The amoeba must surely be everyone's favorite protozoan. If you asked an 8 year old what was the best thing about science, right after dinosaurs, he would probably say. "The amoeba." Giant amoeba like creatures are the most loveable creation of science fiction, except mabye for Mr. Spock. All my years of loving science, I never actually saw a live amoeba; Dead ones in slides only. But they can get nasty too. I believe giardia is caused by an amoeba, and for a while, hikers in the Rocky Mountains were cautioned about drinking water from fresh mountain lakes and streams because of giardia. Sales of small filtration pumps for back packers went through the roof, and and outsold ponchos at REI and Dicks Sporting Goods. I never knew anyone that got giardia. I asked my doctor if he ever had to treat giardia. I think he said he had a patient who might have had it once. I think amoebas are known to cause some other sicknesses too.
Oops! I just checked. Giardia is caused by a flagellated microorganism, not an ameoba.