BIOL 152 1st Edition Lecture 10Outline of Last Lecture I. Case Studya. Symbiosisb. EndosymbiosisII. Organismal Structure and function a. Single-celled organismsb. Multi-cellular organismsIII. Protistsa. Classificationi. Excavataii. Chromalveolataiii. Archeoplastidaiv. Green AlgaeOutline of Current Lecture I. The green algae are the closest relatives of the land plantsa. Green algae and land plants share many featuresb. Green algae are NOT monophyleticc. The Caryophyceans are sister to the land plantsII. The colonization of Earth presents many challengesa. Consider the habitat(s) of the ancestors of land plantsb. Review the major challengesIII. A series of key innovations permit colonizing Eartha. Reflect upon the synapomorphies of land plantsb. Leaf morphology illustrates some of the solutions to desiccationc. Stoma (or stomates) regulate water loss in many plantsIV. One clade of land plants evolved complex vascular tissuesa. Xylem is a complex tissue that functions to transport waterb. Energy is not required to move waterc. Phloem is a complex tissue that functions to transport the product of photosynthesis d. Energy IS required for phloem to move sugars via bulk flow These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Current LecturePlant Structures and FunctionGreen Algae- Very diverseo Unicellular or multicellularo Filamentous, colonial- Habitato Freshwater to marineo Terrestrial: soil, snowo Symbiotic: lichens- Synapomorphy?o None, not monophyletico Phylogenetically classify 2 choices Recognize as two separate lineages Combine green algae and land plantsChlorophyta and Plants-Many similarities- Chlorophyll A and B- Storage CHO: starch inside plastids- Cell walls: sometimes cellulose- Some have plasmodesmataCharophyceans- Most closely related to plantsMajor challenges to move to land Communication between cells- Plasmodesmata- pores between cells, provides an efficient mechanism for translating informationDesiccation- Many adaptationsGas Exchange- Stomata-pores on leaf and stem surface, have the ability to open and close for gas exchangeSexual Reproduction- Alternation of multicellular generationsBasic anatomy of a plantCellstissuestissue systemorgansTissue systems: dermal, ground and vascular- Continuous in plant, vary in appearance in different organsAnatomy of a typical leaf - Many adaptations and variations on this general theme - Must balance uptake of CO2 and loss of H2Oo Epidermiso Mesophyllo StomaReview: Water and LifeBasics of water movement same for all - Water not actively pumped between cellsMoves passively by osmosis: diffusion of water across a semi-permeable membrane- Diffusion tendency of a substance to move down its concentration gradient - Semi permeable membrane: water moves passively, often solutes do notStoma and Guard Cells- Stoma open in response to sunlight- Pump in solutes and water- If stoma were blocked, photosynthesis would stop due to the inability to obtain CO2Vascular tissue: A key innovationFunction-transport all plant organsTwo types:- Xylem-moves water and dissolved minerals- Phloem-moves nutrients (solutes)Water H2O- Molecules (+) on one end and (-) on the othero Forms hydrogen bonds between molecules- Cohesive-stick togethero Surface tension- AdhesionTranspiration-where plants lose most of their water- Trade offo Gain CO2 for photosynthesis, get rid of excess O2o Lose water- More water loss=more pull Forces that pull water from the soil- Pressures extend all the way down to rootCohesion-tension model- Cohesiono Water column in xylemo H-bonds between water- Tension (-Ψp)o From evaporating water in leaveso Pulls column upwards- Adhesiono H-bonds with xylem wallso Helps counter gravityWater moves up a plant by moving down a pressure gradientVascular BundleComposed of xylem and phloem- Phloem tissueo Transport of photosynthateo Living cellso Photosynthates are sugars, which require energy to move between cells- Two kinds of cells:o Sieve cells Cell to cell connections= “simple sieve areas” Passage of materials cell to cell Contain nucleio Sieve tube elements Cell to cell connections= complex “sieve plates” Very efficient, rapid movement of materials Lack nuclei Companion cells: contain nuclei and work in partner with sieve tube elements to help regulatePhloem transport:Sourcesink- Source=leaves (usually)- Sink=area of active growth- Sink= storage aresBulk flow of phloem sap- Sucrose from sourceo Into sieve tubeo By active transport o Requires energy transport- Water from xylemo Into sieve tube by diffusion- Hydrostatic pressure flow o Carries sucrose along- Sucrose in sieve tubeo Into sink by active transport- Watero From sieve tube into xylem by
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