Factors in favor of mitochondrial and chloroplast endosymbiosis. Outer membrane is similar to the plasma membrane. Both have prokaryotic type and size ribosomes . Inner membrane lipids of mitochondria and chloroplasts are similar to their prokaryotic counterparts. Mitochondria and chloroplasts seem to divide independently of the rest of the eukaryotic cell.
Eukaryotes are very good at endocytosis .
Mitochondria and chloroplasts only code for a few proteins. Because of this, it is not surprising that mitochondria nor chloroplasts have been shown to be able to live on their own when isolated from the eukaryotic cell.