You encounter someone who has never heard of evolution, and they ask you about a population of ducks that live in their grandmothers pond. They tell you that 10 years ago the pong had both large eyed ducks and small eyed ducks. But one day 2 of the large eyed ducks were killed by some wild dogs. Now, the population of ducks has entirely small eyed. Identify the mechanism of change in the duck scenario and use it as evidence to explain evaluation to that person.