Symbiosis is when two organisms live very close to each other in a beneficial way. An even more intimate relationship is Endosymbiosis where a microbe lives extremely close to a host and in fact is engulfed by them but not harmed. Kind of swallowed like being eaten by an amoeba, but not digested. Allowed to go on living within the host and work for the host, providing it with some benefit.
The best known examples are chloroplasts and mitochondria which ...
Explain the relationship between ancient bacteria and cyanobacteria which lead to the formation of chloroplasts and mitochondria.