MICROORGANISMS FRIEND AND FOE
JKBOSE Solutions for Class 8 Science
JKBOSE Solutions for Class 8 Science :
JKBOSE solutions have been provided below to aid the students with answering the questions correctly, using a logical approach and methodology. The solutions provide best and smartest material to enable students to form a good base and improve the fundamentals of the subject.
This page provides you all the links to JKBOSE Solutions for Class 8 Science. You can anytime copy or download, Copy paste each and every chapter Solutions to your desktop. Science JKBOSE class 8 solutions are helpful resource developed by our science experts to help students in their class 8 exam.
JKBOSE Solutions for Class 8 Science
The links below provide the detailed solutions for JKBOSE science class 8 textbook.
JKBOSE Solutions for Class 8 Science
JKBOSE textbooks are prescribed by JK BOARD OF SCHOOL EDUCATION as the best books for preparation of the school as well as board examinations. The textbooks are considered as more than enough, without any aid from other refreshers. The solutions are made and designed keeping in mind the lucid language and the simplicity of the explanations that are given in the NCERT textbooks. These are not just the board and school examinations, NCERT textbooks are known to play a very important role in JEE and NEET.
JKBOSE science book class 8 acts as a stepping stone for further higher classes where u might feel that the topic is out of your league and hard to comprehend. The concepts of science social science math syllabus form the backbone of higher classes. JKBOSE class 8 science solutions help to clear our basic concepts and make them very easy and interesting for the students.
We prepared JKBOSE Solutions as per CBSE remodeled assessment structure. We have discussed and elaborated extensively how are different food crops produced. Which living organisms do we see under a microscope in a drop of water etc ? Are some of our clothes synthetic? How do we conserve biodiversity? What is the internal structure of a plant? and many more.
JKBOSE solutions will help in the following manner:
- Authentic Homework Guide
- The base for the preparation of competitive exams like JEE and NEET
- Strengthening basic concepts of subjects
- Error-free solutions
- Extra problems to build upon the basic concepts
TEXTBOOK SOLUTIONS JKBOSE CLASS 8TH
CHAPTER 1 MICROORGANISMS FRIEND AND FOE
MICROORGANISMS OR MICROBES.
Microbes are Single celled Organisms That are invisible To the naked eye.
Microbes are minute Unicellular organisms. That are invisible to the naked eye. They are also known as Microscopic Organisms. As they could only be seen Under a microscope. They make up Almost. 60% of the earths Living matter.
MICROORGANISMS live almost in every environment from cold to hot places deserts to lands and inside the body of other organisms.
Activity 1.
Take a small soil in a beaker and add some water when soil settles take a drop of water on a slide and observe it under microscope. You will see tiny moving creatures which are microorganisms.
Drop of water from pond also shows these creatures under microscope.
Microorganisms or manly divided into four major groups
• BACTERIA.
• FUNGI
• PROTOZOA
• ALGAE.
BACTERIA:
Bacteria are microbes with a cell structure simpler than that of many other organisms. Their control centre, containing the genetic information, is contained in a single loop of DNA. Some bacteria have an extra circle of genetic material called a plasmid rather than a nucleus.
The main types of bacteria are
spherical (cocci), rod (bacilli), spiral (spirilla), comma (vibrios) or corkscrew (spirochaetes). They can exist as single cells, in pairs, chains or clusters.
FUNGI:
Fungi can be single celled or very complex multicellular organisms. They are found in just about any habitat but most live on the land, mainly in soil or on plant material rather than in sea or fresh water. A group called the decomposers grow in the soil or on dead plant matter where they play an important role in the cycling of carbon and other elements. Some are parasites of plants causing diseases such as mildews, rusts, scabs or canker. In crops fungal diseases can lead to significant monetary loss for the farmer. A very small number of fungi cause diseases in animals. In humans these include skin diseases such as athletes’ foot, ringworm and thrush.
Main types of fungi are
PROTOZOA
Protozoa are one-celled animals found worldwide in most habitats. Most species are free living, but all higher animals are infected with one or more species of protozoa.
Protozoa are microscopic unicellular eukaryotes that have a relatively complex internal structure and carry out complex metabolic activities. the protozoa are currently classified into six phyla. Most species causing human disease are members of the phyla Sacromastigophora and Apicomplexa.
Binary fission, the most common form of reproduction, is asexual; multiple asexual division occurs in some forms. Both sexual and asexual reproduction occur in the Apicomplexa.
Main types of protozoa are
ALGAE
Listed below are some of the general characteristics of algae.
Algae are photosynthetic organisms
Algae can be either unicellular or multicellular organisms
Algae lack a well-defined body, so, structures like roots, stems or leaves are absent
Algaes are found where there is adequate moisture.
Reproduction in algae occurs in both asexual and sexual forms. Asexual reproduction occurs by spore formation.
Algae are free-living, although some can form a symbiotic relationship with other organisms.
VIRUSES
A virus is an infectious agent of small size and simple composition that can multiply only in living cells of animals, plants, or bacteria.
Viruses are small obligate intracellular parasites, which by definition contain either a RNA or DNA genome surrounded by a protective, virus-coded protein coat.
When some disease-causing viruses enter host cells, they start making new copies of themselves very quickly, often outpacing the immune system's production of protective antibodies. Rapid virus production can result in cell death and spread of the virus to nearby cells. Some viruses replicate themselves by integrating into the host cell genome, which can lead to chronic illness or malignant transformation and cancer.
Types of VIRUSES
Properties of Viruses
They are non-cellular organisms, which is enclosed in a protective envelope.
The presence of spikes helps in attaching the viruses to the host cell.
These viruses do not grow, neither respire nor metabolize, but they reproduce.
They are surrounded by a protein coat – capsid and have a nucleic acid core comprising DNA or RNA.
They are considered both as living and non-living things. These viruses are inactive when they are present outside of host cells, but become active within host cells. These viruses cause several infections and reproduce within the host cell by using the enzymes and raw materials.
MICROORGANISMS are with us from ages working for us make our life comfortable but at the same time are hazardous to us as they cause diseases in humans animals and plants. Hence we classify them as friends and foes.
ADVANTAGES OF MICROORGANISMS.
Bacteria like Lactobacillus convert milk into curd.
Bacteria are also involved in the making of cheese.
Acetobacter aceti is used for producing acetic acid from alcohol.
Yeast is used in the commercial production of alcohol, wine and bakery products.
Some specific microorganisms are helpful in manufacturing of antibiotics.
Microorganisms act as cleansing agents and decompose the waste products into manure.
Dead or weakened microbes are used in the preparation of vaccines.
Some bacteria fix atmospheric nitrogen and increase soil fertility.
Algae, yeast, fungi or bacteria may be used as an ingredient or a substitute for protein-rich foods that are suitable for human or animal consumption.
Some microorganisms are taken as probiotics, that are believed to provide health benefits when consumed.
DISADVANTAGES OF MICROBES
Microorganisms are harmful to us in many ways. For example, microorganisms, called pathogens cause disease in humans, plants and animals. Pathogens or germs enter a healthy body through air, water, contaminated food and infected person by direct or indirect contact or by the carrier. Common ailments like cold, influenza (flu), cough, polio, chicken pox are caused by viruses. Foot and mouth diseases in the cattle are also caused by viruses. Typhoid, tuberculosis (TB) are caused by bacteria. Anthrax a dangerous human and cattle diseases is also caused by bacteria.
Diseases like dysentery and malaria are caused by protozoa. Ringworm is caused by fungi. Several microbes causes diseases in plants and thus reduces the yield. Citrus canker, a bacterial disease, affects trees of citrus fruit and is spread by air. Bhendi yellow vein mosaic disease is caused by a virus and is spread by insects in lady fingers. Rust of wheat is a fungal disease spread through air. Microorganisms that grow on our food sometimes produce toxic substances. These make the food poisonous causing serious illness and even death. This food-borne illness is called food poisoning.
CHAPTER 1 TEXTBOOK QUESTIONS
Question 1. Fill in the blanks.
(a) Microorganisms can be seen with the help of a _____
(b) Blue-green algae fix ______ directly from the air to enhance the fertility of soil.
(c) Alcohol is produced with the help of _____
(d) Cholera is caused by ______
Answer: (a) microscope (b) nitrogen (c) yeast (d) bacteria
Question 2. Tick the correct answer.
(a) Yeast is used in the production of
(i) sugar (ii) alcohol (iii) hydrochloric acid (iv) oxygen
Answer:
(ii) alcohol
(b) The following is an antibiotic:
(i) sodium bicarbonate (ii) streptomycin (iii) alcohol (iv) yeast
Answer:
(ii) streptomycin
(c) Carrier of malaria-causing protozoan is:
(i) female Anopheles mosquito (ii) cockroach (iii) housefly (iv) butterfly
Answer:
(i) female Anopheles mosquito
(d) The most common carrier of communicable diseases is
(i) ant (ii) housefly (iii) dragonfly (iv) spider
Answer:
(ii) housefly
(e) The bread or idli dough rises because of:
(i) heat (ii) grinding (iii) growth of yeast cells (iv) kneading
Answer:
(iii) growth of yeast cells
(f) The process of conversion of sugar into alcohol is called
(i) nitrogen fixation (ii) moulding (iii) fermentation (iv) infection
Answer:
(iii) fermentation
Question 3.
Match the organisms in column A with their action in column B.
A | B |
(i) Bacteria | (a) Fixing nitrogen |
(ii) Rhizobium | (b) Setting of curd |
(iii) Lactobacillus | (c) Baking of bread |
(iv) Yeast | (d) Causing malaria |
(v) A protozoan | (e) Causing cholera |
(vi) A virus | (f) Causing AIDS |
(g) Producing antibodies |
Answer: (i) (e) (ii) (a) (iii) (b) (iv) (c) (v) (d) (vi) (f)
Question 4. Can microorganisms be seen with the naked eye? If not, how can they be seen?
Answer: The microorganisms cannot be seen with our naked eyes because they are very small in size. Some of these, such as fungus growing on bread, can be seen with a magnifying glass. Others cannot be seen without the help of a microscope.
Question 5. What are the major groups of microorganisms?
Answer: Microorganisms are classified on the basis of their size into four major groups. These groups are: (a) Bacteria (b) Fungi (c) Protozoa (d) Some algae
Question 6. Name the microorganisms which can fix atmospheric nitrogen in the soil.
Answer: Rhizobium, Clostridium and Azotobacter.
Question 7. Write 10 lines on the usefulness of microorganisms in our lives.
Answer: Microorganisms are useful to us in many ways. For example,
Bacteria like Lactobacillus convert milk into curd.
Bacteria are also involved in the making of cheese.
Acetobacter aceti is used for producing acetic acid from alcohol.
Yeast is used in the commercial production of alcohol, wine and bakery products.
Some specific microorganisms are helpful in manufacturing of antibiotics.
Microorganisms act as cleansing agents and decompose the waste products into manure.
Dead or weakened microbes are used in the preparation of vaccines.
Some bacteria fix atmospheric nitrogen and increase soil fertility.
Algae, yeast, fungi or bacteria may be used as an ingredient or a substitute for protein-rich foods that are suitable for human or animal consumption.
Some microorganisms are taken as probiotics, that are believed to provide health benefits when consumed.
Question 8. Write a short paragraph on the harms caused by microorganisms.
Answer: Microorganisms are harmful to us in many ways. For example, microorganisms, called pathogens cause disease in humans, plants and animals. Pathogens or germs enter a healthy body through air, water, contaminated food and infected person by direct or indirect contact or by the carrier. Common ailments like cold, influenza (flu), cough, polio, chicken pox are caused by viruses. Foot and mouth diseases in the cattle are also caused by viruses. Typhoid, tuberculosis (TB) are caused by bacteria. Anthrax a dangerous human and cattle diseases is also caused by bacteria.
Diseases like dysentery and malaria are caused by protozoa. Ringworm is caused by fungi. Several microbes causes diseases in plants and thus reduces the yield. Citrus canker, a bacterial disease, affects trees of citrus fruit and is spread by air. Bhendi yellow vein mosaic disease is caused by a virus and is spread by insects in lady fingers. Rust of wheat is a fungal disease spread through air. Microorganisms that grow on our food sometimes produce toxic substances. These make the food poisonous causing serious illness and even death. This food-borne illness is called food poisoning.
Question 9. What are antibiotics? What precautions must be taken while taking antibiotics?
Answer: Antibiotics are the medicines which kill or stop the growth of the disease-causing microbes. They are manufactured by growing specific microorganisms. They are used to cure a variety of diseases. It is important to take antibiotic only on the advice of a qualified doctor. One must finish the course prescribed by the doctor to make the drug more effective. Antibiotics must not be taken unnecessarily because it may kill beneficial bacteria also. Antibiotics are, however, not effective against cold and flu as they are caused by viruses.
Activities Solved
Activity 1
Collect some moist soil from the field in a beaker and add water to it. After the soil particles have settled down, observe a drop of water from the beaker under a microscope. What do you see?
Solution:
It is observed that some tiny organisms are moving around.
Activity 2
Take a few drops of water from a pond. Spread on a glass slide and observe through a microscope.
Solution: It is observed that some tiny organisms are moving around.
Activity 3
Jake 1/2 kg flour (atta or maida), add some sugar and mix with warm water. Add a small amount of yeast powder and knead to make a soft dough. What do you observe after two hours? Did you find the dough rising?
Solution: It is observed that the dough begins to rise up in volume. Yeast reproduces rapidly and releases C02 during respiration. Etubble of this gas fill the dough and increase its volume.
Activity 4
Take 500 ml. beaker filled upto 3/4 with water. Dissolve 2-3 teaspoons of sugars in it. Add half a spoon of yeast powder to the sugar solution. Keep it covered in a warm place for 4-5 hours. Now smell the solution. Can you get a smell?
Solution: It is observed that the solution smell like alcohol. This process of conversion of sugar in alcohol is known as fermentation.
Activity 5
Take two pots and fill each pot half with soil. Mark them A and B. Put plant waste in pot A and things like polythene bags, empty glass bottles and broken plastic toys in pot B. Put the pots aside. Observe them after 3-4 weeks.
Solution: It is observed that plant waste in pot A has been decomposed, whereas the polythene bags, empty glass bottles and broken plastic toys in pot B did not undergo such changes.
Question 1.
Name the bacteria responsible for the disease typhoid.
Answer: Salmonella typhi.
Question 2. Chicken pox is caused by ………. virus.
Answer: Varicella zoster.
Question 3. ………….. (disease) is caused by mycoplasma.
Answer: Pleuropneumonia.
Question 4. Name the toxin released by T.B. bacteria.
Answer: Tuberculin toxin is released by T.B. bacteria.
Question 5. Which microorganism is the cause of malaria ? [NCT 2006]
Answer: A Protozoan, Plasmodium.
Question 6. Write two diseases caused by bacteria. [NCT2005]
Answer: Two diseases caused by bacteria are tuberculosis and diphtheria.
Question 7. Name any two items that are prepared by using yeast. [KVS 2005]
Answer: Yeast is used to prepare bread and alcohol.
Question 8. Name the microorganisms which can fix atmospheric nitrogen in the soil. []
Answer: Rhizobium, Clostridium md Azotobacter fix atmospheric nitrogen.
Question 9. Can microorganisms be seen with the naked eye ? If not, how can they be seen ? []
Answer: No, microorganisms cannot be seen with the naked eye. They can only be seen with the help of microscope.
Question 10. What are microorganisms ?
Answer: Microorganisms are organisms that are so small that they can only be seen through a microscope.
Question 11. Name two diseases caused by viruses.
Answer: Influenza and cough.
Question 12. Name two diseases caused by protozoans.
Answer: Dysentery and malaria.
Question 13. Which microorganisms are unicellular ?
Answer: Bacteria and protozoa are unicellular.
Question 14. Name two multicellular microorganisms.
Answer: Algae and fungi are multicellular.
Question 15. Name the bacterium used for production of acetic acid from alcohol.
Answer: Acetobacter aceti.
Question 16. Define fermentation.
Answer: The process of conversion of sugar into alcohol is called fermentation.
Question 17. Why antibiotics are not effective against cold and flu ?
Answer: Cold and flu are caused by viruses, so the antibiotics are not effective against them.
Question 18. What are antibodies ?
Answer: When a disease carrying microbe enters our body, the body produces antibodies to fight the invader.
Question 19. Name two diseases which can be prevented by vaccination.
Answer: Cholera and tuberculosis can be prevented by vaccination.
Question 20. Name the diseases for which oral drops are given as vaccination.
Answer: Polio.
Question 21. What are biological nitrogen fixers ?
Answer: Some bacteria and blue-green algae are able to fix nitrogen from the atmosphere to enrich soil with nitrogen and increase fertility, are known as biological nitrogen fixers.
Question 22. What are pathogens ?
Answer: Diseases-causing microorganisms are called pathogens.
Question 23. What are communicable diseases ?
Answer: Microbial diseases which can spread from an infected person to a healthy person through air, water, food or physical contact are known as communicable diseases.
Question 24. Name two communicable diseases.
Answer: Chicken pox and tuberculosis.
Question 25.Name two carriers of disease-causing microbes.
Answer: Housefly and female Anopheles mosquito.
Question 26. Name the causative microorganism of tuberculosis and its mode of transmission.
Answer: Causative microorganisms – Bacteria.
Mode of transmission – Air.
Question 27. How are cholera and typhoid transmitted ?
Answer: Cholera is transmitted through water or food.
Typhoid is transmitted through water.
Question 28. Which microorganism causes foot and mouth disease of cattle ?
Answer: Virus.
Question 29. Name one plant disease caused by bacteria and its mode of transmission.
Answer: Citrus canker is caused by bacteria and transmitted through air
Question 30. Name one plant disease transmitted by insects and caused by virus.
Answer: Yellow vein mosaic of bhindi.
Question 31. Name one plant disease caused by fungi and its mode of transmission.
Answer: Rust of wheat. It is transmitted through air and seeds.
Question 32. What is meant by food poisoning ?
Answer: Food poisoning is caused by consuming food that has bean spoilt by some microorganisms.
Question 33. What are preservatives ?
Answer: Chemicals (salts, etc.) that check the growth of microorganisms are called preservatives.
Question 34. How are pickles preserved ?
Answer: Pickles are preserved by adding salt or acid.
Question 35. Name the chemicals used to preserve jams and squashes.
Answer: Sodium benzoate and sodium metabisulphite are added to jams and squashes to preserve them.
Question 36. How are meat and fish preserved ?
Answer: Meat and fish are preserved by covering them with dry salt to check the growth of bacteria.
Class 8 Science Chapter 1
Microorganisms: Friends and Foe
This chapter manages destructive and valuable kinds of microbes and their significance in different areas. The places where microorganisms live, microorganisms and us, harmful microorganisms, food preservation, nitrogen fixation, and nitrogen cycle are a portion of the primary topics covered in this chapter.
Class 8 Science Chapter 2
Class 8 Science Chapter 3
Conservation of Plants and Animals
Conservation of plants and animals is a critical subject of science. This part will push the students to not just to understand the human exercise that negatively affects the nature’s abundance yet in addition to manners by which they can ensure the fauna and flora of the ecosystem.
Class 8 Science Chapter 4
Class 8 Science Chapter 5
Class 8 Science Chapter 6
Food Production and Management
This chapter explains rural practices related to the creation of yield and their administration.It includes the presentation of various harvest, their climatic and nourishing necessities and the preparation of soil for comprehensive improvement of the crops
Class 8 Science Chapter 7
Class 8 Science Chapter 8
Class 8 Science Chapter 9
Class 8 Science Chapter 10
Reaching the Age of Adolescence
In this chapter, the student will find out about changed that happen in the human body after which an individual ends up fitting for reproduction.in this chapter we will learn about the human conceptive organs and the role of hormones in the development of an individual.
Comments
Post a Comment
If you want to understand computer science let me know..