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The lipid bilayer is made of phospholipids. They are arranged in a double layer because one of their ends is attracted to water while the other is repelled by water.
It is believed that the Incas used anesthesia. Evidence supports the theory that shamans chewed cocoa leaves and drilled holes into the heads of patients (letting evil spirits escape), spitting into the wounds they made. The mixture of cocaine, saliva, and resin numbed the site enough to allow hours of drilling.
Bacteria have flourished on the earth for over three billion years. They were the first life forms on the planet.
Congestive heart failure is a serious disorder that carries a reduced life expectancy. Heart failure is usually a chronic illness, and it may worsen with infection or other physical stressors.
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.
![Mutualisms, such as those that occur among plants and pollinators, generally involve large numbers o](https://biology-forums.com/gallery/47/medium_33_17_02_12_5_40_33_198392.jpeg)
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