Final answer:
When a population becomes more weather resistant due to extreme temperatures affecting survival and reproduction, this is an example of natural selection, which leads to advantageous traits becoming more common in the next generation.
Step-by-step explanation:
If a population is subjected to extreme temperatures and, as a consequence, the next generation is more weather resistant, natural selection has occurred. Natural selection is a process where individuals with traits better suited to their environment have higher survival rates and reproductive success, leading to those traits becoming more common in subsequent generations. This notion is in contrast with genetic drift, which involves random changes in allele frequencies, particularly in small populations. It's also different from gene flow, which is the transfer of genetic variation from one population to another. Lastly, while mutation can introduce new genetic variation, it does not select for traits that might confer an advantage in certain environmental conditions.