What does the theory of endosymbiosis suggest?

The theory of endosymbiosis suggests that mitochondria and chloroplasts originated from free-living prokaryotic organisms, specifically ancient aerobic bacteria and photosynthetic bacteria, respectively. This theory posits that these prokaryotes were engulfed by ancestral eukaryotic cells through a process similar to endocytosis, forming a symbiotic relationship. Over time, these engulfed organisms became essential components of the eukaryotic cell, evolving into organelles.

Mitochondria, which are responsible for energy production via aerobic respiration, are thought to have derived from aerobic bacteria that were engulfed by an early ancestral eukaryotic cell. Similarly, chloroplasts are believed to have originated from photosynthetic bacteria. This endosymbiotic theory is supported by evidence such as the presence of their own circular DNA, double membranes, and similarities in ribosomal structures to prokaryotes.

The other options do not accurately represent the core idea of endosymbiosis. For instance, suggesting that mitochondria and chloroplasts originated from viruses neglects the extensive genetic and functional similarities they share with bacteria. The option that states all cells are formed from prokaryotic organisms doesn’t clarify the specific role of end