Answer: Understanding our fragile environment often begins with recognition of the importance of certain elements, such as zinc and iron, in relation to animals and plants. This recognition is well deserved because these essential elements are necessary for the life or health of an organism. Some elements such as carbon, hydrogen, oxygen, magnesium, potassium, and phosphorus are required in relatively large amounts by organisms. However, others are required in smaller quantities; these are referred to as trace elements. At the same time, if these or other elements occur in quantities great enough, toxicity can result. An element, or any substance, that occurs in the environment and contains concentrations above what are considered to be safe may be considered a contaminant. When contaminants occur at levels that are potentially harmful to organisms, they are labeled as hazards. Often the quantitative difference between essential amounts and toxic concentrations of these elements is very small. For example, the trace element selenium is required at a level of no less than 0.4 parts per million in the diet of cattle but can be toxic at levels greater than approximately 4 parts per million.
There are 15 essential elements to all animals and plants, these include:
Hydrogen(H)
Carbon (C)
Nitrogen (N)
Oxygen (O)
Sodium (Na)
Magnesium(Mg)
Phosphorus(P)
Sulfur(S)
Chlorine (C)
Potassium (K)
Calcium (Ca)
Manganese (Mn)
Iron (Fe)
Copper (Cu)
Zinc (Zn), and
Selenium (Se)
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U.S. Department of the Interior |
U.S. Geological Survey