Hypothetical types of biochemistry in the late 1960s, these machines are often classed as computers (or computer-guided robots) and filed under "silicon-based life", even though the silicon backing matrix of these processors is not nearly as fundamental to their operation as carbon is for "wet life". Arsenic, which is chemically similar to phosphorus, while poisonous for most life forms on Earth, is incorporated into the biochemistry of some organisms. Some marine algae incorporate arsenic into complex organic molecules such as arsenosugars and arsenobetaines. Fungi and bacteria can produce volatile methylated arsenic compounds. Arsenate reduction and arsenite oxidation have been observed in microbes ("Chrysiogenes arsenatis").
The Spiral of Life Mural Series The Spiral of Life Mural Series The Spiral of Life mural series is a collection of phylogenetic tree public art murals currently housed by the Pittsburgh Zoo & PPG Aquarium, the National Aviary and the Carnegie Science Center. The murals reinterpret Charles Darwin's Tree of Life model appearing in "On the Origin of Species" by using the spiral shape in order to show the evolutionary relatedness among species over time. The models accurately depict a modern phylogenetic tree, along with a time scale and illustrations of various plants, animals, fungi, insects, and bacteria. Opposite Darwin's illustration, which has often led