Which simple ecological concept best explains why resistant organisms can colonize after antibiotic therapy?

Antibiotics create magnetic gradients in mucosal surfaces that physically attract resistant organisms while repelling commensals, driving colonization by magnetotaxis.

Resistant organisms are always the fastest growing regardless of niche availability, so antibiotics have no role in shifting community composition by competition.

Removal of competitors opens unoccupied niche space and resources (competitive release), enabling resistant taxa to expand because they face less competition.

Antibiotics create new chemical energy in the gut that exclusively feeds resistant organisms and not commensals, producing colonization advantages unrelated to competition.