Protozoa

Characteristics

Mostly unicellular, and free-living

Found in soil and water

More animal like than plant like

Not photosynthetic

Characteristics

• A typical protozoan life cycle has 2 stages – a trophozoite and a cyst.

• The trophozoite is the motile, feeding, dividing stage.

• The cyst is the nonmotile, dormant, survival stage.

Characteristics

• Protozoa are divided into groups, based on their method of locomotion:– Amebae move by means of pseudopodia (“false

feet”) Look for them in the video below!– Ciliates move by means of hairlike cilia– Flagellates move by means of whiplike.– Sporozoa have no visible means of locomotion

Ameba Movement

Paramecium

Protozoa That Cause Human Diseases

Plasmodium spp. – cause malaria, transmitted by Anopheles mosquito

Enormous impact on human history

Sickle-cell hemoglobin

Normal hemoglobin1 2 3 4 5 6 7. . . 146

1 2 3 4 5 6 7. . . 146

SE

MS

EM

Prevalence of sickle cell gene

Historical distribution of malaria

Protozoa That Cause Human Diseases

Trypanosoma brucei gambiense – causes African Sleeping Sickness... transmitted by Tsetse flies

Trypanosoma cruzi – causes Chaga’s disease

Protozoa That Cause Human Diseases

Trichomonas vaginalis – trichomoniasis (STD)

Giardia lamblia – persistent diarrheal disease