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Author Question: The upstream part of a stream profile usually has a steeper gradient than the downstream part. ... (Read 33 times) |
Bacteria have flourished on the earth for over three billion years. They were the first life forms on the planet.
Egg cells are about the size of a grain of sand. They are formed inside of a female's ovaries before she is even born.
As the western states of America were settled, pioneers often had to drink rancid water from ponds and other sources. This often resulted in chronic diarrhea, causing many cases of dehydration and death that could have been avoided if clean water had been available.
Giardia is one of the most common intestinal parasites worldwide, and infects up to 20% of the world population, mostly in poorer countries with inadequate sanitation. Infections are most common in children, though chronic Giardia is more common in adults.
There are approximately 3 million unintended pregnancies in the United States each year.