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Chapter 30 Notes Plant Diversity II: The Evolution of Seed plants
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Concept 30.1 Seed plants are vascular plants that produce seeds Sporophyte is the dominant generation - becomes diploid and can carry recessive alleles from one generation to the next
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Concept 30.1 All seed plants are heterosporous Megasporangia: produce megaspores that will produce female (egg- containing) gametophytes Microsporangia: produce microspores that will produce male (sperm- containing) gametophytes
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Concept 30.1 Layers of sporophyte tissue called integuments envelop the megasporangium The developing embryo is encased in a protective seed coat and supplied with its own source of food (endosperm or cotyledons)
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Concept 30.1
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Seeds allow the embryo to be moved away from the parent by wind, water, and animals Seed plants are not tied to water for fertilization; pollen grains do not need to be transported by liquid
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Concept 30.1
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Concept 30.2 Gymnosperms lack enclosed chambers in which seeds develop; instead, seeds develop on the surfaces of specialized leaves called sporophylls. About 900 species of gymnosperms are divided into 4 phyla: ginkgo, cycads, gnetophytes, and conifers
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Concept 30.2 Phylum Ginkgophyta: - Ginkgo biloba is the only extant species - used in herbal medicine - produce pollen and seeds on separate trees (dioecious: “two houses”)
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Concept 30.2
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Phylum Cycadophyta: - about 100 cycad species - palm-like appearance (but not a palm) - seeds are often passed by beetles and bees
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Concept 30.2
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Phylum Gnetophyta: - consists of three genera that are very different in appearance - Ephedra grows in U.S. deserts - Welwitschia grow in Africa
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Concept 30.2
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Phylum Coniferophyta: - conifer = “cone bearer” - called evergreens because they retain their needle-shaped leaves - male and female gametophytes appear on the same tree (monoecious: “one house”)
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Concept 30.2 - conifers are among the oldest and largest organisms on Earth - we get much of our lumber and paper pulp from conifers
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Concept 30.2
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Concept 30.3 Phylum Anthophyta: - all angiosperms are placed in one phylum Two classes: monocots and dicots - monocots: parallel veins in leaves - dicots: branched veins in leaves
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Concept 30.3 - all are heterosporous - gametophyte is greatly reduced reproductive parts of the flower male parts: stamen contains the anther and filament female parts: carpel contains the stigma, style, and ovary
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Concept 30.3
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- after fertilization, the ovule develops into a seed; the endosperm is retained in the cotyledon - as the seed develops, the ovary begins to mature around the seed to form fruit
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Concept 30.3
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