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There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
Dogs have been used in studies to detect various cancers in human subjects. They have been trained to sniff breath samples from humans that were collected by having them breathe into special tubes. These people included 55 lung cancer patients, 31 breast cancer patients, and 83 cancer-free patients. The dogs detected 54 of the 55 lung cancer patients as having cancer, detected 28 of the 31 breast cancer patients, and gave only three false-positive results (detecting cancer in people who didn't have it).
The strongest synthetic topical retinoid drug available, tazarotene, is used to treat sun-damaged skin, acne, and psoriasis.
Sperm cells are so tiny that 400 to 500 million (400,000,000–500,000,000) of them fit onto 1 tsp.
Hyperthyroidism leads to an increased rate of metabolism and affects about 1% of women but only 0.1% of men. For most people, this increased metabolic rate causes the thyroid gland to become enlarged (known as a goiter).