Does the educational mission of zoos justify captivity, culling, and public dissection of animals?

The issue of keeping animals in captivity was recently in the news with the announcement of the last performance of Ringling Bros. and Barnum & Bailey Circus this May. While many applaud the announcement, the future of the captive animals is in question. In a related story, The New Yorker featured in its January 16, 2017 issue the shooting and public dissection of a healthy young giraffe named Marius at the Odense Zoo in Denmark last year.