29.3-34.3

29.3-34.3 - The diversification of life 29.3 This chapter...

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The diversification of life 29.3 This chapter goes into protists and how they evolved Eukaryotes today have a nucleus and endomembrayne system, a mitochondria or genes that are usually in a mitochondria, and a cytoskeleton. WHich feature did the earliest eukaryotes not have? They didn’t have a cell wall The first eukaryotes also had a flagellum, but it’s different than the flagellum in bacteria. Bacteria rotates the flagella, but eukaryotes have flagellum that’s made of microtubules and dynein. Protists developed a nuclear envelope and an endoplasmic reticulum. The plasma membrane developed folds. Mutation and natural selection detached the folds from the plasma membrane, forming the ER and the nuclear envelope. HOw does having a nuclear envelope help the cell? It separates transcription and translation, so they can occur at the same time. The nuclear envelope also allows for alternative splicing, so the cell can control gene expression. After the nuclear envelope was developed diversification occurred. Some protists have tons of nuclei and some only have one. Ciliates have two nuclei : one is in charge of reproduction and the other is in charge of transcription. Dinoflagellates have chromosomes that lack histones and attach to the nuclear envelope. Mitochondria are organisms that generate ATP. It was created by a combination of symbiosis and endosymbiosis. WHat is symbiosis? Symbiosis occurs when two different species live in physical contact. WHat is endosymbiosis? endosymbiosis occurs if one species lives inside another species. The endosymbiosis theory says that an aerobic bacterium started to live in an anaerobic eukaryote when the eukaryote engulfed it. The bacterium absorbed carbon molecules with high potential energy from the eukaryote and oxidized them. So the eukaryote protected the bacterium and gave it carbon compounds and the bacterium made tons of ATP for the eukaryote. A lot of people thought that this theory was really far fetched at first, but this is the only explanation that could be thought of, so it was accepted unless someone was able to come up with something better. Then people started developing some support for this theory. They looked at a-proteobacteria. In that group there’s actually some bacteria that are only found in eukaryotic cells.
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the mitochondria is the size of a proteobacterium The mitochondria replicates separately from the cell division Mitochondria have their own ribosomes, which look like bacterial ribosomes, and they manufacture their own proteins mitochondria have double membranes They also have their own genomes which have sequences closely related to bacteria instead of the nuclear dna of eukaryotes. As time went on the mitochondria started to change in different bacteria:
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This note was uploaded on 02/12/2012 for the course SCI 2341 taught by Professor Yates during the Spring '11 term at Alabama.

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29.3-34.3 - The diversification of life 29.3 This chapter...

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