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Bacteria have flourished on the earth for over three billion years. They were the first life forms on the planet.
After a vasectomy, it takes about 12 ejaculations to clear out sperm that were already beyond the blocked area.
About 3% of all pregnant women will give birth to twins, which is an increase in rate of nearly 60% since the early 1980s.
There are major differences in the metabolism of morphine and the illegal drug heroin. Morphine mostly produces its CNS effects through m-receptors, and at k- and d-receptors. Heroin has a slight affinity for opiate receptors. Most of its actions are due to metabolism to active metabolites (6-acetylmorphine, morphine, and morphine-6-glucuronide).
Cancer has been around as long as humankind, but only in the second half of the twentieth century did the number of cancer cases explode.