<Li> Cyanophyta Steinecke, 1931 </Li> <Li> Oxyphotobacteria Gibbons & Murray, 1978 </Li> <P> Cyanobacteria / saɪˌænoʊbækˈtɪəriə /, also known as Cyanophyta, is a phylum of bacteria that obtain their energy through photosynthesis, and are the only photosynthetic prokaryotes able to produce oxygen . The name "cyanobacteria" comes from the color of the bacteria (Greek: κυανός (kyanós) = blue). Cyanobacteria (which are prokaryotes) used to be called "blue - green algae". They have been renamed' cyanobacteria' in order to avoid the term "algae", which in modern usage is restricted to eukaryotes . </P> <P> Unlike heterotrophic prokaryotes, cyanobacteria have internal membranes . They are flattened sacs called thylakoids where photosynthesis is performed . </P>

Where does blue green algae get their energy from