Question

1. What is mutualistic symbiosis?
2. How does mutualistic symbiosis relate to the endosymbiont theory?
3. Which 2 organelles could be the result of endosymbiosis?
4. What specific evidence is used to show how these organelles could have once been independent prokaryotic cells?

                                                                             

Answer 1

1- Mutualistic Symbiosis is also called Mutualism. In Mutualism, the interaction of two species is such that ultimately both are benefitted. The interaction will have a net benefit on both sides, and they both share the advantages. Mutualistic Symbiosis ultimately helps in growth, survival or reproduction of both sides in some way. One side never enjoys the complete benefits of this relationship, hence it is named as Mutualism.

2- Mutualistic Symbiosis is somewhat related to Endosymbiont Theory. Endosymbiosis is basically a result of mutually beneficial relationship between the host organism and the organism which is internally associated.

3- The two cell organelles which are the result of Endosymbiosis are Chloroplast and Mitochondria. Long ago, they used to have an independent existance, but now they are a part of Eukaryotic cells. Thus they were now in an endosymbiotic relationship with the host Eukaryote. The bacteria took shelter in the host organism, hence both enjoying the survival advantages

4- These organelles were evolved from specific bacteria, that later got engulfed / swallowed by Eukaryotic cells through the process of Phagocytosis. There are plenty of evidences to prove that these organelles were once independent ---->

- Mitochondria and Chloroplast replication occurs through Binary fission only, which is actually a medium of reproduction in archaea and bacterial cells,

- Porins are present on outer membrane of these organelles, just like in Bacterial Cell Membrane. Porins are basically the proteins involved in the transportation of biomolecules.

- New Mitochondria and Chloroplast cannot be regenerated by the cell, if existing ones are removed from the cell.

- Cardiolipin is present in both mitochondrial membrane and Bacterial cell membrane. Cardiolipin is basically a membrane lipid.

- The extent of similarity between Ribosomes of Mitochondria & Chloroplast and Bacterial Ribosomes is quite high, in comparison to Eukaryotic Ribosomes.

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