TAILIEUCHUNG - Lecture Biology: Chapter 29 - Niel Campbell, Jane Reece

Chapter 29 - Plant diversity I: How plants colonized land. After studying this chapter you will be able to: Describe four shared characteristics and four distinct characteristics between charophytes and land plants, diagram and label the life cycle of a bryophyte, explain why most bryophytes grow close to the ground and are restricted to periodically moist environments,. | Chapter 29 Plant Diversity I: How Plants Colonized Land Overview: The Greening of Earth Since colonizing land at least 475 million years ago, plants have diversified into roughly 290,000 living species. Plants supply oxygen and are the ultimate source of most food eaten by land animals. Green algae called charophytes are the closest relatives of land plants. Note that land plants are not descended from modern charophytes, but share a common ancestor with modern charophytes. Morphological and Molecular Evidence Land plants share key traits only with green algae charophytes: DNA comparisons of both nuclear and chloroplast genes. Rose-shaped complexes for cellulose synthesis. Peroxisome enzymes - minimize loss from photorespiration. Structure of flagellated sperm. Formation of a phragmoplast - allignment of cytoskeletal elements and Golgi vesicles for cell plate. Rosette cellulose-synthesizing complexes Found only in land plants and charophycean green algae 30 nm Figure Rosette cellulose-synthesizing complexes Adaptations Enabling the Move to Land In green algae charophytes a layer of a durable polymer called sporopollenin prevents dehydration of exposed zygotes. The movement onto land by charophyte ancestors provided advantages: unfiltered sun, more plentiful CO2, nutrient-rich soil, and few herbivores or pathogens. Land presented challenges: a scarcity of water and lack of structural support. Three Clades are candidates for Plant Kingdom ANCESTRAL ALGA Red algae Chlorophytes Charophytes Embryophytes Viridiplantae Streptophyta Plantae Figure Three possible “plant” kingdoms Derived Traits of Plants A cuticle and secondary compounds evolved in many plant species. Symbiotic associations between fungi and the first land plants may have helped plants without true roots to obtain nutrients. Four key derived traits of plants are absent in the green algae charophytes: Alternation of generations - with multicellular, dependent embryos. Walled spores produced in .

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