How do you explain the analogy used with a zoo in And Then There Were None?

In "And Then There Were None" by Agatha Christie, the analogy of the zoo is used to describe the guests on Soldier Island feeling trapped and manipulated, much like animals in a zoo. The guests are isolated on the island, under constant surveillance, and ultimately left to their fate by an unseen captor, mirroring the lack of control and captivity experienced by animals in a zoo setting.