View full lesson: http://ed.ted.com/lessons/jellyfish-predate-dinosaurs-how-have-they-survived-so-long-david-gruber Some are longer than a blue whale. Others are barely larger than a grain of sand. One species unleashes one of the most deadly venoms on earth; another holds a secret that’s behind some of the greatest breakthroughs in biology. They’ve inhabited the ocean for at least half a billion years, and they’re still flourishing. David Gruber investigates the secret powers of jellyfish. Lesson by David Gruber, animation by Silvia Prietov.