1. Ms. Powell’s 8th Grade Science Class
Disease Unit
Ms. Powell’s
8th Grade Science Class

2. Types of Disease Causing Organisms
Virus
Bacteria (includes Rickettsia)
Protozoa (includes trypanosomes)
Fungus
Worms

3. Viruses
A small nonliving particle that invades and reproduces inside a living cell
Considered nonliving because:
Viruses are not made of cells
Do not use energy to grow and develop
or to respond to their environment
Do not make food, take in food or produce waste
Have ability to multiply when inside a living cell

4. Virus Vocabulary
Host: a living thing that provides a source of energy for a virus or other organism
Parasite: organisms that live on or in a host and cause harm to the host
Active virus: enters a cell and immediately begins to multiply
Hidden virus: the genetic material lies dormant in a cell for a period of time before becoming active
Ex. Cold sore virus (Herpes) lies dormant in nerve cells

5. Potential Hosts of Viruses
No organisms are safe from viruses
Viruses can attack:
Plants, Animals, Bacteria, Protists, Fungi
Viruses are generally very host specific
Ex. A plant virus does not attack people

6. Naming Viruses Viruses are not living organisms
Scientists name the virus for the disease it causes
Ex. Polio
Scientists name the virus for the organism it infects
Ex. Tomato mosaic virus
Scientists name the virus after themselves
Epstein–Barr virus ( causes mono)

7. Virus Appearance Very small (smaller than a bacteria -750 nm)
22 to 250 nanometers
Shape: round, rod shaped, bricklike, threadlike, robotlike or bulletlike

8. Structure of a Virus Two basic parts:
Outer coat that protects the virus
Made of protein
Protein shape allows virus to lock onto certain cells
Cell surface and virus coat is like a “lock and key fit” – makes virus specific to certain cells
Inner core made of genetic material
Analogy: chocolate covered cherry

9. Structure of Viruses

10. Parts of a Virus

11. Virus Photos

12. Rhinovirus (Common Cold)

13. Hepatitis B

14. How Viruses Multiply
Once inside the cell the virus’s genetic material takes over the cell’s functions
The genetic material tells the cell to produce the virus’s proteins and genetic material
These proteins and genetic material are assembled into new viruses that are released from the cell

15. How Viruses Multiply

16. How HIV Invades a Human Cell

17. Herpes zoster Shingles/Chickenpox

19. Virus: Smallpox

20. Polio Virus: Neuromuscular Damage

21. Bacteria Are unicellular microorganisms.
Are typically a few micrometres long
Are prokaryotes – their cells do not have nuclei
Shapes: spherical, rodlike or spiral

22. Bacteria
Rod Shape,
Spherical,
Spiral

23. Bacteria Two types: archaebacteria – ancient bacteria
Live in hot springs and other extreme environments
Eubacteria – live everywhere else

24. Bacteria (blue and purple rods) and other microorganisms lurk in a kitchen sponge

25. Bubonic Plague: Bubos –swollen gland

26. Rickettsia Rickettsia species are a type of bacteria
Are carried as parasites by many ticks, fleas, and lice
Cause diseases such as Rocky Mountain spotted fever, and typhus in humans

27. Rickettsia: Lyme Disease: “Bull’s Eye” Rash at Site to Tick Bite

28. Rickettsia: Rocky Mountain Spotted Fever Rash

29. Rocky Mountain Spotted Fever

30. Typhus

31. Protozoan Parasites
Protozoa (in Greek proto = first and zoa = animals) are single-celled eukaryotes (organisms whose cells have nuclei)
Commonly show characteristics usually associated with animals
Most notably mobility and heterotrophy

32. 4 Types of Protozoa
Dinoflagellates
Cilliates
Sporozoans
Amoeba

33. 4 Types of Protozoa - Locomotion
Flagellates are cells with one or more whip-like tail called flagella. (trypanosomes?)
Ciliates –use hair-like cilia to move (malaria)
Amoeba move by means of temporary projections called pseudopods,
Sporozoans spore-forming, parasites of animals. Motile structures such as flagella or pseudopods are absent

34. Protozoa: Life Cycle of Malaria

35. Mosquito Transmission of Malaria

36. Protozoa - Trypanosomes
Undergo a complex lifecycle which may include several different morphological forms
Often transmitted by invertebrates.
African Sleeping Sickness/Tsetse fly
Chagas Disease, Triatome bug

37. Tsetse Fly

38. African Sleeping Sickness

39. Trypanosome and Red Blood Cells

40. Trypanosomiasis – Parasite Seen in Blood Sample

41. Fungal Diseases Eukaryotic organisms (nucleus in cell)
Digest their food externally, absorbing nutrient molecules into their cells.
Related to yeasts, molds, and mushrooms
Ringworm, Athletes foot, Nail fungus

42. Fungus: Ringworm

43. Helminths - Parasitic worms
Intestinal parasites - tape worm, pin worm
Onchocerciasis/River Blindness is an infection caused by the parasite Onchocerca volvulus (worm)
Spread by the bite of an infected blackfly.
Lymphatic filariasis

44. African River Blindness - ParsiticWorm

45. Parasitic Worm: Lymphatic Filariasis

46. Parasitic worm

47. Parasitic Worm: Liver Fluke