Crash Course Biology
      Old & Odd: Archaea, Bacteria & Protists (1x35)
      
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      Hank veers away from human anatomy to teach us about the (mostly) single-celled organisms that make up two of the three taxonomic domains of life, and one of the four kingdoms: Archaea, Bacteria, and Protists. They are by far the most abundant organisms on Earth, and are our oldest, oddest relatives.