This episode details the relationship between flowers and insects. There are some one million classified species of insect, and two or three times as many that are yet to be labelled. Around 300 million years ago, plants began to enlist insects to help with their reproduction, and they did so with flowers. Although the magnolia, for instance, contains male and female cells, pollination from another plant is preferable as it ensures greater variation and thus evolution. Flowers advertise themselves by either scent or display. Some evolved to produce sweet-smelling nectar and in turn, several insects developed their mouth parts into feeding tubes in order to reach it.
In the wild North Atlantic, massive whale pods, giant turtles and monstrous jellyfish ride the Gulf Stream, a huge ocean current that becomes a migration superhighway and helps warm northern Europe. Meanwhile, fishermen battle for survival in mountainous seas as they try to reap the current's natural fertility.
First transmitted in 1965. David Attenborough continues his journey along the Zambezi River. This episode begins at Victoria Falls, the largest waterfall in the world. At the foot of the falls, with its moist climate, a wealth of plants and animals can be found, such as hyraxes. To coax the hyraxes out of hiding, David Attenborough illustrates why taking a dog whistle with you while on an African adventure is a very good idea indeed. Other highlights encountered on the way include an estivating lungfish and a herd of elephants washing and dust bathing at a water hole.Further along his journey David Attenborough explores a Portuguese fortress at Tete, believed to have been built over 400 years ago, and assesses the impact of the then newly constructed Kariba Dam, one of the largest dams in the world, on the displaced Tonga people and surrounding countryside.