New books from professors in the School of Natural Resources and Environment examine the ecology of streams and fish. Running waters are enormously diverse - from mountain brooks to great river systems whose basins occupy whole continents but the processes acting in running water are general, according to Allan. In an article in Nature , Gans and co-authors from the University of Texas and Scripps note that changes in the ancient animals in the fossil record support the hypothesis that oxygen concentration began to rise about 400 million years ago and peaked 290 million years ago, before declining to today's levels. The hypothesis says oxygen reached an estimated 35 percent of the atmosphere compared with the present 21 percent. The rise in oxygen and simultaneous drop in carbon dioxide would have made the primitive lungs of water-dwelling backbone animals more effective and that may have helped the creatures make the transition to living on land.
Arthropods are a group of animals with jointed legs and a hard exterior skeleton.
By comparing the arrangement of genes encoded in arthropod mitochondrial DNA to those found in other kinds of animals, the researchers have provided convincing evidence that all living arthropods stem from one common ancestor which lived roughly one billion years ago. The results of the UM study are reported in Nature . Also a major split must have occurred early in arthropod evolution, resulting in two major groups that came to have different types of mouth parts, says Wesley Brown ,, professor of biology. Funding was provided by the National Science Foundation, the National Institutes of Health, and the University of Michigan. The work of professor of human genetics Sally Camper , has been featured on the covers of three journals.