Question

Describe how some cells came to have chloroplasts, according to the theory of endosymbiosis.

Answer 1

According to the Theory of Endosymbyosis chloroplasts were "primitive" cells that formed a symbiotic relationship with other prokaryotic cells. Some cells have chloroplasts because it was believed by "compelling evidence" that the organelles of chloroplasts could undertake photosynthesis.

Answer 2

The endosymbiotic theory concerns the mitochondria, plastids (e.g. chloroplasts), and possibly other organelles of eukaryotic cells. According to this theory, certain organelles originated as free-living bacteria that were taken inside another cell as endosymbionts. Mitochondria developed from proteobacteria (in particular, Rickettsiales, the SAR11 clade,[1][2] or close relatives) and chloroplasts from cyanobacteria. Enjoy!