Final answer:
The APOB gene in polar bears is under strong selection due to their high-fat diet of seals, necessitating efficient cholesterol metabolism. White fur and thick blubber also contribute to their adaptation to the Arctic climate. These adaptations are examples of natural selection's influence on species survival in specific environments.
Step-by-step explanation:
The gene APOB in polar bears encodes a protein that is crucial for binding to cholesterol, which has undergone strong selection in the species due to their dietary needs. Polar bears primarily feed on seals, which are high in fat content, so efficient cholesterol metabolism is likely a vital adaptation for their survival. This adaptation helps polar bears maintain their energy requirements as top predators in the harsh Arctic environment where they live. Similarly, other species such as arctic foxes and rabbits have experienced selection for temperature-sensitive proteins that affect their fur coloration as an adaptation for camouflage in different seasons, and both the Tibetan population and hibernating species have exhibited genetic adaptations for survival in their respective environments.
Thick fur and a layer of blubber are other adaptations that help polar bears stay warm in the Arctic ecosystem, with white fur providing camouflage against the icy backdrop. Genetic adaptations are key to the survival of species in their respective habitats, and they illustrate the principles of natural selection as outlined by Charles Darwin's observations and our modern understanding of evolution. The changing environment, such as the melting of sea ice, also has implications for these adaptations and the survival of species like polar bears.