The chloroplasts are the organelles in plant cells that provide energy to the cell. The equivalent organelle in eukaryotic (animal) cells is the…

The chloroplasts are the organelles in plant cells that provide energy to the cell. The equivalent organelle in eukaryotic (animal) cells is the mitochondria. Both are also unusual in that they have double membranes and contain their own set of DNA. What is the current explanation for this observation?