AP BIOLOGY

Detailed explanation-1: -The leading hypothesis, called the endosymbiotic theory, is that eukaryotes arose as a result of a fusion of Archaean cells with bacteria, where an ancient Archaean engulfed (but did not eat) an ancient, aerobic bacterial cell.

Detailed explanation-2: -The hypothesis that eukaryotic cells evolved from a symbiotic association of prokaryotes-endosymbiosis-is particularly well supported by studies of mitochondria and chloroplasts, which are thought to have evolved from bacteria living in large cells.

Detailed explanation-3: -The endosymbiotic theory is usually used to explain the origin of eukaryotic cells, but it can also be applied to bacterial cells.

Detailed explanation-4: -According to the Endosymbiotic Theory, endosymbiosis became the means by which organelles such as mitochondria and chloroplasts within eukaryotic cells came about.