BIOL120 Study Guide - Psilotopsida, Lycopodiopsida, Trimerophytopsida
4 Feb 2014
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Strengthen cell walls by replacing water and coating or encrusting the cellulose (the principle building block of plant cells walls: chains of glucose molecules) Allow for increase in size and height. Paleobotanists are not certain how svps evolved because fossil record is incomplete. Have a vascular system of phloem and xylem. Speculate that vascular tissue, waxy epidermis and other characteristics evolved over millions of years in fresh water algae. Svps dominated landscape around 350 mya and persisted as dominant plants for about. 100 mya (but still need water for fertilization) Today they represent only about 5% of living plant species. Three extinct ancestors without roots and leaves: Rhyniophytes: stems with dichotomous branching (arms of equal length) Ancestors to lycophyta - club mosses: arose from the zosterophylls, all lycophytes have microphylls (leaves that have a single vascular trace or leaf vein (no leaf gap, sporangia on modified leaves (sporophylls)
