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The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
The Babylonians wrote numbers in a system that used 60 as the base value rather than the number 10. They did not have a symbol for "zero."
Autoimmune diseases occur when the immune system destroys its own healthy tissues. When this occurs, white blood cells cannot distinguish between pathogens and normal cells.
There can actually be a 25-hour time difference between certain locations in the world. The International Date Line passes between the islands of Samoa and American Samoa. It is not a straight line, but "zig-zags" around various island chains. Therefore, Samoa and nearby islands have one date, while American Samoa and nearby islands are one day behind. Daylight saving time is used in some islands, but not in others—further shifting the hours out of sync with natural time.
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.
![Competition can be (a) direct, or (b) indirect interaction among individuals of the same or differen](https://biology-forums.com/gallery/47/medium_33_17_02_12_5_28_58_19442225.jpeg)
![Simple food web of an Arctic island. NOTE: The indication of detritivores and pathogens was not part](https://biology-forums.com/gallery/47/medium_33_17_02_12_5_42_58_20001060.jpeg)