Today, we're going to talk about one of the earliest animal senses, one that every life form we've ever found seems to have -- chemosensation -- or our sense of taste and smell. We'll discuss how animals use these senses to explore their environment and communicate, and how that pair of nostrils of yours is an example of convergent evolution. Also, before we wrap up our discussion of animal senses we're going to talk about a couple so specialized that seem straight from the pages of comic books -- the ability to sense electric and magnetic fields!