The term which describes any relationship in which two species live closely together is called SYMBIOSIS.
Tryptophan self-controls its synthesis. If we have a large amount of tryptophan in the sense that it exceeds, tryptophan would act as a co-repressor which prevents synthesis of more enzymes for its production. Hope this answers the question.
<span>Defines cell shape= </span><span>cytoskeleton
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Hcg secreted by placenta not the fastest method to detect pregnancy nor it is specific