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There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
Your skin wrinkles if you stay in the bathtub a long time because the outermost layer of skin (which consists of dead keratin) swells when it absorbs water. It is tightly attached to the skin below it, so it compensates for the increased area by wrinkling. This happens to the hands and feet because they have the thickest layer of dead keratin cells.
The most common treatment options for addiction include psychotherapy, support groups, and individual counseling.
In 1835 it was discovered that a disease of silkworms known as muscardine could be transferred from one silkworm to another, and was caused by a fungus.
The familiar sounds of your heart are made by the heart's valves as they open and close.