what theory suggest that mitochondria were once independent cells that were captured by another cell

Answer 1

The theory that suggests mitochondria were once independent cells that were captured by another cell is known as the endosymbiotic theory. This theory posits that mitochondria (and chloroplasts in plants) originated from prokaryotic cells that were engulfed by a primitive eukaryotic cell. Over time, these engulfed prokaryotes developed a symbiotic relationship with their host cell, eventually evolving into the organelles we see today. This theory is supported by several lines of evidence, including the presence of their own DNA, similarities in ribosomal structure to bacteria, and their replication process, which resembles bacterial fission.