Biology 2 Marks Questions

Primary (1°) treatment is a physical process that involves for removal of particulate as settelable particle. Secondary (2°) treatment is purely a biological treatment involving microbial oxidation.

Sewage is the municipal waste matter that is carried away in sewers and drains. It includes both liquid and solid wastes, rich in organic matter and microbes. Many of these microbes are pathogenic and can cause several water - borne diseases. Sewage water is a major cause of polluting drinking water. Hence, it is essential that sewage water is properly collected, treated, and disposed.

1. Making of dough for bread, dosa and idli with the help of fermenting microbes. Heat expels the gases and makes the food spongy.
2. Production of biogas.

1. Cyclosporin-A is obtained from the fungus Trichoderma polysporum.
2. Statins is obtained from Monascus purpureus.

Soil
Microbes play an important role in maintaining soil fertility. They help in the formation of nutrient-rich humus by the process of decomposition. Manyspecies of bacteria and cyanobacteria have the ability to fix atmospheric nitrogen into usable form. Rhizobium is a symbiotic bacteria found in the root nodules of leguminous plants. Azospirillium and Azotobocter are free living nitrogen-fixing bacteria, whereas Anabena, Nostoc, and Oscillitoria are examples of nitrogen-fixing cyanobacteria.

Single cell protein (SCP):
A single cell protein is a protein obtained from certain microbes, which forms an alternate source of proteins in animal feeds. The microbes involved in the preparation of single cell proteins are algae, yeast, or bacteria. These microbes are grown on an industrial scale to obtain the desired protein. For example, Spirulina can be grown on waste materials obtained from molasses, sewage, and animal manures. It serves as a rich supplement of dietary nutrients such as proteins, carbohydrate, fats, minerals, and vitamins. Similarly, micro-organisms such as Methylophilus and methylotrophus have a large rate of biomass production. Their growth canproduce a large amount of proteins.

Curd can be used as a sample for the study of microbes. Curd contains numerous lactic acid bacteria (LAB) or Lactobacillus. These bacteria produce acids that coagulate and digest milk proteins. A small drop of curd contains millions of bacteria, which can be easily observed under a microscope.

Saccharomyces cerevisiae- ethanol/alcohol.
Monascus purpureus- statin.

Azospirillium/Azotobacter, Rhizobium.
They enrich soil nutrient/nitrogen fixation.

In anaerobic sludge digester, methanogens, i.e. anaerobic bacteria, digest the bacteria and fungi of the floe in the activated sludge.
This produces mixture of methane, hydrogen sulphide and carbon dioxide, i.e. biogas. This gas is used as a source of energy as it is inflammable.

• Trichoderma polysporum, cyclosporin A.
• Aspergillus niger, citric acid.
• Monascus purpureus, statin.
• Saccharomyces cerevisiae, ethanol/alcohol.
• Penicillium notatum, Penicillin.

Supernatant from the primary treatment is passed into large aeration tanks during secondary treatment. In these tanks, the effluent is agitated mechanically and air is pumped into it. This causes vigorous growth of the bacteria that lead to the formation of floc, which consists of bacteria and fungal filaments in a mesh-like structure. While growing, these microbes consume the major part of organic matter in the effluent; it decreases the biological oxygen demand (BOD).
After a significant drop in BOD is observed, effluent is passed on to the settling tank.

1. Monascus purpureus.
2. Aspergillus niger.
3. Penicillium notatum.
4. Clostridium butylicum.

Physical removal of particles (large and small), mutualism by filtration and sedimentation, forming primary sludge/sedimented solids, forming effluent (supernatant) for secondary treatment.

Species specific, narrow spectrum, insecticidal application (IPM), no negative impact on plants/mammals/birds/fish/even non target insects.

1. Defective gene not producing ADA, immune system is affected.
2. A retroviral vector is used, recipient cells are lymphocytes.

Streptokinase,
Used as a clot buster/for removing clots from the blood vessels (in a patient suffering from myocardial infarction/or in a heart patient).

Restriction enzymes cut the DNA sequence a little away from the centre of the palindrome site but between the same two bases on the opposite strands, leaving single stranded portions at the ends these over hanging stretches are called sticky ends on each strand. They form hydrogen bonds with the complementary cut counterparts, facilitates the action of ligase enzymes to join the foreign and the vector DNA strands.

1. Lactobacillus.
2. Trichoderma polysporum.
3. Yeast.
4. Penicillin.

Cyclosporin ASource- Trichoderma polysporum.
Purpose- Immuno suppressive agent.

Sedimentation of flocs to form activated sludge, sludge pumped to anaerobic sludge digester, growth of anaerobic bacteria, digestion of sludge by bacteria to release biogas.

Glomus forms mycorrhizal association, absorbs phosphorus, provide resistance to root borne pathogens, enhanced to tolerate salinity/drought.

Effluent from the primary settling tank passed into aeration tank, agitated mechanically and air is pumped into it, vigorous growth of aerobic microbes into flocs, microbes consume major part of the organic matter in effluent.

Oxygen is used up by microorganisms involved in biodegradation resulting in sharp decline at the point of sewage discharge, the concentration of oxygen increases as we move farther from the point of sewage discharge.

During the secondary treatment of the primary affluent (Primary effluents are passed into a large aeration tank, where it is constantly agitated, and air is pumped into it) vigorous growth of useful aerobic microbes, into flocs takes place, these microbes use major part of the organic matter, and this reduces BOD.

1. Penicillium notatum.
2. Acetic acid.
3. Fungus.
4. Saccharomyces cerevisiae.

During secondary treatment of primary effluents, vigorous growth of useful aerobic microbes into flocs occur when it is agitated mechanically and air is pumped into it in a large aeration tank. These microbes while growing consume major part of the organic matter in the effluent. This significantly reduces BOD.

• Useful aerobic microbes grow rapidly and form flocs.
• Flocs are masses of bacteria associated with fungal filaments to form mesh-like structures.
• The growing microbes consume organic matter and thus reduce the biochemical oxygen demand (BOD).

Anaerobic methane producing bacteria are called methanogens. Methanogens generate biogas when they act by anaerobic decomposition on cellulose rich biowaste (anaerobically).

• Swiss cheese: Propionibacterium
• Roquefort cheese: Penicillium roqueforti

Due to increasing urbanisation, sewage is being produced in much larger quantities than ever before. However the number of sewage treatment plants has not increased enough to treat such large quantities. So the untreated sewage is often discharged directly into rivers leading to their pollution and increase in water-borne diseases.

Cyanobacteria as biofertilisers:

• They fix atmospheric nitrogen and increase the organic matter of the soil through their photosynthetic activity, e.g., Nostoc, Anabaena, Oscillatoria, etc.
• Blue-green algae increase the soil fertility by adding organic matter to the soil.

Azotobacter is a free-living bacteria serving as a biofertiliser. This bacteria absorb free nitrogen from the soil, air and convert it into salts of nitrogen compounds and enrich the soil nutrients.
Rhizobium is a symbiotic bacterium that lives in the root nodules of legumes and fixes atmospheric nitrogen into organic compounds and enrich the soil nutrients.

• The fungus absorbs phosphorus from the soil and passes it to the plant.
• Plants with mycorrhiza show resistance to root-borne pathogens.
• They show increased tolerance to salinity and drought.
• There is an overall increase in plant growth and development.

The gas produced by the anaerobic action of bacteria on biomass is known as biogas. It is preferred over other conventional energy fuels because it is a cleaner fuel, has no foul smell and can be used as a source of energy as it is inflammable.

It is a traditional drink of some parts of Southern India. It is made by fermenting sap from palm trees, coconut, etc. Microbes are also used to ferment fish, soybean, bamboo shoos, etc. to make food.

1. Lipases.
2. Pectinases and proteases.

BOD stands for biochemical oxygen demand which represents the amount of dissolved oxygen that would be consumed if all the organic matter in one litre of water were oxidised by microorganisms. More BOD value means the water sample is polluted by organic matter.

Toddy is a traditional drink of southern India which is prepared by the yeast fermentation of coconut water.

Fungi	Products/ Bioactive molecules produced
Trichoderma polysporum	Cyclosporin A
Aspergillus niger	Citric Acid
Monascus purpureus	Statin
Saccharomyces cerevisiae	Ethanol/alcohol
Penicillium notatum	Penicillin

Streptococcus bacterium produces streptokinase.
It is used for removing clots from the blood vessels in a patient suffering from myocardial infarction/ or in a heart patient.

The microbial flora in the rumen of cattle facilitates digestion of cellulose. If such microbial flora will be present in our intestine then humans will also be able to digest cellulose.

Leguminous plants possess root nodules where nitrogen is fixed by symbiotic nitrogen fixing bacteria Rhizobium whereas cereals do not possess nitrogen fixing bacteria in their root nodules, so, they cannot fertilise the soil.

Some molecules are called bioactive molecules, because microbes like bacteria or fungi are used in their production.
Example:

• Citric acid: Acetic acid
• Butyric acid: Lactic acid
• Ethanol: Lipase
• Streptokinase: Cyclosporin A

Flocs are masses of bacteria associated with fungal filaments to form mesh like structure. Flocs digest most of the organic material from the sludge. Thus, floc helps in reducing the BOD (Biochemical Oxygen Demand) of the effluent. This helps in further treatment of sludge.

Ganga Action Plan tends to save the major rivers from pollution. Under these plans, a large number of sewage treatment plants were built so that only treated sewage is discharged in the rivers.

Bacillus thuringiensis products are endotoxin which when ingested and released in the gut of the larvae of insect pest disrupts the insect gut lining thereby killing them.