Question

How can Cyanobacteria make its own food?

Answer 1

Cyanobacteria live in the water, and can manufacture their own food through "photosynthesis." Although the oldest known fossils, more than 3.5 billion years old, are cyanobacteria, they are still around in large numbers; in fact, they one of the largest and most important groups of bacteria. Individual cyanobacteria are very small and usually just single cells, either round, ovoid, or stringlike in shape. Some types grow in colonies that can be large. These colonies are built of many layers, and are called stromatolites (if more or less dome-shaped) or oncolites (if round). The characteristic layered structure of fossilized stromatolites advertises their presence, helping scientists locate them and identify their age through radioactive dating of the surrounding rocks.
To the upper left is a drawing of such a layered colony, then of the layered surface, and to the lower left of a fossil cynaobacterium such as would live near the surface.