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“Endosymbiosis & Cyanobacteria” Algae Seminar Peshawa Yasin

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Biology Dept. / Algae Seminar

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  • 1. Algae SeminarEndosymbiosis & CyanobacteriaPeshawa Yasin

2. Contents Definition What is Endosymbiosis? How important is Endosymbiosis? Primary & Secondary endosymbiosis Endosymbiosis Hypothesis 3. Definition:- Endosymbiosis (Greek: endon= "within",sym = "together" and biosis = "living"). An endosymbiont is any organism that lives withinthe body or cells of another organism. 4. What is Endosymbiosis? The endosymbiosis theory attempts to explain theorigins of organelles such as mitochondria andchloroplasts in eukaryotic cells. According to Endosymbiosis theory: modern eukaryotic cells evolved from simple,phagotrophic cells that ingested bacteria andcyanobacteria; the prey was not digested, andphysiological processes of the endosymbionts wereused by the host. 5. From prokaryote to eukaryote Mitochondria developedfrom proteobacteria,and chloroplastsfrom cyanobacteria. 6. How important is endosymbiosis? Endosymbiosis explains the origin of mitochondria andchloroplasts, but could it also explain other features ofthe eukaryotic cell? Maybe. Endosymbiotic origins havebeen suggested for many structures, including flagella,cilia, and even the nucleus! However, scientists are stillactively debating whether ornot these structuresevolved throughendosymbiosis. 7. Mitochondria and chloroplasts (and maybe otherorganelles) evolved from endosymbiotic bacteria.Heterotrophic prokaryotes were engulfed and function asmitochondria.Photosynthetic prokaryotes were engulfed and function aschloroplasts.Eukaryotic cell is a chimera of prokaryotic ancestors [Theterm chimera refers to the mixture of three prokaryotes].a. Original contributes genomeb. One becomes mitochondrionc. One becomes chloroplast 8. Primary & Secondary Endosymbiosis Primary endosymbiosis involves the engulfment of abacterium by another free living organism. Secondaryendosymbiosis occurs when the product of primaryendosymbiosis is itself engulfed and retained byanother free living eukaryote. Secondaryendosymbiosis has occurred several times and hasgiven rise to extremely diverse groups of algae andother eukaryotes. 9. Endosymbiosis HypothesisAA prokaryote ingested some aerobic bacteria. The aerobeswere protected and produced energy for the prokaryote A BC DCyanobacteriaAerobic bacteriaMitochondriaChloroplastsN NN Prokaryote Plant cellNAnimal Cell 10. Endosymbiosis HypothesisBOver a long period of time the aerobes becamemitochondria, no longer able to live on their own A BC D CyanobacteriaAerobic bacteria Mitochondria ChloroplastsN NN Prokaryote Plant cellNAnimal Cell 11. Endosymbiosis HypothesisCSome primitive prokaryotes also ingested cyanobacteria,which contain photosynthetic pigments A BC DCyanobacteriaAerobic bacteriaMitochondriaChloroplastsN NN Prokaryote Plant cellNAnimal Cell 12. Endosymbiosis HypothesisD Cyanobacteria became chloroplasts, unableto live on their own A BC DCyanobacteriaAerobic bacteria Mitochondria ChloroplastsN NN Prokaryote Plant cellNAnimal Cell 13. Secondary Endosymbiosis and Origin of Algal Diversity Algae AB NNSecondary endosymbiosis N Heterotroph CAlgae ABCMany membrane layers