I have to disagree with Joanna. I don’t believe all animals have brains, only those animals with distinct body cavities possess brains. This includes life forms as diverse as earth worms, clams, fish, insects, birds, and of course, human beings. As a general rule, animals with more tissue types have more intricate brains. But for example jelly fish or starrish don’t have brains, instead they have a cluster of nerves that is called ganglia.