1-24-11 Prokaryotes

1-24-11 Prokaryotes - The Tree of Life: 3 Domains A note on...

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1 1 A note on Diversity powerpoints : Please note there is a lot of content in the powerpoints of the Diversity section. Please know the entire content of the diversity powerpoints (unless noted otherwise on a slide). They will serve you as a guide for studying - rather than learning the entire chapter in the text. We will work with some of the topics in more detail in class. Please make sure that your class notes reflect the class discussion, e.g. how to work with the content and what the implications are. Please work through remaining slides after class if we don’t get done in class 2 The Tree of Life: 3 Domains Carl Woese: discovered a new domain of life (published in 1990) Origin of life here (based on RNA sequences) Crawford Prize 2003 3 Q1. Who are the closest relatives ? a. Archae & Bacteria b. Archae & Eukaryotes c. Bacteria & Eukaryotes d. All equally related 4 Clicker Q2. Does the term prokaryotes represent a correct evolutionary classification? a. Yes, and I can explain why b. No, and I can explain why c. Yes, but I cannot explain why d. No, but I cannot explain why 5 Archae & Bacteria Two domains of Life 6 Prokaryotic form and function: Bacteria & Archae Most prokaryotes are unicellular, or loosely colonial, some can have simple multicellular forms such as a chain or filament, and some of the photosynthetic Cyanobacteria can even have a division of labor between specialized cells. Single cells (rods, cocci and spirilla) Cyanobacteria colonies
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2 7 The prokaryotic genome 1/1000 as much DNA as the eukaryotic genome: usually one double-stranded, circular DNA molecule that is not surrounded by a membrane (no true nucleus). very little protein associated with the DNA, unlike the eukaryotic chromosome which has a lot of protein (histones). no cell organelles or internal membranes (ER, Golgi) many bacteria also have plasmids (smaller rings of DNA with additional genes for functions such as antibiotic resistance or metabolism of unusual chemicals). These plasmids replicate independently of the chromosome, and can be transferred between partners during conjugation. conjugation pilus 8 The prokaryotic cell wall Prokaryotes vary in cell wall structure (~ amount of peptidoglycans) Domain Archae: No peptidoglycans in cell wall (same as eukaryotes) Domain Bacteria: Peptidoglycans present Gram+ bacteria: thick layer of peptidoglycans Gram- bacteria: thin layer of peptidoglycan 9 The 3 domains: traits No peptidoglycans DNA packaging Start of protein synthesis RNA synthesis Archae & Eukaryotes Circular chromosomes Archae & Bacteria No nucleus No organelles 10 Practice (HW) Draw and label a cladogram of the three domains of life and mark where on the cladogram the following traits most likely evolved. Explain whether the traits are shared primitive or shared derived traits and justify your answer.
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1-24-11 Prokaryotes - The Tree of Life: 3 Domains A note on...

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