The earliest cells detectable in fossils were different from the cells in animals, plants, fungi, and protists living today. The
se first prokaryotic cells gave rise to eukaryotic cells approximately 1.7 billion years ago. The structure of eukaryotic cells today suggests how they might have evolved from their prokaryotic ancestors. Scientists examining mitochondria and chloroplasts now think that these organelles were probably free-living prokaryotes before becoming a part of eukaryotic cells long ago.What evidence suggests that mitochondria might have evolved before chloroplasts?
In the 1960s, Lynn Magulis came up with the theory of endosymbiosis. Different evidence supports this theory that the cell organelles like chloroplasts and mitochondria were once utilized by the independent living species. Both of these organelles exhibit their own genetic material. The mitochondria cannot differentiate to produce chloroplasts and vice versa.
However, the fact that the mitochondria are found in all the cells of eukaryotes, while the chloroplast is witnessed only in certain specific cells, shows that the evolution of mitochondria took place much earlier than the chloroplasts.
