Protists-07-web

Protists-07-web - Protists 1 Protists Eukaryotes/Protists...

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Protists Protists Eukaryotes/Protists Last lecture we discussed the diversity of prokaryotes. Now we’re going to move up the tree of life to the eukaryotes. The kingdom Protista contains the most earliest-branching eukaryotes. Note that the Protista is NOT a monophyletic or “natural” group. Historically, all eukaryotes that are not animals, plant or fungi have been called ‘protists’. Even as we speak, the classification of organisms in the kingdom Protista is changing rapidly. Today we’ll focus on the kingdom Protista and the origin of eukaryotic cells. The origin of eukaryotic cells Remember that prokaryotes are thought to have originated at least 1 billion years before eukaryotes. How did the prokaryotic cell evolve into a eukaryotic cell? It is thought that the eukaryotic cell was derived by a couple of processes: 1. The invagination of cell membranes , leading to the double-membrane nucleus, the endoplasmic reticulum (the site of most protein synthesis) and other structures. One primitive eukaryote, Giardia lamblia , appears to give some insight into the origin of the nucleus. Giardia is a protist that appears to represent a sort of “missing link” between prokaryotes and eukaryotes. One of the neat things about Giardia is that it has not one but two nuclei. However, the two nuclei are haploid. This existence of two haploid nuclei in Giardia suggests that nuclei could have
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This note was uploaded on 03/14/2009 for the course BIOL 94 taught by Professor Gaut/summers during the Winter '08 term at UC Irvine.

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Protists-07-web - Protists 1 Protists Eukaryotes/Protists...

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