Plot Synopsis

Scientists reveal how animals have adapted to their strange surroundings, with each 30-minute episode focusing on a different environment: "Salt and Acid," showing how they manage to live in water as acid as vinegar or as alkaline as washing powder; "Heat," spotlighting how life has managed to develop between 122 and 248 degrees; "Cold," documenting how species manage to survive in environments as unstable as snow and ice with temperatures as low as -22; and "Darkness," chronicling how species survive with little oxygen, food and light in the most inhospitable caves on the planet.