There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
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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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Since 1988, the CDC has reported a 99% reduction in bacterial meningitis caused by Haemophilus influenzae, due to the introduction of the vaccine against it.
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Opium has influenced much of the world's most popular literature. The following authors were all opium users, of varying degrees: Lewis Carroll, Charles, Dickens, Arthur Conan Doyle, and Oscar Wilde.
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The familiar sounds of your heart are made by the heart's valves as they open and close.
Parallel Light Rays from Distant Objects
back of neck diagram
Interactions of Light and Matter
Testing Back Pressure with a Pressure Gauge
Sensitive areas of the hand
A thin cleft, called the synapse, separates one cell from another.