Topic 9 - Plant Science A.S. 9.1 Plant Structure & Growth IB Biology HL Domain Eukaryota Domain Bacteria Domain Archcaea 425 mya 2 bya 488 mya 385 mya 400 mya 5 Main Groups Plants • 1) Chlorohyta (green algae):chloroplasts-usually, unicellular, aquatic environments • LAND PLANTS: • 2) Bryophytes (mosses): spores, not vascular, no true roots, need moisture • 3) Ferns: Roots, leaves, short stems. Spores on underside of frond. • 4) Conifers: Roots, stems, leaves, seeds. Narrow leaves w/waxy cuticle, seeds produced from ovules on scales of cones • 5) Angiosperms (flowering plants): Roots stems, leaves, seeds. Seeds produces in ovary in flower. 3 Groups Land Plants Plant Group Major features Non-vascular land plants • • • • • • ~488 mya Paleozoic Ordovician Seedless vascular plants ~425 mya Paleozoic Silurian Seeded vascular plants ~385 mya Paleozoic Devonian (Gymn) Less dependent on water-live on land No conducting tissue (so need moist environ) Produce spores (not seeds) Often grouped together as bryophytes Usually small and grow close to ground Include mosses, liverworts, and hornworts • Well-developed vascular tissue • Produce spores (underside of frond-no seeds) • Include horsetails, ferns, club mosses, and whisk ferns (most extant specimens small—some extinct species very large) • Most living plant species are in this group • Seeds contain an embryo, a supply of nutrients, and a protective outer coat • Have extensive vascular tissue and include some of the world’s largest and oldest organisms seeds Vasc non-vasc Non-Vascular: Bryophytes ~ 450 mya • • • • • • • • • Simple plants, limited size Hold loose dirt in place Live in moist areas Depend on external water transport for reproduction: motile male gamete No vascular tissue = movement through osmosis/diffusion No true roots = have rhizoids like root hairs (absorb water, anchor plant) No stems No leaves = similar structures but only one cell thick. Produce spores in a capsule at end of a stalk moss liverwort Filicinophytes Vascular tissue—spores on underside of frond Vascular-Alternating Life Cycle Filicinophytes, or Ferns frond • Have vascular tissue: can be bigger – Xylem: H2O + minerals – Phloem: sap (sugar, AAs, hormones...) • Live in moist areas • Have roots, stems and leaves (fronds) • Motile male gametes: can occupy terrestrial environments BUT still needs water for reproduction • Spores (no seeds) produced in sporangia, generally on the underside of the leaf • Leaves are curled, and then uncurl as they mature young frond rhizome roots http://www.biology87.org/apbio/diversity/PlantLabPicts/s tatio6.jpg http://www.biology87.org/apbio/diversity/PlantLabPicts/statio4.jpg Spermatophytes (seeded vascular plants) Synapomorphy--seeds 2 Groups Seeded Plants ~144 mya Mesoozoic Cretaceous (Angioperms) ~385 mya Paleozoic Devonian (Gymnosperms) ORIGIN OF SEEDS (Progymnosperms) – 385 mya 385 mya Coniferophytes Conifer • Contain a well developed vascular tissue (big plants!), roots, stems (woody) and leaves • Produce male (contain pollen) and female (contain ovules) cones • Produce seeds which develop on the scales of the female cones • Gametes are not motile: does not depend on water for reproduction • Tough, needlelike leaves with thick cuticles and sunken stomata: adaptations for dry environments • NO REAL FLOWERS + NO FRUITS e.g. pines, spruces, firs, cypress, yews Sequoias National Park in California Angiospermophytes Flowering Plants • Flowering plants with roots, stems and leaves • Occupy all environments • Gametes are not motile (does not need water for reproduction) • Seeds are produced – develop inside the ovaries in the flower • Ovary develops into a fruit which aids in seed dispersal Why are angiosperms so successful? • Seed protected in fruit • Fruit skin and flowers can be different colors, have different scents, and have different nutritional values • Can attract dispersers (reds and yellows attract birdsothers bear, primates, and so on • Pollen easily dispersed by wind, birds, insects including butterflies Drawing a flower: • Female Reproductive Organs: stigma + style + ovary = PISTIL • Male Reproductive Organs: anther + filament = STAMEN • Petals: attract animals • Sepals: protection Monocotiledonous x Dicotiledonous • Two types of angiospermophytes • Cotyledon= seed leaf • Differences in leaves, arrangement of vascular tissue, root system and stem composition. Monocotiledonous x Dicotiledonous Characteristic Cotyledons Leaf Flowers Roots Stem Mono 1 Parallel veins Floral organs x 3 No main root Vascular tissues scattered Di 2 Netlike veins Floral organs x4 or x5 Main root present Vascular tissue in ring Monocotyledenous Plants Corn and wheat, etc. Dicotyledenous Plants Bean, etc. 9.1.1 Draw and label plan diagrams to show the distribution of tissues in the stem and leaf of a dicotyledonous plant. 9.1.1 Draw and label plan diagrams to show the distribution of tissues in the stem and leaf of a dicotyledonous plant. 9.1.1 Tissues in stem of dicotyledonous plant 9.1.1 Tissues in leaf of dicotyledonous plant 9.1.1 Tissues in leaf of dicotyledonous plant 9.1.2 Outline three differences between the structures of dicotyledonous and monocotyledonous plants. From BioNinja.com Upper Epidermis •Function: Main function is water conservation (secretes cuticle to create a waxy outer boundary) •Distribution: On top of leaves where light intensity and heat are greatest Palisade Mesophyll •Function: Main photosynthetic tissue (cells contains many chloroplasts) •Distribution: Upper half of leaf where light intensity is greatest (upper epidermal cells are transparent) Spongy Mesophyll •Function: Main site of gas exchange (made of loosely packed cells with spaces) •Distribution: Lower half of leaf, near the stomatal pores (where gases and water are exchanged with the atmosphere) Vascular Tissue •Function: Transport of water (xylem) and the products of photosynthesis (phloem) •Distribution: Found in middle of leaf (allowing all cells optimal access) 9.1.4 Identify modifications of roots, stems, and leaves for different functions: bulbs, stem tubers, storage roots, and tendrils. A storage organ is a part of a plant specifically modified to store energy (e.g. carbohydrates) or water They are usually found underground (better protection from herbivores) and may result from modifications to roots, stems or leaves: Storage roots: Modified roots that store water or food (e.g. carrots) Stem tubers: Horizontal underground stems that store carbohydrates (e.g. potato) Bulbs: Modified leaf bases (may be found as underground vertical shoots) that contain layers called scales (e.g. onion) Some plants (called succulents) have modified leaves or stems (thickened, fleshy and wax-covered) to enable water storage (e.g. cacti) Other plants (e.g. vines) have modifications to their leaf or stem to enable climbing support and attachment - these are called tendrils 9.1.4 Identify modifications of roots, stems, and leaves for different functions: bulbs, stem tubers, storage roots, and tendrils.
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