Survey
* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project
Download Bacteria, Viruses, Protists, and Prions
Document related concepts
Transcript
Bacteria Bacteria • Unicellular • Prokaryotes • Cells walls containing peptidoglycan Bacteria • Extremely Abundant – Cover nearly every square centimeter of Earth Bacterial Shapes • Bacilli: rod shaped – Bass-ill-eye • Cocci: spherical – Cox-eye • Spirilla: spiral, corkscrew – Spy-rill-uh What are the differences between eubacteria and archaebacteria? Eubacteria versus Archaebacteria • Cell walls of Eubacteria have lots peptidoglycans (mesh of sugar and amino acids) – Archaebacteria do not • Archaebacteria often live in very extreme environments (hot springs, digestive tracts, Great Salt Lake, etc.) Cell Walls Gram staining is a diagnostic tool used to classify bacteria • Gram positive: stain violet – due to thick peptidoglycan walls – Eubacteria or archaebacteria? • Gram negative: stain pink/red – No peptidoglycans in cell walls Metabolism • Bacteria can be heterotrophic or autotrophic – Remember: autotrophs are not ALL photosynthesizers! – Some are chemosynthesizers (convert carbon into organic compounds) How Bacteria Reproduce: Binary Fission • When a bacterium has doubled in size, it replicates its DNA and divides in half • Sexual or asexual? • Identical or different daughter cells? If bacteria are identical, how do they evolve? Where does genetic variety come from (besides natural mutation rate)? Genetic Variety in Bacteria • Conjugation: cell-to-cell contact • Transformation: bacterium takes up foreign DNA from surrounding environment • Transduction: DNA is transferred from one bacterial cell to another by a virus Conjugation • A hollow bridge (pilus) forms between two bacteria and genes move from one cell to the other • Increases genetic diversity of a population Conjugation Transformation • Bacteria take in foreign DNA from surroundings and incorporate it into their own DNA *Remember Griffith’s experiment Transduction • DNA is transferred from one bacterium to another by a virus • When new bacteriophages are made, they may contain a small amount of the host cell’s DNA Benefits of Bacteria • Some are producers that undergo photosynthesis • Some are decomposers that break down dead matter to recycle the nutrients • Some convert nitrogen gas to a form that can be used by plants (nitrogen fixation) What are some dangers of bacteria? Dangers of Bacteria • Break down cells and tissues for food Example: Tuberculosis (destroys lung tissue) • Release toxins (poisons) that travel through the body Example: Streptococcus releases toxins into the blood stream causes strep throat and scarlet fever Viruses • A virus is a core of DNA or RNA surrounded by a protein coat (capsid) Viruses • They can only reproduce by infecting living cells • They enter a cell and use its cell machinery to produce more viruses Retroviruses • Contain RNA as genetic information instead of DNA Would you consider viruses living? Are Viruses Living? • Cannot reproduce alone, must have a host cell • Do not undergo growth or development • Do not obtain or use energy • Evolve Prions • Diseases such as Scrapie (in sheep) and Mad Cow Disease are not caused by bacteria or viruses. What could cause them? Prions • Contain only protein • Cause disease by forming protein clumps which then induce normal proteins to become Prions • The build up eventually damages nerve tissue Protists • Domain? • Kingdom? • Prokaryotic or Eukaryotic? Protists • Domain: Eukarya • Kingdom: Protists • Eukaryotic Protists • Protists are defined by what they are not. Protists are eukaryotes that are not animals, plants, or fungi. They were the first eukaryotic organisms on earth. Types of Protists • Animal-Like Protists: heterotrophs • Plant-Like Protists: produce food through photosynthesis • Fungus-Like Protists: obtain food by external digestion Animal-Like Protists • Heterotrophs cilliate sporozoan zooflagellate Sarcodine (amoeba) Animal-Like Protists • Malaria • African Sleeping Sickness Plant-Like Protists • Carry out photosynthesis Fungus-Like Protists • Grow in damp, nutrient rich environments • Absorb food through cell membranes Review!
