Give one piece of evidence that supports the theory that mitochondria evolved from prokaryotic cells.

Mitochondria contain 70S ribosomes (as opposed to 80S which would be found in other eukaryotic organelles) the same as prokaryotic cells. They also have their own DNA (mtDNA) which is separate from the DNA of their eukaryotic hosts, suggestive of endosymbiosis having occurred in the past, the non-meiotic reproductive strategy of which is similar to that of asexually reproducing prokaryotic cells.