Answer:
bacteria are mostly free-living organisms often consisting of one biological cell. This means they are unicellular organisms, unlike humans, who are composed of millions of cells. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, and the deep biosphere of Earth's crust.
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