Question

cyanobacteria were the first photosynthetic organisms. how were they responsible for allowing higher life forma to evolve?

Answer 1

Suppose you could say they helped to produce oxygen, which is necessary for the survival of many of the more complex lifeforms

Answer 2

Or rather their production of oxygen helped to accumulate it in the Earth's atmosphere

Answer 3

Must also have been a good source of energy, so food, for slightly more evolved species

Answer 4

Oxygen is probably a major point though, go with that