By 124 chapter 29 - CHAPTER 29 PLANT DIVERSITY I The kingdom Plantae is defined by embryophytes(plants with embryos Charophytes are the closest

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CHAPTER 29: PLANT DIVERSITY I The kingdom Plantae is defined by embryophytes (plants with embryos) Charophytes are the closest relatives of land plants Charophytes share the following four distinctive traits with land plants o Rosette-shaped cellulose-synthesizing compounds o Peroxisome enzymes o Structure of flagellated sperm o Formation of a phragmoplast Phragmoplast - a group of microtubules that forms between the daughter nuclei of a dividing cell Plants are not descended from charophytes; however, present-day charophytes may tell us something about what the algal ancestors of plants were like In environments around shallow ponds and lakes, natural selection favors algae that can survive periods when they are not submerged in water. o Sporopollenin - a layer of a durable polymer prevents exposed zygotes from drying out in charophytes o Descendants of charophytes with sporopollenin were probably the first land plants Benefits of a terrestrial habitat o Bright sunlight unfiltered by water and plankton o The atmosphere offers more plentiful carbon dioxide than water o The soil is rich in mineral nutrients o In the beginning there were relatively few herbivores and pathogens Land plants diversified as adaptations evolved that enabled plants to thrive despite terrestrial habitat challenges Four traits that appear in nearly all land plants but not in the charophyte algae o Alternation of generations and multicellular, dependent embryo Alternation of generations - a life cycle in which there is both a multicellular diploid form, the sporophyte, and a multicellular haploid form, the gametophyte 1. The gametophyte produces haploid gametes by mitosis 2. Two gametes unite (fertilization) and form a diploid zygote 3. The zygote develops into a multicellular diploid sporophyte 4. The sporophyte produces haploid spores by meiosis
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5. The spores develop into multicellular haploid gametophytes Gametophyte - “gamete-producing plant” Sporophyte -“spore-producing plant” As part of a life cycle with alternation of generations, multicellular plant embryos develop from zygotes that are retained within tissues of the female parent (a gametophyte). The parental tissues provide the developing embryo with nutrients. The embryo has specialized placental transfer cells, sometimes present in the adjacent
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This note was uploaded on 08/07/2009 for the course BY 124 taught by Professor Cusic during the Spring '08 term at University of Alabama at Birmingham.

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By 124 chapter 29 - CHAPTER 29 PLANT DIVERSITY I The kingdom Plantae is defined by embryophytes(plants with embryos Charophytes are the closest

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