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Liz Bonnin presents a controversial and provocative episode of Horizon, investigating how new scientific research is raising hard questions about zoos - the film explores how and why zoos keep animals, and whether they need to change to keep up with modern science or ultimately be consigned to history.Should zoos cull their animals to manage populations? Liz travels to Copenhagen Zoo, who killed a giraffe and fed it to the lions, to witness their culling process first hand. They think it is a natural part of zoo keeping that is often swept under the carpet. Should some animals never be kept in captivity? In a world exclusive, Liz visits SeaWorld in Florida and asks if captivity drove one of their orcas to kill his trainer.But could zoos be the answer to conserving endangered species? Liz examines their record, from helping breed pandas for the wild to efforts to save the rhinos. She meets one of the last surviving northern white rhinos and discovers the future of this species now lies in a multimillion-dollar programme to engineer them from stem cells. Veteran conservation scientist Dr Sarah Bexell tells Liz the science of captive breeding is giving humanity false hope.每走过一处，那里必然一片鸡飞狗跳。这一路走来，越国的风土人情倒还是其次，其国力强盛，百姓生活富足都是可以看出来的。What is the legendary Sous Vide刘邦稳定心神，略微沉思之后，点头道：嗯，尽管越军短时间内不会有什么大动作，但是我们的防备还是要做好，就这样做吧。Random medicine above mushroom for heartbeat acceleration这下三人更奇怪了：到底是谁，有这样大的威风。