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There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
If all the neurons in the human body were lined up, they would stretch more than 600 miles.
Asthma cases in Americans are about 75% higher today than they were in 1980.
For about 100 years, scientists thought that peptic ulcers were caused by stress, spicy food, and alcohol. Later, researchers added stomach acid to the list of causes and began treating ulcers with antacids. Now it is known that peptic ulcers are predominantly caused by Helicobacter pylori, a spiral-shaped bacterium that normally exist in the stomach.
It is believed that humans initially contracted crabs from gorillas about 3 million years ago from either sleeping in gorilla nests or eating the apes.