (microscopic/planktonic)

 12th Biology practical book answers pdf Maharashtra board 

~Study of water samples collected from different water bodies for their pH, clarity and presence of living organisms (microscopic/planktonic)

Observation:

1) In tap water, no any microorganism is observed as tap water is given treatment to purify it.

2) In stream water different microorganisms are observed as Paramecium, diatoms, Spirogyra, Nosoc, nematode larvae, Mosquito larva, rotifers and daphnia, different types of algae.

 

Inference:

1) As tap water shows no any organism, tap water is clear and suitable for drinking.

2) As stream water shows presence of no of microorganisms, it has organic pollutants and therefore not suitable for drinking.

 

 

Questions

1. Why is turbid water not suitable for consumption?

Water becomes turbid due to pollutants, waste discharges, algae, humic acid, organic components. If such a water is used for drinking it may cause gastrointestinal diseases, nausea, headache, etc.

 

2. What is Biochemical Oxygen Demand (BOD)?

The amount of oxygen needed by aerobic biological organism to break down organic material present in a given water at certain temperature over a specific time period.

 

3. What is water pollution?

When an excess material that is harmful to humans, animals or desirable aquatic life is added to water then it is called water pollution.

 

4. What are the causes of water pollution?

Major causes of water pollution are domestic wastes, industrial effluents released into water bodies, agricultural waste and shipping waste, mining activities, marine dumping.

 

5. What are planktons? Is there any difference in the planktons occurring in fresh water and sea water?

Planktons are the diverse collection of organisms found in water that are unable to propel themselves against a current.

No, there is no any major difference but sea water planktons are more and forms food for fishes, bivalves & whales.

 

 

Multiple Choice Questions

1. ... arthropods found in fresh water bodies.

a. Daphnia

 

2. BOD of water means .........

b. Biochemical oxygen demand

 

3. Methylene blue stain is used to observe ……….

b. Bacteria

 

4. Experimental set up devised by......... is used to observe water clarity.

b. Tyndall

 

5. If pH is less than ............ then water is acidic.

a. 6.5