Did you know that you and I are only 1% human — we've 90 trillion cells which don't belong to us. Yes we are more bacteria than human.
This episode is devoted to the evolution of reptiles. They are not as restricted as their amphibian ancestors, since they can survive in the hottest climates. The reason is their scaly, practically watertight skin. The scales protect the body from wear and tear and in the case of some species of lizard, such as the Australian thorny devil, serve to protect from attack. The horned iguana from the West Indies is also one of the most heavily armoured. The skin is rich in pigment cells, which provide effective means of camouflage, and the chameleon is a well-known example. Temperature control is important to reptiles: they cant generate body heat internally or sweat to keep cool.
Humans, octopi and pine trees alike are all made up of cells, tiny but sophisticated systems that keep life going. Cells are almost like tiny factories run by robots, with the nucleus, DNA, proteins, lipids, and vitamins and minerals all playing critical roles. George Zaidan and Charles Morton lay out the blueprint of a cell and explain how biochemistry binds all life together.
The first programme shows how sharks are the ocean's great predators, living in every ocean and hunting in every way. Blacktip sharks hunt in huge packs and herd fish into baitballs, tasselled wobbegongs are ambush hunters, Greenland sharks live under the arctic ice, and whitetip reef sharks are the masters of hunting at night. The finale shows the great white in its hunt for fur seals off the coast of South Africa.
The journey begins on the Galapagos' west side at the youngest and most volcanically active islands in the archipelago, Isabela and Fernandina, which are home to a richly diverse wildlife scene. Here, Liz and the team journey into the clouds above Wolf, the tallest volcano in the Galapagos, where they join a group of biologists hunting for the elusive pink iguana, which teeters on the edge of extinction. But how and why did it come to live on the top of a volcano? Back on the research vessel, Liz boards Alucia's Triton submersible to descend a kilometre into the ocean abyss in search of a new species hiding in the darkness. Liz also travels to one of the most remote locations in the Galapagos, Alcedo Volcano, in search of the largest population of giant tortoises. Plagued by drought in recent months, scientists are keen to find out how this prehistoric species has fared. Finally, Liz helps out with a groundbreaking science experiment to x-ray marine iguanas that have so far stunned the scientific community with a new mutation. As with all life on these remote islands, the key to survival is adaptation.