Natural selection leads to the evolution of new traits. In this educational video, see how stickleback fish have adapted to live permanently in freshwater environments. Explore a case study of natural selection with this classroom-ready biology video.

Though stickleback fish once lived in the ocean, some populations now thrive in freshwater environments. This change resulted in drastic physical transformations. Explore topics in gene expression and adaptation in this fascinating short film.

Free classroom resources supporting this short film can be found at http://www.hhmi.org/biointeractive/making-fittest-evolving-switches-evolving-bodies