Watch The Shape of Life Season 1 Episode 2 Online

When we think of animals, we think of movement. Surprisingly, the diverse and graceful ballet of animal movement may have started with cnidarians, a group that includes corals, sea anemones, sea pens and jellyfish. All of these animals, with few exceptions, have nerves and muscles. Because cnidarians are the simplest animals to possess this complexity, their direct ancestors were very likely the first animals to bundle the power of nerves and muscles together, enabling them to move and exhibit discernible behavior.