Chapter 4 Biology And Human Welfare Microbes In Human Welfare Long Answer Type Questions
Question 1 Give a brief account of different microbial bio-control agents.
Answer:
Different microbial bio-control agents:
Different bacteria, viruses, fungi, and protozoa can be used as bio-control agents.
1 Bacteria as a bio-control agent:
Bacillus thuringiensis produces a poison, called Bt toxin, which is used to control the 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 fluorescence has been commercially used as a fungicide. Bacillus papillae is used to control the Japanese beetle, a pest of maple and rose plants.
2 Virus as a bio-control agent:
1. 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 diarrhea.
2. 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.
Read and Learn More Class 9 Life Science Long Answer Questions
3 Protozoa as a bio-control agent:
1. Nosema locustae is a protozoan microbe, which is used to control some insect pests.
2. Mattesia grandis, another protozoan, effectively controls cotton ball weevils.
WBBSE Class 9 Microbes in Human Welfare Long Answer Questions
4 Fungus as a bio-control agent:
Beauveria bassiana is a fungus, which can control mosquito populations 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.
WBBSE Life Science And Environment Class 9 Solutions
Question 2. What is meant by biofertiliser? Mention the roles of bacteria as biofertilisers.
Answer:
Biofertilizer:
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 biofertilizers.
Roles of different bacteria as biofertilizers:
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 dwells 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., and Chlorobium sp. are mentionable.
5. Some bacteria like Thiobacillus, Micrococcus, and Acrobacter are capable of solubilizing inorganic phosphorus from insoluble compounds in the soil. The use of these bacteria as biofertilizers enhance the phosphate nutrition of plants.
Important Long Answer Questions for Chapter 4 Life Science
Question 3. What do you mean by nitrogen fixation? Mention the roles of cyanobacteria as biofertilizers.
Answer:
Nitrogen fixation:
Nitrogen fixation is a process in which nitrogen (N2) in the atmosphere is converted into ammonia (NH3). The nitrogen fixation process occurs naturally in the soil by nitrogen-fixing bacteria.
Roles of cyanobacteria as biofertilizers:
Some cyanobacteria can trap atmospheric nitrogen. These include Anabaena sp., Nostoc sp., Aulosira sp., Stigonema sp., Plectonema sp., etc. These are now cultured in the water of paddy fields. When these organisms die and decompose, nitrates get absorbed in the 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 the atmosphere and supply it to Azolla.
Azolla die and get decomposed in the soil. Through this process, soil get nitrogen from the decomposed body of this fern. In Southeast Asian countries, the cultivation of Azolla in paddy fields is a regular practice now.
It has reduced the need for chemical fertilizers and has cut down the cost of paddy cultivation. Besides this, cyanobacteria secrete ascorbic acid, Vit. B and auxin in the soil.
WBBSE Life Science And Environment Class 9 Solutions
Question 4. Mention the roles of mycorrhiza as a bio-fertilizer. Why are bio fertilizers and bio-control agents getting more acceptance all over the world?
Answer:
Roles of mycorrhiza as bio-fertiliser:
Mycorrhiza is a symbiotic association between the roots of some vascular plants and some fungi. In this association, the fungi develop hyphae (fine filaments of the fungal vegetative body) around the root tip or inside the cortex of the roots of the vascular plants.
The fungal hyphae can absorb phosphorus and nitrogenous nutrients from the 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 biofertilizers and bio-control agents:
Chemical fertilizers are expensive. Production of these fertilizers needs large infrastructure and power. Chemical fertilizers reduce natural soil fertility and change soil pH. The same is applicable in the case of pesticides, these are very expensive and all of these materials increase environmental pollution.
However, in comparison with chemical fertilizers, the production cost of biofertilizers is negligible. Pest control by biological agents does not need any infrastructure at all.
Production of bio-fertilizer does not need heavy infrastructure and power. Moreover, bio-control is an eco-friendly procedure and biofertilizers do not cause soil pollution.
Bio-fertilizer and pest control by biological agents not only retain the natural resources of the earth but also prevent them from getting amalgamated with chemical precipitations. So bio-fertilizers and bio-control agents are getting more acceptance all over the world.
Practice Long Answer Questions on Microbial Benefits
Question 5. What is a pest? Write about the role of microbes in the biological control of pests.
Answer:
Pest:
Pests are species whose presence directly or indirectly affects the benefits, advantages, and welfare of human beings.
Examples: Tryporyza incestuous, Leptocoriza varicosis, Hispa armiger, Bandicota bengalensis, Bandicota indicia, etc.
Role of microbes in the biological control of pests:
WBBSE Life Science And Environment Class 9 Solutions
Question 6. What do you mean by biological pest control? Mention its advantages and disadvantages.
Answer:
Biological pest control:
The control of pests with the aid of biological agents (bacteria, viruses, protozoa, etc.) is known as biological pest control. Example-Use of bacteria, and birds to control pest moths.
Advantages:
1. Biofertilizers 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 bioaccumulation of chemicals in food chains occurs due to the use of biofertilizers.
4. Long-term usage of biofertilizers does not generate any resistance to pests.
Disadvantages:
1. A 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.
Understanding the Role of Microbes for Long Answers
Question 7. Write different characteristics or properties of bio-fertilizer. Mention the advantages and disadvantages of biofertilizers.
Answer:
Characteristics or properties of biofertilizers:
1. Biofertilizers contain living microorganisms.
2. They improve the 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 biofertilizers:
1. They are cost-effective.
2. They supplement chemical fertilizers.
3. They are eco-friendly.
4. They reduce the cost of the use of fertilizers, especially regarding nitrogen and phosphorus.
5. They improve the texture, structure, and water-holding capacity of the soil.
6. There are no adverse effects on plant growth and soil fertility due to the usage of biofertilizers.
Disadvantages of biofertilizers:
1. Biofertilizers 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.
Concepts Related to Microbes in Human Welfare for Long Answers
Question 8. Differentiate between organic manure and bio-fertilizer.
Answer:
Difference between organic manure and bio-fertilizer:
Sample Long Answer Questions from WBBSE Class 9 Life Science
Question 9. Differentiate between inorganic manure and bio-fertilizer.
Answer:
Difference between inorganic manure and bio-fertilizer:
