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Transcript
Chapter 19: Kingdom Plantae 19.1 Land plants evolved from green algae Multicellular Usually photosynthetic Mostly terrestrial Plant: multicellular autotroph, embryo develops in female parent Origins of Plants from Algae Closest ancestors = multicellular green algae – Charophytes Some shallows dried out – plants adapted Challenges of Life on Land 4 challenges – 1. obtaining resources – 2. staying upright – 3. maintaining moisture – 4. reproducing 1. Resources Air – light, carbon dioxide (photosynthesis) – Shoots, leaves Soil – water, mineral nutrients – Roots Vascular tissue – System of tube-shaped cells that branches throughout the plant – Materials – roots/shoots 2. Staying Upright Water - buoyancy Air – rigid support tissue – Lignin – hardens plants’ cell walls 3. Moisture Internal watery environment for cell processes Adaptations: – Waxy cuticle – retain water, slow exchange gases between air and leaves – Stomata – pores in leaf’s surface Gas exchange Guard cells 4. Reproduction Gametes / offspring – moist – Sperm – pollen grain – Egg – female tissues Dispersal – Sperm – wind / animals Embryo develops in female parents seeds Overview of Plant Diversity 4 major periods plant evolution – 1. Bryophytes – mosses No seeds, no lignin – 2. Pteridophytes – ferns Lignin – vascular tissue – 3. Gymnosperms – naked seeds, conifers – 4. Angiosperms – flowering plants Fig. 19-5 Figure 19-5 Fossil evidence indicates that bryophytes are the oldest and angiosperms the youngest of the four major plant groups. Alternation of Generations Diploid (Sporophyte) / haploid (Gametophyte) Multicellular Fig. 19-6 Figure 19-6 A plant's life cycle alternates between the gametophyte and sporophyte generations Spores vs. Gametes Spore Gamete New organism without another cell 2 gametes fuse to form a zygote Tough coat – harsh environments Not adapted for harsh conditions 19.2 Mosses and Bryophytes Damp habitats Lack rigid support tissues grow close to ground Bryophyte Adaptations Dominant generation = gametophyte (1n) Nonvascular – no lignin Fig. 19-7 – overhead Separate male/female gametophytes – Flagellated sperm swim to eggs – Fertilization – zygote grows from female gametophyte into sporophyte – Sporophyte (2n) = stalklike, capsule at top – Capsule produces/releases spores new gametophytes Diversity of Bryophytes Hornworts – hornlike sporophytes Mosses – Moss mat = many gametophytes in tight pack – Stalks = sporophytes – Spongy – absorb / retain water Liverworts – liver-shaped gametophytes 19.3 Pteridophytes: Ferns / other seedless vascular plants Pteridophyte adaptations: Fig. 19-10 - overhead – Vascular tissue – lignin – water, sugar – Carboniferous period – fossil fuel – Dominant generation = sporophyte – Underside of fronds – spore capsules Haploid spores, gametophytes – Underside of gametophyte Produce sperm / egg Sperm swim to egg zygote new sporophyte Diversity of Pteridophytes Ferns – most diverse Leaves = fronds Shady forests Club “mosses” – little pine tree – Vascular tissue, no seeds, forest floors Horsetails Marshy, sandy areas Outer layer = silica – gritty Scrub pots/pans “scouring rushes” 19.4 Pollen and Seeds Evolved in Gymnosperms Gymnosperm adaptations Gymnosperms = plants that bear seeds that are “naked” – Not enclosed in an ovary – Most common - conifers 3 more adaptations than ferns: 1. Smaller gametophyte – Dominant generation = diploid sporophyte = pine tree – Tiny gametophytes are in cones- protection 2. Pollen – Reduced male gametophyte – Contain cells that become sperm – Wind – pollen from male to female- no water needed 3. Seeds – Plant embryo with a food supply in a protective coat Life Cycle of Gymnosperms Male pollen cone - spore sacs with haploid spores become pollen grains (male gametophyte) Female gametophytes develop within ovules – On scale of cone – 2 ovules – Large spore cell – meiosis – 4 haploid cells – 1 survives female gametophyte Wind – blows pollen between trees Pollen lands in female cone Sperm matures and fertilizes egg in female gametophyte 2 eggs fertilized often – still only 1 zygote into embryo (seed) = new sporophyte Diversity of Gymnosperms 4 phyla today Gingkos – Gingko biloba Fan-like leaves Shed in autumn Cities– Tolerates – pollution Gnetophytes – Mormon tea, desert shrub Cycads – large, palm-like leaves – Not true palms which are flowering plants Conifers – Spruce, pine, fir, junipers, cedar, redwood – evergreen 19.5/20.1 Flowers and fruits evolved in angiosperms Angiosperm Adaptations – Gametophytes develop in flowers of sporophyte – Flower = specialized type of plant shoot that functions in reproduction, only in angiosperms animal pollinators – variety Insects transfer pollen between flowers Grasses – wind pollinated – small flowers Attract Flower Anatomy Flower – specialized shoot 4 rings modified leaves – Sepals – protect flower bud – Petals – color – insects – Stamens – male, many – Carpels (pistils) – female,1+ Stamen – produces male gametophytes Filament + anther Filament – supports anther Anther – pollen – meiosis – spores – pollen grains = male haploid gametophytes Each pollen grain – 2 cells with thick protective wall Fig 20-2 in packet Carpels – female gametophytes stigma – style – ovary – Stigma – sticky – pollen – Style – supports stigma – pollen tube – Ovary - ovules Angiosperm Life Cycle Pollen on stigma - pollination Pollen tube to ovule in ovary - style – 2 sperm cells in pollen grain in tube – In ovules – diploid cell – meiosis haploid spores – ¾ die survivor enlarges – 3 cycles mitosis embryo sac – 7 cells (1 egg cell + 1 large cell with 2 haploid nuclei) 4 Water lilies Star Anise – 1st sperm fertilizes 1 egg = zygote embryo – 2nd sperm fuses with nucleus in larger center cell triploid cell = endosperm (nutrient storage) – “double fertilization” – zygote and endosperm develop into seed Many ovules, many seeds Seeds develop, ovary wall thickens fruit Fruit = ripened ovary of a flower – Protects, disperses seeds – Colorful, attract animals, eat, digest, waste Monocots – day lilies, orchids, irises, palms, grasses – Flower petals – multiples of 3 Dicots – poppies, roses, peas, sunflowers, oaks, maples – Flower petals – multiples of 4 or 5 Human Dependence on Angiosperms Food – human, domestic animals – Corn, rice, wheat, fruit, vegetables Furniture, medicines, perfumes, decorations, clothing fibers Threat – tropical rain forest 20.1 Reproductive Adaptations contribute to angiosperm success Seed Development and Dispersal Seed parts – Seed coat – outer layer – protects embryo and endosperm – Mini root and shoot – Cotyledon – food storage Monocot, dicot Seed Dispersal Animals – fur – burr – Eat, digest fruit, waste Water – coconut Wind - dandelion Seed Germination Plant embryo grows in favorable conditions Soak up water Expands Seed coat splits Adaptations to Germination Dicot – hooked shoot tip Monocot – sheath around shoot tip Light – 1st leaves – photosynthesis = seedling Environment needed for Germination Usually just warm, moist Others – Heavy rainfall – soil – Long cold – Intense heat - clearing Challenges to sexual reproduction Pollination Damaged seeds Bad environment for germination Delicate seedlings – eaten, water Asexual Reproduction in Plants Vegetative Propagation – offspring identical to parent Cacti- drop stems Strawberries - runners Lifespan Annuals – one growing season Biennials – 2 years Perennials – multiple years 20.2 Plant Tissues / Organs Roots – Anchor, support, absorb water, minerals Monocots – – fibrous roots: many thin roots – grass Dicots – – Taproot: 1 large vertical root with small root hairs – carrots, turnips, beets Angiosperm shoots – stem, leaves, flower Stems – Support leaves, flowers – Nodes – where leaves are attached – Internodes – between nodes – Transport – vascular tissue – leaves and roots Buds – Underdeveloped shoots – Terminal bud – tip of stem – Axillary buds – found in angles of leaf and main stem – branches Leaves – Photosynthesis – food – Blade – main leaf part – Petiole – connects leaf to stem – Veins – carry water, nutrients – Modified leaves – no petiole Celery – large petiole – eat Cactus spines Grass Main Tissue Systems: Dermal, Vascular, Ground Vascular – transport roots / shoots – Support – 2 types: Xylem: water, dissolved minerals up from roots to shoots Phloem: food from leaves to roots, non foodmaking leaves, fruits Locations: – Roots – center – Stems – vascular bundles • Monocot – scattered • Dicot - ring Dermal – outer covering – Epidermis – protects young plant parts Ground – makes most young, nonwoody plants – Photosynthesis, storage, support – Root - cortex Plant Cells: Parenchyma, Collenchyma, Sclerenchyma Parenchyma – Food storage, photosynthesis, cellular respiration – Fruits, phloem Collenchyma – In strands, Celery strings – young parts Sclerenchyma – Lignin-rich cell walls - ‘skeleton’ for mature plant – xylem 20.3 Primary Growth Meristematic tissue – Meristems – create new tissue - always Mitosis, cell then differentiate – Apical meristems Tip of roots, bud of shoots Lengthen, branch – Primary growth Growth in plant length Primary growth in Roots Root cap = root tip – protects dividing cells of apical meristem Root apical meristem – 1. Replaces root cap cells – 2. Produces cells for primary growth Primary growth cells – 3 concentric circles – Out – dermal – Middle – bulk root tip – root’s cortex (ground) – In – vascular tissue Primary growth depends on – Addition of new cells – Cells elongating – more water – Elongation – forces root tip through soil Primary growth of shoots Apical meristem – tip terminal bud Elongation – just below meristem – push cells upward Some cells left behind – Become axillary buds - branches 3 concentric circles – dermal, ground, vascular 20.4 Secondary Growth Woody plants – vines, shrubs, trees Growth in plant width Cell division in 2 meristematic tissues: vascular cambium and cork cambium Vascular Cambium Between xylem and phloem Adds cells both sides – Secondary xylem inside – Secondary phloem outside Added to primary tissues during primary growth Secondary xylem becomes wood each year during growing season – Dormant in winter – Stem / root thickens with each new xylem Cork cambium cork Cork cells die – thick, waxy walls left – water loss, helps protect internal tissues Bark = everything outside vascular cambium = Phloem, cork cambium, cork The Rings Age from annual growth rings Result of vascular cambium activity each year Environment Each ring – Spring wood – large, thin-walled Cool temps, lots water – Summer wood – narrow, thick-walled Hot, dry 21.2 Vascular Tissue Roots – absorb water, minerals Roots hairs –epidermal cells – Grow between soil particles – Surface area Root pressure – Pushes water up xylem – night – Root epidermal and ground tissue cells use ATP to get minerals – into xylem – Endodermis – around vascular tissue, waxy cell walls – doesn’t let water back out – Water enters (osmosis) – pushes xylem sap upward The Upward Movement of Xylem Sap Transpiration – loss of water through leaves due to evaporation – “transpiration pull” Cohesion – same kind molecules stick together (water) Adhesion – attraction between unlike molecules (water sticks to cellulose in xylem walls) http://www.pearsonsuccessnet.com/snpapp/iText/products/0-13-115075-8/text/chapter21 Regulating water loss Transpiration – lots water loss Evaporative cooling – keep good temp. More transpiration than water delivery = wilting Adaptations for water loss Leaf stomata – open / close – guard cells Day – Stoma open – Carbon dioxide in – Sunlight and low carbon dioxide – more potassium – water follows – Guard cells swell and open Night – Stomata close – Potassium ions leave with water – Sag together Flow of Phloem Sap Phloem Move sugar from source to sink (storage or use) Different sinks, different seasons – Summer – taproots, tubers – storage – Next Spring – become sugar source Pressure – Flow Mechanism Sugar produced Active transport to phloem tube Up sugar conc. at source end of phloem – water follows = up water pressure at source pressure low at sink Sink end = sugars leave phloem, water follows, pressure drops = water flows high to low 21.3 Carnivorous Plants Some plants – N from animals Ex: sundews, Venus's flytraps, pitcher plants Little organic N where they live (wetlands, cold, acidic water, decay slow) Still photosynthesize 22.1 Plant Hormones Plant hormones – chemical messengers (only takes a little) Control: – Germination – Growth – Flowering – Fruit production Functions of 5 Major Hormones: Balance of hormones acting together Auxins Apical meristems – shoot tips Cell elongation Auxin builds – shaded side Shaded cells lengthen more, more water Uneven sides = bending Secondary growth – vascular cambium Seeds – auxin – signal ovary to fruit Auxins - no pollination seedless fruit Cytokinins Cell division – made in roots Cytokinin with auxin – Fewer / shorter branches near tip Gibberellins Fruit – seedless, larger Abscisic Acid (ABA) Limits cell division Stops growth Dormancy “stress hormone” Ethylene Fruit ripening “leaf drop” 22.2 Plant Responses Rapid plant movements – Touch – Rapidly reversible Tropisms – slowly grow toward or away from a stimulus – Slow to reverse Thigmotropism Touch Climbing plants – tendrils Seedling - obstacle Phototropism Light Uneven auxins – light one side Gravitropism Gravity Mature plant Seedling root / shoot Stressful Environments Drought – Water loss, wilting, drop photosynthesis – Succulents – water fleshy stems Flooding – Clogs air spaces, less cellular respiration – Mangrove trees Salt stress – Root cells drop water – osmosis – Halophytes – salt glands, pump out salt Disease Viruses, bacteria, fungi Adaptations – Epidermis – Chemicals – lignin – Resistant genes – Thorns, poisons