Jellyfish are a very primitive life form. It is thought that life first evolved in the oceans, near sea vents eventually evolving into simple multi-cellular organisms similar in structure to the jellyfish. Without a nervous system, circulatory system, brain or respiratory system, they move on the currents of the sea enrapturing their prey with venom. Aside from being potentially deadly, jellyfish are beautiful to watch as they glide through the ocean with no particular destination. They are the true Zen Masters of the seas. However, overpopulation of jellyfish in recent years has become a cause for concern. Warming waters and ocean acidification are thought to be primary factors contributing to the increase in numbers.