Endosymbiosis is a union between species, where one of them lives within the other. Certain organelles of eukaryotic cells, such as chloroplasts and mitochondria, which are derived from their original symbiosis with some bacteria. In the process of endosymbiosis, the symbiotic element inhabits the intracellular space of the host. An example of these specimens are: zooxanthellae, which are a species of algae that inhabit the cells of some corals.
The endosymbiotic theory states that a eukaryotic cell has the ability to attach itself to another, in order to sustain a coexistence where both benefit, since the host would enjoy the fruit released by the endosymbiont. On the other hand, this theory also affirms that the first organelles to evolve were the mitochondria and then, through serial endosymbiosis, the ancestral eukaryotic corpuscle obtains an endosymbiont capable of performing photosynthesis, which would later develop eukaryotic cellular organelles that would come to generate what are the first green algae.
There is certain evidence that affirms that mitochondria and plastids are born from the endosymbiosis process, one of them is the size of the mitochondria, which is similar to that of some bacteria. Both chloroplasts and mitochondria are composed of covalently closed circular double-stranded DNA. They are covered by a double fabric. Chloroplasts and mitochondria are split by binary fission, as are prokaryotes. Protein synthesis, both in mitochondria and chloroplasts, is independent.
