What is natural selection and how does it work? Life processes - Living things in their environments - Evolution Learning Points Genes are passed down from both parents to their young during reproduction. A mutation is a change in genes. Natural selection is the process by which a characteristic that was once rare becomes common. A Twig Curriculum Film. Delivering key learning points. Get straight to the facts in just three minutes – directly linked to core learning, Twig's curriculum films will fit neatly into your lesson plans.