Endosymbiosu

Endosymbiosu, also known as endosymbiosis, is a biological relationship in which one organism lives inside the cells or body of another. In the context of eukaryotic evolution, endosymbiosis describes how certain organelles originated through long-term associations between a host cell and engulfed prokaryotes, leading to integration and mutual dependence.

The most widely cited examples are mitochondria and plastids (such as chloroplasts) in plants and algae. The endosymbiotic theory, proposed and developed by Lynn Margulis and others in the 20th century, posits that these organelles began as free-living bacteria that were englulfed by a host cell and gradually evolved into integral components of the cell, protected by a double membrane and adapted to a coordinated life cycle with the host.

Evidence for the theory includes double membranes surrounding these organelles, DNA that is circular and resembles bacterial genomes, ribosomes that more closely resemble bacterial ribosomes than those of the host, and the transfer of many genes from the endosymbionts to the host nucleus over evolutionary time. Modern endosymbiosis is also found in ongoing associations between organisms, such as bacteria that living inside insects (for example Buchnera providing essential nutrients to aphids; Wolbachia affecting host reproduction) and photosynthetic symbionts within corals and other marine life.

Endosymbiosu has been central to understanding the origin of eukaryotic cells, the evolution of organelles, and the diversity of symbiotic relationships in biology. It remains an active area of research, integrating genetics, cell biology, and evolutionary theory.