Microorganisms

Overview

Microorganisms (or microbes) are living things too small to be seen with the naked eye. They include bacteria, viruses, fungi, protozoa, and algae. This topic forms a core part of the Science section in UPTET Paper II and connects biology with everyday life, health, agriculture, and the environment.

For UPTET, you must know the classification of microorganisms, their basic structure, and most importantly, their useful and harmful roles. Questions often test whether you can distinguish between types of microbes, recall examples of diseases caused by each, and identify beneficial applications like fermentation, nitrogen fixation, and antibiotic production. A clear understanding of this topic also supports pedagogy questions on how to teach life sciences through real-world examples.

Master the characteristics that separate bacteria from viruses from fungi, memorise key disease-microbe pairs, and understand the economic importance of microbes in food, medicine, and agriculture.

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Key Concepts

• **Microorganisms are classified into five major groups:** bacteria, viruses, fungi, protozoa, and algae. Of these, viruses are unique because they show living characteristics only inside a host cell.

• **Bacteria are single-celled prokaryotes** (no true nucleus). They can be spherical (cocci), rod-shaped (bacilli), or spiral (spirilla). Some are autotrophic; most are heterotrophic.

• **Viruses are non-cellular and acellular**—they consist of genetic material (DNA or RNA) surrounded by a protein coat. They reproduce only inside living cells and are hence called obligate parasites.

• **Fungi may be unicellular (yeast) or multicellular (mushrooms, moulds)**. They are eukaryotic, lack chlorophyll, and obtain food by absorbing nutrients from dead or living organic matter (saprophytes or parasites).

• **Protozoa are unicellular eukaryotes** found in water and soil. Examples: Amoeba, Paramecium, Plasmodium (causes malaria).

• **Algae are simple, chlorophyll-containing organisms**—mostly aquatic. They perform photosynthesis and are primary producers in aquatic ecosystems.

• **Microorganisms can be useful or harmful.** Useful roles include fermentation, decomposition, nitrogen fixation, antibiotic production, and vaccine preparation. Harmful roles include causing diseases in humans, animals, and plants, as well as food spoilage.

• **Antibiotics are medicines derived from microorganisms** (mainly fungi and bacteria) that kill or inhibit other microorganisms. Example: Penicillin from the fungus Penicillium.