Final answer:
Purifying selection, or negative selection, is a process that removes harmful mutations from a population. There is evidence for purifying selection at the molecular level, such as the conservation of genes and the presence of genetic diseases caused by harmful mutations.
Step-by-step explanation:
Yes, there is evidence for purifying selection at the molecular level. Purifying selection, also known as negative selection, occurs when deleterious mutations are removed from a population. It helps to maintain the functional integrity of genes and the fitness of individuals. One example of evidence for purifying selection is the conservation of certain genes or protein sequences across different species, indicating that changes in those sequences are detrimental and selected against. Another example is the presence of genetic diseases caused by harmful mutations, which are often maintained at low frequencies in populations due to purifying selection.