BIOL 227 Lecture Notes - Lecture 9: Ginkgoales, Microsporangia, Tracheid
3 May 2016
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Biol 227 tutorial 9 evolution and homology in plant. Simple water-conducting cells and tissues, leaves, terrestrial reproduction and life cycle preceded more complex ones. The molecular tree is consistent with the hypothesis that plants evolved from a simpler, restricted-range autotrophic organism to wide ranging and diverse terrestrial organisms with complex structures supporting highly derived reproductive strategies. The seed plants including gymnosperms are monophyletic group, or, flowers, pollen, seeds and fruit only evolved once. Stoneworts get their common name because they accumulate calcium carbonate crusts over their surface. Charales have several characters seen in land plants (1) retention of the egg cell within sterile parental tissue prior to fertilization (2) enclosure of gamete-producing structures within sheaths of protective sterile tissue. Arly land plants contained specialized reproductive organs called gametangia that protected gametes from drying and damage. All living land plant grades but angiosperms still have these. Individuals produce distinctive male and female gametangia: sperm producing = antheridium, egg-producing = archegonium.
