Sunday, August 21, 2011

The Fungi

The fungi were once regarded as simple plants, but their chemical makeup is very different from that of plants and they are now placed in a separate kingdom. A fungus consists essentially of a mass of slender threads, called hyphae, which absorb food from other living or dead organisms. The familiar mushrooms and toadstools are the reproductive stages of the fungi and are often called fruiting bodies. They are composed of tightly compacted hyphae and their role is to produce and scatter the dust like spores. If a spore reaches a place with enough food and moisture for survival, it will grow sending out a hypha. The name mushroom was originally used for just one or two species of fungi with edible fruiting bodies, all the other fungi with umbrella shaped fruiting bodies being called toadstools. However, the modern tendency is for all umbrellas shaped fruiting bodies, whether edible or not, to be called mushrooms. Although many species are edible and very tasty, they contain little food value.
Relatively few of the 100,000 or more known fungi are really poisonous but a handful is truly deadly. The death cam probably kills more people than any other fungus. Growing in broad leaved woodlands, this fungus has a greenish cap with white gills. One specimen is more than enough to kill a person, with a slow and painful death. Several related fungi can produce sever illness if eaten although they are not necessarily deadly. These include the fly agaric, common under birch and pine trees, the blusher common I both deciduous and coniferous woodland, and the verdigris fungus common in grass and woodlands.

Saturday, August 20, 2011

Convergent Evolution

Convergent evolution is a common phenomenon, in which unrelated plants or animals come to resemble each other because they have adapted to similar ways of life. The similarity of some species of American cacti and certain desert living spurges in Africa is a good example. Seals and Penguins are apparently very different animals, but both are superbly adapted for swimming. Their limbs and general body shapes appear similar when observed in the water.
Few animals have a clear fossil record as the horse. The oldest known fossils of this family, from rocks some 55 million years old, are of a fox sized creature called Hyracotherium. Its teeth indicate that it ate leaves, and it probably lived in the forests. Fossils from successively younger rock layers show that the descendants of Hyracotheium gradually became larger and were represented by several distinct genera before producing the modern horse about two million years ago. Their toes were reduced to one on each foot and their teeth became larger and stronger to deal with tough grasses.