LIFESCI 1 Chapter Notes - Chapter 33: Vascular Cambium, Vascular Plant, Lycopodiophyta
Document Summary
Four major transformations in life cycle and structure characterize the evolutionary history of plants. First major transformation was the evolution of alternation of generations. Ancestral life cycle: form gametes by mitosis, fertilization results in a zygote, which is the only diploid cell. The zygote then underwent meiosis, producing haploid cells that developed into new multicellular algae. Now the diploid zygote develops by mitosis into a multicellular spore- producing plant, called a sporophyte, which still attached to and supported by the haploid gamete-producing plant, called a gametophyte. First plant lacked roots and thus would have depended entirely on surface water both for fertilization and to maintain hydration. Plants would have been small, with their photosynthetic tissues and gamete-producing structures remaining in close contact with the ground. Second transformation is evolution of vascular plant. Produce elongate cells for the internal transport of water and other materials. Xylem cells transport water and dissolved nutrients, and phloem cells transport carbohydrates produced by photosynthesis.
