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Microorganisms were the first living creatures on earth. It is estimated there are a total of 5 nonillion microorganisms on earth (5x1020). You will find nearly 10 million a millilitre of ocean water and 40 million in a gram of soil. They are also ubiquitous on the human body.
Examples of microorganisms include algae, fungi, protozoa, bacteria and viruses. Microorganisms play many unique and complex roles within an ecosystem, and they can perform a variety of functions, such as photosynthesis, breaking down waste, and infecting other organisms.