Only 12 hours after an egg cell is fertilized by a sperm cell, the egg cell starts to divide. As it continues to divide, it moves along the fallopian tube toward the uterus at about 1 inch per day.
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In the United States, there is a birth every 8 seconds, according to the U.S. Census Bureau's Population Clock.
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Illicit drug use costs the United States approximately $181 billion every year.
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There are 20 feet of blood vessels in each square inch of human skin.
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Immunoglobulin injections may give short-term protection against, or reduce severity of certain diseases. They help people who have an inherited problem making their own antibodies, or those who are having certain types of cancer treatments.
Three ways that factors affect mortality in response to changes in population density.