62 KINGDOM PLANTAE Part 3: SEED PLANTS A. Introduction:Since the evolution of the seed about 350 million years ago, seed plants have become the most dominant feature of the terrestrial landscape. Seeds offer both protection and stored food reserves for developing embryos and it is these two characteristics which are thought to have given seed plants their great selective advantage over their free-sporing ancestors. All seed plants are heterosporous, with a dominant sporophyte generation and a much reduced gametophyte generation that develops on the sporophyte, rather than existing as a free-living stage on or in the soil. Dispersal of male gametes via pollen grains eliminated the requirement for water as the fertilization medium. As you complete this exercise, think about the modifications necessary to evolve seed plants, using the seedless vascular plants examined last week as your starting point. Please read Chapter 30 of Campbell and Reece (2005) prior to attending lab.
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