Ep 4. A Multitude of Mollusks

Invertebrates are among the most varied, and oldest, living organisms. Mollusks are among the oldest living organisms, their fossils dating back 600 million years. And to this day, wherever there's water -- fresh or salty -- you'll find at least one of these fascinating Invertebrates. The second largest group in the Animal Kingdom, they come in a wide variety of sizes, shapes, and surroundings, from high-mountain Snail to deep-ocean Squid.