01:119:116 Lecture 7: Lecture 7 - Plant Diversity I
24 Oct 2016
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Document Summary
Closed relatives of land: characteristics of charophytes that enabled movement to land, spp inhabit shallow waters. Edges of ponds + lakes subject to occasional dying. Nat. sel. favors survival for periods w/o being submerged: sporopollenin. Similar adaptation found in plant spores wall: land plants shared traits w/ only charophytes, rings of cellulose-synthesizing proteins. Rings synthesize cellulose microfibrils of cell walls: structure of flagellated sperm. Group of microtubules + forms btw nuclei during cell division. Cell plate: forms in middle of phragmoplast gives rise to new cross walls that separate daughter cells: derived traits of plants. 5 key traits appear in nearly all land plants but are absent in the charophytes: alternation of generations, multicellular dependent embryos, walled spores produced in sporangia, multicellular gametangia, apical meristems, alteration of generations. Alternate btw 2 multicellular stages: haploid gametophyte. Produces haploid gametes by mitosis: diploid sporophyte.
