Endosymbioottiset

Endosymbioottiset refers to the phenomenon of endosymbiosis, a biological relationship where one organism lives inside another organism in a mutually beneficial way. This type of symbiotic relationship is crucial for understanding the evolution of many life forms, particularly eukaryotic cells.

The most well-known example of endosymbiosis is the origin of mitochondria and chloroplasts within eukaryotic cells. It is widely believed that early eukaryotic cells engulfed prokaryotic cells, such as aerobic bacteria and cyanobacteria. Instead of digesting these engulfed cells, the host cell formed a symbiotic relationship with them. The engulfed aerobic bacteria eventually evolved into mitochondria, which are responsible for cellular respiration and energy production in eukaryotic cells. Similarly, the engulfed cyanobacteria evolved into chloroplasts, the sites of photosynthesis in plant and algal cells.

This theory, known as the serial endosymbiotic theory, explains the presence of double membranes around mitochondria and chloroplasts, as well as their own circular DNA, which is similar to bacterial DNA. Endosymbiotic relationships are not limited to the origin of organelles; they can be observed in various other organisms today, demonstrating the ongoing evolutionary significance of this biological strategy.