In this episode of the renowned nature series, David Attenborough takes us on a journey to explore the evolution of sea-living invertebrates. Beginning in Morocco, the episode examines the 600 million-year-old limestone fossils that fall broadly into three categories: shells, crinoids, and segmented shells.
Attenborough demonstrates the evolution of shelled creatures through the flatworm, which eventually changed its body shape in response to the need for burrowing for food or safety. This evolution led to the development of shielded tentacles and the eventual envelopment of the entire body in casings, resulting in the creation of the brachiopods. The episode also delves into the most successful shelled animals, the mollusks, of which there are some 80,000 different species, including the cowrie, scallop, and giant clam.
The episode also explores the evolution of crinoids, illustrated by sea lilies, starfish, and sea urchins on the Great Barrier Reef, and segmented worms, exemplified by trilobites and crustaceans, as well as the horseshoe crab. The episode also highlights the unique characteristics of the nautilus, which has remained unchanged for millions of years, and the robber crab, which is a land animal in all respects except for breeding in the sea.
Attenborough’s expert narration and the stunning visuals transport the viewer to remote locations, immersing them in the world of sea-living invertebrates and their evolution. This episode is a must-watch for nature enthusiasts and anyone interested in learning about the natural world and the diversity of life on our planet.
