Question

Lynn Margulis proposed the mechanism of endosymbiosis to explain the origin of

Answer 1

check the paragraph marked II. The Endosymbiotic Theory

https://www.biology.iupui.edu/biocourses/N100/2k2endosymb.html

Answer 2

Plasmids like Mitochondria and chloroplasts were once separate individual prokaryotes that were engulfed by larger prokaryotes, leading to the presence of eukaryotes and compartmentalization of cells.
Evidence:
1. Presence of intraorganelle metabolism in plasmids
2. DNA and RNA in those plasmids
3. Ribosomes in plasmids
4. Plasmomembranes in those plasmids
5. Several more related to genomic positioning