Disease Unit Ms. Powell’s

8th Grade Science Class

Types of Disease Causing Organisms

Virus Bacteria (includes Rickettsia) Protozoa (includes trypanosomes) Fungus Worms

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 developor to respond to their environment Do not make food, take in food or produce waste

Have ability to multiply when inside a living cell

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

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

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)

Virus Appearance Very small (smaller than a bacteria -750

nm) 22 to 250 nanometers

Shape: round, rod shaped, bricklike, threadlike, robotlike or bulletlike

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

Structure of Viruses

Parts of a Virus

Virus Photos

Rhinovirus (Common Cold)

Hepatitis B

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

How Viruses Multiply

How HIV Invades a Human Cell

Herpes zoster Shingles/Chickenpox

Virus: Smallpox

Polio Virus: Neuromuscular Damage

Bacteria Are unicellular microorganisms. Are typically a few micrometres long Are prokaryotes – their cells do not have

nuclei Shapes: spherical, rodlike or spiral

Bacteria Rod Shape,

Spherical,

Spiral

Bacteria Two types:

archaebacteria – ancient bacteria Live in hot springs and other extreme

environments Eubacteria – live everywhere else

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

Bubonic Plague: Bubos –swollen gland

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

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

Rickettsia: Rocky Mountain Spotted Fever Rash

Rocky Mountain Spotted Fever

Typhus

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

4 Types of Protozoa Dinoflagellates Cilliates Sporozoans Amoeba

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

Protozoa: Life Cycle of Malaria

Mosquito Transmission of Malaria

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

Tsetse Fly

African Sleeping Sickness

Trypanosome and Red Blood Cells

Trypanosomiasis – Parasite Seen in Blood Sample

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

Fungus: Ringworm

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

African River Blindness - ParsiticWorm

Parasitic Worm: Lymphatic Filariasis

Parasitic worm

Parasitic Worm: Liver Fluke