Primary metabolites are those which are essential for growth, development and reproduction of organisms, such as amino acids, sugars, nucleotides, etc. On the other hand, many secondary metabolites are not directly involved in these processes but they have ecological importance. They help the organisms in defense, signaling, competition and interactions with other organisms. Examples include alkaloids, pigments, essential oils, resins, gums and rubber. Hence, the metabolites that have ecological importance are only secondary metabolites.

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