WBBSE Class 9 Life Science Solutions Chapter 4.2 Microbes in Human Welfare

Detailed explanations in West Bengal Board Class 9 Life Science Book Solutions Chapter 4.2 Microbes in Human Welfare offer valuable context and analysis.

WBBSE Class 9 Science Chapter 4.2 Question Answer – Microbes in Human Welfare

Very Short Questions and Answers : (1 mark for each question)

Question 1.
Who is known as the father of microbiology?
Answer:
Louis Pasteur is known as the father of microbiology.

Question 2.
Give an example of a species of bacteria that is used for biological control of insect pest?
Answer:
Bacillus thuringiensis is used for biological control of insect pest.

Question 3.
Name a symbiotic bacterium, which can trap atmospheric nitrogen for its plant partner.
Answer:
Rhizobium leguminosarum can trap atmospheric nitrogen for its plant partner.

Question 4.
Which soil-living bacterium is applied in crop fields to increase nitrogen content of the soil?
Answer:
Azotobacter is a soil-living bacterium, which is applied in crop fields to increase nitrogen content of the soil.

Question 5.
Name a common viral bio-control agent against insect pest.
Answer:
Nuclear Polyhedrosis Virus is a common viral bio-control agent against insect pest.

Question 6.
Crystalline protein from which bacterium is popularly known as ‘cry protein’?
Answer:
Crystalline protein is produced from Bacillus thuringiensis bacteria, which is popularly known as ‘cry protein’.

Question 7.
Which bacterium is used to kill the larvae of Anopheles mosquito?
Answer:
Members of the Bacillus sphaericus bacteria are used to kill the larvae of Anopheles mosquito.

Question 8.
Name a bacterial species dwelling in the root nodules of leguminous plants.
Answer:
Rhizobium leguminosarum is a bacterial species dwelling in the root nodules of leguminous plants.

Question 9.
Name an endomycorrhiza, used as biofertiliser.
Answer:
VAM is an endomycorrhiza used as biofertiliser.

Question 10.
What is vermiculture?
Answer:
Vermiculture is the process in which earthworms are reared in a portion of soil to prepare organic manure to enhance the productivity of soil.

Question 11.
Name two fungal associates of mycorrhiza.
Answer:
Amanita and Boletus are two common fungal associates of mycorrhiza.

Question 12.
How does mycorrhiza help in reducing soil pollution?
Answer:
Mycorrhiza helps in reducing soil pollution removing harmful heavy metals like lead, mercury etc. from soil.

Question 13.
What is the full form of VAM?
Answer:
Full form of VAM is Vesicular Arbuscular Mycorrhiza.

Question 14.
Which types of mycorrhiza are found in nature?
Answer:
Three different types of mycorrhiza are found in nature, which are ectomycorrhiza, endomycorrhiza and ectendomycorrhiza.

Question 15.
Give examples of two fungi, which form ectomycorrhiza.
Answer:
Boletus and Amanita form ectomycorrhiza.

Question 16.
Give examples of two fungi, which form VAM or endomycorrhiza.
Answer:
Glomus and Acaulospora form VAM or endomycorrhiza.

Question 17.
Give exampies of two fungi, which forms ectendomycorrhiza.
Answer:
Clavaria and Endagon form ectendomycorrhiza.

Question 18.
Name two plants in which ectomycorrhiza grows on the roots.
Answer:
Ectomycorrhiza grows on the roots of oak and pine.

Question 19.
What is the full form of NPV?
Answer:
Full form of NPV is Nuclear Polyhedrosis Virus.

Question 20.
What is the full form of CPV?
Answer:
Full form of CPV is Cytoplasmic Polyhedrosis Virus.

Question 21.
Mention of the importance of NPV and CPV as bio-control agent.
Answer:
NPV and CPV are used to destroy several caterpillar pests of vegetable plants, hence, are bio-control agents.

Question 22.
Which type of phage virus is used to kill Salmonella bacteria in water bodies?
Answer:
Caudovirales is a group of phage virus used to control Salmonella build-up in water bodies.

Question 23.
Name a protozoan microbe, used to control insect pest.
Answer:
Nosema locustae is a protozoan microbe, used to control insect pests.

Short Questions and Answers : (2 marks for each question)

Question 1.
What are microhes?
Answer:
Microscopic organisms (less than 0.1 mm in diameter) present in air, water and soil are commonly known as microbes.

Question 2.
Which organisms are called bacteria?
Answer:
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 70 S ribosomes are called bacteria. Example-Bacillus, Salmonella etc.

Question 3.
Which organisms are called protozoa?
Answer:
Eukaryotic, unicellular microorganisms, carrying well-defined nucleus with chromosomes and membrane-bound cell organelles, are known as protozoa. Example-Amoeba, Plasmodium etc.

Question 4.
What is meant by bio-control agents?
Answer:
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 biocontrol agents.

Question 5.
What is meant by biological control?
Answer:
The technique by which abundance of pests and harmful organisms is controlled by application of their specific natural enemies is known as biological control.

Question 6.
Name two bacterial and two cyanobacterial species, commonly used as bio-fertilisers.
Answer:
The two bacterial species commonly used as bio-fertilisers are Rhizobium and Azotobacter. The two cyanobacterial species commonly used as bio-fertilisers are Anabaena and Nostoc.

Question 7.
What is meant by GM0?
Answer:
Full form of GMO is Genetically Modified Organism. By application of modern biotechnology, in recent days, 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 organism.

Question 8.
What are viruses?
Answer:
Viruses are ultra-microscopic, nucleoproteinated, acellular intermediate entity between living and non-living. Examples-HIV, Rotavirus etc.

Question 9.
What is biomagnification?
Answer:
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.

Question 10.
What is bioaccumulation?
Answer:
Bioaccumulation refers to accumulation of toxic substance in a organism. It occurs when an organism absorbs a toxic substance at a rate faster than that at which substance is lost by catabolism or excretion.

Question 11.
How do GMO help in bio-control of insect pests?
Answer:
Bacillus thuringiensis can produce a toxin, called Bt-toxin, which is fatal for insect pests. Biotechnologists have singled out the 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.

Question 12.
Mention the role any of two viruses as biocontrol agents.
Answer:
1. Nuclear Polyhedrosis Virus can potentially kill the larvae of moths and beetles.
2. Granulosis virus destroys larvae of Spodoptera litura, an insect pest.

Question 13.
Mention the role of Caudovirales in controlling water pollution.
Answer:
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.

Question 14.
Mention the roles of any two protozoa as biocontrol agents.
Answer:
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.

Question 15.
Mention the role of a symbiotic bacteria as bio-fertiliser.
Answer:
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 their plant partners as an essential nutrient.

Question 16.
What is Azolla? Mention its importance.
Answer:
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.

Question 17.
Why Azolla is an effective bio-fertiliser for paddy fields but not effective in wheat and vegetable fields?
Answer:
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 Azolla as bio-fertiliser is not effective for wheat and vegetable cultivation.

Question 18.
How do bacteria increase soil fertility?
Answer:
Bacteria can increase soil fertility in two different ways. One type increases nitrogen level in soil by trapping atmospheric nitrogen. Another type makes soil-borne phosphorus, soluble and absorbable to root system.

Question 19.
How Azotobacter can be applied in a crop field as bio-fertiliser?
Answer:
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.

Question 20.
How do phosphobacteria act as bio-fertiliser?
Answer:
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.

Question 21.
Mention the role of Bacillus thuringiensis as bio-control agent.
Answer:
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 commerciallv prepared and applied in cotton and vegetable crop fields to control caterpillar and grub.

Question 22.
How do different bio-fertilisers work?
Answer:
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.

Question 23.
What is the full form of IPM? Mention its objective.
Answer:
Full form of IPM: Integrated Pest Management.
Objective of IPM: The concept of Integrated Pest Management is developed in view of sustainable development of agriculture. Its main objective is to reduce the use of chemical fertilisers, insecticides, herbicides, fungicides by using bio-control agents or protect the future generation from harmful effects of these harsh chemicals and to keep the world as much pollution free as possible.

Question 24.
Mention the advantages of bio-control or biological controi.
Answer:
The advantages of biological control procedure are as follows-

1. Bio-control is more eco-friendly, because it does not pollute environment.
2. In bio-control, 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.

Question 25.
Define mycorrhiza.
Answer:
Mycorrhiza is a symbiotic relationship between fungi and root systems of vascular plants. Mycorrhiza is formed in plants like pine, orchids etc. The fungi involved in the formation of the mycorrhiza are Glomus, Boletus etc.

Question 26.
Mention the disadvantages of bio-control measures.
Answer:
The disadvantages of bio-control procedures are-
1. Many bio-controlling organisms cannot adapt themselves with the new environment and often die.
2. The effectiveness of a bio-control agent on a pest cannot be assumed before application.

Question 27.
Describe the importance of VAM as biofertiliser.
Answer:
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.

Long Questions and Answers : (5 marks for each question)

Question 1.
Give a brief account of different microbial bio-control agents.
Answer:
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 some genetic materials of these bacteria in corn, vegetables and cotton plants. As a result, Bt-toxin is synthesized in it, so that insect parasites cannot attack these plants. 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:
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.

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:

• Nosema locustae is a protozoan microbe, which is used to control some insect pests.
• 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.

Question 2.
What is meant by bio-fertiliser? Mention the roles of bacteria as bio-fertiliser. 1 + 4
Bio-fertiliser
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 bio-fertiliser.

Roles of different bacteria as bio-fertilisers

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 Thiobaccilus, Micrococcus, Acrobacter are capable of solubilizing inorganic phosphorus from insoluble compounds in the soil. Use of these bacteria as bio-fertilisers enhance phosphate-nutrition of plants.

Question 3.
What do you mean by nitrogen fixation? Mention the roles of cyanobacteria as bio-fertiliser. 2 + 3
Answer:
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 bio-fertilisers

Some cyanobacteria 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.

Question 4.
Mention the roles of mycorrhiza as a bio-fertiliser. Why are bio-fertilisers and bio-control agents getting more acceptance all over the world? 2 + 3
Answer:
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 bio-fertilisers 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 bio-fertilisers is negligible.

Pest control by biological agents do not need any infrastructure at all. Bio-fertiliser does not need heavy infrastructure and power. Moreover bio-control is an eco-friendly procedure and bio-fertilisers do not cause soil pollution. Bio-fertiliser and pest control by biological agents not only retain the natural resources of earth, but also prevent it from getting amalgamated with chemical precipitations. So bio-fertilisers and bio-control agents are getting more acceptance all over the world.