Primitive life photos
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Primitive life photos Presentation Transcript

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