Botany/Pinophyta
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Chapter 14. Pinophyta
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The Division Pinophyta in the Kingdom Plantae comprises those species of plants that were formerly classified as the "modern" gymnosperms of the Class Coniferales—that is the conifers. Unlike many of the gymnosperm groups covered in the previous chapter, pinophytes are today still broadly represented on the landscape, forming extensive forests in both the Northern and Southern hemispheres. This does not mean this is a recent group in the paleontological record. Pinophytes are found as fossils as far back as the Upper Carboniferous (Paleozoic Era). Thus, it is a very ancient group, but one still having significant ecological importance on the planet. Pinophytes are mostly evergreen trees (some are shrubs) and many have great commercial value for their wood.
- Reread Gymnosperm (Links need not be pursued at this time)
- Read Conifers (Links need not be pursued at this time)
These terms, gymnosperm and conifer no longer have standing in modern taxonomic treatments of plants. However, both terms are still widely used, so you should have a grasp of what they mean, and how they fit into the taxonomic terms that have replaced them.
- Read Division Pinophyta (The following links are included:)
- Order Pinales
- Family Pinaceae (Follow links to Pinus (pines) and read accounts for each of the Pinus species)
Be sure to read about and understand each of the following terms: softwood, evergreen, pine needle, pine cone, pine nuts, resin, wood pulp, timberline - Family Cupressaceae (Follow links to each of the listed genera and read accounts for each species)
Be sure to read about and understand each of the following terms: Bald Cypress, cypress knees, Giant Sequoia, redwoods, swamp - Family Taxaceae (Follow links to each species)
Be sure to read about and understand each of the following terms: aril, yew, alkaloid
- Family Pinaceae (Follow links to Pinus (pines) and read accounts for each of the Pinus species)
- Order Pinales
Evolution of the Gymnosperms
[edit | edit source]Gymnosperms are very different from the earliest vascular plants. Gymnosperms have very reduced gametophyte generations- female ovules and male pollen. Many gymnosperms, like the Pinophytes, have secondary growth from a vascular cambium. While tree ferns are tall and have a trunk resembling a tree, they are only very superficially similar. They do not have woody growth the way trees with secondary growth from a vascular cambium do. A single mutation of a fern or a horsetail could not produce a functioning seed plant. So gymnosperms must be descended from some progymnosperm ancestor that evolved these adaptations from the ferns, but was not fit enough to remain on earth. One possible example of a progymnosperm is the spore bearing woody tree Archaeopteris, which was at one point probably prevalent on earth.
Laboratory Exercises for Chapter 14 >>
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