BIO 002, Week 2 Notes
BIO 002, Week 2 Notes BIOL 002
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ANTH 120 001
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This 6 page Class Notes was uploaded by Emilly LaFleur on Sunday January 31, 2016. The Class Notes belongs to BIOL 002 at University of Vermont taught by John J. Mitchell in Spring 2016. Since its upload, it has received 29 views. For similar materials see Principles of Biology in Biological Sciences at University of Vermont.
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Date Created: 01/31/16
Lecture January 25, 2016 Plant Diversity “Plant” has many definitions: a. Chlorophyll containing b. Photosynthetic organisms Land plants: primary producers - they trap the energy and carbon needed by all land dwelling organisms, and they provide ecosystem services, such as formation soil, water storage, and gas exchange. Characteristics: Alteration of generations Walled spores produced in ‘sporangia’(in cell wall) - protectant Multicellular ‘gametangia’-> produces gametes, holds egg Apical meristems -> linking Multicellular ‘gametangia’ Female - archegonium Male - antheridia Meiosis 2n->1n Greater genetic environment -> could fit into new environment Land Plant Varieties Nonvascular Plants Vascular Plants Liverworts Mosses Ferns Gymnosperms Angiosperms |____________________| |______________| ancestral griepalga seed plants |____________________________________| true vascular tissue + lignin |_____________________________| seeds + pollen |_______________________| flowers + fruits adaptations: cuticle, stomata, protected embryos (seeds), association with Fungi, production of secondary compounds stomata: openings in cell lignin Life Cycle of Moss: Male or Female gamete (sperm or egg) > fertilization (capsules) > meiotic cell division (spores) > gametophytes Newly evolved elements of the conducting system in vascular plants Tracheids are first to appear, long thin cells, as the cell matures the cytoplasm dies, leaving jus the cell wall. Life Cycle of a Fern: a ‘simple’vascular plant (Spores) Mitosis and development > (Gametophyte plant) Mitosis > (sperm and egg) Fertilization > (zygote) Mitosis and development > (mature sporophyte) Meiosis Life Cycle of a Pine: a Gymnosperm ‘seed plant’ Male or Female cone > ovule> fertilization (sperm or eggs) > embryo (seed, seedlings) > mature sporophyte Looking specifically atAngiosperms ‘Flower plants’are monocots or eudicots, categories are based on the number of seed leaves. Monocots: Flower parts are in 3s or multiples of 3, smooth leaf edges, narrow parallel veins, vascular bundles are scattered, fibrous roots. 1 seed leaf. Eudicots: Flower parts are in 4s and 5s, leaves are palmate, oval, veins are net like, vascular bundles are in a ring, taproot system. Seed leaves. Lecture January 27, 2016 The Meristem + The Developmental Organization of Plants Indeterminate > growth can continue indefinitely (due to existence of a mass of pluripotent stem cells. (the meristem) at the apexes of the Plant body. Meristems: clumps of small cell with dense cytoplasm + proportionality large nuclei. They divide relatively frequently, giving rise to two cells, on remains meristematic, while other may ‘differentiate’to contribute to the plant body. Plant Cell Division (Cytokinesis) Begins with formation of a cell plate, around which membrane deposits process continues with the incorporation of Cellulose + other Polysaccharides + the formation of the ‘primary’cell wall. Primary wall formation will continue (until growth elongation is complete) Division plate > right angles to the long axis of the plant, increases the ‘size’or width of the plant. (opposite plate will grow in height) Plant Systems Organs: leaves, stems, + roots VEGETATIVE Flowers + fruit/seed > ‘reproductive phase’organs Systems Individual roots are organized into root system the stem module is a component of the stem system (stem + leaf are in the ‘shoot system’)cytokinesis The Stem Organ System The growing stem consists of modules, one growing on top of one another. TheApical Meristem gives rise tot eh Stem Modules Growth, Deposition, + Differentiation of apical shoot meristem cells is responsible for the development + growth of the ‘stem’ Periodic side bulges can be left behind as the tip grows, these develop into finger like leaf primordia. Branches Lateral buds (left behind meristem cells) when stimulated by the right hormones the cells are activated + the bud will grow. Plant Tissues Apical meristem of stoma + root give rise to a set of cylindrical primary meristems Dermal Tissue Outer protective covering Tightly packed epidermal cells, often with a waxy coating called the cuticle, which protects the plant from excess water loss. Sieve-Tube *May be specialized structures ex) stoma guard cells Guard Tissue Cells Parenchymal Cells > classic plant cells, vacuoles, chloroplast, (carry on photosynthesis) dermal cells on surface take in light. Collenchyma > found in upright portion, thickens walls, supports weight, flexible (can have bend) why is this good? environmental conditions > for example, does not break in harsh winds. Sclerenchyma > also support (not as long) grow in stacks, lay down a thick layer (secondary cell wall) ex) nut’s shell *cement like Vascular Tissue - Xylem H2O + mineral conducting vascular tissue of plants Primary conducting all > tracheids Vessel elements > found in angiosperms Build up cell types somewhat complex secondary cells. *leaves hollow tube structure > for fluid transport Vascular Tissue - Phloem Located toward the outside of root/stem is the principle food + metabolic transporting system *Sieve-Tube elements (direct transport cells) live cells at functional maturity (unlike the xylem cells) HIGHLY MODIFIED Internal Stem Organization as plant stems + their systems support/separate the leaves, they lift them + expose them to air (vulnerable) Leaves Major Photosynthetic Organ Extension of shoot + stem development *not committed to becoming leaves, yet they expand by enlargement + cell division once initiated. a) Simple leaf > single, undivided blade b) Compound leaf > Blade consists of multiple leaflets (no auxiliary bud) c) Double compound leaf > each leaflet is divided into smaller leaflets Lecture January 29, 2016 Leaf Structure Thin epidermis w/waxy cuticle to maintain water, often accompanied by guard cells. Vascular bundles ramify through the blade (so no cell is more than three to four cell diameters away) Photosynthetic Parenchyma (mesophyll) divided into two sections a) Upper layer > Elongated cells (palisade layer) *dense b) Lower layer > Irregularly shaped + distributed around air spaces *spongy Root System Anchors the plant - absorbs water + nutrients, may store food Taproot system: single, large, deep, less prominent lateral roots Fibrous root system: large surface area, many thin roots, clingy Internal root structure Root apical meristem > quiescent center cell, below the center divide + gives rise to root cap cells, which protect the tip + sense gravity. Cells ‘above’the center divide, and become the three primary meristems (zone of division) above this area > The cells elongate pushing the root deeper into the soil (zone of elongation) Farther along the root cylinder the cells begin to differentiate taking on their ultimate functions (zone of maturation) ^Epidermal cells often produce exponentially long root hairs, increasing surface area + absorptive potential. Resources and Transport Primary resources 1) access to sunlight 2) access to gases CO2 +O2 3) access to H2O 4) access to minerals Phyllotaxy> growing tall + arrangement of leaves Root modifications ^ to enhance absorption of needed nutrients plants cannot use nitrogen in the N2 form that is abundant in the air. They absorb it from the soil as NO3 or NH4 (nitrogen fixing bacteria) About 80% of plants have Mycorrhizae, a mutualistic association between roots + fungi. The fungus increases the volume of soil available to the plant + renders some soil compounds more H2O soluble in exchange for sugars, amino acids + vitamins. (give + take) Cellular mechanism of Transport Requires a transport protein for hydrophilic subs against a lipid membrane. Plant cells have an array of such proteins. H+ATPase > primary controller of transport in plant cells active transport protein uses energy inATP to generate a Hydrogen gradient + the membrane potential for plant cells little energy is required to pump hydrogen out Water movement H2O can move by diffusion down it’s concentration gradient (solute or osmotic potential of H2O) Water can also move from high pressure to low pressure. Transport pathways 1)Apoplast: the continuum of the extracellular space + porous cell walls of plant tissues as well as the dead interiors of Xylem cells. 2) Symplast: the cytoplasmic continuum, each plant cell is connected to its neighbors via plasmodesmata. Dissolved molecules can move from cell to cell throughout a tissue via this path. 3) Transmembrane Route: Here a substance must be transported across multiple cell membranes to transverse a tissue. Root Uptake Mechanisms Mineral solutes can enter the apoplast + passively diffuse through the outer regions of the root. Minerals can also be actively transported into cytoplasm of the root hairs (water will follow passively) They can diffuse through the symplast toward the center of the root.At the endodermis the apoplectic route is blocked by the hydrophobic casparian strip. The endodermal cell membranes are the ‘Gate Keepers’for mineral entry into the stele. *The endoderm prevents its return to the soil solution. Transportation + Guard CellAction 1) In the presence of light, potassium ions are actively transported into the guard cells from the epidermal cells. 2) Higher internal K+ and CI- concentrations give guard cells a more negative potential, causing them to take up water, increase in pressure, and stretch, opening the stoma. 3) In the absence of light, as K+ diffuses passively out of the guard cells, water follows by osmosis, the guard cells go limp, and the stoma changes. Xylem Transport (Transportation - Cohesion - Tension Mechanism) 1) Transportation: water vapor diffuses out of the stomata 2) Water evaporates from mesophyll cell walls 3) Tension pulls water from the veins into the apoplast of the mesophyll 4) Tension pulls the water column upward and outward in the xylem of veins in the leaves 5) Tension pulls the water column upward in the xylem of the root and stem 6) Water molecules from a cohesive water column from the roots to the leaves 7) Water moves into the xylem by osmosis 8) Water enters root from soil by osmosis
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