Scientists believe that mitochondria evolved before chloroplasts because of the following reasons:
B. because all eukaryotic cells have mitochondria but not all eukaryotic cells have chloroplasts.
This is because mitochondria are essential for the process of cellular respiration, which is necessary for producing ATP (the primary energy source for cells) in eukaryotic cells. All eukaryotic cells need energy to survive, which is why they all have mitochondria. On the other hand, chloroplasts are only found in plant cells (and some protists), where they are involved in photosynthesis (the process of converting sunlight into energy). Therefore, scientists believe that chloroplasts evolved later in the evolution of eukaryotic cells, after mitochondria had already evolved