Final answer:
The split of Eukarya from Archaea led to the rise of complex eukaryotic cells, which may have resulted from an endosymbiotic event where an Archaean cell and a bacterial cell fused, combining Archaeal and Bacterial characteristics.
Step-by-step explanation:
After the split of Eukarya from Archaea, a significant evolutionary event occurred. This split is believed to have given rise to the complex cells of Eukarya, characterized by intracellular organelles including a nucleus. There is a hypothesis suggesting that the origin of Eukarya was a result of an endosymbiotic event, where an Archaean cell merged with a bacterial cell leading to a more complex eukaryotic cell that contains a mixture of traits from both Archaea and Bacteria. The evidence for this includes the sharing of several traits between Archaea and Eukarya that are absent in Bacteria, such as certain genetic sequences like the TATA box in genes' promoter region. Moreover, DNA analysis supports that some eukaryotic genes are more closely related to bacterial DNA than to Archaeal DNA, prompting the theory that a fusion of genomes from an Archaeal ancestor and Bacteria through endosymbiosis could be the event that led to the evolution of Eukaryotic cells.