Parasite and Parasitism are terms that define a way of life rather than a coherent and evolutionary related group of organisms
Symbiosis, Commensalism, Mutualism, Parsitism
PARASITE – A living organism dependent on another living organism for its survival in the form of nutrition as well as shelter. Parasites may be simple unicellular protozoa or complex multicellular metazoa
Cysts (infective stage) in contaminated food or water – excystation in intestinal tract – trophozoite (ileum) --- each divides to form 8 trophozoites – colonize cecum & colon – invasion of epithelium– till muscularis layer (flask shaped ulcers) – reaches sub mucosa- --- portal blood– liver abscess.
Some trophozoites in intestine encyst – passed in stools – contaminate food & water.