Why do scientists think that eukaryotes evolved from prokaryotes.

Question

Why do scientists think that eukaryotes evolved from prokaryotes.

Answer 1

Genetic/structural/functional similarities between mitochondria, chloroplasts, and prokaryotes suggest these organelles began as symbionts.

Answer 2

There's a theory out there called the symbiotic theory which theorizes that a prokaryote got inside another prokaryote and instead of being digested, they lived symbiotically. This theory is evidenced by the fact that mitochondria and chloroplasts both have membranes, their own DNA, ribosomes, etc.  

Answer 3

They  think that one prokaryote absorbed another, making it an internal source of energy,