Complex sentence: Margulis later formulated a theory to explain how symbiotic relationships between organisms of often different phyla or kingdoms are the driving force of evolution and genetic variation is proposed to occur mainly as a result of transfer of nuclear information between bacterial cells or viruses and eukaryotic cells.
Split into simpler sentences: Margulis later formulated a theory to explain how symbiotic relationships between organisms of often different phyla or kingdoms are the driving force of evolution. Genetic variation is proposed to occur mainly as a result of transfer of nuclear information between bacterial cells or viruses and eukaryotic cells.