Researcher is a type of Worker. Slave is a type of Worker. Slave is a type of Work. Work is related to Experiment. 
Crowd is related to Excessive. Excessive is the opposite of Conservation. Conservation is related to Nature. 
Researcher --IsA--> Worker <--IsA-- Slave --IsA--> Work <--RelatedTo--> Experiment 
Crowd <--RelatedTo--> Excessive <--Antonym--> Conservation <--RelatedTo--> Nature 