Read and download free pdf of CBSE Class 8 Science Microorganisms Assignment Set A. Get printable school Assignments for Class 8 Science. Class 8 students should practise questions and answers given here for Chapter 2 Microorganisms Friend Or Foe Science in Class 8 which will help them to strengthen their understanding of all important topics. Students should also download free pdf of Printable Worksheets for Class 8 Science prepared as per the latest books and syllabus issued by NCERT, CBSE, KVS and do problems daily to score better marks in tests and examinations
Assignment for Class 8 Science Chapter 2 Microorganisms Friend Or Foe
Class 8 Science students should refer to the following printable assignment in Pdf for Chapter 2 Microorganisms Friend Or Foe in Class 8. This test paper with questions and answers for Class 8 Science will be very useful for exams and help you to score good marks
Chapter 2 Microorganisms Friend Or Foe Class 8 Science Assignment
A. Fill in the blanks
1.Microrganisms may be unicellular or ___
2. __ bacteria help to make curd from milk.
3. Disease causing microorganisms are called ___.
4.Ammonium salt in the soil is converted first into nitrites by____ bacteria.
5. The ability of one's body to resist a disease is called ___.
6. Salting draws out ___from food.
7. Nitrates in the soil are converted by __ bacteria into nitrogen gas.
8. The process of preventing food spoilage by chemical or physical methods is called food___.
Answers…
1. multicellular 5. immunity
2.lactobacillus 6. water(moisture)
3.pathogens 7. pseudomonas
4.nitrosomonas 8. Preservation
ANSWER THE FOLLOWING QUESTIONS
B.Very short questions.
Q.1 Name any two antibiotics.
Answer. Streptomycin 2. Tetracycline
Q.2 Give the names of any two communicable diseases.
Answer. Common cold and chicken pox
Q.3 Name any two common diseases each that occur in plants and animals.
Answer. Plant disease – Citrus canker and Rust
Animal disease – Anthrax and bird flu
Q.4 Name two microbial diseases that spread through air.
Answer. Tuberculosis and Pneumonia
Q.5 What are microorganisms?
Answer. The organisms that cannot be seen with the naked eye and can only be observed through a microscope are called microorganisms.
Q.6 Name any disease caused by virus in humans.
Answer. Smallpox
C. Short Questions
Q.1 What is pasteurization?
Answer. Pasteurization is a process for preservation of milk. In this method, milk is heated at about 70°C for 15 to 30 seconds to kill the bacteria present in it and cooled quickly to 10º C to prevent the remaining bacteria from growing.
Q.2 How do legiuminous plants increase the soil fertility?
Answer. Rhizobium bacteria present in the root nodules of leguminous plants absorb nitrogen gas from the atmosphere and convert it into simple nitrogenous compound called nitrates. After harvesting , when the roots decompose, the nitrates present in the root nodules mix with the soil and enrich it with nitrogenous compounds and hence increase the soil fertility.
Q.3 What do you mean by nitrifying bacteria?
Answer. The bacterias that change nitrite into nitrate from ammonia or ammonium in nitrogen cycle are called nitrifying bacteria. Nitrosomonas, Nitrobacter are the nitrifying bacteria found in soil.
Q.4 How does female Anopheles mosquito spread malaria.
Answer. The female Anopheles mosquito sucks the blood of human beings. While sucking blood, it transmits plasmodium into human blood. Plasmodium causes malaria
Q.5 How do antibiotics work?
Answer. Antibiotics fight bacterial infections either by killing bacteria or slowing and suspending its growth. They do this by: attacking the wall or coating surrounding bacteria. Or by interfering with bacteria reproduction.
Q.6 (a) How do viruses differ from other microorganisms?
(b) What is meant by fermentation?
Answer. (a) 1. Viruses are microscopic organisms, generally very smaller than bacteria. They are parasitic in nature, i.e. they can thrive and reproduce only on the host cell like animals, bacteria and plants etc.
2.Viruses are non-living in nature until they come in contact with the living cells. Most of the viruses are infectious in nature. Whereas some of the other microorganisms are useful in nature. Viruses can multiply very rapidly than the microorganisms.
(b) The process of conversion of sugar into alcohol by the action of yeast is known as fermentation.
Q.7 What are communicable diseases? Name any two diseases each caused by viruses and bacteria.
Answer. Microbial diseases that are spread from an infected person to other healthy person through air, water, food, physical contact or by animals are called communicable diseases.
Two diseases caused by
Viruses - measles and AIDS
Bacteria-typhoid and cholera
Q.8 What is vaccine? How does it work?
Answer. A small dose of dead and weakened disease causing microbes used to stimulate immune response in the body is called vaccine.
When a vaccine is introduce in the body of a healthy person, it acts like a antigen . The body of the person produces antibodies against these introduced microbes. These antibodies remain in the body and protect him/her against future infections of the same microbe.
Q.9 Microorganisms decompose dead organic waste of plants and animals and help in keeping the environment clean.
(a) What would happen, if microorganisms do not perform this function?
(b) Being a student, how can you contribute in keeping the environment clean? Give two ways.
Answer. (a) If decomposers disappeared from a ecosystem, wastes as well as the remains of the dead organisms would pile up, and producers (plants) would not have enough nutrients.
(b) The two ways through which we can keep the environment clean –
(i) Reduce the usage of your electrical appliances.
(ii) Reduce usage of chemicals and pesticides.
D. LONG QUESTIONS
Q.1 Explain two methods of food preservation. Also, discuss the advantages of food preservation.
Answer. The two methods of food preservation are-
a. Chemical method
b. Preservation by sugars
(a) Chemical method :- Food can be preserved by using food preservatives like sodium benzoate, sodium metabisulphite etc.. Most chemicals preservatives prevent microbial growth by removing oxygen from the food items. Sodium benzoate is used for preserving fruit juices and squashes. Citric acid is used as a preservative in confectioneries.
(b) Preservation method :- Jams, jellies and squashes are preserved for a long time because of the presence of sugar in them. Sugar inhibits the growth of food - spoiling microorganisms by reducing the moisture content of the food.
Advantage of food preservation are –
(i) It decreases the wastage of food by avoiding spoilage.
(ii) It increases the storage period of food materials.
(iii) Nutritional value of the food is retained for a long period.
(iv) It ensures the availability of food at distant places and during the off season.
Q.2 Draw a neat diagram to show nitrogen cycle and explain the process of nitrification and denitrification.
Answer
(1) Nitrification–The conversion of ammonia into nitrates by nitrifying bacteria is called nitrification.
(2) Denitrification–The conversion of nitrates into free nitrogen gas by denitrifying bacteria (pseudomonas) is called denitrification.
Q.3 Describe the principal on which the following methods of food preservation are based:
(1) Boiling (2) Canning (3) Freezing (4) Dehydration
Answer.
1. Boiling. Boiling kills bacteria. So, boiling also helps in the preservation of liquid food like milk. Boiled milk can be preserved for 2-3 days, otherwise it goes sour within 8 to 10 hours.
2.Canning. Certain foodstuffs are kept in airtight time or containers. These containers keep away moisture and thus, help in preserving food for a longer time. Foods like fruits and fishes are boiled, sterilised and put into tins and closed airtight.
3. Freezing. Microbes such as fungi and bacteria cannot survive at very low temperature. So milk, eggs, and vegetables are preserved by keeping them in a refrigerator.
4.Dehydration. Dehydrayion means removal of water which is the key requirement of microbial growth from foodstuffs. So, pulses and grains are well dried and perserved. These are stored in moisture free places or vessels. Sun drying is a traditional method for preserving food.
More Questions
Q.1 Give one example of the following :
i) A unicellular algae
ii) A filamentous algae
iii) Algae forming clusters/colonies
iv) A brown algae
v) The bacteria found in curd
vi) One rod-shaped bacteria
vii) One spherical bacteria
viii) A protozoan which can photosynthesize
Q.2 Match the columns:
i) Entamoeba histolytica a) Botulism
ii) Giardiasis b) Giardia
iii) Trypanosoma c) AIDS
iv) HIV d) Curd
v) Yeast & lactobacillus e) Amoebiasis
vi) Penicillium notatum f) Sleeping sickness
vii) Streptococcus pneumonia g) Antibiotic
viii) Clostridium botulinum h) Pneumonia
Q.3 Write briefly about the following:
i) Diatoms ii) Mildew iii) Cyanobacteria iv) Zooplanktons v) Algal bloom
vi) Spores vii) Anaerobic bacteria viii) Binary fission ix) pasteurization x) Microbiology
Q.4 Answer the following questions:
a) List some methods of food preservation
b) Write two uses and two harms caused by the following :
i) Algae ii) Bacteria iii) Protozoa iv) Fungi
c) Draw well labelled diagram of the following :
i) Euglena ii) A bacterial cell iii) Paramecium
d) How do bacteria reproduce?
e) What is the major difference between bacterial cell and the cells of other organisms?
f) Why is “Virus” thought of as something in between the living and non-living ? How do they multiply within a host cell?
Please click the link below to download CBSE Class 8 Science Microorganisms Assignment Set A
CBSE Class 8 Science Conservation Of Plants And Animals Assignment Set A |
CBSE Class 8 Science Conservation Of Plants And Animals Assignment Set B |
CBSE Class 8 Science Sound Assignment Set A |
CBSE Class 8 Science Sound Assignment Set B |
CBSE Class 8 Science Sound Assignment Set C |
More Study Material
CBSE Class 8 Science Chapter 2 Microorganisms Friend Or Foe Assignment
We hope you liked the above assignment for Chapter 2 Microorganisms Friend Or Foe which has been designed as per the latest syllabus for Class 8 Science released by CBSE. Students of Class 8 should download and practice the above Assignments for Class 8 Science regularly. We have provided all types of questions like MCQs, short answer questions, objective questions and long answer questions in the Class 8 Science practice sheet in Pdf. All questions have been designed for Science by looking into the pattern of problems asked in previous year examinations.
Assignment for Science CBSE Class 8 Chapter 2 Microorganisms Friend Or Foe
Our team of expert teachers have referred to NCERT book for Class 8 Science to design the Science Class 8 Assignments. If you practice at least one test paper daily, you will get higher marks in Class 8 exams this year. Daily practice of Science course notes and related study material will help you to clear all your doubts and have stronger understanding of all concepts. You can download all Revision notes for Class 8 Science also from www.studiestoday.com absolutely free of cost.
Chapter 2 Microorganisms Friend Or Foe Assignment Science CBSE Class 8
All questions and their answers for the assignment given above for Class 8 Science have been developed as per the latest curriculum and books issued for the current academic year. The students of Class 8 can rest assured that the best teachers have designed the questions of Science so that you are able to revise the entire syllabus if you do the assignments. Lot of MCQ questions for Class 8 Science have also been given in the worksheets and assignments for regular use. All study material for Class 8 Science students have been given on studiestoday.
Chapter 2 Microorganisms Friend Or Foe Assignment CBSE Class 8 Science
Regular assignment practice helps to get a more comprehensive understanding of Chapter 2 Microorganisms Friend Or Foe concepts. Assignments play a crucial role in understanding Chapter 2 Microorganisms Friend Or Foe in CBSE Class 8. Students can download all the assignments of the same chapter in Class 8 Science in Pdf format. You can print them or read them online on your computer or mobile.
CBSE Science Class 8 Chapter 2 Microorganisms Friend Or Foe Assignment
CBSE Class 8 Science latest books have been used for coming up with the latest questions and solutions for the above assignment. If you have revised all concepts relating to Chapter 2 Microorganisms Friend Or Foe then you should attempt all questions given in the test sheets above. We have also provided lot of Worksheets for Class 8 Science which you can use to further make your self stronger in Science
You can download free Pdf assignments for CBSE Class 8 Science Chapter 2 Microorganisms Friend Or Foe from StudiesToday.com
The Chapter 2 Microorganisms Friend Or Foe Class 8 Science Assignments have been designed based on latest CBSE syllabus for Class 8 Science issued for the current academic year
Yes, These printable assignments for Chapter 2 Microorganisms Friend Or Foe Class 8 Science are free to download and print
All topics given in Chapter 2 Microorganisms Friend Or Foe Science Class 8 Book for the current academic year have been covered in the given assignment
No, all Printable Assignments for Chapter 2 Microorganisms Friend Or Foe Class 8 Science have been given for free and can be downloaded in Pdf format
Just click on the View or Download button below, then another window with the Pdf will be visible, just click on the Pdf icon to download the free assignments for Chapter 2 Microorganisms Friend Or Foe Class 8 Science
Yes, apart from Science you can download free assignments for all subjects in Class 8
Our team of expert teachers at studiestoday.com have provided all answers for the practice questions which have been given in Class 8 Science Chapter 2 Microorganisms Friend Or Foe assignments