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There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
The heart is located in the center of the chest, with part of it tipped slightly so that it taps against the left side of the chest.
Astigmatism is the most common vision problem. It may accompany nearsightedness or farsightedness. It is usually caused by an irregularly shaped cornea, but sometimes it is the result of an irregularly shaped lens. Either type can be corrected by eyeglasses, contact lenses, or refractive surgery.
Asthma cases in Americans are about 75% higher today than they were in 1980.
Amoebae are the simplest type of protozoans, and are characterized by a feeding and dividing trophozoite stage that moves by temporary extensions called pseudopodia or false feet.