Define 'natural selection' in biology.

Natural selection is a fundamental mechanism of evolution, first articulated by Charles Darwin. It describes the process by which certain traits become more or less common within a population due to the reproductive success of organisms with those traits. In particular, it emphasizes that individuals who are better adapted to their environments are more likely to survive and reproduce, passing their advantageous traits onto the next generation.

In this context, the correct choice effectively captures the core idea of natural selection: that advantageous adaptations improve the likelihood of survival and reproductive success, leading to the gradual evolution of species over time. This aligns with the principle that, over generations, traits that confer a survival benefit will dominate a population as the less adapted individuals fail to thrive and reproduce as successfully.

The other options do not fully encompass the essence of natural selection. While random mating and adaptation to new environments may play roles in the broader context of evolution, they do not define natural selection itself. Similarly, focusing solely on extinction overlooks the positive aspect of survival and reproduction that is central to natural selection’s operation. The emphasis on the survival of the fittest is what fundamentally sets this process apart as a key driver of the diversity of life on Earth.