Primitive life photos


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Primitive life photos

  1. 1. Lecture 6b: ‘Primitive’ Lifeforms
  2. 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. 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>
  5. 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>
  6. 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>
  7. 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>
  8. 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>
  9. 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>
  10. 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>
  11. 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>
  12. 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>
  13. 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>
  14. 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>
  15. 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>
  16. 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>
  17. 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>
  18. 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>
  19. 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>
  20. 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>
  21. 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>
  22. 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>
  23. 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>
  24. 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>
  25. 31. Potato blight- a water mold Slime molds