How is the finding of ribosomes inside mitochondria and chloroplasts explained?
It is a strong hypothesis that mitochondria and chloroplasts were prokaryotes that associated to primitive eukaryotic cells under mutualism (gaining protection and offering energy). This explains why within those organelles there are DNA and protein synthesis machinery, including ribosomes. This hypothesis is known as the endosymbiotic hypothesis on the origin of mitochondria and chloroplasts.
