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30_Lectures_2008_class

30_Lectures_2008_class - Exam LE 29-13 Vascular tissue...

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Exam
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LE 29-13 Vascular tissue Microphylls Megaphylls Other stems become re- duced and flattened. Overtopping growth Webbing develops. Sporangia Microphyll
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Chapter 30 Plant Diversity II: The Evolution of Seed Plants
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Key concepts 30.1 Seeds and pollen grains are key adaptations for life on land 30.2 Gymnosperms bear “naked” seeds, typically on cones 30.3 The reproductive adaptations of angiosperms include flowers and fruits 30.4 Human welfare depends greatly on seed plants
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Overview: Feeding the World Seeds changed the course of plant evolution, enabling their bearers to become the dominant producers in most terrestrial ecosystems A seed consists of an embryo and nutrients surrounded by a protective coat Living seed plants can be divided into two clades: gymnosperms and angiosperms
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30.1 Seeds and pollen grains are key adaptations for life on land In addition to seeds, the following are common to all seed plants: Reduced gametophytes Heterospory Ovules Pollen
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Advantages of Reduced Gametophytes The gametophytes of seed plants develop within the walls of spores retained within tissues of the parent sporophyte protection (desiccation, UV) gametophytes also obtain energy from sporophyte While the gametophytes of seedless vascular plants are visible to the naked eye, the gametophytes of seed plants are mostly microscopic.
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Fig. 30-2 Reduced (usually microscopic), dependent on surrounding sporophyte tissue for nutrition Reduced, independent (photosynthetic and free-living) Gametophyte Sporophyte (2 n ) Sporophyte (2 n ) Gametophyte ( n ) Sporophyte Example Gametophyte ( n ) Dominant Dominant Dominant Reduced, dependent on gametophyte for nutrition Mosses and other nonvascular plants Ferns and other seedless vascular plants Seed plants (gymnosperms and angiosperms) PLANT GROUP Gymnosperm Angiosperm Microscopic female gametophytes ( n ) inside ovulate cone Microscopic male gametophytes ( n ) inside pollen grain Sporophyte (2 n ) Sporophyte (2 n ) Microscopic female gametophytes ( n ) inside these parts of flowers Microscopic male gametophytes are made ( n ) inside these parts of flowers
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Heterospory : The Rule Among Seed Plants The ancestors of seed plants were likely homosporous, while modern seed plants are heterosporous At some point Seed plants changed: megasporangia , which produce megaspores that give rise to female gametophytes microsporangia , which produce microspores that give rise to male gametophytes
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Ovules and Production of Eggs An ovule consists of a megasporangium , megaspore , and one or more protective integuments Ovule - A structure that develops within the ovary of a seed plant and contains the female gametophyte. Integuments - Layer of sporophyte tissue that contributes to the structure of an ovule of a seed plant.
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