Answer
According to the endosymbiosis theory, organelles such as mitochondria and chloroplasts in modern eukaryotic cells were once protobacterial cells that were engulfed by archaea-like prokaryotes to form a mutualistic relationship. The protobacterial cells acquired protection from larger prokaryotes and offered a method of harvesting and breaking down energy in return.
Work Step by Step
According to the endosymbiosis theory, organelles such as mitochondria and chloroplasts in modern eukaryotic cells were once protobacterial cells that were engulfed by archaea-like prokaryotes to form a mutualistic relationship. The protobacterial cells acquired protection from larger prokaryotes and offered a method of harvesting and breaking down energy in return.