Metabolic Waste
Metabolic wastes or excretes are substances left over from excretory processes, which cannot be used by the organism (they are surplus or have lethal effect), and must therefore be excreted. This includes nitrogen compounds, water, CO2, phosphates, sulfates, etc. Animals treat these compounds as excretes. Plants have chemical "machinery" which transforms some of them (primarily the nitrogen compounds) into useful substances, and it has been shown by Brian J. Ford that abscissa leaves also carry wastes away from the parent plant. In this way, Ford argues that the shed leaf acts as an excretory (an organ carrying away excretory products).
All the metabolic wastes are excreted in a form of water solutes through the excretory organs (nephridia, Malpighian tubules, kidneys), with the exception of CO2, which is excreted together with the water vapor throughout the lungs. The elimination of these compounds enables the chemical homeostasis of the organism.
Read more about Metabolic Waste: Nitrogen Wastes, Water and Gases, Solids
Famous quotes containing the word waste:
“As they are not seen on their way down the streams, it is thought by fishermen that they never return, but waste away and die, clinging to rocks and stumps of trees for an indefinite period; a tragic feature in the scenery of the river bottoms worthy to be remembered with Shakespeare’s description of the sea-floor.”
—Henry David Thoreau (1817–1862)