NCERT Solutions for Class 8th Science
Chapter 2. Microorganisms : Friend And Foe
- There are other living organisms around us which we cannot see with eyes alone. These are called microorganisms or microbes.
- Microorganisms are classified into four major groups. These groups are bacteria, fungi, protozoa and some algae.
- Viruses are quite different from other microorganisms. They reproduce only inside the host organism; bacterium, plant or animal cell.
- Microorganisms are found in air, water and in the bodies of plants and animals.
- They can live in all kinds of environment, ranging from ice cold climate to hot springs and deserts to marshy lands.
- Some microorganisms are useful for commercial production of medicines and alcohol.
- Some microorganisms decompose the organic waste and dead plants and animals into simple substances and clean up the environment.
- There are some insects and animals which act as carriers of disease causing microbes. Like housefly.
- Disease causing agents are called pathogens.
- When a disease-carrying microbe enters our body, the body produces antibodies to fight the invader.
- Several diseases, including cholera, tuberculosis, smallpox and hepatitis can be prevented by vaccination.
- Process of conversion of sugar into alcohol is known as fermentation.
- Medicines which kill or stop the growth of the disease-causing microorganisms. Such medicines are called antibiotics.
- Microorganisms like amoeba can live alone, while fungi and bacteria may live in colonies.
- Microorganisms are used to increase soil fertility by fixing nitrogen.
- Lactobacillus bacteria are found in curd, which promotes the formation of curd.
- Sugar is converted into alcohol by yeast.