Biology - Excretion
All living cells produce wastes  as a result of the chemical reactions
that occur within them.
For example, humans produce carbon dioxide when they respire. This waste
substance, along with others, needs to be removed from the cell as they
will become toxic. Excretion is the name of the process that removes wastes
from the organism. Whenever you breathe out carbon dioxide or urinate,
wastes are removed form the body. Plants also produce wastes and these need
to be removed.