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# Microorganisms ## Biology Grade 12 ### Unit 2: Microorganisms #### Keywords * **Microbiology:** is the scientific study of microorganisms * **Biosphere:** the regions of the surface and atmosphere of the earth occupied by living organisms * **Microscopic organisms:** too small to be seen with...

# Microorganisms ## Biology Grade 12 ### Unit 2: Microorganisms #### Keywords * **Microbiology:** is the scientific study of microorganisms * **Biosphere:** the regions of the surface and atmosphere of the earth occupied by living organisms * **Microscopic organisms:** too small to be seen with the naked eye, only visible with a microscope. The rich diversity of microorganisms is reflected in their profound influence on all aspects of life. Most microorganisms are harmless or indeed beneficial. For example, they are essential to the recycling of nutrients that form the bodies of all organisms that sustain all the metabolic cycles of life. Also, they produce about 50% of the oxygen gas we breathe and provide other nutrients to many other organisms. Microorganisms survive in, or are purposely put in, many of the foods we eat. Microorganisms and viruses are also in the air we breathe and in the water we drink. Even, some 100 billion microorganisms inhabit in/on our skin and grow in our mouth, ears, nose, throat, and digestive tract. Fortunately, the majority of these microbes, called our natural microbiota are actually beneficial in helping us resist diseases, and regulating development and nutrition. When most of us hear the word "bacterium" or "virus", we think infection or disease although such pathogens (disease-causing agents) are rare. ### 2.2. Types of microorganisms In the life sciences, high priority is placed on the identification and recognition of the different types of microorganisms to treat or use them for various purposes. For example, antibiotics treat a bacterial infection but have no effect on viruses or other microbes. Based on evolutionary lines, there are three main kinds of microorganisms, and these are bacteria, archaea, and eukarea (Figure 2.1). #### Self-Questioning * **List the types of microorganisms?** * **What are the bases for microbial classifications?**