Final answer:
The chimera-like organism theory is another theory used to explain the evolution of eukaryotic cells from prokaryotic organisms.
Step-by-step explanation:
Endosymbiosis is the major theory describing the evolution of eukaryotic cells from prokaryotic organisms. Another theory that has been used to explain this process is the chimera-like organism theory, which suggests that eukaryotes are descendants of a composite organism formed through a symbiotic relationship between a host cell and an alpha-proteobacterium cell. This theory proposes that over time, the two cells became dependent on each other and evolved into the eukaryotic cells we see today.