Final answer:
The excretions of living organisms are best categorized as 'biotic' factors.
Step-by-step explanation:
The excretions of living organisms are best categorized as biotic factors. Biotic factors refer to the living components of an ecosystem, including plants, animals, and microorganisms. Excretions, such as urine and feces, are produced by living organisms as waste products and contribute to the biotic interactions within an ecosystem.
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