BIOL 1101 Lecture Notes - Lecture 76: Defecation, Succulent Plant, Coevolution
27 Jun 2016
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Document Summary
Flowering plants dominate the earth"s flora in the same way that arthropods dominate its fauna (and maybe these two dominances occur because of each other). The flowering plants have about 300,000 species, nearly 30 times as many as the next most diverse phylum, the ferns. All of our important food, fiber and medicinal plants, and most of our lumber trees, are angiosperms. Angiosperms not only feed almost every animal on the planet, but they may be responsible for the evolution of many kinds of insects, mammals and birds. If we ignore reproductive technique, large angiosperms are very similar to gymnosperms. They reach about the same size and their trunks consist mostly of secondary xylem that conducts between the massive crown and the root system. Gymnosperm xylem is mostly tracheids, while angiosperm xylem is mostly cylindrical vessel elements. Of course, angiosperms have sheetlike rather than needlelike leaves, but remember the broad leaves of the ginkgoes and some gnetophytes.
