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Chapter 27

Chapter 27 - Chapter 27 The Origin and Diversification of...

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Chapter 27: The Origin and Diversification of Eukaryotes 27.1 – How did the eukaryotic cell arise? o Eukaryotes that are not plants, animals or fungi are protists Paraphyletic o Protists are extremely diverse because they existed in all atmospheres Some are motile/others aren’t Multicellular/unicellular Photosynthetic/heterotrophic Microscopic/huge o Modern eukaryotic cell arose in several steps The origin of a flexible cell surface The origin of a cytoskeleton The origin of a nuclear envelope, which enclosed a genome organized into chromosomes The appearance of digestive vacuoles The acquisition of certain organelles via endosymbiosis o First step towards the modern eukaryotic cell is getting rid of the cell wall o Flexible membrane has multiple advantages, including exchanging materials with its environment (endocytosis) Folding, which leads to altered surface area o Eukaryote evolution also needed the Formation of ribosome studded internal membranes (some surround DNA) Appearance of cytoskeleton Evolution in digestive vacuoles, o Cytoskeleton leads to Changes in shape
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Helping the distribution of daughter chromosomes Move materials from one part of the cell to the other o First step towards nucleus was probably the folding of membrane over nuclear material o Phagocytosis may have led to endoplasmic reticulum, golgi apparatus and flagellum o One crucial endosymbiotic event was the incorporation of a proteobacterium that made it evolve into a primitive mitochondrion o Chloroplasts are also a result of primary endosymbiosis o Original chloroplasts had two membranes due to being cyanobacteria o Euglenids got their chloroplasts from secondary endosymbiosis o Secondary endosymbiosis is when the cell devours a chlorophyte and extracts its chlorophyll pigments o Tertiary endosymbiosis occurred when a dinoflagellate lost its chloroplast and took up a haptophyte o Lateral gene transfer complicates the origin of eukaryotic cells o LGT also led to the increase in chromosomes found in eukaryotic cells 27.2 – What features account for protist diversity?
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