Chapter 37

Summary		Questions		Media Resources
37.1 Plants have multicellular haploid and diploid stages in their life cycles.
• Plants evolved from a multicellular, freshwater green algae 470 million years ago. The evolution of their conducting tissues, cuticle, stomata, and seeds has made them progressively less dependent on external water for reproduction. • All plants have a haplodiplontic life cycle in which haploid gametophytes alternate with diploid sporophytes.		1.  Where did the most recent ancestors of land plants live? What were they like? What adaptations were necessary for the "move" onto land? 2.  What does it mean for a plant to alternate generations? Distinguish between sporophyte and gametophyte.		•Introduction to Plants •Plant Characteristics •Life Cycles of Plants • Plant Biodiversity in New Hampshire •A Rum Affair by Sabbagh
37.2 Nonvascular plants are relatively unspecialized, but successful in many terrestrial environments.
• Three phyla of plants lack well-developed vascular tissue, are the simplest in structure, and have been grouped as bryophytes. This grouping does not reflect a common ancestry or close relationship. • Sporophytes of mosses, liverworts, and hornworts are usually nutritionally dependent on the gametophytes, which are more conspicuous and photosynthetic.		3.  Distinguish between male gametophytes and female gametophytes. Which specific haploid spores give rise to each of these? 4.  What reproductive limitations would a moss tree (if one existed) face?		•Non-Vascular Plants • Moss Life Cycle
37.3 Seedless vascular plants have well-developed conducting tissues in their sporophytes.
• Nine of the 12 plant phyla contain vascular plants, which have two kinds of well-defined conducting tissues: xylem, which is specialized to conduct water and dissolved minerals; and phloem, which is specialized to conduct the sugars produced by photosynthesis and hormones. • In ferns and other seedless vascular plants, the sporophyte generation is dominant. The fern sporophyte has vascular tissue and well-differentiated roots, stems, and leaves.		5.  In what ways are the gametophytes of seedless plants different from the gametophytes of seed plants? 6.  Which generation(s) of the fern are nutritionally independent?		•Seedless Vascular Plants •Seedless Vascular Plants, cont. • Fern Life Cycle
37.4 Seeds protect and aid in the dispersal of plant embryos.
• Seeds were an important evolutionary advance providing for a dormant stage in development. • In gymnosperms, ovules are exposed directly to pollen at the time of pollination; in angiosperms, ovules are enclosed within an ovary, and a pollen tube grows from the stigma to the ovule. • The pollen of gymnosperms is usually disseminated by wind. In most angiosperms the pollen is transported by insects and other animals. Both flowers and fruits are found only in angiosperms and may account for the extensive colonization of terrestrial environments by the flowering plants.		7.  What is a seed? Why is the seed a crucial adaptation to terrestrial life? 8.  What is the principal difference between gymnosperms and angiosperms? 9.  If all the offspring of a plant were to develop in a small area, they would suffer from limited resources. Compare dispersal strategies in moss, pine, and angiosperms.		•Gymnosperms •Angiosperms •The Orchid Thief by Orlean • Pine Life Cycle •Angiosperm Flower •Angiosperm Life Cycle

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