Life in the Undergrowth - Invasion of the Land ()

Synopsis:
The documentary tells how invertebrates became the first creatures of any kind to colonise dry land. Their forerunners were shelled and segmented sea creatures that existed 400 million years ago. Some of them ventured out of the water to lay their eggs in safety, and Attenborough compares those first steps with today's mass spawning of horseshoe crabs off the Atlantic coast of North America. The oceans were abandoned altogether when the land became green with algae, mosses and liverworts. The earliest ground-dwellers were millipedes, which were quickly followed by other species. Springtails are shown to be smaller than the head of a pin and, for their size, can jump immense heights. The velvet worm hunts nocturnally and has scarcely changed over millennia, while the giant centipede can kill instantly and is shown hunting bats in Venezuela. Mating habits are explored, including the unusual ritual of leopard slugs and the meticulous nest maintenance of the harvestman. The arrival of earthworms was of great importance since they changed the nature of the soil, leading to a proliferation of plant life. Despite their aquatic ancestry, many invertebrates, particularly with those with no exoskeleton, need a moist environment to keep themselves from drying out. Finally, a creature that has adapted to a desert habitat, the scorpion, is shown as it pursues its dangerous courting dance, followed by the birth of up to fifty individuals.
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