Roland Piquepaille writes: "The Tree of Life was an expression used by Charles Darwin to describe the diversity of organisms on Earth and their evolutionary history. There are only two life forms, eukaryotes, which gather their genetic material in a nucleus, and prokaryotes, such as bacteria, which have their genetic material floating freely in the cell. Until recently, eukaryotes, which include humans, were divided in five groups. But now, European researchers have found that the Tree of Life has lost a branch. After doing the largest ever genetic comparison of life forms, they concluded that there are only four groups of eukaryotes. But read more for additional references and see how the Tree of Life has lost one of its branches."