Final answer:
The complexity in eukaryotic cells can be attributed to endosymbiosis and gene duplication.
Step-by-step explanation:
The complexity found in eukaryotic cells can be attributed to two main events. The first event is believed to be endosymbiosis, where an early eukaryotic cell engulfed a prokaryotic cell, leading to a symbiotic relationship in which the prokaryote became an organelle, such as mitochondria or chloroplasts. This process increased the metabolic capability of eukaryotic cells. The second event is thought to be gene duplication and diversification, which allowed for the evolution of new genes and increased cellular complexity.
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