Final answer:
The origin of eukaryotic cells is explained by the endosymbiotic theory, which involves steps such as membrane infolding, endosymbiosis resulting in mitochondria formation, the development of a nucleus, and eventually the appearance of complex organelles.
Step-by-step explanation:
The Steps in the Origin of Eukaryotic Cells
The endosymbiotic theory provides a framework for the origin of eukaryotic cells, with several hypothesized steps leading to their evolution. Initially, prokaryotic cells underwent membrane infolding, which led to the creation of internal compartments including a primitive nucleus. Following this, an event of endosymbiosis occurred where a larger prokaryotic cell engulfed smaller prokaryotic cells. These engulfed cells were not digested; instead, they coexisted and later evolved into the cell's organelles, such as mitochondria (and chloroplasts in plants).
Subsequent steps involved the development of the nucleus, shaping a more complex cellular architecture. In fact, nuclear eukaryotic genes are believed to have an origin in the Archaea, indicating an evolutionary link. Later, as eukaryotic cells became more complex, they evolved complex organelles, and eventually, some eukaryotic cells gained the ability to adhere to and communicate with one another, leading to the development of multicellularity.
Among the options provided, (b) Endosymbiosis, formation of mitochondria, development of nucleus, appearance of complex organelles best represents the sequence of events leading to the origin of eukaryotic cells.