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Lecture 7 - Model organisms Genetics Cell biology...

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1 E. coli Arabidopsis Human Mouse Drosophila C. elegans • Genetics Cell biology • Development Model organisms Prokaryotes • Classification • Features • Diversity – Genetic diversity – Metabolic diversity Ecological importance – Ecosystem function – Symbioses – Diseases of plants and animals Technological importance – Biotechnology and prokaryotic diversity Prokaryotes They’re (Almost) Everywhere! They make a living in a stunning variety of ways They are way small (usually 1-5um, except when they form filaments or mats) The number of prokaryotes in a single handful of fertile soil – Is greater than the number of people who have ever lived – Might include as many as 10,000 species Prokaryotes thrive almost everywhere – Including places too acidic, too salty, too cold, or too hot for most other organisms Figure 27.1 Thermophiles live at high temperatures Grand Prismatic Spring, Yellowstone National Park Halophiles live in high saline environments Figure 27.14
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2 NASA’s “clean room” Prevent “forward contamination” 193 species, 13 new to science Live on paint, cleaning fluids Adapted to clean rooms? Cataloging microbes - extraterrestrial life or hitchhikers? The three domain system This implies that we share a more recent common ancestor with the Archaea than the Archaea do with the other prokaryotic domain (Bacteria) Also, the amount of genetic diversity among prokaryotes is far greater than among all Eucarya put together. Horizontal transfer The tree of life Is not necessarily a neatly bifurcating tree. Figure 25.18 Bacteria Eukarya Archaea 4 Symbiosis of chloroplast ancestor with ancestor of green plants 3 Symbiosis of mitochondrial ancestor with ancestor of eukaryotes 2 Possible fusion of bacterium and archaean, yielding ancestor of eukaryotic cells 1 Last common ancestor of all living things 4 3 2 1 1 2 3 4 0 Billion years ago Origin of life Five Kingdoms (how it used to be) Monera - prokaryotes (included both Bacteria and Archaea) Protista - (mostly) single-celled eukaryotes. Plantae - plants Fungi - Fungi Animalia - animals Structural, metabolic, and genetic adaptations contribute to prokaryotic success Cell diameters tend to be 1/10th or 1/100th that of eukaryotic cells Most prokaryotes are unicellular – Although some species form colonies
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3 Features of prokaryotic cells 1. Variety of shapes 2. Unicellular but… 3. Move and behave 4. Cell wall 5. Lack complex compartmentalization 6. Reproduction and adaptation 1. Prokaryotic cells have a variety of shapes The three most common of which are spheres (cocci), rods (bacilli), and spirals 1 μ m 2 μ m 5 μ m (a) Spherical (cocci) (b) Rod-shaped (bacilli) (c) Spiral Figure 27.2a–c 2. Most prokaryotes are unicellular but some are multicellular (cooperation) Cyanobacteria - heterocytes fix nitrogen, other cells carry out photosynthesis Gingivitis Dental plaque - biofilm that forms on tooth surfaces biofilms - 1st colonists secrete chemicals that recruit other cells,
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