The Evolution of 3-D

You and an oak tree have something in common: you're both big. Unlike viruses and bacteria, you and an oak tree are both made up of trillions of cells. There's something else you and an oak tree have in common: you both began as an individual cell, which then divided again and again, its daughter cells differentiating along the way to produce tissues. In your case, they turned into bone, muscle, liver, and such. In the oak's case, the cells became bark, leaf, root. You and an oak tree have a third thing in common: you evolved from single-celled ancestors. By analyzing DNA from a wide range of species, scientists have been closing in on the closest microbe relatives of plants and animals in recent years. For animals, the evidence is pointing to a protozoan called a choanoflagellate. For plants, a few lineages of green algae are emerging as the ...