SECONDARY ENDOSYMBIOSIS Meaning and
Definition
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Secondary endosymbiosis refers to a type of symbiotic relationship between two organisms in which one organism (the endosymbiont) is engulfed by another organism (the host) to establish a stable association within the host's cell. This process occurs after primary endosymbiosis, in which a free-living organism is engulfed by another cell, leading to the formation of a cell with a nucleus (eukaryotic cell).
In the case of secondary endosymbiosis, the endosymbiont itself is already an organelle that resulted from primary endosymbiosis. The host engulfs this pre-existing organelle, resulting in a second internal cell membrane surrounding the organelle within the host cell.
This phenomenon has been observed in various eukaryotic organisms, particularly in protists, such as algae. Through secondary endosymbiosis, these single-celled organisms acquire additional organelles, such as chloroplasts. Consequently, the host cell benefits from the metabolic activities performed by the endosymbiont. For instance, photosynthetic protists gain their photosynthetic ability from secondary endosymbiotic events.
The process of secondary endosymbiosis has led to a significant increase in organismal complexity and diversity. It has also played a crucial role in the evolution of eukaryotic lineages, contributing to the emergence of photosynthetic organisms in various ecological niches. By studying secondary endosymbiosis, scientists gain insights into the origins of organelles, their transfer between cells, and the intricate mechanisms that shape the evolutionary trajectory of organisms.
Etymology of SECONDARY ENDOSYMBIOSIS
The word "secondary endosymbiosis" can be broken down into its components to understand its etymology:
1. Secondary: From the Latin word "secundarius" meaning "following, next in order" or "subordinate". This term is used to indicate something that comes after or subsequent to something else.
2. Endosymbiosis: A combination of two Greek words. "Endo" means "inside" or "within", and "symbiosis" comes from "sym", meaning "together", and "biosis", meaning "living". The term symbiosis refers to a close and long-term interaction between different species living together in a mutually beneficial relationship.
Therefore, "secondary endosymbiosis" refers to a type of symbiotic relationship in which one organism is taken in and lives inside another organism, but this event occurs after an initial or primary endosymbiotic event.
