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Vascular Seed Plants (Spermatophytes): Figure 1. The fleshy cones of an Alligator Juniper, Phylum Coniferophyta. The Gymnosperms Phylum Cycadophyta Phylum Ginkgophyta Phylum Coniferophyta Phylum Gentophyta 206 species 1 species 601 species 71 species Figure 2. A male cycad with a strobilus, Phylum Cycadophyta. Figure 3. Ginkgo biloba, phylum Ginkgophyta and Ephedra (Mormon Tea) in phylum Gnetophyta. The genus found in the United States. Objectives 1. Survey vascular seed plants. 2. Understand a sporophyte dominate life cycle 3. Identify pines, conifers and their close relatives. Ferns can survive in fairly dry places, but they still need wet conditions for reproduction. The vascular seed plants are better adapted to life on dry land; they have extra tricks that facilitate reproduction even in dry conditions. The most important of these tricks are seeds and pollen. 1 Some key differences between seed plants (including both gymnosperms and angiosperms) and ferns: • Seed plants have seeds. Seeds contain a diploid sporophyte embryo with a food supply and a protective outer seed coat. Seeds can survive harsh environments by remaining dormant, and when conditions improve they can germinate and allow the embryo to grow rapidly using its stored energy. In ferns, the sporophyte embryo grows Figure 4. Pollen grains of Pinus enclose a male gametophyte. Pollen grains have ‘wings’ needed for dispersion. directly out of the gametophyte. Ferns have spores, which are thickwalled haploid cells that can grow into haploid gametophytes. However, the spores don’t have the same kind of protective coat and food supply found in seeds. • Seed plants have pollen. Pollen grains are tiny male gametophytes, consisting of just a few cells. They have a tough outer coating, allowing them to survive being carried by wind or animals to land on a female gametophyte some distance away. The male gametophyte then grows out of the pollen grain and produces sperm to fertilize an egg. In ferns, the only way sperm can get to eggs is by swimming; this means they can’t get far and must reproduce when it’s wet. • The gametophyte is even smaller in seed plants. In ferns, the gametophyte is small and short-lived, but it is separate from the sporophyte. In seed plants, the gametophyte consists of a very small number of cells and grows completely within the sporophyte. Conifers such as pine trees are the most familiar examples of gymnosperms. Gymnosperm Survey Observe pine branches and twigs. Observe the male and female pine cones. Note how different they are in size. Why is this? What does the male gametophyte look like? What does the female gametophyte look like? Where does fertilization occur? What part of the moss Figure 5. Pine needles and ovulate cones. life cycle corresponds to the cones of gymnosperms? 2 Gymnosperm Slides • Observe the prepared slide of the pine needle. Notice how structured this is compared to the moss. The pine needle has a thick cuticle, protecting it from water loss. In order to absorb carbon dioxide from the air, the pine needle has openings, called stomata. Remember that a pine needle is part of the sporophyte, unlike the green “leaves” of the moss you saw earlier. What part of the moss life cycle corresponds to the needles and branches of gymnosperms? • Observe the prepared slide of the pollen grain. Are you looking at haploid cells or diploid cells? What part of the moss life cycle corresponds to the pollen of gymnosperms? • Observe the prepared slide of the pine seed. Note the protective seed coat. Are the seed tissues haploid or diploid? How do pines demonstrate both a "dependent gametophyte" and a "dependent embryo"? • Study the pine life cycle diagram. Compare and contrast this with the other life cycle diagrams. Remember these terms about the life cycle diagram: fertilization, mitosis, meiosis, haploid, diploid, gametophyte, sporophyte, spore, sperm, and egg. Figure 6. The Life Cycle of a Gymnosperm. 3 Worksheet for Gymnosperm Lab Sources 1. Lab content http://faculty.deanza.edu/heyerbruce/bio6a 2. Figure 1 www.backwaterbotanics.wordpress.com 3. Figure 2 www.moplants.com 4. Figure 3 www.flora.nhm-wien.ac.at , www.botanikus.de , www.dtc.pima.edu 5. Figure 4 www.plantphysio-info.com 6. Figure 5 www.dec.ny.gov 7. Figure 6 www.edtech2boisestate.edu 4