CBSE Class 8 Science Microorganism Frind and Foe Chapter Notes

Scroll down for PDF

CBSE Class 8 Science Microorganism Frind and Foe Chapter Notes. Learning the important concepts is very important for every student to get better marks in examinations. The concepts should be clear which will help in faster learning. The attached concepts made as per NCERT and CBSE pattern will help the student to understand the chapter and score better marks in the examinations.

MICROORGANISMS : FRIEND AND FOE

INTRODUCTION
r Microorganisms: The living organisms which cannot be seen by naked eyes and can be seen only through a microscope are called microorganisms or microbes.
• The branch of biology which deals with the study of microorganisms is known as microbiology.
• Father of Microbiology-Louis Pasteur
• The microorganisms include bacteria, fungi, viruses, algae and protozoans. Microorganisms may be unicellular like bacteria, some algae and some fungi and protozoa, or multicellular such as algae and fungi.

OCCURRENCE OF MICROBES
• Microorganisms can survive under all types of environment, ranging from ice cold climate to hot springs and deserts to marshy lands.
• They are also found inside the bodies of animals including humans.
• Some microorganisms grow on other organisms while other exist freely.
• Microbes can live alone, while fungi and bacteria may live in colonies.

MILESTONE IN MICROBIOLOGY
Antony van Leeuwenhoek (1632-1723) born in Holland, was the first person known to have viewed microbes with the help of self designed microscope. He discovered bacteria first, and then red blood cells, yeast in dough, sperm cells and many unicellular organisms. He drew a sketch of each tiny object he viewed and described its source, shape and structure to the best of his understanding.

class_8_science_concept_037

MICROSCOPES
There are two types of microscopes – a light microscope, which is commonly used in a school laboratory and an electron microscope. In a compound (light) microscope one of the two lenses used is as an "eye piece" and the other as an "objective". Eye is kept over the 'eye piece' and the object to be viewed is kept under the 'objective' on a transparent glass plate on the dias or the stage. This way the image of the object being viewed is magnified upto a thousand times.


class_8_science_concept_038

Electron microscope is a special type of microscope that uses beams of electrons instead of light, to provide magnification. Magnetic fields are used to bend the electron beams, just as rays of light are bent by the refractive power of a glass lens. Virus could be identified only through an electron microscope.

REVIEW QUESTIONS
1. What are microorganisms?
2. Define microbiology.
3. ______is known as father of microbiology.
4. Which type of microscope is commonly used in school laboratory?
5. Who is Antony van Leeuwenhoek?

GROUPS OF MICROORGANISMS
(A) Bacteria (B) Virus (C) Algae (D) Fungi (E) Protozoa

BACTERIA
• Bacteria were first observed in rainy water and later in teeth scum by Leeuwenhoek and he called them "animalcule".
• Cohn and Ehrenberg first of all coined the name "bacteria".
• Study of bacteria is known as bacteriology.
• They are basically unicellular but can exist as a chain or group of cells.
Occurrence : Bacteria are ubiquitous i.e., they occur anywhere and everywhere, in water in air, in soil and in all living organisms.
Size : Bacteria are very small organisms which are barely visible under the light microscope. Their sizes vary from 0.2 to 100 μ (micron) (1 micron = 10–6 meter).
1. Smallest bacterium = Haemophilus influenze
2. Largest bacterium = Epulospiscium fishelsoni
3. Longest filamentous bacterium = Beggiatoa mirabilis

class_8_science_concept_039

BACTERIAL CELL STRUCTURE
• Bacteria are unicellular microorganisms.
• They have a primitive cell structure.
• Each bacteria cell has rigid cell wall around it.
• There is no well-developed nucleus but chromatin or nuclear or genetic material or chromosome or DNA is found scattered in the jelly-like granular substance known as cytoplasm present inside the cell. This kind of nucleus is described as incipient nucleus or nucleoid.
 

Please click the link below to download pdf file for CBSE Class 8 Science Microorganism Frind and Foe Chapter Notes.


Click on the text For more study material for Science please click here - Science

Latest NCERT & CBSE News

Read the latest news and announcements from NCERT and CBSE below. Important updates relating to your studies which will help you to keep yourself updated with latest happenings in school level education. Keep yourself updated with all latest news and also read articles from teachers which will help you to improve your studies, increase motivation level and promote faster learning

JEE in Punjabi too after English, Hindi and Gujarati

Punjab Minister Tript Rajinder Singh Bajwa requested the joint technology entrance exam (main) to be conducted in Punjabi and other regional languages too. In his letter to Union HRD Minister Ramesh Pokhriyal Nishank, the Punjab Minister for Higher Education and...

CBSE examination board hike the fee for class 10th and 12th

The CBSE (Central Board Secondary Education) increased the examination fees for classes 10 and 12 of the 2020 boards, with no profit no loss principle, from Rs. 750 to Rs 1500, for all categories of students, including SC/ST candidates for all schools throughout India...

Tips for exam preparation

Students often get nervous during their exams. The reason behind this nervousness is either a lack of confidence or a lack of preparedness. To overcome these fears students are advised to do their preparation in such a way that will retain their confidence. For this...

Registration of NEET 2020 starts

The NEET 2020 registration process would start on Monday, December 2nd, 2019. National Testing Agency, NTA would carry out the county’s undergraduate entrance exam for medical and dental admissions.  The examination is scheduled to take place in English, Hindi, and...

JEE Entrance Exam 2020 Dates Registration Admit Cards Exam Pattern

JEE Entrance exam is conducted for students who wish to pursue engineering in different subjects or categories like mechanical, CS, etc.. It is officially organized and conducted by NTA. Formerly it was organized by CBSE. It avails seats for students in IITs, NITs, and...

How to crack a competitive examination

“How I crack a competitive examination” is a frequently asked question by today’s students. Cracking a competitive exam is a challenging task. Attaining a huge amount of study and solving several complex problems in a limited amount of time is a huge task. Competitive...

×
Studies Today