Ecosystem is a type of System. System is a type of Substance. Substance is related to Drug. Drug is related to Weed. 
you would Camp because Entertainment. Camp is the opposite of School. 
Ecosystem --IsA--> System --IsA--> Substance <--RelatedTo--> Drug <--RelatedTo--> Weed 
Entertainment <--MotivatedByGoal-- Camp <--Antonym--> School 