Protozoans Flashcards
Key features of protozoans
- Single celled
- Eukaryotic
- motile
- heterotrophic
- complex
Locomotion in Protozoans (Flagella)
Some have flagellum (wave of motion propels organism forward)
Locomotion in Protozoans
(Cillia)
Many move one after the other - metachronal waves
Locomotion in Protozoans (Pseudopodia)
Pseudopodia (false feet)
Temporary extension of the body
Directional movement
Changes in the ectoplasm
Food acquisition of protozoans
Engulf particles
Form vesicles
Receptors on the outside detect food - latch onto food and engulf
Food vesicle, lysosomes within release
Some protozoans are specialised for different forms of feeding
Origin of Protozoans
Endosymbiont Theory
Endosymbiont Theory
mitochondria and chloroplast in eukaryotic cells were once aerobic bacteria (prokaryote) that were ingested by a large anaerobic bacteria (prokaryote).
Examples of Protozoans
- Amoeba
- Paramecium
- Euglena
- Trypansoma
Amoeba characteristics
Free living organims
found in freshwater
some parasitic forms (Entamoeba histolytica)
Entamoeba histolytica life cycle
- humans ingest cysts from food/ surfaces/water etc
- organism break down intestinal wall and make their way to blood system
- can make their way to the liver, lungs and even brain
Only amoeba that effects humans
3 stages of the Malaria plasmodium
- Exo-erythrocytic cycle (human liver)
- Erythrocytic cycle (human blood)
- Sporogonic cycle (within mosquito)
What does malaria need to complete it’s lifecycle?
Mosquito and human host
Malaria plasmodium - Exo-erythrocytic cycle (human liver)
Sporozoites injected into to human by a feeding mosquito.
carried to liver
infect liver cells (schizont)
infected cells rupture and enter blood.
Malaria plasmodium. Erythrocytic cycle (human blood)
- Form trophozoites in blood cells
- Asexual cycle of immature trophozoites causes continued replication
- Sexual cycle creates gametocytes which are then passed back into mosquitos when feeding
Malaria Plasmodium. Sporogonic cycle (within mosquito)
Sexual reproduction takes place within the mosquito.
Zygote (oocyte) forms in mosquito gut
Sporozoites form (cycle begins again).
Why do humans experience a fever with malaria?
Trophozoites bursting out of red blood cells causes fever
How do we treat malaria?
Tu Youyou - Chemical used for treating fever (sweet-wormwood)
Gene editing (Crispr) modifies double sex gene to stop females from feeding or laying.
Make males infertile
Some vaccines
Toxoplasma gondii (cat - rodent parasite)
- Can manipulate hosts behaviour
- Rodent show no fear to cats when infected
- Cat must eat rodent for parasite to be transmitted
- Lack of fear - good for parasite, bad for rodent
- Parasite reproduces in cat (definitive host)
Does toxoplasma affect humans?
Up to 50% of population infected due to close relationship with cats
Possible modification to human behaviour
Trypanosoma brucei (causes sleeping sickness)
Hard to develop immune response because parasite can change its expression.
Relies on transmission by tsetse fly (vampire fly)
Two subspecies of trypanosoma brucei (from tsetse fly)
- Gambiense (fly-human-fly)
- Rhodesiense (fly-game-fly)
Zoonosis (when a human is infected by rhodesiense by accident)
Zebra theory (trypanosoma brucei)
Colour patterns could protect from being bitten
stripes reflect type of polarised light that tsetse flys like
Ciliates
Have Cilia
Can be aquatic
free-living, symbionts or parasitic.
what is the only parasitic ciliate that infects humans?
Balantidium coli
