Endosymbiontní

Endosymbiontní refers to a symbiotic relationship where one organism lives inside another. This is not merely a surface association but involves the intimate presence of one cell or organism within the cytoplasm or cells of another. A well-known example is the theory of endosymbiosis, which proposes that mitochondria and chloroplasts within eukaryotic cells originated from free-living prokaryotic organisms that were engulfed by a larger host cell. Over evolutionary time, these engulfed organisms became integrated into the host, losing their independence and developing into essential organelles. The host cell provided protection and nutrients, while the endosymbiont offered metabolic advantages, such as energy production through respiration (mitochondria) or photosynthesis (chloroplasts). This theory is supported by evidence such as the presence of their own circular DNA, similar to bacterial DNA, and their double membrane structure, the inner membrane resembling prokaryotic membranes and the outer membrane possibly derived from the host's engulfing vesicle. Endosymbiotic relationships can be obligate, meaning neither organism can survive without the other, or facultative, where the relationship is beneficial but not essential for survival.