Chapter 22 Lecture Outline 22-1 What Is a plant? Eukaryotic Multicellular Photosynthetic Contains chlorophyll a and b Has cellulose cell walls Live in a variety of terrestrial habitats – 22-2 And a few shallow aquatic habits Exhibits alternation of generations Plant Diversity 22-3 Alternation of Generations A life cycle that involves two generations 1. Sporophyte generation 2. Gametophyte generation 22-4 Diploid Undergoes meiosis to generate haploid spores Spores germinate and divide by mitosis to give rise to a haploid gametophyte generation. Haploid generation Undergoes mitosis to produce haploid gametes Gametes unite to form a zygote. Zygote divides by mitosis to form the sporophyte generation. Alternation of Generations 22-5 The Evolution of Plants Freshwater green algae are thought to be the ancestors of plants. – – The evolution of plants shows two trends. – – 22-6 Green algae have the same types of chlorophyll. There is great similarity in the DNA of green algae and plants. Toward greater specialization for living in a dry environment Toward a more prominent sporophyte generation The Evolution of Plants Primitive plants – – – More advanced plants – – – 22-7 Lack vascular tissue to carry water Usually live in moist situations Have dominant gametophyte generation Have specialized cells that transport water Typically live in dryer situations Have dominant sporophyte generation The Evolution of Plants 22-8 Nonvascular Plants Commonly known as the bryophytes Include – Common features – – – – – 22-9 Mosses, hornworts, liverworts Lack vascular tissue Do not have true roots or leaves Gametophyte is dominant Sperm swim to egg Are small and confined to moist habitats Moss Life Cycle 22-10 Kinds of Nonvascular Plants Mosses – – Liverworts and hornworts – – 22-11 Grow as a carpet of many individual gametophyte plants Each individual is less than 5 cm tall. Form flat sheets only a few cells thick Cells of hornworts only contain one large chloroplast. The Significance of Vascular Tissue Vascular tissue allows plants to transport water and nutrients throughout the plant Vascular tissue is associated with development of – – – – – Two types of vascular tissue – 22-12 Leaves for photosynthesis Stems for positioning leaves and transporting materials Roots for absorbing water and minerals An increase in plant size The appearance of a waterproof coating on the plant surfaces – Xylem Phloem Xylem 22-13 A series of dead, hollow cells that form tubes Transports water and minerals from the soil to the leaves Xylem 22-14 Phloem Carries organic molecules produced in the leaves to the rest of the plant – – 22-15 Sugar Amino acids Phloem 22-16 The Development of Roots, Stems, and Leaves 22-17 The appearance of vascular tissue allowed for the development of specialized plant parts. Roots are specialized for absorption. Stems are specialized for transport. Leaves are specialized for photosynthesis. Roots Underground parts of a plant that – – Anchor in the soil Absorb water and nutrients 22-18 Move the nutrients into the vascular system Grow from the tips Important storage sites for food Stems Above-ground structures that – – – 22-19 Support the leaves Transport raw material from the roots to the leaves Transport manufactured material from the leaves to other parts of the plant The Love TreeRAY: This was sent to us by Bob Powers from Shreveport, LA. Here it is.A teenage boy smitten with a teenage girl in his high school freshman class, made his feelings known. Overjoyed at finding them reciprocated, he took pen knife to a young hard wood in the vicinity and carved their initials within a heart, five feet up the tree's trunk. TOM: I see the puzzler already. RAY: By their senior year, however, the girl's ardor had cooled. She took her diploma, went away to the big city and married. The boy was crushed, inconsolable. Bidding his family farewell, he took his small savings that he got from selling lemonade, bought a bus ticket, went to the east coast and shipped out in a menial job on a broken down freighter. Twenty-five years later, captain of his own vessel, owner of a small freighter fleet and with a major interest in a few oil tankers, he indulged in a nostalgic whim and returned for the first time ever, to his old hometown. Imagine his joy, when he discovered his old sweetheart living there, now a widow.One thing led to another. The flame reignited, and one day they searched for their tree. It was not hard to find. It was near a rock, near a river, and they immediately found it. Now, here's the puzzler. If the tree had added 35% to its height in the first 15 years of his absence, 10% in the following in the five years and 2.5% in the ensuing eight years, how far up the trunk did they have to look to find the carving with their initials? Think you know? Drop Ray a note! Leaves Specialized for photosynthesis – – – Have large surface area to collect sunlight Relatively thin to allow light penetration Have bundles of vascular tissue to support leaf tissue and provide transport – – 22-20 Water and minerals transported to the leaf Sugar produced by photosynthesis from the leaf Are arranged to minimize shading of lower leaves Covered by a waxy coating to minimize water loss The Structure of a Leaf 22-21 Leaves Transpiration, stomates, and photosynthesis – Transpiration involves several processes – Role of stomates 22-22 Water evaporates and exits leaves through stomates. Stomates must be open to allow water and oxygen to exit, and carbon dioxide to enter leaves and allow for photosynthesis. Stomates can close to regulate water loss in drought or during dry part of the day Stomates 22-23 Seedless Vascular Plants Include – – – Have vascular tissue – Are not limited to aquatic environments Do not have seeds – – 22-24 Horsetails Club mosses Ferns Have flagellated sperm Must have moist conditions to reproduce Fern Life Cycle 22-25 Kinds of Seedless Vascular Plants Ferns – 22-26 Most common seedless vascular plant Kinds of Vascular Seedless Plants Horsetails – – – 22-27 Low-growing plants with jointed stems Most photosynthesis occurs in the stems. Have silicon dioxide in their cell walls Called (and used as) scouring brushes by pioneers Club mosses Seed-Producing Vascular Plants Gymnosperms and angiosperms produce seeds. A seed is a specialized structure that contains – – – Seeds allow plants to live in dry habitats. – – 22-28 An embryo Stored food A protective outer coating (seed coat) that prevents drying Germinate and grow when conditions are right Aid in dispersal Gymnosperms Gymnosperm means “naked seed”. Produce seeds that are not enclosed (naked) – 22-29 Produce seeds in cones Woody, perennial plants The Pine Life Cycle 22-30 Kinds of Gymnosperms Cycads – – Woody plants with a ring of fern-like leaves at the top Live in tropical regions Ginkgo – – Ginkgo biloba is the only living species. A tree with fan-shaped leaves 22-31 Used in many herbal medicines Kinds of Gymnosperms Conifers – – – Trees and shrubs that bear cones Have needle-shaped leaves Called evergreens because they do not lose their leaves all at one time – 22-32 Do shed needles throughout the year Used in the production of lumber Several Gymnosperms 22-33 Angiosperms Produce flowers Have vascular tissue, seeds, and pollen Have seeds enclosed in a fruit – 22-34 A modification of the ovary wall Flower Structure Composed of highly modified leaves – – – – 22-35 Petals and sepals surround pistils and stamens. Petals and sometimes sepals are large and showy in insect-pollinated plants. Flowers of insect-pollinated plants typically produce nectar and odors to attract insects. Much variation in structure of flowers Flower Structure (continued) Specialized for sexual reproduction – Female parts in the center – Male parts surround the pistil. – – 22-36 Pistil (stigma, style, and ovary) – Ovary produces eggs Stamens (filament and anther) – Anther produces pollen which contains sperm nucleus. Perfect flowers have both pistils and stamens. Imperfect flowers have either pistils or stamens. Flower Structure 22-37 The Life Cycle of a Flowering Plant 22-38 Pollination Strategies Wind pollination – – Plants with inconspicuous flowers are usually wind-pollinated. Produce many flowers and much pollen – Responsible for hay fever 22-39 Grasses and sedges Many trees such as aspens, birches, and oaks Some people have allergic reactions to certain kinds of pollen. Strategies for Pollination Animal pollination – – Plants with showy flowers are usually animal-pollinated. Flowers attract insects, birds, and small mammals. – The animals feed on the nectar and pick up the pollen. 22-40 These flowers usually produce nectar. Also produce odors that attract animals Then move to another plant for more nectar, transferring the pollen Wind- and Insect-Pollinated Flowers 22-41 Fruit A modification of the ovary that contains seeds Involved in dispersal of seeds Many fruits are nutritive to animals. – – 22-42 The animals eat the fruit and ingest the seeds. The seeds pass through the digestive tract unharmed and get “planted” in the animals’ feces. Other fruits burst open and release light seeds that are dispersed by wind. Other fruits have sticky surfaces that cling to animals that pass by. Types of Fruits 22-43 Angiosperm Diversity Classified as either monocots or dicots – Cotyledons (seed leaves) store food for the growing embryo. – Monocot and dicot refers to the number of cotyledons found in the seeds of the species. 22-44 They emerge as the first leaves. Monocots have one cotyledon (grasses, lilies, etc). Dicots have two cotyledons (beans, apples, etc). Embryos in Dicots and Monocots 22-45 Monocots vs. Dicots 22-46 Growth of Woody Plants All gymnosperms and many dicots are woody plants. Woody plants are perennials that have the ability to grow continuously for many years. – 22-47 They get taller and grow in diameter each year. Growth in length occurs at the tips of the roots and stems. Growth in diameter occurs by adding new xylem and phloem to the outside of the stem. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Phototropism 22-48 Coevolution of Plants and Animals The first terrestrial organisms were plants. Insects and amphibians were the terrestrial animals. Symbiotic relationships evolved between plants and animals. – Many flowering plants are pollinated by insects and birds. – Grasses and grazers have coevolved. – Grass has silicon that wears down grazers’ teeth. Grazers have very long teeth that take a long time to wear down. Many angiosperms produce nutritive fruit. 22-49 These flowers are brightly colored, have nectar, and have odor. Animals eat the fruit and distribute the seeds.