Inside the blue whale
With the help of computer graphics, David Attenborough gets right inside the body of the blue whale to show off its amazing mammalian anatomy. Housed in a vast rib cage, its lungs can carry 2,000 litres of air - 500 times the human capacity. A heart the size of a small family car beats 5 or 6 times a minute and drives 10 tonnes of blood through a million miles of blood vessels. All that's left of the back legs are two isolated hip bones buried in a mountain of muscle. David Attenborough rides on a boat next to a whale as it breaches and he remarks that no animal of this size could survive on land as no bone is strong enough to support such huge bulk out of the water. The blue whale has the ability to store oxygen within the tissues of its body as well as in its blood, allowing it to stay underwater without breathing for half an hour or more. It has a thick layer of blubber, in some places 20 inches thick, which helps to insulate it from the chill of the deep water. It collects food wholesale, taking in a tonne of krill-filled water with one sideways gulp. The blue whale's shape is near-perfectly hydrodynamic, uninterrupted by hind limbs, ears or genitals. As it tilts its 100 tonne bulk downwards from the surface of the water, the whale plunges to the black world 500 feet or more below the surface.