Final answer:
The internal double membrane structure of eukaryotes likely developed from the endosymbiotic fusion between early eukaryotic cells and prokaryotic cells, resulting in the engulfed cell becoming part of the host cell.
Step-by-step explanation:
The internal double membrane structure around the chromosome, indicating the characteristic feature of eukaryotes, has been theorized to have formed through the endosymbiotic fusion of archaeal and bacterial species.
This concept, known as the endosymbiotic theory, suggests that an early eukaryotic cell absorbed a prokaryotic cell through endocytosis. As a result, the engulfed cell became a part of the host cell, forming the double membrane structure that is observed around the nucleus, mitochondria, and chloroplasts in modern eukaryotic cells.
This absorbing process would result in the inner membrane deriving from the engulfed cell, while the outer membrane would be from the host. However, this is just one among several theories about the origin of eukaryotic cells, and while the evidence supports endosymbiotic events, especially in the case of mitochondria, scientific discussion and research continue to explore different aspects of eukaryotic evolution.