Starting Materials: The Chemical Elements of Life
Around two dozen of the 92 naturally-occurring chemical elements are essential to various kinds of biological life. Most rare elements on Earth are not needed by life (exceptions being selenium and iodine), while a few common ones (aluminum and titanium) are not used. Most organisms share element needs, but there are a few differences between plants and animals. For example ocean algae use bromine but land plants and animals seem to need none. All animals require sodium, but some plants do not. Plants need boron and silicon, but animals may not (or may need ultra-small amounts).
Just six elements—carbon, hydrogen, nitrogen, oxygen, calcium, and phosphorus—make up almost 99% of the mass of a human body (see composition of the human body for a complete list). In addition to the six major elements that compose most of the human body, humans require smaller amounts of possibly 18 more.
Read more about this topic: Biochemistry
Famous quotes containing the words elements of life, starting, chemical, elements and/or life:
“But all subsists by elemental strife;
And Passions are the elements of Life.”
—Alexander Pope (1688–1744)
“A hook shot kisses the rim and
hangs there, helplessly, but doesn’t drop
and for once our gangly starting center
boxes out his man and times his jump
perfectly, gathering the orange leather
from the air like a cherished possession”
—Edward Hirsch (b. 1950)
“We do not want actions, but men; not a chemical drop of water, but rain; the spirit that sheds and showers actions, countless, endless actions.”
—Ralph Waldo Emerson (1803–1882)
“Let us have a fair field! This is all we ask, and we will be content with nothing less. The finger of evolution, which touches everything, is laid tenderly upon women. They have on their side all the elements of progress, and its spirit stirs within them. They are fighting, not for themselves alone, but for the future of humanity. Let them have a fair field!”
—Tennessee Claflin (1846–1923)
“To see self-sufficiency as the hallmark of maturity conveys a view of adult life that is at odds with the human condition, a view that cannot sustain the kinds of long-term commitments and involvements with other people that are necessary for raising and educating a child or for citizenship in a democratic society.”
—Carol Gilligan (20th century)