This episode of the documentary series focuses on the new giants, the heavyweights of the dinosaur world. It is only in recent years that experts have unearthed the biggest dinosaurs that ever lived. One monster eclipsed all others; more than seven times as heavy as diplodocus was the immense argentinosaurus - a single backbone was bigger than a human. For years, these giants were considered immune to attack from any predator - until the discovery of mapusaurus, a new giant killer whose fate appeared to be inextricably linked to argentinosaurus

In the Land of the Cave Bear, Alice ventures to the parts of the northern hemisphere, hit hardest by the cold - Europe and Siberia. High in the mountains of Transylvania, a cave sealed for thousands of years reveals grisly evidence for a fight to the death between two staving giants, a cave bear and a cave lion. Yet Alice discovers that for woolly rhinos and woolly mammoths, the Ice Age created a bounty. The Mammoth Steppe, a vast tract of land which went half way round the world, provided food all year round, for those that liked the cold. It was these mammoths that Europe's most dangerous predators hunted for their survival.

The plant eaters take on the largely indigestible, spiny and poisonous defences of plants with some spectacular physical adaptations to diet. Plant Predators demonstrates the particular (and often peculiar) adaptations of herbivores

The second episode is about how plants gain their sustenance. Sunlight is one of the essential requirements if a seed is to germinate, and Attenborough highlights the cheese plant as an example whose young shoots head for the nearest tree trunk and then climb to the top of the forest canopy, developing its leaves en route. Using sunshine, air, water and a few minerals, the leaves are, in effect, the "factories" that produce food. However, some, such as the begonia, can thrive without much light. To gain moisture, plants typically use their roots to probe underground. Trees pump water up pipes that run inside their trunks, and Attenborough observes that a sycamore can do this at the rate of 450 litres an hour — in total silence. Too much rainfall can clog up a leaf's pores, and many have specially designed 'gutters' to cope with it. However, their biggest threat is from animals, and some require extreme methods of defence, such as spines, camouflage, or poison. Some can move quickly to deter predators: the mimosa can fold its leaves instantly when touched, and the Venus flytrap eats insects by closing its leaves around its prey when triggered. Another carnivorous plant is the trumpet pitcher that snares insects when they fall into its tubular leaves. Attenborough visits Borneo to see the largest pitcher of them all, Nepenthes rajah, whose traps contain up to two litres of water and have been known to kill small rodents.

The first episode looks at how birds first took to the skies in the wake of the insects. It begins in Mexico, where Sir Attenborough observes bats being outmanoeuvred by a red-tailed hawk. Pterosaurs were the birds' forerunners, some 150 million years after dragonflies developed the means of flight, but eventually went extinct together with the dinosaurs. Birds had by then already evolved from early forms like archaeopteryx, the first creature to possess feathers. Its ancestry can be traced through reptiles, and some current species, such as the flying lizard, possibly show paths this evolution may have taken." One of the biggest birds to have ever existed was the terror bird, which proliferated after dinosaurs vanished and stood up to 2.5 metres tall. By comparison, the ostrich, while not closely related, is the largest and heaviest living bird. It was probably the evasion of predators that drove most birds into the air, so their flightless cousins evolved because they had few enemies. Accordingly, such species are more likely to be found on islands, and Sir Attenborough visits New Zealand to observe its great variety, most especially the kiwi. Also depicted is the moa, another huge creature that is now gone. The takahē is extremely rare, and high in the mountains of New Zealand, Sir Attenborough discovers one from a population of only 40 pairs. Finally, another example on the brink of extinction is the kakapo, which at one point numbered only 61 individuals. A male is heard calling — an immensely amplified deep note that can be heard at great distances from its nest.