Eukaryotic cells are thought to have evolved due to which event?

Eukaryotic cells are believed to have evolved through the process of endosymbiosis, which is a key event in evolutionary biology. This theory posits that certain organelles, particularly mitochondria and chloroplasts, originated from free-living prokaryotic organisms that were engulfed by a primitive host cell. Instead of being digested, these prokaryotes formed a mutually beneficial relationship with the host cell, eventually evolving into organelles.

This process provides a plausible explanation for the complexity of eukaryotic cells compared to prokaryotic cells. The engulfed prokaryotic cells contributed their metabolic capabilities, which allowed the host to perform processes like cellular respiration and photosynthesis more efficiently. Over time, the symbiotic relationship solidified, leading to the evolution of more complex cellular structures and functions typical of eukaryotic life.

The other options, while related to cellular functions and processes, do not explain the origin of eukaryotic cells themselves. Cellular respiration, photosynthesis, and cellular differentiation are important biological processes but do not address the evolutionary mechanism that gave rise to eukaryotic cells. Thus, endosymbiosis is the most accurate answer, as it captures the historical transition from simpler