TExES Life Science 7-12 Certification

The endosymbiotic theory posits that certain organelles in eukaryotic cells, specifically mitochondria and chloroplasts, originated from free-living prokaryotic organisms that were engulfed by ancestral eukaryotic cells. The evidence supporting this theory includes several key features of mitochondria and chloroplasts that are similar to prokaryotic cells.

The fact that mitochondria contain circular genomes aligns with the genetic structure of prokaryotes, which typically possess circular DNA, thus lending support to the idea that they originated from bacteria. This circular genomic structure is a direct link to their prokaryotic ancestry.

Similar structural membranes are also relevant evidence, as both mitochondria and chloroplasts have double membranes, which could indicate their engulfment. This is a characteristic of many bacterial cell walls, reinforcing the endosymbiotic theory.

The ability of both organelles to reproduce through binary fission, a method of asexual reproduction used by bacteria, further supports the idea that these organelles share a common origin with prokaryotic cells.

In contrast, the process by which mitochondria reproduce through mitosis is not considered supportive evidence for the endosymbiotic theory. While the replication of organelles is crucial for