Ch26 Lecture Bacteria Archaea - 26 Bacteria and Archaea:...

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26 Bacteria and Archaea: The Prokaryotic Domains
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26 Bacteria and Archaea: The Prokaryotic Domains 26.1 How Did the Living World Begin to Diversify? 26.2 What Are Some Keys to the Success of Prokaryotes? 26.3 How Can We Resolve Prokaryote Phylogeny? 26.4 What Are the Major Known Groups of Prokaryotes? 26.5 How Do Prokaryotes Affect Their Environments? 26.6 Where Do Viruses Fit into the Tree of Life?
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26.1 How Did the Living World Begin to Diversify? The three domains of life: Bacteria—prokaryotes Archaea—prokaryotes Eukarya—eukaryotes
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26.1 How Did the Living World Begin to Diversify? Members of all the domains: Conduct glycolysis Replicate DNA conservatively Have DNA that encodes peptides Produce proteins using the same genetic code Have plasma membranes and ribosomes
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26.1 How Did the Living World Begin to Diversify? Prokaryotic cells differ from eukaryotic cells: Prokaryotes lack a cytoskeleton and divide by binary fission DNA is a single circular molecule, not in a membrane-enclosed nucleus Prokaryotes have no membrane- enclosed organelles
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Figure 26.1 The Three Domains of the Living World
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26.1 How Did the Living World Begin to Diversify? Some genes of eukaryotes are more closely related to those of archaea, while others are more closely related to those of bacteria. The tree of life therefore contains some merging of lineages, as well as the predominant diverging of lineages.
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26.1 How Did the Living World Begin to Diversify? Among the bacteria, three shapes are common: Sphere— coccus (plural cocci ), occur singly or in plates, blocks, or clusters Rod— bacillus (plural bacilli ) Spiral or helical— helix (plural helices ) Rods and helical shapes may form chains or clusters
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26.1 How Did the Living World Begin to Diversify? Less is known about shapes of archaea; many have never been seen, and are known only from DNA samples from the environment. Morphology of known species includes cocci, bacilli, triangular, and square- shaped; the latter grow on surfaces, arranged like sheets of postage stamps.
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26.1 How Did the Living World Begin to Diversify? All three domains are the result of billions of years of evolution and are well adapted to present-day environments. None is “primitive.” The earliest prokaryote fossils date back at least 3.5 billion years, and even then there was considerable diversity.
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26.2 What Are Some Keys to the Success of Prokaryotes? Prokaryotes are the most successful organisms on Earth in terms of number of individuals. The number of prokaryotes in the ocean is perhaps 100 million times as great as the number of stars in the visible universe. They are found in every type of habitat on Earth.
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26.2 What Are Some Keys to the Success of Prokaryotes? Nearly all prokaryotes are unicellular.
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This note was uploaded on 03/30/2011 for the course MATHMATICS 1101 taught by Professor Zhong during the Spring '11 term at Georgia State University, Atlanta.

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Ch26 Lecture Bacteria Archaea - 26 Bacteria and Archaea:...

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