Natural selection, a cornerstone of evolutionary biology, shapes the adaptations organisms develop to survive environmental pressures. This paper explores how natural selection drives biological adaptations to radiation exposure. We examine the genetic mechanisms at play, exemplified by the enhanced DNA repair capabilities observed in bacteria like Escherichia coli (E. coli) following exposure to radiation. We then investigate adaptations in humans residing in high-background radiation areas, highlighting potential genetic variations for radiation resistance. Finally, the contemporary relevance of natural selection is discussed, emphasizing its role in the emergence of antibiotic-resistant bacteria and the need for sustainable medical practices. By studying these adaptations, we gain a deeper understanding of evolution and its implications for medicine, conservation, and our overall understanding of life.