Final answer:
Evolution by natural selection is Darwinian evolution, which explains how species adapt and change over time based on environmental pressures and genetic variations.
Step-by-step explanation:
Evolution by natural selection is Darwinian evolution. This concept, originally proposed by Charles Darwin and Alfred Russel Wallace, describes a mechanism by which species change over time. The idea is that not all members of a population can survive, but those who are most 'fit'—that is, most adapted to their environment—tend to survive and reproduce more effectively. Over time, this results in the population evolving, with heritable characteristics that provide a survival or reproduction advantage becoming more common in the population. Therefore, the correct answer to the question is 'b. Darwinian evolution'.