Define endosymbiosis What is the difference between primary and secondary endosy

Question

Define endosymbiosis What is the difference between primary and secondary endosymbiosis? Which group of protists are thought to have resulted from primary endosymbiosis? Which group of protists are thought to have resulted from secondary endosymbiosis? Why do some of the excavates have reduced, non-functioning mitochondria? Explain Know the distinguishing characteristic of each "branch" of protists that we have discussed in class. Several of the protist groups have developed symbiotic relationships with other organisms. Give some examples of these symbiotic relationships. If possible, list the benefit that these partnerships provide. Which protists are the closest relatives to the land plants?

Explanation / Answer

Endosymbiosis Theory: This theory may be explained by the fact through which prokaryotes gave rise to the first eukaryotic cells. It is considered as one of the most important theories among evolutionary theories. In 1960, Lynn Margulis’s work helped explain the origin of the eukaryotic cellular organelles like chloroplast and mitochondria origin from bacteria. In nut shell, chloroplast and mitochondria of eukaryotic cells are believed to descend from bacteria. Endosymbiosis is further strengthened by the fact that both prokaryotic cells and mitochondria and chloroplast contain 70S ribosomes unlike 80S in eukaryotes. Moreover, both prokaryotes and mitochondria and chloroplast don’t contain cholesterol in membrane unlike eukaryotes. Furthermore, prokaryotes and chloroplast and mitochondria contain circular double stranded DNA unlike eukaryotes which contain double stranded linear DNA. More recent sequence of nucleotides in the DNA further indicates their origin from prokaryotes. In conclusion, these all evidences favour the endosymbiosis theory.

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