Planet Earth - Episode 11 (Ocean Deep) (ATOM Study Guide)

Planet Earth is a BBC production with five episodes in the first series (episodes one through five) and six episodes in the second series (episodes six through eleven). Each episode examines a specific environment, focussing on key species or relationships in each habitat; the challenges they face; the behaviours they exhibit and the adaptations that enable them to survive. Recent advances in photography are used to achieve some spectacular 'first sights' – in particular, stabilised aerial photography gives us remarkable views of migrating animals and the techniques used by their predators to hunt them.

As the series examines pristine environments where possible, they are often extreme. These are the parts of the world where few humans have chosen to live as the climate and landscape is too challenging, too difficult and dangerous. The plants and animals that do survive here have made some spectacular adaptations in forms and behaviour to live in these far reaches of the planet.

The series is suitable for middle secondary students studying Science and SOSE, and for senior secondary students of Biology, Environmental Science and Geography.

The deep oceans, the pelagic zone covers more than half our planet's surface and is one of the least explored areas. Much of it is simply an empty blackness but the upper reaches are a vital part of the earth's habitat and climatic systems and even the deepest, darkest zones hold some remarkable surprises.

We begin with the largest fish of all, the harmless whale shark that was almost unknown a few years ago but has now become a tourist spectacle in many places. It cruises the warm waters of the sub-tropical reefs, swallowing huge quantities of plankton and small fish, as does the manta ray, master of underwater flight. These are the great grazers of the ocean, scooping up the microscopic plants and some small animals too. True predators like the white tip shark are long distance hunters, cruising the vast reaches of the open ocean in the constant hunt for scarce food while large tribes of dolphins take a more proactive approach, herding their prey into tight bunches before they strike mercilessly.

But beneath the warm and sunlit waters of the surface lie unimaginable depths of dark, cold water. Some animals may dive down there hunting food but most of it is a high pressure desert, inhabited by strange beasts that live on whatever falls, dead, from the upper levels. These are highly specialised creatures, adapted to filter their food blindly from the downward drifting 'snow' or to hunt each other in the total dark above the great plains of sand and ooze. Like the vampire squid which can light up to confuse its predators or prey and the scavengers of the plains sifting out any organic particles from the ocean floor. Eventually even the giants die and the carcass of a huge sperm whale is slowly consumed by the scavengers of the abyss.

There are odd communities down here, discovered only in the last few years. Communities of strange worms and crustaceans that huddle around volcanic fissures on the ocean floor, outpourings of superheated water in so called 'black smokers'. The plumes of mineral rich hot water form huge chimneys and whole, unique ecosystems tread a fine line between that water venting at hundreds of degrees and the freezing deeps around them. These are contrasted with the great seamounts, undersea volcanoes that rise kilometres from the abyss to provide a platform for life. Some like Ascension Island in the Atlantic break the surface and create a special habitat for frigate birds and turtles. Finally we return to the ocean giants, creatures that could only live here with the limitless space and the support of the water. But this time it is the great blue whale, the largest animal ever to have lived on earth and now endangered more by the threats to its food source than hunting, as in the past.