Complex sentence: Competition is a negative affect that happens when two or more organisms attempt to directly use the same resource, allelopathy, on the other hand differs by indirectly affecting other organism after the input of substances into the environment.
Split into simpler sentences: Competition is a negative effect which presents when two or more organisms attempt to directly use the same resource. Allelopathy, on the other hand differs by indirectly affecting other organisms after the input of substances into the environment.