Lecture15_handout_28Sep11 - BioEE1780 Evolution and...

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BioEE1780 Evolution and Biodiversity Today’s lecturer: Cole Gilbert Lecture 14: Sept. 28, 2011 Diversity 4 page -1 “Algae” and the origin of plants Readings: Life, 9 th ed. Chapter 27, pp. 573-574, 579-580 Chapter 28, pp. 586-600. Once some archeans ingested, but failed to digest, an α -proteobacteria, eukaryotic cells arose. These cells contained not just their own original prokaryotic biochemistry, but complementary metabolic pathways from an oxygen using, ATP-producing symbiont that became a mitochondrion. There were five great radiations of primarily single-celled, mostly aquatic, eukaryotes: 1. Chromalveolates, 2. Plants, 3. Excavates, 4. Rhizaria, and 5. Unikonts. One of these groups, the plants, evolved another organelle by ingesting a cyanobacterium that used light energy to fix atmospheric CO 2 into useable carbohydrates, and which ultimately evolved into a chloroplast. This was the primary plastid endosymbiosis and the first organism probably was autotrophic and heterotrophic. As we discussed in Diversity Lecture 3, several other groups of microeukaryotes subsequently ingested one of these single-celled autoheterotrophs and became photosynthetic by 2 o or 3 o endosymbiosis. Today, however, we return to the clade that resulted from 1 o endosymbiosis, the plants.
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Lecture15_handout_28Sep11 - BioEE1780 Evolution and...

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