Transcript Plant Unitx
Plants... • • • • Eukaryotic Multicellular Cell walls Reproduction – Asexually – Sexual via spores or seeds • Photosynthetic (most are autotrophs) Cellular components of plants • • • • • Cell wall made of cellulose Nucleus containing DNA Mitochondria Vacuole Chloroplasts Plant Characteristics • They make their own food – Chloroplasts contain chlorophyll Photosynthesis 6CO2 + 6H2O C6H12O6 + 6O2 Chloroplasts: What is a Cuticle? • A waxy layer that coats the surface of plant parts. • Keeps plants from drying out. • Plants Have a Cuticle Plant Characteristics • Plant Cells have Cell Walls What is a Cell Wall? – a plant cell is surrounded by a rigid cell wall – outside of the cell membrane – helps support and protect the plant How did Plants Originate? • First plants lived in water – similar to today’s green algae • Links b/w algae and plants – Cell walls – Some multicellular – Chlorophyll used in photosynthesis – Reproductive cycles How did plants evolve? • Land adaptations: –Resistance to drying –Conserving water –Reproducing w/o water Overview of the Plant Kingdom • Divided into 5 groups based on 4 derived characters: – Embryo formation – Water conducting tissues – Seeds – Flowers Alternation of Generations • Plants reproduce w/ spores + sex cells –There are two stages in a plant’s life: • Sporophyte (diploid 2N stage) • Gametophyte (haploid N stage) • Alternating b/w both phases is called alternation of generations! What is a Sporophyte? • A plant in the spore producing stage of life. • Spores can grow directly into an adult plant What is a Gametophyte? • The stage in a plant’s life where it produces male and female sex cells. More on Gametophytes • The stage in a plant’s life where it – produces male and female sex cells. • Male and female sex cells must join in order to grow into a new plant. – This is called Fertilization. Alternation of Generations 1. Sporophyte (2N) 2. Undergoes meiosis => haploid spores 3. Spores become a gametophyte (N) 4. Gametophytes produce gametes (sperm and egg) 5. Fertilization creates zygote which becomes sporophyte and cycle starts over! 16 Alternation of Generations 1. Which generation of a plant is diploid? Haploid? 2. Why does it make sense that the sporophyte generation is diploid? 3. What does the sporophyte produce? 4. What process produces spores? 5. Are the spores diploid or haploid? Trends in Plant Evolution • As plants evolved: – the size of the gametophyte became smaller, while the sporophyte became larger. Seedless Plants – Chapter 22.2 Mosses and Liverworts Ferns, Horsetails, and Club Mosses Essential Questions • What are the characteristics of green algae? • What factor limits the size of bryophytes? • How is vascular tissue important? Green Algae • First plants appeared on Earth 550 mya • Absorb nutrients from their surroundings Plants can be divided into 2 groups Plant Kingdom Non-vascular Plants Vascular Plants Plants w/o Seeds (Seedless) Plants w/ Seeds (Seeded) Naked Seeds Seeds in Fruits 22 How are Plants Classified? • Nonvascular Plants (Bryophytes): –no pipes to transport water and nutrients –depend on diffusion and osmosis –small: mosses, liverworts, hornworts Mosses and Liverworts • Small • Live on bark, rocks, and soil • No vascular system • Must live in places that are wet • No true roots, stems, or leaves Mosses Liverworts Hornworts Mosses and Liverworts • Live together in large groups • Waxy coating • Each moss has rhizoids (root-like structures) • Rhizoids help anchor the plant Bryophyte Life Cycle How are Plants Classified? • Vascular Plants (Tracheophytes) – Have tissues that deliver needed materials throughout a plant - called vascular tissues. – Can be almost any size. – Are divided into gymnosperms and angiosperms Vascular Plants • Tracheids – Cells that transports water – Lignin – Compound in cell walls that makes them rigid • Formation of vascular tissue – Xylem (water) – Made up of tracheids – Phloem (food) – True leaves, roots, and stems • Sporophyte generation dominate • Sperm with flagella Seedless Vascular Plants • Ferns, Horsetails, and Club Mosses: – Grow tall – Have vascular systems Ferns Horsetails Fern Life Cycle Division: Pterophyta Seed Plants – Chapter 22.3 Gymnosperms Angiosperms Adaptations to land… – Reproduce by cones or flowers – Pollination instead of water fertilization – Protection of developing embryos in seeds The selective advantages of invading this new habitat… – Less competition for sunlight – Mineral-rich soil Seed Plants Two groups of seed plants: – Gymnosperms – Angiosperms Gymnosperms include the conifers and cycads – Seeds in cones Angiosperms are the flowering plants – Seeds in flowers Gymnosperms: Phylum Coniferophyta (conifers) Female cones Male cones Well adapted to cold & dry summers – “naked seeds” (no fruit) – Two kinds of cones • Males produce pollen grains (male gametophyte) • Female produce ovules (produce female gametophyte) Pollen (Gymnosperms) Outer layer of pollen is impermeable – Winged for wind dispersal – Male gametophyte – Lots of pollen is produced, and randomly reaches receptive ovules within female cones. Gymnosperm seed development Gymnosperm Life • vascular Cycle • diploid dominant • Non-motile gametes • naked seeds • not water dependent Flowering Plants – Chapter 22.4 Flowers and Fruits Angiosperm Diversity Essential Questions What are the key features of angiosperm reproduction? How are different angiosperms conveniently categorized? Evolution of Plants: From Algae to Angiosperms Angiosperms (Enclosed Seed) Most diverse and geographically widespread Benefits to humans and other animals – Medicines, cosmetics, food, building materials, etc... – Fascinating examples of co-evolution with animal species Flowers and Fruits Flower: Reproductive structure – Contain ovaries (surround and protect seeds) – Improved vascular system – Pollen in anthers After pollination, the ovary develops into a fruit Fruit – Protect seeds – Disperse seeds Flower Structure Flower to Fruit Pollen Dissemination Hummingbird “floral tubes” red flowers Baobab tree night pollinator Scotch Broom... anthers “swing” up to brush bee’s back. Seed Dispersal Rivers and Floods Wind Carried Angiosperms • • • • • vascular diploid dominant Non-motile gametes seeds not water dependent Angiosperm Classification Monocot and Dicot: – # of cotyledons (seed leaves) – within the seed of a plant – becomes 1st leaves of a seedling – one leaf are called monocots – two are dicots Angiosperm Diversity Since flowering plants are so diverse, they are now also classified by: – # of seed leaves – Strength and composition of their stems – Thick cell walls (Trees, shrubs) Herbaceous – No wood as they grow Woody – Number of growing seasons – Die after 1st growing season Biannual – Dies after 2nd year Perennial – Continue to grow from year to year Annual Monocots and Dicots Now determined by more than just their # of seed leaves Monocot vs. Dicot: Root System Monocots - Fibrous root system i.e. Grasses, lilies, orchids, palm trees Rice, wheat, corn Dicots- Primary root or main root grows straight down TAPROOT: Often fleshy and stores food. Carrots, beets, turnips and radishes have taproots. A. Preventing Water Loss Cuticle: waxy coating that prevents tissues from drying out Stomata-openings in the cuticle that allow gas exchange to take place and also regulate water loss Prevent Desiccation? Desiccation= Drying Out As plants evolved further away from water –needed to evolve a waterproof structure/coating (cuticle) Stomata B. Autotrophic Leaf-organ that enables the plant to trap and absorb light energy Leaf Layers via microscope C. Stabilization and Nutrient Absorption (Accomplished with roots and mycorrihizea) Roots: – organ that is used to transport water and minerals – anchor plants and store food Earliest roots are rhizoids The Root Main function = absorb water Functional Part = root hair Structure from outside in: – Epidermis with root hair= protection – Cortex=support/storage – Vascular Bundle: Phloem, Vascular Cambium*, Xylem *Vascular Cam: growth of new vascular tissue Root Structure D. Transportation System Stem- Transport of water, food, and minerals Support of plant Storage of materials Structures of the Stem Epidermis (bark or green)=protection Cork cambium =new growth of bark/ epidermis Cortex = thick layer, sometimes contains chloroplasts, mostly for support Vascular Bundle = contain transport tissues towards the middle of the stem Xylem = transports water and minerals (generally in the middle) More Structures Phloem = transports sugars to all cells, located outside the xylem Vascular cambium = separates the X and P, contains new cells for vascular growth Pith = central portion of stem of tree, for storage E. Reproduce Without Water Spores/Cones/Seed-protective coat – prevents a developing embryo from drying out Pollen and seeds – can reproduce far away from water Pollen = plant sperm – light weight and won’t dry out, carried via wind, water, animal, etc..