1. Penguins

At first sight, penguins seem ill-suited to their environment - rotund abdomens, stubby little legs and stiff wings appear to make the going tough. But in fact it is these very traits that enable this bird to thrive. Chris explores details of the penguin's anatomy, using new scientific research to reveal how its legs, wings and body shape have allowed it to conquer an extraordinary range of habitats, from deep forests to tropical waters, bustling cities and even the toughest place on the planet - Antarctica.