Biology, 9th ed, Sylvia Mader Chapter 24 Evolution and Diversity of Plants Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. seed cones seed cones pollen cones a. A northern coniferous forest of evergreen trees b. Cones of lodgepole pine, Pinus contorta c. Fleshy seed cones of juniper, Juniperus a: © Corbis Royalty Free; b: © Walt Anderson/Visuals Unlimited; c: © The McGraw Hill Companies, Inc./Evelyn Jo Johnson, photographer

Outline Evolutionary History Nonvascular Plants Vascular Plants The Green Algal Ancestor Alternation of Generations Nonvascular Plants Vascular Plants Seedless Seed Angiosperms Monocots and Eudicots Flowers

Evolutionary History of Plants Plants are multicellular, photosynthetic eukaryotes. Plants evolution is marked by adaptations to a land existence. A land environment does offer certain advantages. Plentiful light for photosynthesis Carbon dioxide is present in higher concentrations and diffuses more readily in air than in water.

Evolutionary History of Plants A land environment does offer certain advantages Constant threat of desiccation (drying out). Protect all phases of reproduction (sperm, egg, embryo) from drying out Seed plants disperse their embryos within the seed, which provides the embryo with food within a protective seed coat. The water environment provides plentiful water. support for the body of the plant.

Evolutionary History of Plants To conserve water, the land plant body, is covered by a waxy cuticle. Impervious to water while still allowing carbon dioxide to enter so that photosynthesis can continue Vascular system transports water in the body of the land plant. Thought to have evolved from freshwater green algae over 450 mya Evolution of plants marked by four evolutionary events associated with four major groups of plants Nonvascular Plants Advent of nourishment of a multicellular embryo within the body of the female plant

Evolutionary History of Plants Seedless vascular plants Advent of vascular tissue Gymnosperms and angiosperms Produce seeds Flowering Plants Attract pollinators that give rise to fruits

Evolutionary History of Plants Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. flowers, double fertilization, endosperm, fruit common ancestor seeds Flowering plants Seed megaphylls Gymnosperms vascular tissue Vascular Ferns and allies apical growth microphylls Seedless Lycophytes embryo protection Mosses Hornworts Bryophytes Nonvascular common green algal ancestor Liverworts Charophytes 550 500 450 400 350 300 250 PRESENT Million Years Ago (MYA)

Close Algal Relatives of Land Plant Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chara Coleochaete (Coleochaete): © T. Mellichamp/Visuals Unlimited; (Chara): © Heather Angel/Natural Visions © INTERFOTO Pressebildagentur

Alternation of Generations Life cycle involves alternation of generations Multicellular 1n individuals (gametophytes) produce multicellular 2n individuals (sporophytes) Multicellular 2n individuals (sporophytes) produce multicellular 1n individuals (gametophytes) Sporophyte (2n): Multicellular individual that produces spores by meiosis Spore is haploid cell that will become the gametophyte Gametophyte (1n): Multicellular individual that produces gametes Gametes fuse in fertilization to form zygote Zygote is a diploid cell that will become the sporophyte

Alternation of Generations Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. sporophyte (2n) Mitosis sporangium (2n) zygote (2n) diploid (2n) FERTILIZATION MEIOSIS haploid (n) (n) spore (n) (n) gametes Mitosis Mitosis gametophyte (n)

Alternation of Generations Appearance of generations varies widely In ferns, female portions are archegonia and are fertilized by flagellated sperm In angiosperm, female gametophyte (embryo sac), consists of an ovule Following fertilization, ovule becomes seed In seed plants, pollen grains are mature sperm-bearing male gametophytes

Reduction in the Size of the Gametophyte Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. spores seed seed spores G a m e t o p h y t e (n) S p o r o p h y t e (2n) roots roots rhizoids roots rhizoids Moss Fern Gymnosperm Angiosperm

Other Terrestrial Adaptations Vascular tissue transports water and nutrients to the body of the plant Cuticle provides an effective barrier to water loss Stomata bordered by guard cells that regulate opening, and thus water loss

Leaf Adaptation cuticle a. Stained photomicrograph Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. cuticle a. Stained photomicrograph of a leaf cross section Plant leaves have a Cuticle and stomata Stomata Stomata 400 x b. Falsely coloured scanning Electron micrograph of leaf surface (Left): © Kingsley Stern; (Right): © Andrew Syred/SPL /Photo Researchers, Inc.

Nonvascular Plants: Bryophytes Lack specialized means of transporting water and organic nutrients Do not have true roots, stems, and leaves Gametophyte is dominant generation Produces eggs in archegonia Produces flagellated sperm in antheridia Sperm swim to egg in film of water to make zygote

Nonvascular Plants Hornworts (phlym Anthocerophyta) have small sporophytes that carry on photosynthesis Liverworts (phylum Hepatophyta) have either flattened thallus or leafy appearance Mosses (phylum Bryophyta) usually have a leafy shoot, although some are secondarily flattened Can reproduce asexually by fragmentation Dependent sporophyte consists of foot, stalk, and sporangium

B. Runk/S. Schoenberger/Grant Heilman Photography Hornwort Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. sporophyte gametophyte B. Runk/S. Schoenberger/Grant Heilman Photography

Liverwort, Marchantia male gametophyte female gametophyte gemma cup Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. male gametophyte female gametophyte gemma cup thallus rhizoids gemma a. Thallus with gemmae cups b. Male gametophytes bear antheridia c. Female gametophytes bear archegonia a: © Ed Reschke/Peter Arnold, Inc.; b: © J.M. Conrarder/National Audubon Society/Photo Researchers, Inc.; c: © R. Calentine/Visuals Unlimited

Moss (Polytrichum) Life Cycle Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4. The sporophyte: The mature sporophyte has a foot buried in female gametophyte tissue, a stalk, and an upper capsule (the sporangium), where meiosis occurs and spores are developing sporophyte 3. The zygote: The zygote and developing sporophyte are retained within the archegonium. capsule 5. The spores: When the calyptra and lid (operculum) of a capsule fall off, the spores are mature. One or two rings of teeth project inward from the margin of the capsule. The teeth close the opening, except when the weather is dry. Sporangium calyptra Mitosis stalk Sporophyte teeth operculum zygote diploid (2n) FERTILIZATION MEIOSIS haploid (n) 2. Fertilization: Flagellated sperm produced in antheridia swim in external water to archegonia, each bearing a single egg. egg foot (n) Spores sperm 6. Spore dispersal: Spores are released when they are most likely to be dispersed by air currents. Mitosis Archegonia buds Antheridia Protonema 1. The mature gametophytes: In mosses, the leafy gametophyte shoots bear either antheridia or archegonia, where gametes are 7. The immature gametophyte: A spore germinates into a male or female protonema, the first stage of the male and the female gametophytes. Gametophytes rhizoids (Top): © Heather Angel/Natural Visions; (Bottom): © Bruce Iverson

Vascular Plants Dominate the natural landscape Xylem conducts water and dissolved minerals up from roots Phloem conducts sucrose and other organic compounds throughout the plant Lignin strengthens walls of conducting cells in xylem Most seedless vascular plants are homosporous Windblown spores are dispersal agents All seed plants are heterosporous and have male and female gametophytes Seeds disperse offspring

Seedless Vascular Plants: Lycophyta Club Mosses (phylum Lycophyta) Typically, branching rhizome sends up short aerial stems Leaves are microphylls (have only one strand of vascular tissue) Most likely evolved as simple side extensions of the stem Sporangia occur on surfaces of sporophylls Grouped into club-shaped strobili

Seedless Vascular Plants Roots evolved simply as lower extensions of the stem Today’s lycophytes, also called club mosses, include three groups of 1,150 species: Ground pines (Lycopodium), Spike mosses (Selaginella), and Quillworts (Isoetes)

Ground Pine sporangia strobili sporophyll Strobilus leaves Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. sporangia strobili sporophyll Strobilus leaves (microphylls) stoma branches vascular tissue Leaf xylem phloem arial stem rhizome root Root

Courtesy Hans Steur, the Netherlands Cooksonian Fossil Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. sporangia Courtesy Hans Steur, the Netherlands

Seedless Vascular Plants: Pteridophytes Includes Ferns and their Allies (horsetails and whisk ferns) Have megaphylls (broad leaves) Allow plants to efficiently collect solar energy, Produce more food and the possibility of producing more offspring than plants without megaphylls. Horsetails Rhizome produces tall aerial stems Contains whorls of slender, green branches Small, scalelike leaves also form whorls at the joints

© Robert P. Carr/Bruce Coleman, Inc. Horsetail, Equisetum Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. strobilus branches node leaves rhizome root © Robert P. Carr/Bruce Coleman, Inc.

Microphylls and Megaphylls Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. single strand of vascular tissue branched vascular tissue a. Microphyll Megaphyll One branch began to dominate the stem system. The side branches flattened into a single plane. Tissue filled in the spaces between the side branches. branched stem system megaphyll leaf b. Megaphyll evolution process

Ferns Whisk Ferns (phylum Psilotophyta) Ferns (phylum Pterophyta) Branched rhizome has rhizoids Mutualistic mycorrhizal fungus helps gather nutrients Ferns (phylum Pterophyta) Large conspicuous fronds Divided into leaflets Dominant sporophyte produces windblown spores

Whisk fern, Psilotum sporangium scale aerial stem root rhizome Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. sporangium scale aerial stem root rhizome © CABISCO/Phototake

Diversity of Ferns spores on fertile frond stipe Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. spores on fertile frond stipe Cinnamon fern, Osmunda cinnamomea frond (undivided) frond (divided) axis leaflet Hart's tongue fern, Campyloneurum scolopendrium Maidenhair fern, Adiantum pedatum © CABISCO/Phototake

© Matt Meadows/Peter Arnold, Inc. Fern Life Cycle Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 7. The fronds: The sporophyte develops a root- bearing rhizome from which the aerial fronds project. 1. The sporophyte: The sporophyte is dominant in ferns. sori Sporophyte Dryopterus 6. The zygote: The resulting sporophyte zygote begins its development inside an archegonium. As the distinctive first leaf appears above the prothallus, and as the roots develop below it, the sporophyte becomes visible. leaflet sporangium Sorus young sporophyte on gametophyte fiddlehead rhizome roots 2. The sporangia: In this fern, the sporangia are located within sori (sing., sorus), on the underside of Mitosis annulus zygote diploid (2n) Sporangium FERTILIZ A TION MEIOSIS haploid (n) 5. Fertilization: Fertilization takes place when moisture is present, because the flagellated sperm must swim in a film of water from the antheridia to the egg within 3. The spores: Within a sporangium, meiosis occurs and spores are produced. When a sporangium opens, the spores are egg Spores prothallus (underside) sperm Archegonium Mitosis germinating spore Antheridium 4. The gametophyte: A spore germinates into a prothallus (the gametophyte), which typically bears archegonia at the notch and antheridia at the Gametophyte rhizoids © Matt Meadows/Peter Arnold, Inc.

The Uses of Ferns Edible ferns are used as a food source Harbor nitrogen-fixing cyanobacteria Azolla is grown in rice paddies, where it fertilizes rice plants. Ferns and their allies are used as medicines in China. Extracts from ferns have also been used to kill insects Used as decoration

Seed Plants Seed plants are the most plentiful plants in the biosphere Seed coat and stored food allow an embryo to survive harsh conditions during long period of dormancy Heterosporous Drought-resistant pollen grains Ovule develops into seed

Seed Plants seed cones seed cones pollen cones Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. seed cones seed cones pollen cones a. A northern coniferous forest of evergreen trees b. Cones of lodgepole pine, Pinus contorta c. Fleshy seed cones of juniper, Juniperus a: © Corbis Royalty Free; b: © Walt Anderson/Visuals Unlimited; c: © The McGraw Hill Companies, Inc./Evelyn Jo Johnson, photographer

Gymnosperms Gymnosperms have ovules and seeds exposed on the surface of sporophylls Conifers Cycads Ginkgoes Gnetophytes

Conifers Conifers, as well as other gymnosperm phyla, bear cones Tough, needlelike leaves of pines conserve water with a thick cuticle and recessed stomata Considered a “soft” wood because it consists primarily of xylem tissue

Pine Life Cycle Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1. The pollen cones: Typicall y , the pollen cones are quite small and develop near the tips of lower branches. The seed cones: The seed cones are larger than the pollen cones and are located near the tips of higher branches. 7. The sporophyte: After fertilization, the ovule matures and becomes the seed composed of the embryo, reserve food, and a seed coat. Finally, in the fall of the second season, the seed cone, by now woody and hard, opens to release winged seeds. When a seed germinates, the sporophyte embryo develops 2. The pollen sacs: A pollen cone has two pollen sacs (microsporangia) that lie on the underside of each scale. Sporophyte seed wing pollen cones seed cone The ovules: The seed cone has two ovules (megasporangia) that lie on the upper Pollen sac (microsporangium) Ovule (megasporangium) embryo seed coat stored food pollen cone scale seed cone scale seed mitosis 3. The microspores: Within the pollen sacs, meiosis produces four microspores. zygote microspore mother cell megaspore mother cell 6. The zygote: Once a pollen grain reaches a seed cone, it becomes a mature male gametophyte. A pollen tube digests its way slowly toward a female gametophyte and discharges two nonflagellated sperm. One of these fertilizes an egg in an archegonium, and a zygote results. diploid (2n) FERTILIZATION haploid (n) MEIOSIS MEIOSIS The megaspore: W ithin an ovule, meiosis produces four megaspores, only one survives. Mature female gametophyte Pollen grain Microspores archegonium Mitosis Megaspore ovule wall Pollination ovule wall 4. The pollen grains: Each microspore becomes a pollen grain, which has two wings and is carried by the wind to the seed cone during pollination. Mature male gametophyte mitosis pollen tube pollen grain sperm 5. The mature female gametophyte: Only one of the megaspores undergoes mitosis and develops into a mature female gametophyte, having two to six archegonia. Each archegonium contains a single large egg lying near the ovule opening. 200 µm

The Uses of Pine Used in construction of all sorts. Although technically a softwood, some pinewoods are actually harder than so-called hardwoods. The foundations of the Brooklyn Bridge are made of Southern yellow pine. Used for parks and gardens, and Christmas decorations. Pine needles are rich in vitamins A and C. Used as a medicine Pine oil is distilled from the twigs and needles of Scotch pines and used to scent a number of household and personal care products

Cycads Cycads (phylum Cycadophyta) Large, finely divided leaves that grow in clusters at the top of the stem Pollen and seed cones on separate plants Pollinated by insects

Ginkgoes Ginkgoes (phylum Ginkgophyta) Dioecious Some trees producing seeds Others producing pollen One surviving species (Gingko biloba)

The Ginkgo Tree ovule seed b. Ginkgo biloba, a native of China Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. ovule seed b. Ginkgo biloba, a native of China b(Main): © Runk/Schoenburger/Grant Heilman Photography; b(Inset): Courtesy Ken Robertson, University of Illinois/INHS

c(Main): © Daniel L. Nickrent; c(Inset): Courtesy K.J. Niklas Ephedra Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. leaves microsporangia c. Ephedra, a type of genetophyte c(Main): © Daniel L. Nickrent; c(Inset): Courtesy K.J. Niklas

Welwitschia miribilis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. pollen cones leaf d. Welwitschia mirabilis, a type of gnetophyte © NHPA/Steve Robinson

Gnetophytes Gnetophytes (phylum Gnetophyta) Have similarly structured xylem None have archegonia Strobili have similar construction

Angiosperms Angiosperms (phylum Anthophyta) An exceptionally large and successful group of plants Ovules are always enclosed within diploid tissues Became dominant group of plants in the late Cretaceous and early Paleocene periods

Amborella trichopoda Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Courtesy Stephen McCabe/Arboretum at University of California Santa Cruz

Monocots and Eudicots Two classes of flowering plants Monocotyledones (Monocots) One cotyledon in seed Eudicotyledones (Dicots) Two cotyledons in seed

Flower Diversity Beavertail cactus, Opuntia basilaris Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Beavertail cactus, Opuntia basilaris Water lily, Nymphaea odorata Blue flag iris, Iris versicolor Snow trillium, Trillium nivale Apple blossom, Malus domestica Butterfly weed, Asclepias tuberosa (Cactus): © Christi Carter/Grant Heilman Photography; (Butterfly weed): © Evelyn Jo Johnson; (Water lily): © Pat Pendarvis; (Iris): © David Cavagnaro/Peter Arnold, Inc.; (Trillium): © Adam Jones/Photo Researchers, Inc.; (Apple blossoms): © Inga Spence/Photo Researchers, Inc.

The Flower Peduncle (flower stalk) expands at tip into a receptacle Bears sepals, petals, stamens, and carpels, all attached to receptacle in whorls Calyx (collection of sepals) protect flower bud before it opens Corolla (collection of petals)

The Flower Each stamen consists of an anther and a filament (stalk) Carpel has three major regions Ovary - Swollen base Fruit Style - Elevates stigma Stigma - Sticky receptor of pollen grains

Generalized Flower anther stigma pollen tube filament style ovary Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. anther stigma pollen tube filament style ovary stamens ovule carpel receptacle petals (corolla) sepals (calyx)

Flowering Plant Life Cycle Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Stamen Carpel anther stigma filament style 2. The pollen sacs: In pollen sacs (microsporangia) of the anthe , meiosis produces microspores. ovary The ovules: In an ovule (megasporangium) within an ovary, meiosis produces four megaspores. ovule 7. The sporophyte: The embryo within a seed is the immature sporophyte. When a seed germinates, growth and differentiation produce the mature sporophyte of a flowering plant. r Mitosis stigma fruit (mature ovary) Sporophyte 1. The stamen: An anther at the top of a stamen has four pollen sacs. Pollen grains are produced in pollen Pollen sac (microsporangium) Ovule (megasporangium) style seed (mature ovule) 6. The seed: The ovule now develops into the seed, which contains an embryo and food enclosed by a protective seed coat. The wall of the ovary and sometimes adjacent parts develop into a fruit that The carpel: The ovary at the base of a carpel contains one or more ovules. The contents of an ovule change during the flowering plant life cycle. ovary seed coat embryo Anther endosperm (3n) Seed diploid (2n) FERTILIZATION MEIOSIS MEIOSIS haploid (n) Pollen grain (Mature male gametophyte) tube cell 5. Double fertilization: On reaching the ovule, the pollen tube discharges the sperm. One of the two sperm migrates to and fertilizes the egg, forming a zygote; the other unites with the two polar nuclei, producing a 3n (triploid) endosperm nucleus. The endosperm nucleus divides to form Pollination mitosis generative cell ovule wall Microspores Megaspores pollen tube polar nuclei sperm ovule wall sperm antipodals egg pollen tube tube cell nucleus polar nuclei degenerating megaspores egg mitosis synergids Embryo sac (mature female gametophyte) 3. The microspores: Each microspore in a pollen sac undergoes mitosis to become an immature pollen grain with two cells: the tube cell and the generative cell. The pollen sacs open, and the pollen grains are windblown or carried by an animal carrier, usually to other flowers. This is pollination. 4. The mature male gametophyte: A pollen grain that lands on the carpel of the same type of plant germinates and produces a pollen tube, which grows within the style until it reaches an ovule in the ovary. Inside the pollen tube, the generative cell nucleus divides and produces two nonflagellated sperm. A fully germinated pollen grain is the mature The mature female gametophyte: The ovule now contains the mature female gametophyte (embryo sac), which typically consists of eight haploid nuclei embedded in a mass of cytoplasm. The cytoplasm differentiates into cells, one of which is an egg and another of which contains two polar nuclei. The megaspores: Inside the ovule of an ovar y , three megaspores disintegrate, and only the remaining one undergoes mitosis to become a female gametophyte.

Flowers and Diversification Wind-pollinated flowers are usually not showy Bird-pollinated flowers are often colorful Night-blooming flowers attract nocturnal mammals or insects Usually white or cream-colored Fruits of flowers protect and aid in dispersal Utilize wind, gravity, water, and animals for dispersal

Uses of Plants Plants define and are the producers in most ecosystems. Humans derive most of their sustenance from three flowering plants: wheat, corn, and rice Simple carbohydrate such as sugar comes almost exclusively from two plants: sugarcane and sugar beets Our most popular drinks—coffee, tea, and cola are also from flowering plants

Cereal Grains ear Wheat plants, Triticum Corn plants, Zea Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. grain head grain head ear Wheat plants, Triticum Corn plants, Zea Rice plants, Oryza (Wheat): © Pixtal/age fotostock; (Rice): © Corbis Royalty Free; (Rice grain): © Dex Image/Getty RF; (Cornfield): © Corbis; (Corn ear): © Nigel Cattlin/Photo Researchers, Inc.

Uses of Plants Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a. Dwarf fan palms, Chamaerops, for basket weaving b. Rubber, Hevea, for auto tires d. Tulips, Tulipa, for beauty c. Cotton, Gossypium, for cloth a: © Heather Angel/Natural Visions; b: © Steven King/Peter Arnold, Inc.; c: © Dale Jackson/Visuals Unlimited; d: © Brand X Pictures/PunchStock

Review Evolutionary History Nonvascular Plants Vascular Plants The Green Algal Ancestor Alternation of Generations Nonvascular Plants Vascular Plants Seedless Seed Angiosperms Monocots and Eudicots Flowers

Biology, 9th ed, Sylvia Mader Chapter 24 Evolution and Diversity of Plants Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. seed cones seed cones pollen cones a. A northern coniferous forest of evergreen trees a: © Corbis Royalty Free; b: © Walt Anderson/Visuals Unlimited; c: © The McGraw Hill Companies, Inc./Evelyn Jo Johnson, photographer b. Cones of lodgepole pine, Pinus contorta c. Fleshy seed cones of juniper, Juniperus