What does the term 'endosymbiosis' refer to?

The term 'endosymbiosis' refers specifically to the process in which one organism engulfs another, allowing the engulfed organism to live within the host organism in a symbiotic relationship. This concept is key in understanding the evolution of eukaryotic cells, as it proposes that certain organelles, such as mitochondria and chloroplasts, originated from free-living prokaryotic cells that were engulfed by ancestral eukaryotic cells. Over time, these engulfed cells and their host developed a mutual dependence, leading to the complex cell structures we see today.

This process is distinct from the formation of new species, which involves the evolution and genetic divergence over time, rather than the internal relationship between two distinct organisms. Similarly, communication between cells refers to signaling mechanisms that allow cells to interact, which is unrelated to the engulfment aspect of endosymbiosis. Genetic mutation, on the other hand, involves changes in the DNA sequence within a cell, and while it is a vital process for evolution, it does not describe the specific mechanics of one cell engulfing another. Thus, the correct identification of endosymbiosis aligns directly with the concept of engulfment, supporting the idea of interdependent evolutionary relationships