Biology 3 Marks Question

Bio-fertilizers are living organisms which help in increasing the fertility of soil. It involves the selection of beneficial microorganisms that help in improving plant growth through the supply of plant nutrients. These are introduced to seeds, roots, or soil to mobilize the availability of nutrients by their biological activity. Thus, they are extremely beneficial in enriching the soil with organic nutrients. Many species of bacteria and cyanobacteria have the ability to fix free atmospheric nitrogen. Rhizobium is a symbiotic bacteria found in the root nodules of leguminous plants. Azospirillium and Azotobocter are free living nitrogenfixing bacteria, whereas Anabena, Nostoc, and Oscillitoria are examples of nitrogen-fixing cyanobacteria. Bio-fertilizers are cost effective and eco-friendly.

BOD (Biochemical Oxygen Demand) is the determination the amount of the oxygen that would be consumed if all the organic matter in one liter of water were oxidised by bacteria.The higher the BOD, higher is the pollution potential of water.
The highest BOD is of sample C and hence, it will be untreated sewage water which is the most polluted. The river water should have least BOD hence, it will be the sample B. The seconday effluent would have higher BOD than river water by less than that of untreated sewage and hence, it is the sample A.

• Sample A- secondary effluent
• Sample B- river water
• Sample C- untreated sewage

• Wheat product: Bread, cake.
• Rice product: Idli, dosa.
• Bengal gram product: Dhokla, Khandvi.

Involves biological organism such as aerobic and anerobic microbes/bacteria and fungi to digest/consume organic waste.
Primary effluent is passed into aeration tank where vigorous growth of aerobic microbes (flocs) take place, BOD reduced (microbes consume major part of organic matter), effluent is passed to settling tank where flocs sediment to produce activated sludge, sludge is pumped to anerobic sludge digester to digest bacteria and fungi.

A small part of the activated sludge is pumped back into aeriated tank to server as the inoculum. The remaining major part of the sludge is pumped into large tanks called anaerobic sludge digesters. Other kind of bacteria which grow anaerobically, digest the bacterial and the fungi in the sludge. During this digestion, bacteria produce a mixture of gases such as methane, hydrogen sulphide and corbondioxide. These gases from biogas and can be used as source of energy as it is inflammable.

Nucleopolyhedrovirus,
They control only species specific pest, do not affect non target organisms/beneficial insects are conserved/they aid in IPM problems/no negative impact on plants or other animals.

Baculoviruses produce narrow spectrum insecticides to kill insects and other arthropods which are species specific, does not affect non-target organisms/no negative impact on other insects, mammals, birds, or fish.Eliminates the use of chemical pesticides/conserve beneficial insects/integrated pest management.

• Bacteria which grow anaerobically on cellulosic material.
• Present in cattle. (rumen)
• Breakdown of cellulose, helps in nutrition of animal/digestion of cellulose.

Mycorrhiza: (Fungal Symbiont of the association) Absorb phosphorus from soil.
Anabaena: Fix atmospheric nitrogen/Adds organic matter to the soil.
Rhizobium: Fix atmospheric nitrogen (in leguminous plants).
Methanobacterium: They digest cellulosic material, and the product/spent slurry can be used as fertiliser.
Trichoderma: Biocontrol agent for several plant pathogens.

1. The fruit juices available in the market are made clarified by treating them with the enzymes – pectinases and proteases. So, they are clearer as compare to those made at home.
2. Trichoderma polysporum is used to produce immune suppressive agent cyclosporine A. Monascus purpureus is used to produce blood-cholesterol-lowering agents statins.

Aerobic and anaerobic // fungi, bacteria.
(After primary treatment) growth of aerobic microbes into aeration tanks reduces BOD // consumes organic matter, Anaerobic bacteria decomposes the sludge (in the anaerobic sludge digesters) forming biogas etc.

Bio wastes are collected and a slurry of dung is fed, a floating cover having gas outlet is placed over slurry which keeps on rising as the gas is produced in the tank, the spent slurry is removed through another outlet and may be used as fertiliser.

1. Sludge loader.
2. Gas holder/CH4 and CO2.
3. Dung and water.

a - Statins,
b - Blood cholesterol lowering agent,
c - Penicillium notatum,
d - Penicillin,
e - Trichoderma polysporum,
f - Immuno-suppressive agent in organ transplant patients.

1. Chemical methods often kills both useful and harmful life forms indiscriminately. Eradication of the creatures that are often described as pests in not only possible, but also undersirable, for without them the beneficial predatory and parasitic insects which depend upon them as food or hosts would not be able to survive.
2. Insects - Ladybird and Dragonflies.

Bacteria - Bacillus thuringiensis.

Fungus - Trichoderma.

1.  

	Column-A		Column-B
(a)	Penicillium notatum	(iii)	Antibiotic
(b)	Trichoderma polysporum	(iv)	Cyclosporin-A
(c)	Monascus purpurea	(i)	Statin
(d)	Saccharomyces cerevisiae	(ii)	Ethanol

2. Swiss cheese develops large holes because of the large amount of carbon dioxide produced by the bacterium Propionibacterium shermanii.

Bt stands for bacteria name Bacillus thuringiensis whose gene has been incorporated in cotton plant to make Bt-cotton. These are available in sachets and are mixed with water and sprayed onto vulnerable plants such as brassicas and fruit trees, where these are eaten by the insect larvae. In the gut of the larvae, the toxin is released and the larvae get killed.

Lipases are added in detergents for removing oily stains, while streptokinase acts as 'clot buster' helps in clearing blood clots inside the blood vessels.

If we take A and a as the traits:

1. Recessive.
2. Autosomal.
3. Parents-Aa and Aa.

Third child-aa.

Fourth child-Aa.

Following are the advantages of using biofertilisers in agriculture:

1. Biofertilisers do not cause any pollution.
2. These are cheap and economical.
3. Some of them act as biopesticides also.
4. In ill-irrigated conditions few biofertilisers can enhance the crop yield.
5. They improve soil structure and function.
6. They make available vitamins and other growth promoting biochemicals.

1. Curd is formed from milk by Lactobacillus.
2. Swiss cheese: Propionibacterium sharmanii.
3. Bread: Saccharomyces cereviseae.

1. Lactic acid bacteria.
2. It play a very beneficial role in checking disease-causing microbes.

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

The symbiotic association of fungi and roots of higher plants is called mycorrhiza. The fungal hyphae absorbs phosphorus from soil and passes it to the soil and thus enriches the soil. It also protects plants by providing resistance from root-borne pathogens, tolerance to salinity and drought.

1. The excreta of cattle commonly called gobar is rich in methanogenic bacteria. Thus, cattle dung can be used for generation of biogas, commonly called gobar gas.
2. Saccharomyces cerevisiae used for bread making and commonly called brewer's yeast.

Biogas plants are most suitable and advantageous in rural areas because of the following reasons:

1. Raw material for biogas plant is mainly cow dung which is available in plenty in rural areas where cattle are used.
2. The biogas is used for lighting and cooking in these areas as distribution is only in short distances.
3. The spent slurry from the biogas plant is used as a fertiliser for agriculture hence are more suitable in rural areas.

Biopesticides are biological agents and their products are used to control pests like weeds, insects and pathogens. Bioherbicides like cochineal insects Lactoblastic cactorum controlled the spread of Opuntia, and Baculoviruses are viral pathogens that kill insects and other arthropods.

Enzymes and their functions:

Enzyme	Uses
Lipases	Used in detergent formulations. They are helpful in removing oily stains from the laudry.
Pectinases and proteases	Used in bottled juices for clearing of juices.
Streptolinase	Obtained from genetically modified form of bacterium streptococcus. It is used as a 'clot buster' for removing clots from the blood vessels of heart patients, who have undergone myocardial infarction leading to heart attack.

1. Increasing hair growth on aerial parts of plants.
2. Rendering the flowers nectar less.
3. Enabling plants to secrete insect killing chemicals (toxins).

1. When the BOD ofefiluent is reduced significantly, it is then passed into a settling tank, where the bacterial 'flocs'' are allowed to sediment' This sediment is called activated sludge.
2. The biogas thus produced is used for cooking and lighting.

They also form symbiotic association with plants, i.e. mycorrhiza, which absorb phosphorus from soil and passes it to the plants. Many members of genus Glomus form mycorrhiza. Plants with mycorrhizal association show other benefits also such as.

1. Resistance to root-borne pathogens.
2. Tolerance to salinity and drought.
3. Increase in plant growth and development.

• Organic farming is a holistic approach that seeks to develop an understanding of the webs of interaction among the myriads of organisms that form the flora and fauna of the field.
• The organic farmer works to create a system where the insects (called pests) are not eradicated, but kept at manageable levels by a complex system of checks and balance within a living and vibrant ecosystem.
• According to the organic farmer, the eradication of the creatures, called pests, is not only possible but also undesirable, because many beneficial predatory and parasitic insects cannot survive without them.
• Biocontrol agents have no impact on other useful organisms, as they are species-specific.
• Such a use of biocontrol measures reduces the use of chemical pesticides and thereby the pollution.

Virus which attacks bacteria is called bacteriophage. The virus enters a bacterial cell and controls the genetic material of bacteria in order to produce more viruses.

Baculoviruses belong to the genus Nucleopolyhedrovirus:

1. They are species-specific, narrow spectrum insecticides that are the pathogens which attack insects and other arthropods.
2. They have no negative impacts on plants, birds, mammals, fish, and even non-target insects.
3. This is desirable because beneficial insects are conserved to aid in integrated pest management (IPM) programmes.

The evolutionary success of ruminants is based on the efficiency of their digestive system in extracting nutrition from low quality food or say cellulose, which is undigestible matter in other mammals. The key to the ruminant digestive system is the presence of symbiotic microorganisms in their stomach.
These microorganisms produce cellulase enzyme, which breaks cell walls of plant material to release fatty acid, which constitute a significant portion of overall energy budget input of a ruminant.

Mechanism of Biogas or Gobar Gas Production:

• The raw material for biogas production is excreta (dung) of cattle.
• The biogas plant has a concrete tank (10–15 feet deep) in which bio-wastes and slurry of dung is collected.
• The tank has a floating cover which rises on production of gas in the tank.
• Methanobacterium in the dung act on the bio-wastes to produce biogas.
• The gas produced is supplied to nearby houses by an outlet.
• Through another outlet, the spent slurry is removed to be used as fertiliser.
• Biogas is used as fuel for cooking and lighting.

• A small amount of activated sludge is pumped back into the aeration tank as inoculum; the microbes grow into flocs and consume the organic matter to reduce the BOD.
• A large part of the activated sludge is pumped into anaerobic sludge digesters where the anaerobic bacteria digest the bacteria and fungi of the flocs; during this process gases like methane, hydrogen sulphide and carbon dioxide are formed, which constitute the biogas.

1. Acetobacter aceti produces acetic acid BE.
2. Clostridium butylicum produces butyric acid.

Aeration tank is meant for agitating the liquid effluent from the primary settling tank, where the air is allowed to pass through agitating mixture to make it aerobic.

The untreated sewage is often discharged directly into rivers leading to their pollution and increase in water-borne diseases. 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 sewage may be discharged in the rivers.

Source: Streptococcus. Streptokinase is a clot buster, i.e., it removes clot from the blood vessels of patients who had a heart attack.

1. Statin.
2. It is a blood-cholesterol lowering agent.
3. Penicillium notatum.
4. Penicillin.
5. Trichoderma polysporum.
6. It is used as an immune suppressive agent in organ-transplant patients.

• A: Streptococcus.
• B: Cyclosporin A.
• C: Immunosuppressive agent.
• D: Removal of clots from blood vessels of patients who had myocardial infarction.

1. It should not kill useful microorganisms found in alimentary canal of man.
2. It should not cause side-effects in the host.
3. It should have quick action and should be broad spectrum, i.e., must have the ability to act on various pathogenic microorganisms which differ from each other.
4. The action of antibiotics must be specific on the pathogens only.

1. A is the floating cover which is placed over the slurry, which keeps on rising as the gas is produced in the tank due to the microbial activity.
2. B is the biogas which is a mixture of gases consisting of methane, hydrogen sulphide and carbon dioxide. It can be used as a source of energy to nearby houses as it is inflammable. C is the spent slurry or sludge which is removed through another outlet and may be used as fertiliser.

Bacillus thuringiensis:

• The spores of this bacterium are insecticidal and used to control the larvae of many insect pests.
• They are available in sachets as dried spores, which have to be mixed with water and sprayed on to the vulnerable plants.
• When they are eaten by the larvae, the toxin becomes active in the gut of the larvae and kills the larvae.
• Through genetic engineering, the gene coding for the toxic protein is introduced into crop plants which makes them resistant to the insect pest. Biological control of pests and pathogens is preferred to chemical pesticides because.

1. The chemicals are toxic and extremely harmful to human beings and other animals.
2. The chemicals also cause pollution of soil, groundwater and our agricultural products.
3. The chemicals kill the useful organisms also.

S.No.	Enzyme	Uses
1.	Lipase	(a)Used in detergent formulations.(b) Helps in removing oily stains from laundry
2.	Pectinase and protease	Used for clarifying bottled juices.
3.	Streptokinase (produced by Streptococcus and modified by genetic engineering)	Used as ‘clot-buster’ for removing clots from blood vessels of patients who have undergone myocardial infarction.

• They are species-specific, narrow-spectrum insecticides, which have no negative impacts on non-target insects and other groups of animals and plants.
• This property helps in an overall integrated pest management (IPM), as beneficial insects are conserved.
• These organisms belong to the genus Nucleo polyhedrovirus.

Streptokinase is the enzyme produced by Streptococcus:

• It is used as a clot-buster to remove clots from the blood vessels of patients who have suffered myocardial infarction.

1. Mycorrhizae:

• 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.

2. Anabaena:

• It is a cyanobacterium that fixes atmospheric nitrogen in the soil; it also adds organic matter to the soil through its photosynthetic activity.

3. Rhizobium:

• It forms nodules in the roots of legumes and fixes atmospheric nitrogen in the form of ammonia which the plants use.

4. Trichoderma:

• This fungus lives freely in the root ecosystem of many plants. It is used as biocontrol agent against many plant pathogens.

1. Aspergillus niger:

• It produces citric acid, which is used as food preservative.

2. Trichoderma polysporumente:

• It produces cyclosporin A, which is used as an immunosuppressive agent for organ transplant patients.

3. Monascus purpureus:

• It produces statins, which are used as blood cholesterol-lowering agent.

1. It is a test cross.
2.  

The test cross ratio is 1 : 1 : 1 : 1

3. Principle of segregation.

1. Dominant.
2. Autosomal.
3. Parents-Mother- aa.

Father-Aa.

Third child-Aa.

First grand-child-Aa.

Antibiotics are chemical substances primarily produced by some microorganisms which in low concentration can kill or retard the growth of other disease causing microorganisms. Antibiotics are mainly produced from three groups of microorganisms:

1. Eubacteria (true bacteria)
2. Actinomycetes (ramified bacteria)
3. Fungi.

1. Bacteria: Azotobacter, Azospirillum, Rhizobium.
2. Cyanobacteria: Nostoc, Anabaena, Oscillatoria.

Mycorrhizae:

• Glomus sp.
• They increase soil fertility by fixing atmospheric nitrogen (bacteria and cyanobacteria) and also by adding organic matter through photosynthesis (Cyanobacteria).
• Fungi in mycorrhizae help the plant to absorb phosphorus from the soil; they also provide resistance to root borne pathogens and tolerance to soil salinity and drought.

Farmers prefer biofertilisers to chemical fertilisers for the following differences between them:

Biofertilisers	Chemical Fertilisers
Biofertilisers are organisms that enrich the nutrient quality of the soil.	Fertilisers are synthetic chemicals added to soil to supply specific nutrient(s) that is/ are lacking.
They provide almost all the nutrients, but slowly.	They supply only the specific nutrient(s), but quickly.
They do not degrade the soil quality.	They degrade the soil quality.
Their culturing does not cause environmental pollution.	Their manufacture causes environmental pollution.

Biofertilizers (microorganisms) are added to soil to increase its fertility.
Nitrogen and phosphorus elements are added by biofertilizers.

To control butterfly caterpillars, bacteria such as Bacillus thuringiensis are used in the form of sprays or sachets as dry spores. These are mixed with water and sprayed onto vulnerable plants like brassicas and fruit trees, where these are eaten by the insects larvae. This kills the larvae due to release of toxin in their gut, thereby eradicating the caterpillars, but leaving other insects unharmed.

This fungus produces a bioactive molecule, called cyclosporin-A, which is used as an immunosuppressive agent in organ transplant patients.

BOD stands for Biochemical oxygen demand. It indicates the rate of uptake of oxygen by microorganisms in a sample of water so it shows the presence of organic matter in water. More valve of BOD means more polluting potential.