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Unformatted text preview: Charophycean ancestor Charophyceans Bryophytes Pteridophytes Gymnosperms Angiosperms (mosses, etc.) (ferns, etc.) (conifers, etc.) (flowering plants) Seed plants and the seed habit seed plants vascular plants land plants Reproduction by flowers Dispersal by seeds Presence of vascular tissue Basic land plant attributes Seed plants and the seed habit To review: Pteridophytes (at least, ferns) have several advances over Bryophytes: vascular tissue , allowing increasing specialization of organs, and much greater size true leaves , including branched vascular systems Like many Bryophytes, Pteridophytes can disperse widely via tough, walled spores-- but these are unicellular and lack significant nutrient stores. Pteridophytes remain dependent on liquid water for reproduction, restricting their range of habitats to fairly moist areas (at least seasonally moist) Seed plants and the seed habit SEED PLANTS became enormously successful in land habitats because of two evolutionary advances over Pteridophytes: A tough-walled male gametophyte -- POLLEN-- that can disperse widely without liquid water Propagation via complex multicellular SEEDS that have protective coverings and significant nutrient stores to assist early growth of the embryo and young plant Seeds may also contain external food stores to entice animals to move them around (fruits) As part of these functional advances: even more reduction of gametophyte generation Seed plants and the seed habit Reduction of gametophyte generation Diploid sporophyte (2N) Haploid gametophyte (N) Bryophytes Pteridophytes Seed plants Sporophyte dependent on gametophyte ( gametophyte dominant) Large sporophyte, small but independent gametophyte Gametophyte small and dependent on sporophyte ( sporophyte dominant) gametophyte sporophtye spores gametophyte sporophtye spores gametophyte sporophtye Seed plants and the seed habit integuments Nucellus ( megasporangium) megaspore micropyle Unfertilized ovule All seed plants are heterosporous: like a few non- seed plants they produce two types of sporangia: Megasporangia -&gt; megaspore -&gt; female gametophyte Microsporangia -&gt; microspore -&gt; male gametophyte For both, a seed plant retains its spores and they develop into gametophytes within the tissues of the parent sporophyte . Female gametophyte is retained within the parent sporophyte until after fertilization -- then it is released as a complex embryo-containing seed Male gametophyte disperses as pollen for fertilization. Seed plants and the seed habit integuments micropyle Megaspore grows. female gametophyte Egg cell All seed plants are heterosporous: like a few non- seed plants they produce two types of sporangia: Megasporangia -&gt; megaspore -&gt; female gametophyte Microsporangia -&gt; microspore -&gt; male gametophyte For both, a seed plant retains its spores and they develop into gametophytes within the tissues of the parent sporophyte ....
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