an animal requires food & an animal requires shelter & if a living thing requires something then that something has a positive impact on that living thing ->  shelter and food have positive impact on animals  shelter and food have positive impact on animals & ants are a kind of animal ->  shelter and food have positive impact on ants  shelter and food have positive impact on ants & the acacia provides shelter and food for ants ->  the acacia providing shelter and food has a positive impact on ants  the ants protect the acacia by removing other insects and vines that might harm it & protecting a living thing has a positive impact on that living thing 's survival / health ->  the ants protecting the acacia has a positive impact on the acacia  the acacia providing shelter and food has a positive impact on ants & the ants protecting the acacia has a positive impact on the acacia & mutualism has a positive impact on both organisms in the relationship -> the relationship between the acacia and ants is mutualism