How cyanobacteria changed the Earth

History of Life Timeline Essay
James C.
Cyanobacteria


Cyanobacteria are unicellular microscopic creatures that were named after their distinct bluegreen color. They are prokaryotes, and as such they don’t have a nuclei. The appearance of Cyanobacteria on Earth is an important event, as it had a major role in shaping the world as we now know it.


Cyanobacteria grow in colonies underwater. If a colony grows large enough, it can be seen as a green tint in the water. It is because of this trait that colonies of Cyanobacteria are called “green scum”, and they are frequently mistaken as pollution when seen in oceans, lakes, or pools. Some types of Cyanobacteria have proven to be toxic. This usually isn’t considered a threat to plants, animals or humans, except for when toxic Cyanobacteria form large and dense colonies.

Cyanobacteria were the first creatures capable of utilizing photosynthesis, which is a process in which light is used to create food. While photosynthesis was an amazing evolutionary accomplishment on its own, it was its byproduct which changed the Earth. In the process of photosynthesis, Cyanobacteria produced oxygen. As Cyanobacteria spread and their colonies grew, the earth’s environment drastically changed as the atmosphere began to oxidize. This made many oxygen-intolerant species go extinct, and paved the way for new generations of species to evolve.