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Bacteria have flourished on the earth for over three billion years. They were the first life forms on the planet.
A cataract is a clouding of the eyes' natural lens. As we age, some clouding of the lens may occur. The first sign of a cataract is usually blurry vision. Although glasses and other visual aids may at first help a person with cataracts, surgery may become inevitable. Cataract surgery is very successful in restoring vision, and it is the most frequently performed surgery in the United States.
Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.
Green tea is able to stop the scent of garlic or onion from causing bad breath.
The familiar sounds of your heart are made by the heart's valves as they open and close.
![In the summer of 1793, a yellow fever epidemic struck Philadelphia, killing nearly 4,000. Tens of th](https://biology-forums.com/gallery/47/medium_374628_16_08_15_9_52_07_222511109.jpeg)
![Pressure testing the cooling system. A typical hand-operated pressure tester applies pressure equal ...](https://biology-forums.com/gallery/29/medium_548020_29_05_17_11_20_04_295761956.png)