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Sperm cells are so tiny that 400 to 500 million (400,000,000–500,000,000) of them fit onto 1 tsp.
Egg cells are about the size of a grain of sand. They are formed inside of a female's ovaries before she is even born.
About 60% of newborn infants in the United States are jaundiced; that is, they look yellow. Kernicterus is a form of brain damage caused by excessive jaundice. When babies begin to be affected by excessive jaundice and begin to have brain damage, they become excessively lethargic.
An identified risk factor for osteoporosis is the intake of excessive amounts of vitamin A. Dietary intake of approximately double the recommended daily amount of vitamin A, by women, has been shown to reduce bone mineral density and increase the chances for hip fractures compared with women who consumed the recommended daily amount (or less) of vitamin A.
There are over 65,000 known species of protozoa. About 10,000 species are parasitic.