Why white bears do not live in Antarctica, but penguins – in the Arctic?
If in a nutshell: so historically developed. If more, you will have to turn to the evolution of these two groups.
The fact is that modern bears have European roots. In the distant times in the territory of the current Europe, the ancestors of the bears, who, settle down, adapted to new conditions and subsequently gave rise to modern species. Moreover, those that have mastered the harsh northern latitudes, developed in the direction of increasing the size, increased predation, adaptation to low temperatures. As an example – brown and white bears.
Those who mastered the southern latitudes, on the contrary, became greater degree of vegetable and insectivorous thermal-loving animals of small size: spectacle, Malay Bears, big panda. Thus, during the development of bearish northern territories, the White Bear was in the Arctic.

The story of penguins was different. Their ancestors originally dwell on the coasts of Antarctic, which at that time was not covered with ice. As a result of climate change, the fluttering seabirds evolved, adapting to increasingly low temperatures. As a result, Penguins avoid high temperatures, so in tropical latitudes appear only with cold currents.
Thus, the following picture. The bears ended to the southern latitudes were thermal-loving consumers of plant and petty animal foods, preferring to keep trees, so they did not advance the south of mountain forests of the Western And Malaya archipelago. White – stayed in the Arctic. And the penguins became hostages of cold currents, and the northernmost point of their distribution are the Galapagos Islands ".
