1. No Life (as we know it) on Earth: Unicellular organisms, like bacteria and archaea, are the foundation of all life on Earth. They were the first forms of life and through billions of years of evolution, they gave rise to all multicellular organisms, including humans. Without them, the entire ecosystem would collapse.
2. No Oxygen in the Atmosphere: A significant portion of the oxygen in our atmosphere comes from photosynthesis by cyanobacteria, a type of unicellular organism. Without them, the atmosphere would be very different, lacking the oxygen necessary for most life on Earth to survive.
