On the basis of a recommendation from a friend of mine who works on environmentally-friendly gardening and landscaping in North Vancouver, I am reading Paul Stamets’s Mycelium Running: a book that details ways in which human beings can achieve ecological outcomes through the intelligent use of fungus. They can be used to increase the rate of forest recovery after logging, clean up contaminated sites, and so forth. I will post a review of the whole book when I finish it.
One aspect of the book I found surprising and interesting are the ways in which the similarities of animals and fungi are emphasized. Both ecologically and genetically, the two are apparently more closely linked than any other two kingdoms. Both breathe oxygen (fungi can be suffocated), both sometimes attack and kill plants or animals. Representatives of both kingdoms sustain themselves on dead organic matter, while others live inside other live organisms and extract nutrition from them parasitically.
Some species of animals extrude their digestive organs when eating. Fungi might be considered an extreme elaboration of this. Instead of having a stomach inside the body, filled with digestive enzymes, the mycelium leaches them out into surrounding matter, then draws in the liberated and partially processed nutrients therein.
In any case, fungi are quite fascinating. For one final example, consider the genus Pleurotus. While their culinary properties are their major claim to fame, their ability to metabolize crude oil is also rather remarkable. You can start with a bucket of crude spilled on a beach somewhere, introduce some spores, and eventually wind up with material that is entirely safe for the natural environment in general.