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a special kind of biological identification key which consists of sets of organised pairs of statements, descriptions or choices about features or structures that the organism may or may not have.
a hormone produced by the adrenal glands which helps to maintain the balance of sodium in the...
substances that have a harmful effect on the environment and also on human health.
a molecule that accelerates (speeds up) a chemical reaction, by lowering its activation energy,...
a collection of tissues joined in a structural unit to serve a common function.