Cyanobacteria (Blue Green Algae):
Salient features of Cyanobacteria are as follows:
i. They are prokaryotic organisms.
ii. They are found in fresh water but some are marine.
iii. They may present alone or in the form of a group called colony.
iv. Cell wall is double layered.
v. Protoplasm is divided into two regions, an outer coloured region is called Chromoplasm and an inner colourless region which is called Centroplasm.
vi. Sexual reproduction is totally absent.
vii. Only asexual reproduction occurs.
viii. They are photosyntesizers that sometimes can also fix atmospheric nitrogen.
ix. They are probably the first organisms which introduced oyxgen into the primitive atmosphere and probably first to colonize land.
Examples: Nostoc, Anabena.