WBBSE 9th Class Science Solutions Life Science & Environment Chapter – 4 Biology and Human Welfare

WBBSE 9th Class Science Solutions Life Science & Environment Chapter – 4 Biology and Human Welfare

West Bengal Board 9th Class Science Solutions Life Science & Environment Chapter – 4 Biology and Human Welfare

WBBSE 9th Class Life Science & Environment Solutions

TOPIC – 1

IMMUNITY AND HUMAN DISEASES

SUMMARY

• The ability of the host to fight and protect against disease-causing organism conferred by the immune system is called immunity.
• Immunity is of two types-(i) Innate Immunity (ii) Acquired Immunity.
• Innate immunity is a non-specific type of immunity in an individual that is present at the time of birth. It works by preventing the entry of pathogens through various barriers. There are various types of barriers such as physical barrier (skin), chemical barrier (lysozyme), by which the body prevents the entry of foreign agents into our body.
• Acquired immunity is pathogen specific and is characterised by a memory of the activities of a pathogen in the body of a living organism. When the pathogen is encountered for the first time a primary response of low intensity is produced. Subsequent encounters with the same pathogen produces high intensity response of high intensity with the help of memory cells. This is called secondary or anamnestic response.
• Primary and secondary response are carried out with the help of 2 special types of lymphocytes-B lymphocytes and T lymphocytes. B lymphocytes produce special proteins called antibodies whereas the T lymphocytes help B lymphocytes to produce antibodies.
• Antigen is a substance usually protein in nature (sometimes polysaccharide or lipid) that generates a specific immune response and induces the formation of specific antibody or specially sensitised T cells or both.
• There are different types of antigens on the basis of antigen: (i) Exogenous antigens are the foreign particles that enter the body system from outside, start circulating in body fluids and are phagocytosed by the antigen processing cells. (ii) Endogenous antigens are the antigenic products, subfragments or any compounds that are produced by the body itself.
• An immune response is a reaction which occurs within an organism for the purpose of defending against foreign invaders.
• Humoral immune response is a kind of immune response that is involved in production of antibodies.These antibodies are present in the blood.
• Cell-mediated immunity is an immune response that does not involve antibodies, but rather involves the activation of phagocytes, antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen. The body is able to differentiate between ‘self and ‘non-self’ and the cell-mediated immune response is responsible for the graft rejection.
• When a host is exposed to antigens, which may be in the form of living or dead microbes or other proteins, antibodies are produced in the host body. This type of immunity is called active immunity. called active Examples-vaccines like BCG, MMR.

Long Answer Type Questions

1. Innate or natural or non-specific Immunity: The innate immunity refers to non-specific defence mechanisms that come into play immediately or within hours of an antigen’s appearance in the body.It consists of various types of physical, and physiological barriers. Example-skin (physical barrier) prevents entry of microorganisms; mucous membrane, acid of the stomach (physiological barrier) kills most microorganisms.
2. Acquired immunity or adaptive or specific Immunity: The immunity that an individual acquires after birth is called acquired immunity. It is specific and mediated by antibodies or lymphocytes or both which make the antigen harmless. It is of two types, active immunity and passive immunity.
   1. Active Immunity: In this case, person’s own cells produce antibodies in response to infection. or vaccination. It is slow and takes time in the formation of antibodies. It is long lasting and is harmless. Active immunity may be natural or artificial (1) A person who has recovered from an attack of small pox or measles or mumps develops natural active immunity. (ii) Artificial active immunity is the resistance induced by vaccines. Examples of vaccines are-BCG vaccine, MMR vaccine, etc.
   2. Passive Immunity: When ready-made antibodies are directly injected in an individual against foreign agents, it is called passive immunity. It provides immediate relief but is not long lasting. It may be natural or artificial-(i) Natural passive immunity is the resistance passively transferred from mother to the foetus through placenta or through colostrum (a yellowish fluid secreted initial days of lactation). (ii) Artificial passive immunity is the resistance passively transferred to a recipient by administration of antibodies. For example, Anti tetanus serum (ATS) is prepared in horses by active immunisation of horses with tetanus toxoid, withdrawal of blood and separation of the serum. ATS is used for passive immunisation against tetanus.

1. Foreignness: The immune system normally discriminates between self and non-self such that only foreign molecules are immunogenic. When an antigen is introduced into an organism, the degree of its immunogenicity depends on the degree of its foreignness.
2. Molecular size: In general, the larger the molecule the more immunogenic it is likely to be. The best immunogens tend to have a molecular mass approaching 100,000 Da. The immunogens with lower efficiency generally have a molecular size between 5000-10000 Da.
3. Chemical composition: They are structurally protein in nature. Sometimes it may be composed of polysaccharide, lipid and nucleic acid.
4. Antigen binding site: It has specific region that interacts with antibody (Ab) which is known as epitope.

1. Antigenicity: The ability to cause the production of antibodies.
2. Antigenic specificity: The ability to enter into an interaction with the corresponding antibodies.
3. Allergenicity: Having the capacity to induce allergy (hypersensitivity).
4. Immunogenicity: Property inducing a detectable immune response.

1. Agglutination: By this process antibodies agglutinate pathogens into clusters, which are then collectively phagocytised by macrophages.
2. Precipitation: Some antigen molecules are clamped by antibodies and are precipitated.
3. Opsonisation: Antibodies form a covering on the antigens so that the phagocytic cells can ingest packed antigens.
4. Neutralisation: Certain toxic antigens are detoxified and inactivated by the antibodies.

1. Killed vaccine: These vaccines contain killed pathogens. Vaccines of cholera, plague, influenza are of this type.
2. Live attenuated vaccine: By some laboratory techniques virulence of the pathogens are reduced to prepare this type of  vaccines. Vaccines of mumps, measles, and rubella (MMR vaccine) are of this type.
3. Toxoid vaccine: This type of vaccine is prepared by inactivated toxins from pathogens. Vaccines of tetanus, diphtheria are of this type.
4. Conjugate vaccine: Generally polysaccharide of bacterial capsule is attached with a protein to prepare this vaccine. Body’s immune system can recognise this conjugated protein and keep it in memory for future immune response. Vaccine against Haemophilus influenzae type-B is of this type.
5. Sub-unit vaccine: This type of vaccine is prepared by small fragments of pathogenic protein. Vaccine against Hepatitis B is of this type.
6. Heterotypic vaccine: This is prepared by pathogens, causing disease to other animals but less or non-virulent to human. Vaccines of small pox and tuberculosis are of this kind.

1. Reducing number of infections: Hand washing can prevent about 30% of diarrhoea related sickness and about 20% of respiratory infections (e.g. common cold, meningitis, flu, hepatitis A) and most types of infectious diseases.
2. Reducing child death: About 1.8 million children under the age of 5 die every year from pneumonia and diarrhoea related diseases. Washing hands carefully and thoroughly can help children and child care providers stay healthy.
3. To remove dirt: Removing dirt through hand washing may even help prevent skin and eye infections.

1. Water: Pure distilled water is the main component used in hand washing.
2. Soap and Detergent: Water is not efficient for cleaning skin because fats and proteins those are components of organic oil are not readily dissolved in water. Removal of micro-organisms from skin may be enhanced with the use of soaps and detergents.
3. Hand antiseptic: Hand sanitizers containing a minimum of 60% to 70% alcohol are and efficient germ killer.
4. Shampoo: Shampoos that contain selenium are effective in controlling dandruff. Dandruff is caused owing to fungal infection on the scalp.
5. Thimerosal: An organic compound containing mercury can be used for dis infection of skin and instruments.
6. Wipes: Hand washing with wipes is also recommended by CDC (Centers for Disease Control and Prevention). This washing is convenient during travelling when water and soap will not be available.
7. Toothpaste and mouth wash: It is used in brushing teeth and washing mouth.
8. Disinfectant: Phenyl, bleaching powder is applied in our surrounding to keep the environment clean.

1. Personal level hygiene: [A] Cleaning hands before taking food, after using toilet and handing any unclean material. [B] Brushing teeth after taking meal and before going to bed. [C] Taking bath once or twice a day. [D] Trimming hair and clipping nails regularly.
2. Household level hygiene: [A] Washing and sun-drying clothing and bedding at regular intervals. [B] Cleaning utensils, kitchen equipment, raw vegetables, fish and meat. [C] Cleaning toilet, basins and sinks. [D] Cleaning and disinfecting water reservoirs.
3. Social level hygiene: [A] Cleaning of sewage system at regular interval. [B] Maintaining general cleanliness in hospitals, educational institutions, market places, railway stations, bus terminus, auditoriums, theaters and other community places. [C] Regular cleaning and disinfecting public toilets.

Short Answer Type Questions

Very Short Answer Type Questions

Multiple Choice Questions & Answers [MCQ]

Answer in a single word or sentence

Fill in the blanks

State True or False

TOPIC – 2

MICROBES IN HUMAN WELFARE

SUMMARY

• The microbes or microorganisms are the organisms which are not visible with naked eyes but can be seen only under the microscope.
• Different virus, bacteria, protozoa and insects can reduce the population growth of various insect pests of crops by causing disease, parasitism and predation.
• Integrated Pest Management (IPM) has been developed in view of sustainable development of agriculture.
• Organisms that enrich the nutrient quality of the soil are called biofertilisers.
• Like nitrogen fixing bacteria, many species of cyanobacteria can fix atmospheric nitrogen.
• There are some fungi which live in close association with the roots of some plants and live symbiotically. Such symbiotic association between fungi and plant roots is known as mycorrhiza.
• Biofertilisers are eco-friendly and cost-effective.

Long Answer Type Questions

1. Give a brief account of different microbial bio-control agents.

Ans. Different microbial bio-control agents

Different bacteria, virus, fungi and protozoa can be used as bio-control agents.

1. Bacteria as bio-control agent: Bacillus thuringiensis produces a poison, called Bt toxin, which is used to control growth of larvae of moths, beetles and flies. Scientists have introduced genetic materials of these bacteria in corn, vegetables and cotton plants. As a result, Bt-toxin is synthesized in these plants, so that insect parasites cannot attack them. Pseudomonas fluonescena has been commercially used as fungicide. Bacillus popillae is used to control Japanese beetle, a pest of maple and rose plants.
2. Virus as bio-control agent: [A] Caudovirales is a group of phage virus, which kill Salmonella (bacteria) from water bodies. This phage virus can be used to eliminate Salmonella from drinking water to protect us from severe diarrhoea. [B] Nuclear Polyhedrosis Virus (NPV) or Cytoplasmic Polyhedrosis Virus (CPV) can kill larvae of moths and butterflies. These viruses are used to destroy some harmful insects like pine sawflies, gypsy moths, tussock moths, etc.
3. Protozoa as bio-control agent: [A] Nosema locustae is a protozoan microbe, which is used to control some insect pests. [B] Mattesia grandis, another protozoa, effectively controls cotton ball weevils.
4. Fungus as bio-control agent: Beauveria bassiana is a fungus, which can control mosquito population effectively. It can be used in those areas, where mosquitoes have developed resistance against chemical insecticides. It can also control termites, whiteflies and many other insects.

2. What is meant by biofertiliser? Mention the roles of bacteria as biofertiliser. 

Ans. Biofertiliser

Certain microorganisms, have the ability to promote plant growth by increasing the supply or availability of primary nutrients to plants. These are applied in crop fields to increase soil fertility. These are known as biofertilisers.

Roles of different bacteria as biofertilisers

[1] Rhizobium leguminosarum is a symbiotic bacteria present in the root nodules of leguminous plants. These bacteria trap atmospheric nitrogen and convert it into nitrates. Ultimately this nitrate is transferred to the plant body as an essential nutrient. [2] Frankia is another symbiotic bacteria, which dwell in the root nodules of plants like Casuarina, Rubus, Alnus, etc. [3] Some soil-living, aerobic bacteria can absorb atmospheric nitrogen into the cells. After death, this nitrogen is released in soil as nitrates and increases its fertility. Azotobacter sp., Azomonas sp., Derxia sp., Azospirillum sp., etc., are some examples. [4] Among the anaerobic nitrogen-fixing bacteria Clostridium sp., Chromatium sp., Chlorobium sp. are mentionable. [5] Some bacteria like Thiobacillus, Micrococcus, Acrobacter are capable of solubilizing inorganic phosphorus from insoluble compounds in the soil. Use of these bacteria as biofertilisers enhance phosphate-nutrition of plants.

3. What do you mean by nitrogen fixation? Mention the roles of cyanobacteria as biofertiliser.

Ans. Nitrogen fixation

Nitrogen fixation is a process in which nitrogen (N₂) in the atmosphere is converted into ammonia (NH₃). Nitrogen fixation process occurs naturally in the soil by nitrogen-fixing bacteria.

Roles of cyanobacteria as biofertilisers

Some cyanobactería can trap atmospheric nitrogen. These include Anabaena sp., Nostoc sp., Aulosira sp., Stigonema sp., Plectonema sp., etc. These are now cultured in water of paddy fields. When these organisms die and decompose, nitrates get absorbed in soil and increase its fertility. Recently Azolla is being cultivated in the irrigated paddy fields. Azolla is an aquatic fern. Nitrogen-fixing cyanobacteria Anabaena azollae live in the leaves of this fern. These cyanobacteria fix nitrogen from atmosphere and supply it to Azolla. Azolla die and get decomposed in the soil. By this process soil get nitrogen from the decomposed body of this fern. In Southeast Asian countries, cultivation of Azolla in paddy fields is a regular practice now. It has reduced the need for chemical fertilisers and has cut down the cost of paddy cultivation. Beside this, cyanobacteria secrete ascorbic acid, Vit. B and auxin in the soil.

4. Mention the roles of mycorrhiza as a bio-fertiliser. Why are biofertilisers and bio-control agents getting more acceptance all over the world? 

Ans. Roles of mycorrhiza as bio-fertiliser

Mycorrhiza is a symbiotic association between roots of some vascular plants and some fungi. In this association, the fungi develop hyphae (fine filaments of fungal vegetative body) around the root-tip or inside the cortex of roots of the vascular plants. The fungal hyphae can absorb phosphorus and nitrogenous nutrients from soil very efficiently. It can also remove harmful heavy metals like lead, mercury, etc., from the soil to reduce soil pollution. Mycorrhiza is formed in oaks, pines, orchids and some crop plants. The fungi involved in the formation of mycorrhiza are Boletus sp., Amanita sp., Glomus, etc.

Reasons behind acceptance of biofertilisers and bio-control agents

Chemical fertilisers are expensive. Production of these fertilisers need large infrastructure and power. Chemical fertilisers reduce natural soil fertility and change soil pH. Same is applicable in case of pesticides, these are very expensive and all of these materials increase environmental pollution. However, in comparison with chemical fertiliser, production cost of biofertilisers is negligible. Pest control by biological agents do not need any infrastructure at all. Production of bio-fertiliser does not need heavy infrastructure and power. Moreover bio-control is an eco-friendly procedure and biofertilisers do not cause soil pollution. Bio-fertiliser and pest control by biological agents not only retain the natural resources of earth, but also prevent them from getting amalgamated with chemical precipitations. So biofertilisers and bio-control agents are getting more acceptance all over the world.

5. What do you mean by biological pest control? Mention its advantages and disadvantages. 

Ans. Biological pest control

The control of pests with the aid of biological agents (bacteria, virus, protozoa, etc.) is known as biological pest control. Example-Use of bacteria, birds to control pest moths.

Advantages

[1] Biofertilisers do not harm non-target organisms, they are very specific. [2] No toxic chemicals are used in their preparation, hence, there are no residues of such chemicals left in soil or water. [3] No bio-accumulation of chemicals in food chains occur due to use of biofertilisers. [4] Long term usage of biofertilisers does not generate any resistance in pests.

Disadvantages

[1] Low level of pests has to be sustained for the maintenance of control agents. [2] Development and research of appropriate control agents is expensive and lengthy.

6. Write different characteristics or properties of bio-fertiliser. Mention the advantages and blo-fertilliser. Mention disadvantages of biofertilisers. 

Ans. Characteristics or properties of biofertilisers

[1] Biofertilisers contain living microorganisms. [2] They improve soil texture and yield of plants. [3] They do not allow pathogens to flourish. [4] They are eco-friendly and cost-effective. [5] They protect the environment from pollutants.

Advantages of biofertilisers

[1] They are cost-effective. [2] They supplement chemical fertilisers. [3] They are eco-friendly. [4] They reduce the cost towards the use of fertilisers, especially regarding nitrogen and phosphorus. [5] They improve texture, structure and water holding capacity of soil. [6] There are no adverse effects on plant growth and soil fertility due to the usage of biofertilisers.

Disadvantages of biofertilisers

[1] Biofertilisers require special care for long term storage because they are alive. [2] They must be used before their expiry date. [3] If other microorganisms contaminate the carrier medium or if a wrong strain is used, they are not as effective. [4] They lose their effectiveness if the soil is too hot or dry.

Short Answer Type Questions

1. What are microbes? Give example.

Ans. Microscopic organisms (less than 0.1 mm in diameter) present in air, water and soil are commonly known as microbes.

Example-Bacteria, protozoa, etc.

2. Which organisms are called bacteria?

Ans. Prokaryotic microbes, having cellular diameter less than 3 μ m with cell wall typically made up of peptidoglycan and cytoplasm carrying a circular DNA and scattered 70S ribosomes are called bacteria. Example-Bacillus, Salmonella, etc.

3. Which organisms are called protozoa?

Ans. Eukaryotic, unicellular microorganisms, carrying well-defined nucleus with chromosomes and membrane-bound cell organelles, are known as protozoa. Example-Amoeba, Plasmodium, etc.

4. What is meant by bio-control agents?

Ans. Different virus, bacteria, protozoa and insects can reduce the population growth of various insect pests of crops significantly, by causing disease, parasitism and predation. These biological agents are commonly called bio-control agents.

5. What is meant by biological control?

Ans. The technique by which abundance of pests and harmful organisms is controlled by application of their specific natural enemies is known as biological control.

6. Name two bacterial and two cyanobacterial species, commonly used as biofertilisers.

Ans. The two bacterial species commonly used as biofertilisers are Rhizobium and Azotobacter. The two cyanobacterial species commonly used as biofertilisers are Anabaena and Nostoc.

7. What is meant by GMO?

Ans. Full form of GMO is Genetically Modified Organism. By application of modern biotechnology, in recent times, plants and animals are produced with tailor made features. For this purpose, unwanted genes of the organisms are replaced by desired genes, from outer source. Such organisms show desired features, and are popularly called genetically modified organisms.

8. What are viruses?

Ans. Viruses are ultra-microscopic, nucleoproteinated, acellular intermediate entity between living and non-living. Example-HIV, Rotavirus, etc.

9. What is biomagnification?

Ans. The chemical fertilisers, insecticides, pesticides, which are used in conventional farming, enter into the food chain through producers. As these toxic chemicals pass along food chain from lower to higher trophic levels, the concentration increases step-by-step. This biological event is known as biomagnification. Biomagnification results into a number of diseases amongst the members of the higher trophic levels.

10. What is bloaccumulation? 

Ans. Bioaccumulation refers to accumulation of toxic substance in an organism. It occurs when an organism absorbs a toxic substance at a rate faster than that at which the substance is lost by catabolism or excretion.

11. How do GMO help in bio-control of insect pests?

Ans. Bacillus thuringiensis can produce a toxin, called Bt-toxin, which. fatal for sect pests. Biothe technologists have singled out toxinproducing gene from the bacterium and placed it in the plant cells. Such GMO or Genetically Modified Crop plants synthesise the Bt-toxin, which potentially kill insect pests feeding on it.

12. Mention the role any of two viruses as biocontrol agents.

Ans. [1] Nuclear Polyhedrosis Virus can potentially kill the larvae of moths and beetles. [2] Granulosis virus destroys larvae of Spodoptera litura, an insect pest.

13. Mention the role of Caudovirales in controlling water pollution.

Ans. Caudovirales is a group of phage viruses which kill Salmonella (bacteria) from water bodies. This phage virus can be used to eliminate Salmonella from drinking water to protect us from severe diarrhoea.

14. Mention the roles of any two protozoa as blocontrol agents.

Ans. [1] Nosema locustae is a protozoan microbe, which is used to control some insect pests.

[2] Mattesia grandis, another protozoa, effectively controls cotton ball weevils.

15. Mention the role of a symbiotic bacterium as biofertiliser. 

Ans. Rhizobium leguminosarum is a symbiotic bacterium present in the root nodules of leguminous plants. These bacteria trap atmospheric nitrogen and convert it into nitrates. Ultimately this nitrate is transferred to their plant partners as an essential nutrient.

16. What is Azolla? Mention its importance.

Ans. Azolla: Azolla is an aquatic floating fern which is commonly known as ‘mosquito fern!

Importance of Azolla: Azolla leaves give shelter to a nitrogen-fixing cyanobacteria named Anabaena azollae. Azolla is gown in water of paddy fields, Anabaena absorbs nitrogen from air. When water gets absorbed, Azolla decays and nitrogen gets mixed in soil to increase its fertility.

17. Why Azolla is an effective biofertiliser for paddy fields but not effective in wheat and vegetable fields?

Ans. Azolla grows in water. Paddy plants also grow in wet soil. So, Azolla is grown in water of paddy fields. On the other hand, wheat and vegetables grow in drier soil. Therefore, application of Azolla as biofertiliser is not effective for wheat and vegetable cultivation.

18. How do bacteria increase soll fertility?

Ans. Bacteria can increase soil fertility in two different ways. One type of bacteria increases nitrogen level in soil by trapping atmospheric nitrogen. While another type, makes soil-borne phosphorus, soluble and absorbable to root system.

19. Now Azotobacter can be applied in a crop be applied in a crop field as blofertiliser?

Ans. Agricultural laboratories prepare mixture of live Azotobacter cells and charcoal powder. This mixture can be applied in fields during soil preparation in the form of dust. This powder can also be mixed in water to prepare a bacterial solution. The seeds or roots of saplings may be given a dip in it before sowing and plantation.

20. Now de phosphobacteria act as biofertiliser?

Ans. Soil contains some phosphate salts, which are not absorbable by roots. Phosphobacteria make these salts soluble and absorbable to root system of plants. Thus, phosphobacteria act as a biofertiliser. Example-Bacillus megaterium is a phosphobacterium.

21. How do different biofertilisers work?

Ans. Nitrogen-fixing bacteria and cyanobacteria propagate in soil and absorb atmospheric nitrogen, which ultimately mix in soil to make it fertile. Phosphobacteria convert phosphate salts into soluble and absorbable forms. Mycorrhiza removes. harmful heavy metals (Pb, Cu, Hg, Cd, etc.) from soil to reduce soil pollution and promotes plant growth. Certain microorganisms remove weeds.

22. Mention the role of Bacillus thuringiensis as ble-control agent.

Ans. Bacillus thuringiensis produces a toxin, called Bt-toxin, which can destroy larvae of many insect pests. In recent days Bt-toxin, popularly known as ‘thuricide’ is commercially prepared and applied in cotton and vegetable crop fields to control caterpillar and grub.

23. What is the full form of IPM? Mention its objective.

Ans. Full form of IPM: Integrated Pest Management.

Objective of IPM: The concept of Integrated Pest Management has been developed in view of sustainable development of agriculture. Its main objective is to reduce the use of chemical fertilisers, insecticides, herbicides, fungicides by using biocontrol agents or protect the future generation from harmful effects of these harsh chemicals and to keep the world as much pollution free as possible.

24. Mention the advantages of bio-control or biological control of pests.

Ans. The advantages of biological control of pests are as follows-[1] Bio-control is more eco-friendly, because it does not pollute environment. [2] In biocontrol, only the target pests are killed, the crop plant and other organisms remain unharmed. [3] This method is less expensive, therefore, reduces the production cost of crops.

25. Define mycorrhiza.

Ans. Mycorrhiza is a symbiotic relationship between fungi and root systems of vascular plants. Mycorrhiza is formed in plants like pine, orchids, etc. Some of the fungi involved in the formation of the mycorrhiza are Glomus, Boletus, etc.

26. Describe the importance of VAM as bio-fertiliser.

Ans. VAM or Vesicular Arbuscular Mycorrhiza is the most popular bio-fertiliser that enhances phosphorus, sulphur and copper absorption by root systems of plants with which it is associated. VAM helps the roots of a vasular plant to capture nutrients from the soil.

27. Mention the disadvantages of bio-control of pests.  

Ans. The disadvantages of bio-control of pests are-[1] Many organisms used as bio-control agents cannot adapt themselves with the new environment and often die. [2] The effectiveness of a bio-control agent in controlling a pest cannot be assumed before its application.

28. Define chemical fertiliser.

Ans. A chemical fertiliser is defined as any inorganic material of wholly or partially synthetic origin that is added to the soil to sustain plant growth. Example-urea.

29. Define bio-fertiliser.

Ans. A bio-fertiliser is a substance which contains living microorganisms which when applied to the seeds, plant surfaces or soil promotes growth by increasing the supply or availability of primary nutrients (NPK) to the host plant.

30. Define vermiculture.

Ans. Vermiculture is the process in which earthworms are reared in a portion of soil to prepare organic manure to enhance the productivity of soil.

31. Why Azotobacter is called benificial bacteria?

Ans. Azotobacter (nitrogen fixing bacteria) convert atmospheric nitrogen into nitrogenous compounds. They are able to pick up free atmospheric nitrogen and fix it in some organic compounds like amino acids. That is why Azotobacter is called beneficial bacteria.

32. Write the role of cyanobacteria as bio fertilisers. 

Ans. There are several free living cyanobacteria such as Anabaena, Nostoc, Aulosira which can fix nitrogen. Aulosira fertilisima is known to be active nitrogen fixer in the paddy field. Cylin drospermum licheniforme grow in the field of maize and sugarcane, fixing nitrogen in the soil.

In some plants cyanobacteria exhibit symbiotic association and promote nitrogen fixation. Association between Azolla and Anabaena is the example of such an association.

33. Write about Bt-toxin.

Ans. Bacillus thuringiensis (Bt) is a Gram positive, spore-forming bacterium that synthesises parasporal crystalline inclusions containing cry and cyt proteins, which are toxic against a wide range of insect orders, nematodes.

Very Short Answer Type Questions

Multiple Choice Questions & Answers [MCQ]

1. Microbes are-

A. Virus

B. Bacteria

C. Protozoa

D. All of these

Ans. D

2. The term ‘microbe’ was coined by

A. Robert Hook

B. Sedillot

C. Robert Brown

D. Leeuwenhoek

Ans. B

3. Azolla maintains symbiotic association with

A. Azotobacter

B. Clostridium

C. Nostoc

D. Anabaena

Ans. D

4. Which is not a bio-fertiliser?

A. Rhizobium

B. Azolla

C. Agaricus

D. Azotobacter

Ans. C

5. Some cyanobacteria are used as bio-fertiliser because

A. They are capable of trapping free O₂ more than other plants

B. They can solubilise phosphorus

C. They can trap atmospheric nitrogen

D. They help the soil to retain more water

Ans. C

6. ‘Bt’ for Bt-cotton stands for

A. Biologically transformed

B. Biotechnology

C. Bacillus thuringiensis

D. None of these

Ans. C

7. Mycorrhiza is an-

A. Association of fungi and algae

B. Association of fungi and flowering plants

C. Association of fungi and bacteria

D. Association of algae and vascular plants

Ans. B

8. Cyanobacteria are-

A. Chemosynthetic bacteria

B. Photosynthetic prokaryotic microorganisms

C. Non-photosynthetic nitrogen-fixing prokaryotic microorganisms

D. Nitrogen-fixing protozoa

Ans. B

9. A soil-dwelling nitrogen-fixing bacterium is-

A. Anabaena

B. Salmonella

C. Clostridium

D. Lactobacillus

Ans. C

10. Which of the following microorganisms can kill insect pests?

A. Bacillus thuringiensis

B. Leptomonas

C. Nosema locustae

D. All of these

Ans. D

11. The virus used in bio-control of insect pests is-

A. Phage virus

B. Rubella virus

C. Nuclear Polyhedrosis Virus

D. Lipovirus

Ans. C

12. An anaerobic nitrogen-fixing non-symbiotic bacterium-

A. Azotobacter

B. Clostridium

C. Rhizobium

D. Azospirillum

Ans. B

13. VAM is a/an-

A. Ectomycorrhiza

B. Ectendomycorrhiza

C.Endomycorrhiza

D. Cyanobacterium

Ans. C

14. Granulosis virus and NPV are similar as both act as-

A. Antibacterial substance

B. Bio-control agents

C. Biofertilisers

D. Disease causing agent for human

Ans. B

15. Bacteria used for controlling Japanese beetle-

A. Bacillus thuringiensis

B. Bacillus popilae

C. Bacillus subtilis

D. Rhizobium fascioli

Ans. B

16. Spodopterin, a bio-control agent for insect pest is composed of

A. Virus

B. Bacteria

C. Protozoa

D. Fungus

Ans. D

17. Example of cyanobacteria is-

A. Anabaena

B. Gleocapsa

C. Oscillatoria

D. All of these

Ans. D

18. Mycorrhizae fungi develop in symbiotic association with

A. Root system of pine

B. Leaf of fern

C. Green algae

D. None of these

Ans. A

19. Application of Azolla in paddy fields are popularly practiced in

A. European countries

B. South American states

C. Southeast Asian countries

D. All of these

Ans. C

20. Mycorrhiza is used as a bio-fertiliser because it-

A. Can remove harmful heavy metals from soil

B. Can absorb water

C. Can help in mineral absorption

D. All of these

Ans. D

21. An antibiotic producing fungus is-

A. Aspergillus

B. Agaricus

C. Penicillium

D. Saccharomyces

Ans. C

22. Nitrifying bacteria are-

A. Parasitic bacteria

B. Chemosynthetic bacteria

C. Autotrophic bacteria

D. None of these

Ans. B

23. Bacteria which are capable of trapping atmospheric nitrogen are-

A. Putrefying bacteria

B. Nitrogen-fixing bacteria

C. Denitrifying bacteria

D. Nitrifying bacteria

Ans. B

24. The bacterium, mostly used in the experiments of biotechnology is-

A. Rhizobium

B. Streptomyces

C. Salmonella

D. E.coli

Ans. D

25. Rhizobium is a-

A. Free-living, nitrogen-fixing bacteria

B. Symbiotic, nitrogen-fixing bacteria

C. Cyanobacteria

D. Denitrifying bacteria

Ans. B

26. Application of Azolla in paddy field increases …….. in soil.

A. Phosphorus

B. Nitrogen

C. Sulphur

D. Potassium

Ans. B

27. Nostoc is a –

A. Nitrogen-fixing protozoa

B. Nitrogen-fixing cyanobacteria

C. Symbiotic fungus

D. Green algae

Ans. B

28. Which of the following organisms is not used as bio-fertiliser?

A. Rhizobium

B. Lichen

C. Azotobacter

D. Azolla

Ans. B

29. Insoluble phosphate of soil is transformed into soluble phosphate by-

A. Azolla

B. Nostoc

C. Rhizobium

D. Pseudmonas putida

Ans. D

30. Sweet pea plant can grow in infertile land because of-

A. Azotobacter

B. Clostridium

C. Rhizobium

D. Anabaena

Ans. C

Answer in a single word or sentence

1. Who is known as the ‘Father of microbiology’?

Ans. Louis Pasteur is known as the ‘Father of microbiology

2. Give an example of a species of bacteria that is used for biological control of insect pest?

Ans. Bacillus thuringiensis

3. Name a symbiotic bacterium, which can trap atmospheric nitrogen for its plant partner.

Ans. Rhizobium leguminosarum

4. Which soil-living bacterium is applied in crop fields to increase nitrogen content of the soil?

Ans. Azotobacter

5. Name a common viral bio-control agent against insect pest.

Ans. Nuclear Polyhedrosis Virus

6. Crystalline protein obtained from which bacterium is popularly known as ‘cry protein’?

Ans. Bacillus thuringiensis

7. Which bacterium is used to kill the larvae of Anopheles mosquito?

Ans. Bacillus sphaericus

8. Name a bacterial species dwelling in the root nodules of leguminous plants.

Ans. Rhizobium leguminosarum

9. Name an endomycorrhiza, used as bio-fertiliser.

Ans. VAM is an endomycorrhiza used as bio-fertiliser.

10. Name two fungal associates of mycorrhiza.

Ans. Amanita and Boletus are two common fungal associates of mycorrhiza.

11. How does mycorrhiza help in reducing soil pollution?

Ans. Mycorrhiza helps in reducing soil pollution removing harmful heavy metals like lead, mercury, etc., from soil.

12. What is the full form of VAM?

Ans. Vesicular Arbuscular Mycorrhiza

13. Which types of mycorrhiza are found in nature?

Ans. Three different types of mycorrhiza are found in nature, these are-ectomycorrhiza, endomycorrhiza and ectendomycorrhiza.

14. Give examples of two fungi, which form ectomycorrhiza.

Ans. Boletus and Amanita

15. Give examples of two fungi, which form VAM or endomycorrhiza.

Ans. Glomus and Acaulospora

16. Give examples of two fungi, which forms ectendomycorrhiza.

Ans. Clavaria and Endagon

17. Name two plants in which ectomycorrhiza grows on the roots.

Ans. Oak and pine

18. What is the full form of NPV?

Ans. Nuclear Polyhedrosis Virus

19. What is the full form of CPV?

Ans. Cytoplasmic Polyhedrosis Virus

20. Mention of the importance of NPV and CPV as bio-control agent.

Ans. NPV and CPV are used as Bio-control agents to destroy several caterpillar pests of vegetable plants.

21. What is an antibiotic?

Ans. Antibiotic is a chemical substance that kills bacteria, secreted by microorganisms which can kill the pathogens. Examples-Penicillin and streptomycin.

22. Which type of phage virus is used to kill Salmonella bacteria in water bodies?

Ans. Caudovirales is a group of phage virus used to control Salmonella build-up in water bodies.

23. Name a protozoan microbe, used to control insect pest.

Ans. Nosema locustae

Fill in the blanks

1. Bacillus thuringiensis produces a poison called ……….

Ans. Bt-toxin

2. Rhizobium is present in the ………… nodules of leguminous plants.

Ans. Root

3. Mycorrhiza exhibits the phenomenon of ………..

Ans. Symbiosis

4. Beauveria bassiana is a fungus, which controls ……….. pest population effectively.

Ans. Insect

5. Mycorrhizal ………… absorb nutrients from soil very efficiently.

Ans. Hyphae

6. ……….. is a protozoan microbe which effectively controls cotton ball weevils.

Ans. Mettasia grandis

7. Anabaena is present in the ………… cavities of Azolla.

Ans. Leaf

8. Agriculture by using only biofertilisers is called ………….

Ans. Organic farming

9. Cyanobacteria serves as important biofertilisers in the fields of ………..

Ans. Paddy

10. One of the free-living anaerobic nitrogen-fixer is ………..

Ans. Rhodospirillum

11. Bacillus thuringiensis is widely used as …………

Ans. Insecticide

12. ………… is a pigment that gives a pinkish hue to rhizobium induced root nodules.

Ans. Leg haemoglobin

13. Antibiotics are the most effective on …………

Ans. Bacteria

14. A nitrogen fixing microbe associated with the fern Azolla in rice fields is …………

Ans. Anabaena

15. Azolla pinnata has been found to be an important bio-fertiliser for paddy crops. The quality is due to the presence of …………

Ans. N₂ fixing bacteria

16. Non-symbiotic bio-fertiliser is …………

Ans. Azotobacter

17. IPM (Integrated Pest Management) discourages the excessive use of …………

Ans. Chemical pesticides

18. ………… used as bio-fertiliser in cotton field.

Ans. Azotobacter chroococcum

19. The symbiotic association between fungi and roots of higher plants is referred to as …………

Ans. Mycorrhiza

20. Baculoviruses are excellent pathogens for ………… specific narrow spectrum insecticidal applications.

Ans. Species

State True or False

1. Nosema locustae is a bacterium, which is used to control harmful grasshoppers.

Ans. False

2. Examples of aerobic nitrogen-fixing bacteria are Azomonas, Azospirillum.

Ans. True

3. Scientists have introduced genetic materials of Bacillus thuringiensis bacterium in corn and cotton plants.

Ans. True

4. Caudovirales is a fungus, which can control pests.

Ans. False

5. Except paddy field, cyanobacterial colony is formed in Cycas.

Ans. True

6. Viruses are also used as bio-control agents to kill insect pests.

Ans. True