Question

why chyno bactareya were pervisouly called blue green algae and now cyano bactareya ? short answere.​

Answer 1

do not have nucleus

Because they are photosynthetic and aquatic, cyanobacteria are often called "blue-green algae". This name is convenient for talking about organisms in the water that make their own food, but does not reflect any relationship between the cyanobacteria and other organisms called algae.