It is worth noting that there are numerous examples of endosymbiosis all over the tree of life and the mitochondrion and plastids aren’t the only ones, just the most successful and most ancient.
There are bacteria that have bacterial endosymbiotes, and I’ve seen electron micrographs of large bacteria with strange uncharacterized archaea hanging off them like tassles. Some animals, mostly insects that drink plant sap, have endosymbiotic bacteria that have had their genomes stripped down to only 150 genes and cannot make their own cellular energy that only exist to make essential amino acids so that the animal does not have to eat them. Large numbers of photosynthetic microbes have taken up eukaryotic green algae as second-order endosymbiotes, or even have taken those organisms up as tertiary endosymbiotes.
EDIT: here’s a chart of the bizarre known history of clades acquiring photosynthesis via known primary, secondary and tertiary endosymbiosis. By the time you are at tertiary endosymbiosis, the plastid has 6 nested membranes and may have some vestigial nuclei between some of them.
It is worth noting that there are numerous examples of endosymbiosis all over the tree of life and the mitochondrion and plastids aren’t the only ones, just the most successful and most ancient.
There are bacteria that have bacterial endosymbiotes, and I’ve seen electron micrographs of large bacteria with strange uncharacterized archaea hanging off them like tassles. Some animals, mostly insects that drink plant sap, have endosymbiotic bacteria that have had their genomes stripped down to only 150 genes and cannot make their own cellular energy that only exist to make essential amino acids so that the animal does not have to eat them. Large numbers of photosynthetic microbes have taken up eukaryotic green algae as second-order endosymbiotes, or even have taken those organisms up as tertiary endosymbiotes.
EDIT: here’s a chart of the bizarre known history of clades acquiring photosynthesis via known primary, secondary and tertiary endosymbiosis. By the time you are at tertiary endosymbiosis, the plastid has 6 nested membranes and may have some vestigial nuclei between some of them.