Both of these topics are probably most effective and useful when presented very early in the biology course. Science deals only with natural patterns and mechanisms. Understanding science enables one to differentiate it from pseudoscience and non- science. Scientific knowledge is uncertain, tentative and subject to revision. Scientific explanations and interpretations can neither be proven nor disproven with certainty.
Scientists use a variety of criteria to compare explanations and select the better ones.
Several independent lines of evidence confirm that the earth is billions of years old. The Second Law of Thermodynamics applies to whole systems rather than to their parts. The scientific view of the origin of life on earth is that it did not involve supernatural processes. Currently scientists assume that life will originate under appropriate geochemical conditions. The origins of DNA and the genetic code remains a puzzle.