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Liver spots have nothing whatsoever to do with the liver. They are a type of freckles commonly seen in older adults who have been out in the sun without sufficient sunscreen.
Approximately one in three babies in the United States is now delivered by cesarean section. The number of cesarean sections in the United States has risen 46% since 1996.
There are 20 feet of blood vessels in each square inch of human skin.
Sperm cells are so tiny that 400 to 500 million (400,000,000–500,000,000) of them fit onto 1 tsp.
Hippocrates noted that blood separates into four differently colored liquids when removed from the body and examined: a pure red liquid mixed with white liquid material with a yellow-colored froth at the top and a black substance that settles underneath; he named these the four humors (for blood, phlegm, yellow bile, and black bile).
![The sexual cycle of flowering plants involves alternation of sporophyte and gametophyte generations.](https://biology-forums.com/gallery/47/medium_33_24_07_11_10_29_04.jpeg)
![Defensive mutualism involves species that receive food or shelter in return for providing protection](https://biology-forums.com/gallery/47/medium_33_02_08_11_9_30_09_14152242.jpeg)