WBBSE Solutions For Class 9 Life Science And Environment Chapter 4 Microbes In Human Welfare

Chapter 4 Biology And Human Welfare Summary

1. Microbes or microorganisms are organisms that are not visible to the naked eye but can be seen only under the microscope.
2. Different viruses, bacteria, protozoa, and insects can reduce the population growth of various insect pests of crops by causing disease, parasitism, and predation.
3. Integrated Pest Management (IPM) has been developed in view of the sustainable development of agriculture.
4. Organisms that enrich the nutrient quality of the soil are called biofertilizers.
5. Like nitrogen-fixing bacteria, many species of cyanobacteria can fix atmospheric nitrogen.
6. There are some fungi that live in close association with the roots of some plants and live symbiotically.
7. Such symbiotic association between fungi and plant roots is known as mycorrhiza.
8. Biofertilizers are eco-friendly and cost-effective

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Chapter 4 Biology And Human Welfare Microbes In Human Welfare Short Answer Type Questions

Question 1. What are microbes? Give example.

Answer:

Microbes:-

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

Example: Bacteria, protozoa, etc.

WBBSE Life Science And Environment Class 9 Solutions

Question 2. Which organisms are called bacteria?

Answer:

Organisms Are Called Bacteria Are :

Prokaryotic microbes, have a cellular diameter of less than 3 μm with cell walls typically made up of peptidoglycan and cytoplasm carrying a circular nitrogen or solubilizing phosphorus for enhancing the productivity of the soil. VAM, cyanobacteria, etc. DNA and scattered 70S ribosomes are called bacteria.

Examples: Bacillus, Salmonella, etc.

Question 3. Which organisms are called protozoa?

Answer:

Organisms Are Called Protozoa:-

Eukaryotic, unicellular microorganisms, carrying well-defined nuclei with chromosomes and membrane-bound cell organelles, are known as protozoa.

Examples: Amoeba, Plasmodium, etc.

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

Answer:

Bio-Control Agents:-

Different viruses, 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.

Question 5. What is meant by biological control?

Answer:

Biological Control:-

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

WBBSE Life Science And Environment Class 9 Solutions

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

Answer:

Bacterial And Cyanobacterial Species, Commonly Used As Biofertilisers:-

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

Question 7. What is meant by GMO?

Answer:

GMO:-

The full form of a GMO is a 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 the outer source. Such organisms show desired features and are popularly called genetically modified organisms.

WBBSE Class 9 Life Science Solutions

Question 8. What are viruses?

Answer:

Viruses:-

Viruses are ultra-microscopic, nucleoproteinated, acellular intermediate entities between living and non-living.

Examples: HIV, Rotavirus, etc.

Question 9. What is biomagnification?

Answer:

Biomagnification:-

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

Question 10. What is bioaccumulation?

Answer:

Bioaccumulation:-

Bioaccumulation refers to the accumulation of toxic substances 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.

WBBSE Class 9 Life Science Solutions

Question 11. How do GMOs help in the bio-control of insect pests?

Answer:

GMOs Help In The Bio-Control Of Insect Pests As Follows:-

Bacillus thuringiensis can produce a toxin, called Bt-toxin, which is fatal for insect pests. Biotechnologists have singled out the toxin-producing gene from the bacterium and placed it in the plant cells. Such GMO or Genetically Modified Crop plants synthesize the Bt-toxin, which potentially kills insect pests feeding on it.

Question 12. Mention the role of any of two viruses as bio- control agents.es as bio-

Answer:

Role Of Any Of Two Viruses As Bio- Control Agents.Es As Bio:-

1. The nuclear Polyhedrosis Virus can potentially kill the larvae of moths and beetles.
2. The granulosis virus destroys larvae of Spodoptera litura, an insect pest.

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

Answer:

Role Of Caudovirales In Controlling Water Pollution:-

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

WBBSE Class 9 Life Science Solutions

Question 14. Mention the roles of any two protozoa as bio-control agents.

Answer:

Roles Of Any Two Protozoa As Bio-Control Agents:-

1. Nosema locustae is a protozoan microbe, which is used to control some insect pests.
2. Mattesia grandis, another protozoan, effectively control cotton ball weevils.

Question 15. Mention the role of a symbiotic bacterium as a biofertilizer.

Answer:

Role Of A Symbiotic Bacterium As A Biofertilizer:-

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.

WBBSE Class 9 Life Science Solutions

Question 16. What is Azolla? Mention its importance.

Answer:

Azolla And Its Importance:

Azolla: Azolla is an aquatic floating fern that is commonly known as ‘mosquito fern!

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

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

Answer:

Azolla Is An Effective Fertilizer For Paddy Fields But Not Effective In Wheat And Vegetable Fields:-

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

Question 18. How do bacteria increase soil fertility?

Answer:

Bacteria Increase Soil Fertility:-

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

Question 19. How Azotobacter can be applied in a crop field as a biofertilizer?

Answer:

Azotobacter Can Be Applied In A Crop Field As A Biofertilizer:-

Agricultural laboratories prepare a 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 them before sowing and plantation.

WBBSE Class 9 Life Science Solutions

Question 20. How do phosphobacteria act as biofertilizers?

Answer:

Phosphobacteria Act As Biofertilizers:-

Soil contains some phosphate salts, which are not absorbable by roots. Phosphobacteria makes these salts soluble and absorbable in the root system of plants. Thus, phosphobacteria act as a fertilizer.

Example: Bacillus megaterium is a phosphobacterium.

Question 21. How do different bio-fertilizers work?

Answer:

Different Bio-Fertilizers Work As Follows:-

Nitrogen-fixing bacteria and cyanobacteria propagate in soil and absorb atmospheric nitrogen, which ultimately mixes in the 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.

WBBSE Class 9 Life Science Solutions

Question 22. Mention the role of Bacillus thuringiensis as a bio-control agent.

Answer:

Role Of Bacillus Thuringiensis As A Bio-Control Agent:-

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

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

Answer:

Full form of IPM: Integrated Pest Management.

The objective of IPM:

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

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

Answer:

The advantages of biological control of pests are as follows:

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

WBBSE Class 9 Life Science Solutions

Question 25. Define mycorrhiza.

Answer:

Mycorrhiza:-

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.

Question 26. Describe the importance of VAM as a bio-fertilizer.

Answer:

Importance Of VAM As A Bio-Fertilizer:-

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

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

Answer:

The disadvantages of bio-control of pests are:

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

Question 28. Define chemical fertilizer.

Answer:

Chemical Fertilizer:-

A chemical fertilizer is defined as any inorganic material of wholly or partially synthetic origin that is added to the soil to sustain plant growth.

Example: Urea.

WBBSE Class 9 Life Science Solutions

Question 29. Define bio-fertilizer.

Answer:

Gio-Fertilizer:-

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

Question 30. Define vermiculture.

Answer:

Vermiculture:-

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

Question 31. Why Azotobacter is called beneficial bacteria?

Answer:

Azotobacter Is Called Beneficial Bacteria:-

Azotobacter (nitrogen-fixing bacteria) converts 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.

Question 32. Write the role of cyanobacteria as biofertilizers.

Answer:

Role Of Cyanobacteria As Biofertilizers:-

There are several free-living cyanobacteria such as Anabaena, Nostoc, and Aulosira that can fix nitrogen. Aulosira fertilizing is known to be an active nitrogen fixer in the paddy field. Cylin is prosperous. licheniforme grows in the field of maize and sugarcane, fixing nitrogen in the soil.

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

Question 33. Mention the role of mycorrhiza as a bio-fertilizer.

Answer:

The role of mycorrhiza as a bio-fertilizer is as follows:

1. Helps to increase the absorption of nutrients from the soil by the roots of vascular plants.
2. Helps to enhance water uptake by the roots of vascular plants.
3. Increases the resistance of plants against soil-borne pathogens.
4. Decreases transplant shocks to seedlings.

Question 34. Write about Bt-toxin.

Answer:

Bt-toxin

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

WBBSE Class 9 Life Science Question And Answer

Question 35. Differentiate between ectomycorrhiza and endomycorrhiza.

Answer:

Differences between ectomycorrhiza and endomycorrhiza:

 

Chapter 4 Biology And Human Welfare Microbes In Human Welfare Answer in a single word or sentence

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

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

WB Class 9 Life Science Question Answer

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

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

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

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

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

Question 9. Name an endomycorrhiza, used as a bio-fertilizer.
Answer: VAM is an endomycorrhiza used as a bio-fertilizer.

Question 10. Name two fungal associates of mycorrhiza.
Answer: Amanita and Boletus are two common fungal associates of mycorrhiza.

WBBSE Class Nine Life Science

Question 11. 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 12. What is the full form of VAM?
Answer: Vesicular Arbuscular Mycorrhiza

Question 13. Which types of mycorrhiza are found in nature?
Answer: Three different types of mycorrhiza are found in nature, these are ectomycorrhiza, endomycorrhiza and ectomycorrhiza.

Question 14. Give examples of two fungi, which form ectomycorrhiza.
Answer: Boletus and Amanita

Question 15. Give examples of two fungi, which form VAM or endomycorrhiza.
Answer: Glomus and Acaulospora

Question 16. Give examples of two fungi, which form ectomycorrhiza.
Answer: Clavaria and Endagon

Question 17. Name two plants in which ectomycorrhiza grows on the roots.
Answer: Oak and pine

Question 18. What is the full form of NPV?
Answer: Nuclear Polyhedrosis Virus

Question 19. What is the full form of CPV?
Answer: Cytoplasmic Polyhedrosis Virus

Question 20. Mention of the importance of NPV and CPV as bio-control agents.
Answer: NPV and CPV are used as Bio-control agents to destroy several caterpillar pests of vegetable plants.

Question 21. What is an antibiotic?
Answer: An antibiotic is a chemical substance that kills bacteria, secreted by microorganisms which can kill the pathogens. Examples-Penicillin and streptomycin.

WBBSE Class Nine Life Science

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

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

Chapter 4 Biology And Human Welfare Microbes In Human Welfare Fill In The Blanks

Question 1. Bacillus thuringiensis produces a poison called

Answer: Bt-toxin

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

Answer: Root

Question 3. Mycorrhiza exhibits the phenomenon of.

Answer: Symbiosis

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

Answer: Insect

Question 5. Mycorrhizal absorbs nutrients from soil very efficiently.

Answer: Hyphae

WBBSE Class Nine Life Science

Question 6. is a protozoan microbe that effectively controls cotton ball weevils.

Answer: Mettasia Grandis

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

Answer: Leaf

Question 8. Agriculture using only biofertilizers is called

Answer: Organic farming

Question 9. Cyanobacteria serve as important biofertilizers in the fields of.

Answer: Paddy

WB Class 9 Life Science Question Answer

Question 10. One of the free-living anaerobic nitrogen fixers is

Answer: Rhodospirillum

Question 11. Bacillus thuringiensis is widely used as

Answer: Insecticide

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

Answer: Leg haemoglobin

WBBSE Class Nine Life Science

Question 13. Antibiotics are the most effective on

Answer: Bacteria

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

Answer: Anabaena

Question 15. Azolla pinata has been found to be an important bio-fertilizer for paddy crops. The quality is due to the presence of

Answer: N₂ fixing bacteria

Question 16. Non-symbiotic bio-fertiliser is.

Answer: Azotobacter

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

Answer: Chemical pesticides

Question 18. used as bio-fertilizer in cotton fields.

Answer: Azotobacter chroococcum

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

Answer: Mycorrhiza

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

Answer: Species

Chapter 4 Biology And Human Welfare Microbes In Human Welfare State True Or False

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

Answer: False

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

Answer: True

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

Answer: True

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

Answer: False

WBBSE Class Nine Life Science

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

Answer: True

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

Answer: True

Chapter 4 Biology And Human Welfare Microbes In Human Welfare Match The Columns

Answer: 1-E; 2-A; 3-B; 4-C

Answer: 1-C; 2-D; 3-F; 4-B; 5-A; 6-G

Answer: 1-C; 2-D; 3-A; 4 B

Answer: 1-E; 2-A; 3-B; 4-C

Answer: 1-D; 2-C; 3-B; 4-A; 5-E; 6-G

Answer: 1-C; 2-B; 3-D; 4-A

Chapter 4 Biology And Human Welfare Microbes In Human Welfare Find The Odd One Out

Question 1. Tetrahymena, Nosema, Trogoderma, Bacillus thuringiensis

Answer: Bacillus thuringiensis

Question 2. Nuclear Polyhedrosis Virus, granulosis virus, Baculovirus; HIV

Answer: HIV

WBBSE Class Nine Life Science

Question 3. Bt-toxin, Thuricide, Cry protein, NPV

Answer: NPV

Question 4. Nostoc, Anabaena, Aulosira, Azotobacter

Answer: Azotobacter

Question 5. Rhizobium, Azotobacter, Clostridium, Azo- spirillum

Answer: Rhizobium

Chapter 4 Biology And Human Welfare Microbes In Human Welfare Fill in the blanks by looking at the first pair

1. Mycorrhiza: Fungi:: Nodules: Bacteria

2. Rhizobium: Bacteria:: Nostoc: Cyanobacteria

3. Anabaena: Azolla:: Rhizobium: Leguminous plant

4. Chemical pesticide: Environment pollutant:: Organic pesticide: Eco-friendly

5. Bacillus thuringiensis: Bio-insecticide:: VAM: Bio-fertiliser

Chapter 4 Biology And Human Welfare Microbes In Human Welfare Among The Four Concepts Given, Three Of Them Belong To One. Find That

Question 1. CPV, NPV, Bacillus thuringiensis, Biological control

Answer: Biological control

Question 2. Insects, Weeds, Biological control, Mite

Answer: Biological control

Question 3. Thuricide, Bacillus thuringiensis, Pest killing, Bt toxin

Answer: Bacillus thuringiensis

Question 4. Bacillus thuringiensis, Biopesticide, Nosema, Baculovirus

Answer: Biopesticide

Question 5. Biofertiliser, Azospirillum, Nostoc, Mycorrhiza

Answer: Biofertiliser

Question 6. N₂ fixing microorganisms, Rhizobium, Azotobacter, Nostoc

Answer: N₂ fixing microorganisms