Final answer:
Natural selection leads to the survival and reproduction of organisms with favorable traits, causing evolutionary changes in populations. It operates based on the inheritance of traits, variational survival and reproduction rates, and is limited to selecting existing genetic traits, not creating new ones.
Step-by-step explanation:
Natural selection is the process by which organisms with traits that better enable them to adapt to their environment tend to survive and reproduce in greater numbers. This fundamental concept explains evolution as a result of differences in survival and reproduction of individuals within a population. Over time, these advantageous inheritable traits become more common in the population, leading to evolutionary change. Natural selection acts on phenotypes, allowing those with favorable traits to have a higher chance of survival and reproduction.
Despite being a significant driving force in evolution, natural selection is limited by the population's existing genetic variation and new alleles introduced through mutation and gene flow. It doesn't create traits; it selects for those that are advantageous within the current environment. Therefore, while natural selection can lead to populations that are better adapted, it does not produce perfect organisms.
Charles Darwin identified three principles as the basis for natural selection: inheritance of traits, production of more offspring than can survive, and variation in traits which affects survival and reproduction. As a result, natural selection results in greater adaptation of the population to its local environment and is recognized as the only mechanism known for adaptive evolution.