Final answer:
Natural selection is the process by which natural factors select for the most adaptive traits. It occurs when individuals with inherited traits that allow them to better compete for limited resources survive and reproduce, leading to the representation of these traits in the next generation.
Step-by-step explanation:
Natural selection, as proposed by Charles Darwin, is the process by which natural factors select for the most adaptive traits. Darwin argued that this is an inevitable outcome of three principles: variation in traits among individuals, limited resources for survival and reproduction, and competition for those resources. Offspring with inherited traits that allow them to better compete for limited resources will survive and have more offspring, leading to the representation of these traits in the next generation and causing populations to evolve over time. This process is known as descent with modification and is the only mechanism known for adaptive evolution.