Final answer:
The APOB gene in polar bears is under strong selection due to the bear’s specialized diet mainly consisting of seals, which are rich in fats and cholesterol. This gene helps polar bears to efficiently process dietary fats, essential for their survival in the harsh Arctic environment. The gene's evolution is an excellent example of natural selection, highlighting the match between an organism's traits and its eco-geographical needs.
Step-by-step explanation:
The APOB gene in polar bears encodes a protein that is crucial for binding to cholesterol, which is a vital part of the polar bear's diet. The gene has undergone strong selection due to the specialized diet of polar bears, which primarily consists of seals.
Seals provide a rich source of fat and cholesterol, and an efficient system to handle dietary fat is essential for polar bears to survive in the Arctic, where they are top predators. This adaptation is more about their dietary requirements for survival in the extreme conditions of the Arctic, rather than camouflage, competing with brown bears, or the ability to dive.
The mutation in the APOB gene can be compared to other genetic adaptations in different species. Tibetan populations, for instance, have a mutation in the EPAS1 gene, which affects lactic acid concentrations, and the PPARA gene mutation involves fatty acid production during hibernation. These adaptations illustrate how mutations can be beneficial in particular environments. For polar bears, the APOB gene mutation fits their dietary habits, which in turn are influenced by their environment and the availability of prey such as seals on the sea ice.
The evolution of such traits is an example of natural selection, where certain characteristics that offer a survival advantage become more common in a population over time. In the context of polar bears, the APOB gene plays a significant role in maintaining their health and survival in the cold climate, by ensuring they can utilize the fat from their prey effectively. This also highlights the importance of sea ice for polar bears, as the melting of sea ice due to climate change could have devastating effects on their primary food source, pushing them towards extinction.