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Author Question: The World Health Organization estimates that there are ____ acts of sexual intercourse occurring ... (Read 78 times) |
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 are over 65,000 known species of protozoa. About 10,000 species are parasitic.
To prove that stomach ulcers were caused by bacteria and not by stress, a researcher consumed an entire laboratory beaker full of bacterial culture. After this, he did indeed develop stomach ulcers, and won the Nobel Prize for his discovery.
Bacteria have flourished on the earth for over three billion years. They were the first life forms on the planet.
Not getting enough sleep can greatly weaken the immune system. Lack of sleep makes you more likely to catch a cold, or more difficult to fight off an infection.