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Name: Alex Beck
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Question:
How many species of protozoa are there? How many are poisonous? What type is most deadly? How do they protozoa catch their food? How do protozoa digest their food? How big is the largest protozoa? How small is the smallest protozoa?



Replies:
There are about 200,000 living species of protists. This is approximate because scientists do not agree on exactly what organisms should be classified as protists, and because all species have not been found yet. I don't know about poisonous ones except for a type called a dinoflagellate that causes the famous "red tide". It can kill fish when it is present in large numbers, and if eaten by clams and other shellfish, it can poison people who eat the shellfish. Protists capture their food in many ways. Some, like the ameba, surround it with their cell membranes. Other, like the paramecium, have a permanent groove in their membrane, and sweep food into it with little hairs called cilia. Digestion is inside the single cell, not inside a gut (which is actually outside your body if you think about it) like more advanced animals. I don't know sizes well enough to answer your last two questions. I checked all this information (most of which was in my head) in a college biology textbook called "Biology" by Solomon et al.

-ProfBill



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