The graph illustrates how organisms maintain or change their internal environment in response to external levels of abiotic factors. The standard labels are:

(I): Conformers – Their internal environment changes directly with the external environment (represented by the diagonal line).

(II): Regulators – They maintain a constant internal environment regardless of external changes (represented by the horizontal flat line).

(III): Partial regulators – They regulate their internal environment over a limited range, beyond which they simply conform (represented by the line that stays flat for a while before curving).

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