Respuesta :

Diatonic254

Cyanobacteria are the major force of the Great Oxygenation Event around 2.35 billion years ago. The organisms that evolved photosynthesis changed the composition of the atmosphere to mainly oxygen. This changed the dynamic of life on earth by allowing organisms to also exist on land. This is because it was possible for ozone to form and reduce the lethal UV rays from the sun reaching the earth's surface to destroy genetic material.

Answer;

Because oxygen atmosphere that organisms such as human beings depend on was generated from them.

Explanation;

  • Cyanobacteria are aquatic and photosynthetic,which means they live in the water, and can manufacture their own food.
  • Cyanobacteria have been  important in shaping the course of evolution and ecological change throughout earth's history.
  • The oxygen atmosphere that we depend on was generated by numerous cyanobacteria during the Archaean and Proterozoic Eras. Before this time, the atmosphere had a very different chemistry, unsuitable for life as we know it today.