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Primitive life photos
Primitive life photos
Primitive life photos
Primitive life photos
Primitive life photos
Primitive life photos
Primitive life photos
Primitive life photos
Primitive life photos
Primitive life photos
Primitive life photos
Primitive life photos
Primitive life photos
Primitive life photos
Primitive life photos
Primitive life photos
Primitive life photos
Primitive life photos
Primitive life photos
Primitive life photos
Primitive life photos
Primitive life photos
Primitive life photos
Primitive life photos
Primitive life photos
Primitive life photos
Primitive life photos
Primitive life photos
Primitive life photos
Primitive life photos
Primitive life photos
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Primitive life photos

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  • 1. Lecture 6b: ‘Primitive’ Lifeforms
  • 2. By far, most living organisms <ul><li>4 groups: </li></ul><ul><ul><li>Viruses </li></ul></ul><ul><ul><li>Viroids and Prions </li></ul></ul><ul><ul><li>Prokaryotes </li></ul></ul><ul><ul><li>Protists </li></ul></ul>
  • 3. Viruses <ul><li>Do not have a cell </li></ul><ul><li>Obligate intercellular parasites: they can not reproduce outside of a cell </li></ul><ul><li>Do have DNA/ RNA </li></ul><ul><li>Tend to be host specific to some degree </li></ul><ul><ul><li>Only attach to specific cells </li></ul></ul>
  • 4.  
  • 5. Viruses <ul><li>Reproduce by taking over machinery of the host cell and using it to their own ends </li></ul><ul><li>Some viruses are specific to bacteria, plants, or animals, and reproduce in slightly different ways </li></ul><ul><ul><li>Sometimes there are periods in which the virus is latent- not reproducing </li></ul></ul>
  • 6. Viruses <ul><li>Retroviruses: have RNA instead of DNA inside, make DNA by integrating with host genome </li></ul><ul><ul><li>Ex. HIV </li></ul></ul>
  • 7. Viruses <ul><li>Examples of human diseases caused by viruses </li></ul><ul><ul><li>Flu </li></ul></ul><ul><ul><li>SARS </li></ul></ul><ul><ul><li>West Nile </li></ul></ul><ul><ul><li>HIV/ AIDS </li></ul></ul><ul><ul><li>Ebola </li></ul></ul><ul><li>Viruses can travel around the world on an airplane, leading to their quick and easy spread </li></ul>
  • 8. Viroids and Prions <ul><li>Even more weird than viruses! </li></ul><ul><li>Viroids are just naked strands of DNA </li></ul><ul><ul><li>Several crop diseases </li></ul></ul><ul><li>Prions are misshapen proteins, the mechanism of damage is not known </li></ul><ul><ul><li>Ex: mad cow, Creutzfeldt-Jacob disease, scrapie </li></ul></ul>
  • 9. Prokaryotes <ul><li>Two main groups to discuss: Bacteria and the Archaea </li></ul><ul><li>Have no membrane- bound organelles </li></ul><ul><li>Oldest prokaryote fossils are 3.5 billion years old </li></ul><ul><li>Origin of life?- Endosymbiotic theory </li></ul>
  • 10.  
  • 11. Bacteria <ul><li>Millions of bacteria exist everywhere! </li></ul><ul><li>We do not know all the different types of bacteria that exist today </li></ul><ul><li>They are in your intestine and on your skin, on the table, in the soil, etc. etc. </li></ul>
  • 12. Bacteria <ul><li>Come in several shapes, most basic are sphere, rod, and spiral </li></ul><ul><li>DNA is in single closed circle chromosome, plus sometimes also plasmids </li></ul><ul><li>Can have flagella to move around </li></ul><ul><li>Reproduce asexually- called binary fission </li></ul><ul><ul><li>Not mitosis because no spindle fibers </li></ul></ul>
  • 13.  
  • 14. Bacteria <ul><li>Can not recombine genes using sex, but have different ways of sharing DNA </li></ul><ul><li>Conjugation - one cell donates DNA to another directly </li></ul><ul><li>Transformation - one bacterium picks up DNA that is floating around in environment </li></ul><ul><li>Transduction - bacterial viruses carry DNA from one bacterium to another </li></ul>
  • 15. Bacteria <ul><li>Some bacteria are able to form endospores, in which the chromosome and some cytoplasm dehydrate and are encased in a protective coat </li></ul><ul><li>Enables them to survive very harsh conditions: extreme heat or dryness, extreme cold, UV radiation </li></ul><ul><ul><li>Ex. botulism </li></ul></ul>
  • 16. Bacteria <ul><li>Can be autotrophs or heterotrophs </li></ul><ul><ul><li>Autotrophs- produce own food </li></ul></ul><ul><ul><ul><li>Photoautotrophs use photosynthesis </li></ul></ul></ul><ul><ul><ul><li>Chemoautotrophs use a source other than the sun for electrons- S compounds, for example </li></ul></ul></ul><ul><ul><li>Heterotrophs- eat something else </li></ul></ul><ul><ul><ul><li>Chemoheterotrophs take in organic nutrients as food, break down large molecules into smaller ones that are absorbable </li></ul></ul></ul><ul><ul><ul><li>Bacteria in our intestines are this type </li></ul></ul></ul>
  • 17. Bacteria <ul><li>Important to our everyday life: </li></ul><ul><ul><li>They fix atmospheric N and make it available for plants to use </li></ul></ul><ul><ul><li>Decompose dead organisms into usable organic materials </li></ul></ul><ul><ul><li>Can be used to clean polluted areas </li></ul></ul><ul><ul><li>Used to make cheese, pickles, etc. </li></ul></ul><ul><ul><li>Can be engineered to make useful molecules, like insulin </li></ul></ul>
  • 18. Bacteria <ul><li>Also cause human diseases </li></ul><ul><li>Some leave behind toxins when they die- </li></ul><ul><ul><li>Ex. tetanus toxin prevents relaxation of muscles </li></ul></ul><ul><li>Some bind to other cells </li></ul><ul><ul><li>Ex. Shigella dysentaeriae binds to intestinal wall, results in severe diarrhea </li></ul></ul><ul><li>Some invade organs or cells </li></ul><ul><ul><li>Ex. Salmonella, may only result in food poisoning, but sometimes can invade the body and cause typhoid </li></ul></ul>
  • 19. Archaea <ul><li>Archaea and eukaryotes probably share a common ancestor, because tRNA, ribosomal proteins, and other characteristics are shared between them but not bacteria </li></ul>
  • 20. Archaea <ul><li>Many found in extreme environments </li></ul><ul><li>Methanogens- produce methane in the production of their ATP- live in intestines and swamps </li></ul><ul><li>Halophiles- found in high saline environments, such as Great Salt Lake </li></ul><ul><li>Thermoacidophiles- found in HOT and acidic environments, such as hot springs, geysers, volcanos </li></ul>
  • 21. Protists <ul><li>Eukaryotic </li></ul><ul><li>Very diverse </li></ul><ul><li>Endosymbiotic theory: Eukaryotes arose when bacterial cells lived in close association with a proto-eukaryote that had a nucleus and ER- the bacterial cells became absorbed into the eukaryote and became what we know as mitochondria and chloroplasts </li></ul>
  • 22. Protists <ul><li>So diverse, we don’t have a good classification system yet </li></ul><ul><li>Book, and therefore we, divide them by modes of nutrition: </li></ul><ul><ul><li>Algae, protozoans, slime molds and water molds </li></ul></ul>
  • 23. Protists- algae <ul><li>Aquatic photosynthesizers </li></ul><ul><li>Phytoplankton in oceans provide base of food web </li></ul><ul><li>Some Oceanic algae form seaweeds </li></ul><ul><li>Can be symbiotic- corals, lichen </li></ul>
  • 24.  
  • 25. Protists- protozoans <ul><li>Unicellular, but complex </li></ul><ul><li>Are heterotrophic, many feed by engulfing food particles </li></ul><ul><li>Usually able to move using cilia, flagella, or pseudopods </li></ul>
  • 26. Protists- protozoans <ul><li>Human diseases caused by protozoans: </li></ul><ul><ul><li>Amoebic dysentery (Entamoeba) </li></ul></ul><ul><ul><li>African sleeping sickness (trypanosome) </li></ul></ul><ul><ul><li>Girardia </li></ul></ul><ul><ul><li>Malaria (Plasmodium) </li></ul></ul><ul><ul><li>Toxoplasmosis (carried by cats) </li></ul></ul>
  • 27.  
  • 28.  
  • 29. Protists- slime molds <ul><li>Help decompose dead plant material in forests </li></ul><ul><ul><li>They are many cells fused together to form a plasmodium with many nuclei </li></ul></ul><ul><ul><li>Can actually move slowly along </li></ul></ul>
  • 30. Protists- water molds <ul><li>Decomposers, but also are parasites </li></ul><ul><ul><li>Potato blight </li></ul></ul><ul><ul><li>Have a cell wall similar to plant cell walls </li></ul></ul>
  • 31. Potato blight- a water mold Slime molds

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