Some slime molds, for instance, have long been classified with fungi, but now are considered stramenopiles. As the tree of life has been re-drawn, scientists have also had to revise some of their ideas about how evolution has proceeded. And as the revision proceeds, scientists are moving tantalizingly close to identifying the first land plant and the first flowering plant. The revision is also providing road maps that could enable scientists to speed up the search for naturally occurring medicines and the development of new strains of drought-resistant crops. But it is primarily the sheer intellectual excitement of figuring out one of nature's grand designs that has lately galvanized the efforts of hundreds of scientists.
Simple bacteria have no cell nuclei.
Archaea are bacteria of ancient origin that today often live in hostile environments like hot springs and are believed by many scientists to have represented the first life on earth. The first simple bacteria emerged at least as far back as 3.5 billion years ago, about a billion years after the earth's formation. Eukarotic cells had materialized by at least 2 billion years ago, maybe earlier. In this efflorescence of life, some eukaryotic cells combined to form multicelled organisms and then began to diversify dramatically. Although their flowering has been spectacular, they constitute only a few small branches of the entire tree of life.