NCERT Exemplar Solution for Class 8 Science Chapter-2 Microorganisms- Friend and Foe
The world around us is filled with tiny living organisms that cannot be seen with naked eyes, yet they play a major role in our daily lives. Chapter 2, Microorganisms- Friend and Foe, introduces students to the fascinating world of microbes and explains how they can be both beneficial and harmful. From preparing curd and medicines to causing diseases and food spoilage, microorganisms affect humans, plants, and animals in many ways. This chapter helps students understand different types of microorganisms such as bacteria, fungi, algae, protozoa, and viruses. By studying the concepts through NCERT Exemplar Solution for Class 8, learners can easily understand scientific terms and practical applications related to microorganisms. The detailed explanations available in the NCERT Exemplar Solution improve conceptual learning and analytical thinking. Students searching for reliable NCERT solutions for class 8 also find this chapter extremely useful because it covers important topics that are frequently asked in examinations and competitive assessments.
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Types of Microorganisms and Their Uses
Microorganisms are microscopic organisms that exist everywhere around us. Some can survive in extreme conditions while others live inside plants, animals, and humans. The chapter explains the four main groups of microorganisms: bacteria, fungi, protozoa, and algae. Viruses are also discussed, although they can reproduce only inside the body of a host organism. Many microorganisms are beneficial to humans. Bacteria are used in the preparation of curd, cheese, and other food products. Lactobacillus bacteria help convert milk into curd by increasing its acidity. Yeast, a type of fungus, is widely used in baking and fermentation industries. It helps in making bread, cakes, and alcoholic beverages through the process of fermentation.
Microorganisms are also important in the medical field. Certain bacteria and fungi are used in the production of antibiotics that help cure diseases caused by harmful microbes. Vaccines prepared from weakened or dead microorganisms protect our bodies from infections by building immunity. Students learn how scientific discoveries involving microorganisms have improved healthcare and increased human survival. Another important use of microorganisms is in agriculture. Some bacteria help increase soil fertility by fixing atmospheric nitrogen into the soil. This natural process supports plant growth and reduces the dependence on chemical fertilizers. Through this chapter, students understand how microorganisms contribute positively to food production and environmental balance.
Harmful Effects of Microorganisms
Although many microorganisms are useful, some are harmful and cause diseases in humans, plants, and animals. Disease-causing microorganisms are known as pathogens. The chapter explains how these pathogens spread through air, water, food, and direct contact. Common human diseases caused by microorganisms include cholera, tuberculosis, typhoid, chickenpox, and malaria. Students also learn about the role of mosquitoes and houseflies in spreading infections. Maintaining cleanliness and proper hygiene is essential to prevent the spread of diseases.
Microorganisms can also spoil food items. Bread, fruits, cooked food, and pickles may get spoiled due to fungal or bacterial growth if not stored properly. Food preservation techniques such as salting, drying, refrigeration, and using preservatives help prevent spoilage and increase shelf life. Pasteurization of milk is another important method discussed in the chapter. In this process, milk is heated at a specific temperature and then cooled rapidly to destroy harmful microorganisms. Plant diseases caused by microbes can damage crops and reduce agricultural production. Citrus canker, rust of wheat, and yellow vein mosaic of bhindi are examples explained in the chapter. Understanding these harmful effects helps students recognize the importance of sanitation, vaccination, and scientific food storage methods.
Nitrogen Cycle and Importance of Microorganisms in Nature
One of the most interesting concepts in this chapter is the nitrogen cycle. Nitrogen is essential for plant growth, but plants cannot directly absorb nitrogen from the atmosphere. Certain bacteria and blue-green algae convert atmospheric nitrogen into usable compounds through nitrogen fixation. When plants and animals die, decomposer microorganisms break down dead organic matter into simpler substances. These substances enrich the soil with nutrients and maintain ecological balance. This natural recycling process supports life on Earth and ensures continuous nutrient circulation in the environment.
The chapter also highlights the importance of microorganisms as decomposers. Without them, dead plants and animals would accumulate everywhere, causing pollution and imbalance in nature. Students learn how microorganisms help keep the environment clean and fertile. Practicing NCERT Exemplar questions from this chapter improves scientific understanding and helps students answer both theoretical and application-based questions effectively. The chapter develops awareness about health, hygiene, environmental protection, and the practical importance of microorganisms in everyday life.