ASIM'S WEBWORLD View: Main School Main AP Biology Chapter Guides RELATED LINKS Chapter Outline		AP BIOLOGY: Chapter Thirty-Three Review Answers 1. Green algae and plants share chlorophylls a and b, carotenoids, cellulose cell walls, and starch as a food storage product. Both groups have cellular division characterized by the development of a cell plate between the daughter cells (animal cells divide by pinching in half). 2. In plants, alternation of generations refers to alternation of a diploid generation with a haploid generation. Sporophytes are diploid, spore-producing reproductive structures; gametophytes are haploid, gamete-producing reproductive structures. The sporophyte is comparable to an adult animal, although it differs in that adult animals produce sperm and egg (gametes), whereas a sporophyte plant does not directly produce gametes. 3. Meiosis takes place in the spore mother cell; these cells produce haploid spores which grow into gametophytes. This growth involves mitosis. Gametes (egg and sperm) are, in turn, produced through mitosis. Fusion is required for the cycle to continue because the egg and sperm unite to form the diploid zygote. The sequence of alternation of generations is as follows: (zygote)-(sporophyte)[meiosis]-(spores)-(gametophyte) [mitosis](gametes = egg and sperm) [syngamy]-(zygote). 4. The gametophyte is green and free living in bryophytes and ferns, and non-green and nutritionally dependent on the sporophyte in the rest of the vascular plants. The sporophyte of the mosses is brownish or yellowish tissue enclosed in and dependent on the bryophyte gametophyte, whereas in the vascular plants the sporophyte is the free-living photosynthetic stage. 5. Microgametophytes produce antheridia, and megagametophytes produce archegonia. The haploid spores that give rise to these are microspores and megaspores, respectively. A plant that produces these spores is heterosporous. The plant that produces only one kind is homosporous. The haploid spores are produced in the sporangium; if two different types are produced, they are called microsporangium and megasporangium. 6. Mosses have rudimentary vascular tissue and may be evolutionary, degenerate, vascular plants; the liverworts and hornworts have no vascular tissue and are probably very primitive. 7. Gametophytes are nutritionally independent of the sporophyte, while sporophytes are attached to the gametophytes and depend on them for nutrition. The gametophytes are the most conspicuous generation. (Sporophytes are dependent upon the gametophyte for nutrition.) 8. Sperm travel by water. 9. Phloem is a vascular tissue containing sieve elements and conducts organic materials away from their sites of production. Xylem is a vascular tissue composed of tracheary elements and conducts water and minerals up from the roots of the plant. 10. A seed is a developing sporophyte in a state of arrested embryonic development surrounded by a protective coat. The seed is crucial because it protects the embryo from drying out or being eaten and provides a source of energy for the growing plant. In angiosperms, the ovule is completely surrounded by the tissue of the sporophyte; in gymnosperms the ovule is partially or totally exposed at pollination. In both plant types, male and female gametophytes develop within the sporophyte and are completely dependent upon it for nutrients and water. 11. The archegonia and antheridia are located on the lower surface of the gametophyte. Both the gametophyte and sporophyte are nutritionally independent. A rhizome is the horizontal stem of the fern. Sporangia are located on the frond or leaf. More gametophytes germinate from the spores produced in the sporangia. 12. The large pine cones are megasporangia. The seed coat and embryo are diploid; the megagametophyte is haploid. The hard seed coat surrounds the embryo and megagametophyte. The nourishment is supplied by the megagametophyte. 13. Angiosperms differ because they contain ovules enclosed within carpels, the parent sporophytic tissue. Fertilization is indirect. Fertilization is indirect because the ovules are enclosed within an ovary, and can only be accessed by a pollen tube generated by the pollen grain. The angiosperm fruit develops from the carpel. 14. Double fertilization occurs when one sperm nucleus fertilizes the egg and the other fuses with one of the polar nuclei. The zygote and endosperm arise from this; the zygote is diploid and grows into the embryo; the endosperm is triploid and supplies nutritive tissue for the embryo.