
Bacteria like E. coli have 2 membranes and a cell wall. Eukaryotes have one and no cell wall. Trying to figure out why? Here's a theory:
"Some competing prokaryote invented an antibiotic that interfered with peptidoglycan [cell wall ingredient] synthesis, as penicillin does today" (
source)
Ok, that's a big leap. But then why lose the outer membrane?
After some searching: no idea or random mutation (
source).
Conclusions from this exercise:
1. Google books is pretty awesome. I've actually gone to the library more because of its picks.
2. You can write a lifetime of novels about proposed evolutionary pathways and mechanisms and sound incredibly academic while doing it.