Habitat is related to Nest. Nest is related to Building. Building can be used for Shelter. Apartment can be used for Shelter. 
Add is etymologically related to Do. Add is a synonym of Enroll. Enroll is related to Join. 
Habitat <--RelatedTo--> Nest <--RelatedTo--> Building --UsedFor--> Shelter <--UsedFor-- Apartment 
Do <--EtymologicallyRelatedTo-- Add <--Synonym--> Enroll <--RelatedTo--> Join 