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Science Class 8 - Microorganisms Notes

Comprehensive study notes for Class 8 - Microorganisms olympiad preparation

Microorganisms

Welcome to the chapter on Microorganisms for Class 8. In this chapter, you will learn about tiny living things called microorganisms, their types, where they are found, and their importance in our lives. By the end of this chapter, you will understand how microorganisms can be both helpful and harmful!

Introduction

Microorganisms are very small living things that cannot be seen with the naked eye. They are found everywhere—air, water, soil, and even inside our bodies. We need a microscope to see them.

Types of Microorganisms

  • Bacteria: Single-celled organisms found in soil, water, and our bodies.
  • Viruses: Smaller than bacteria, can cause diseases like cold and flu.
  • Fungi: Can be single-celled (yeast) or multi-celled (mushrooms, molds).
  • Protozoa: Single-celled organisms found in water, some cause diseases.
  • Algae: Mostly found in water, can be single-celled or multi-celled.

Where Are Microorganisms Found?

  • In soil
  • In water
  • In air
  • On and inside our bodies
  • On food and surfaces

Useful Microorganisms

  • Bacteria help make curd and cheese.
  • Yeast is used in baking bread.
  • Some microorganisms help decompose waste and recycle nutrients.
  • Certain bacteria help in nitrogen fixation in soil.
  • Microorganisms are used to make medicines like antibiotics.

Harmful Microorganisms

  • Some bacteria and viruses cause diseases like tuberculosis, malaria, and COVID-19.
  • Fungi can spoil food and cause infections.
  • Protozoa can cause diseases like dysentery and malaria.

Prevention and Control

  • Wash hands regularly.
  • Cook food properly.
  • Keep surroundings clean.
  • Use vaccines to prevent certain diseases.

Fun Activity: Observe Microorganisms!

Take a drop of pond water and observe it under a microscope. Draw what you see!

Summary

  • Microorganisms are tiny living things found everywhere.
  • They can be useful (making food, medicines) or harmful (causing diseases).
  • We can prevent diseases by keeping clean and using vaccines.

Practice Questions

  1. Name two useful microorganisms.
  2. What is the role of yeast in baking?
  3. How can microorganisms be harmful?
  4. List two ways to prevent diseases caused by microorganisms.
  5. Where can you find microorganisms?

Challenge Yourself

  • Make a chart showing helpful and harmful microorganisms.
  • Find out how antibiotics are made using microorganisms.

Did You Know?

  • Some bacteria can survive in extreme places like hot springs and deep oceans!
  • Louis Pasteur discovered that microorganisms cause diseases and spoil food.

Glossary

  • Microorganism: A tiny living thing seen only with a microscope.
  • Bacteria: Single-celled microorganisms, some helpful, some harmful.
  • Virus: Microorganism that causes diseases.
  • Fungi: Microorganisms like yeast and molds.
  • Protozoa: Single-celled microorganisms, some cause diseases.
  • Antibiotic: Medicine made using microorganisms to kill bacteria.

Answers to Practice Questions

  1. Yeast, bacteria (any two useful microorganisms).
  2. Yeast helps dough to rise and makes bread soft.
  3. They can cause diseases and spoil food.
  4. Wash hands, use vaccines, cook food properly, keep surroundings clean (any two).
  5. In soil, water, air, food, and inside our bodies.

Microorganisms are everywhere! Learn about them and stay healthy by keeping clean.

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