Evolution of the Polar Bear

Ursidae is a young family, evolving from early canids during the late Oligocene and early Miocene epochs, about 20-25 million years ago. The phylogenetic tree as shown on the power point shows the evolutionary and ancestry relationships among the different bear species.   I am going to talk to you today about four of the different species that were discovered before they eventually evolved into what we know today as the polar bear. These five species include Miacids, Cephalogale, Ursus elemensis, Ursus Minimis and Ursus Etruscus. The polar bear has adapted and evolved accordingly to the many selection pressures it has encountered. The Sea ice of the Arctic Ocean and the connected frozen seas is home to the largest and most predatory of the bear family (action bioscience, 2011)
At the bottom of the phylogenetic tree you will see that we have to look back to the Eocene epoch. Throughout the Eocene epoch, climate worldwide was generally warm or mild this type of weather permitted moist mild forests to extent all over the world.   During the mid- period of the Eocene epoch, cooling began and temperatures decreased this caused the once temperate forests to then be replaced by deciduous trees.   As you can see the Eocene epoch was approximately 56 million years ago, Miacids were the first species in the polar bear family they are believed to be the size of your typical house cat but some scientists have discovered that some Miacids were the size of modern day wolves.   Some of the Miacids features include their long small bodies this is a useful making it easier for them to move through the trees.   Another feature of the Miacids is its long retractile claws these claws enabled them to sustain their grip and balance in order to effortlessly manoeuvre themselves above the branches and trees.   Some Miacids were arboreal this is another reason why the claws were an excellent feature and some lived on the ground.   As trees and vegetation were essential parts of the Miacids...