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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.
Approximately 70% of expectant mothers report experiencing some symptoms of morning sickness during the first trimester of pregnancy.
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.
The highest suicide rate in the United States is among people ages 65 years and older. Almost 15% of people in this age group commit suicide every year.
Hippocrates noted that blood separates into four differently colored liquids when removed from the body and examined: a pure red liquid mixed with white liquid material with a yellow-colored froth at the top and a black substance that settles underneath; he named these the four humors (for blood, phlegm, yellow bile, and black bile).
![Addition of mineral nutrients to the boreal forest can have different effects on different plant spe](https://biology-forums.com/gallery/47/medium_33_17_02_12_6_59_59_2025844.jpeg)
![(a) Feeding by bear on salmon results in large allochthonous inputs of nutrients into (b) the forest](https://biology-forums.com/gallery/47/medium_33_17_02_12_7_02_16_2035460.jpeg)