cyanobacteria
Bacteria called cyanobacteria are very important. They are bluish green in color see Figure below because they contain chlorophyll but not chloroplasts, of course . They make food through photosynthesis and release oxygen into the air. These bacteria were probably responsible for adding oxygen to the air on early Earth. This changed the planets atmosphere. It also changed the direction of evolution. Ancient cyanobacteria also may have evolved into the chloroplasts of plant cells.