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Chapter 20: Viruses and Prokaryotes

Chapter 20: Viruses and Prokaryotes. Section 20-2 : Prokaryotes. Classifying Prokaryotes. Unicellular organisms that lack a nucleus DNA free-floating Two groups domains: Bacteria and Archae. Bacteria. Larger domain No agreement about number of phyla

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Chapter 20: Viruses and Prokaryotes

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  1. Chapter 20: Viruses and Prokaryotes Section 20-2: Prokaryotes

  2. Classifying Prokaryotes • Unicellular organisms that lack a nucleus • DNA free-floating • Two groups domains: Bacteria and Archae

  3. Bacteria • Larger domain • No agreement about number of phyla • Live everywhere – fresh/salt water, land, within other eukaryotes, etc • Usually have a cell wall for shape and protection – contains peptidoglycan • Escherichia coli – found in human intestines – have extra membrane around cell wall for more protection • Flagella for movement, pili to anchor bacterium

  4. E. coli

  5. Archae • Look similar to Bacteria under a microscope • Cell walls contain lipids • DNA more like eukaryotes • Many live in harsh/extreme environments – salt lakes, hot springs, no oxygen, etc

  6. Structure and Function • Range in size from 1-5 micrometers • Come in three shapes: • Bacillus (pl. bacilli) – rod shaped • Coccus (pl. cocci) – spherical • Spirillum (pl. spirilla) – spiral/corkscrew shaped • Also three arrangements: • Diplo- (in a pair) • Staphlyo (in a bunch) • Strepto- (in a chain)

  7. Shapes/Arrangements

  8. Structure and Function • Can be distinguished by how and if they move – flagella, slime • Energy released during cellular respiration, fermentation, or both • Vary in the way they obtain energy

  9. Growth, Reproduction, and Recombination • Binary fission occurs when a prokaryote has doubled in size – replicates its DNA and splits • Asexual reproduction • Can be very fast when conditions right • When conditions are unfavorable, many prokaryotes form endospores • Thick wall forms around DNA and part of cytoplasm • Can stay dormant from many years • Bacillus anthracis

  10. Growth, Reproduction, and Recombination • Mutations allow prokaryotes to evolve - inherited through binary fission • Many prokaryotes also exchange genetic information through conjugation • Hollow bridge forms between 2 bacterial cells and genetic information (usually plasmids) move from one cell to another • Increases genetic diversity

  11. Importance of Prokaryotes • Decomposers – break down complex organic molecules into simpler ones, supplying raw materials needed • Actinomycetes in soil • Sewage treatment • Water purification • Production of fertilizers • Producers – cyanobacteria responsible for photosynthesis in ponds/aquatic environments • Nitrogen fixers – convert atmospheric nitrogen gas into usable forms • Symbiotic relationships with plants – Rhizobium and legumes

  12. Human Uses of Prokaryotes • Foods/commercial products (yogurt produced with Lactobacillus) • Digest petroleum • Remove human-made wastes and poisons from water • Synthesize drugs, chemicals by genetic engineering • Those adapted to extreme environments may produce heat-stable enzymes

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