Bio1151 Chapter 29 Plant Diversity I: How Plants Colonized Land
  1. Land plants ( kingdom          ) are a very diverse group that evolved from        algae, and are most closely related to the              .

      Plant evolution. Kingdom Plantae comprises 7 major clades classified into 10 phyla.


      Plant Phyla. Anthophyta (or Angiosperms, the flowering plants) is the most recently evolved, and most diverse, of the 10 plant phyla.


      Kingdom Plantae (Embryophytes) are multicellular, photosynthetic eukaryotes most closely related to the green algae (Chlorophyta). Plants have adapted to life on dry land.


      Green algae called charophytes are the closest living algal relatives of land plants.
     
     
     
     
  2. Four innovations among the kingdom Plantae are:
     
     
     
     
    • Alternation of              , with multicellular, dependent          .

        Plantae alternation of generations. Multicellular, haploid gametophytes produce haploid gametes. Fusion of egg and sperm form a diploid zygote, which undergoes mitosis to produce the diploid sporophyte. A mature sporophyte may undergo meiosis to produce haploid spores, which can germinate into a haploid gametophytes by mitosis.


        Multicellular, dependent embryos. Multicellular plant embryos develop from zygotes within tissues of the female parent. The parent provides nutrients through placental transfer cells.
       
       
       
       
    • Walled spores produced in            .

        Walled spores produced in sporangia. A diploid sporophyte of this Sphagnum (a moss) produces organs called sporangia. The sporangia cells undergo meiosis to generate haploid spores.
       
       
       
       
    • Multicellular             which produce gametes.

        Multicellular gametangia in Marchantia (a liverwort). A female gametangium, called an archegonium, produces a single egg. Male gametangia, called antheridia, produce and release sperm into the environment.
       
       
       
       
    • Apical            in root and shoot systems.


      Apical Meristems. Light and carbon dioxide are above ground, while water and minerals are in the soil. The elongation of shoots and roots at apical meristems maximize exposure to these resources.
     
     
     
     
  3. Bryophytes lack           tissue with three phyla of small herbaceous plants.

      Bryophytes lack vascular tissues; these small herbaceous (nonwoody) plants live in moist habitats. The three phyla are: A) Liverworts (Hepatophyta) B) Hornworts (Anthocerophyta) C) Mosses (Bryophyta) Note the small sporophytes growing on the larger gametophytes.


      Sphagnum, or peat moss, a bryophyte. Note the leafy gametophytes and the smaller sporophytes. The living photosynthetic cells grow on layers of dead water-storing cells, giving the moss a spongy quality. Peat can be harvested from "peat bogs".


      The acid in peat bogs slows down decay of organic materials. a. Dead Sphagnum moss can accumulate in deep layers in these bogs and are harvested for fuel and as a soil conditioner.
    • This Tollund Man has been preserved since the 4th century BC in Denmark. 29_Peat.jpg-->
     
     
     
     
    • The large               produce gametes which fuse to yield small              .

        The large, photosynthetic, gametophytes of bryophytes contain gametangia and are anchored by rhizoids.


        Multicellular gametangia in Marchantia (a liverwort). A female gametangium, called an archegonium, produces a single egg. Male gametangia, called antheridia, produce and release sperm into the environment. 29_05Gamet.jpg-->
       
       
       
       
    • Sporophytes produce haploid         which grow to become the               .

        Life cycle of Polytrichum moss, a bryophyte.
      • Spores develop into haploid protonemata.
      • Protonema produce "buds" that undergo mitosis.
      • Buds develop into gametophyte bearing antheridia or archegonia.
      • Sperm swims to egg in archegonium.
      • Fertilized diploid zygote develops into sporophyte embryo.
      • Sporophyte grows a stalk (seta) that emerges from the archegonium.
      • The small sporophyte is dependent on the large gametophyte.
      • Spores develop by meiosis in sporangium (capsule) whose teethlike peristome regulates spore dispersal.
       
       
       
       
    • Male gametes are flagellated        that       short distances to fertilize the egg.
     
     
     
     
  4. Vascular plants possess specialized vascular tissues called        and         .

      Vascular plants possess vessels that transport water and nutrients throughout the organism. Roots enable them to extract water deep within the soil, and the vascular tissues also provide strength to support a larger body mass.
     
     
     
     
  5. Seedless vascular plants have life cycles with dominant              and form two phyla.

      The life cycle of a fern, phylum Pterophyta.
    • Sporangia release spores.
    • Spore develops into a small, bisexual, photosynthetic gametophyte.
    • Gametophyte produces sperm in antheridia and eggs in archegonia.
    • Sperm swim to eggs in archegonia.
    • Zygote develops into large sporophyte.
    • Clusters of sporangia form in sori on modified leaves called sporophylls.
     
     
     
     
    • Lycophyta includes       mosses,        mosses, and             .

        Lycophytes (Phylum Lycophyta) Spike mosses are small with simple, scale-like leaves. Quillworts are a single genus that lives in marshy areas. Club mosses have sporophylls (modified leaves with sporangia) clustered into club-shaped cones (strobili).
       
       
       
       
    • Pterophyta includes        ,             , and        ferns and their relatives.


      Pterophytes (Phylum Pterophyta) Ferns have large leaves; the sporophylls bear sori (clusters of sporangia). Horsetail stems have a gritty texture and some have been used as "scouring rushes" for pots and pans. Whisk ferns form fused sporangia on stems seen here as yellow knobs.
     
     
     
     
  6. Seedless vascular plants grew to great heights during the                period and may have led to global cooling.

      Carboniferous forest. Most of the large trees are lycophytes. Tree ferns were also abundant in the coal forests of the Carboniferous period, about 300 million years ago. These seedless vascular plant forests eventually became coal and other fossil fuels. The growth of these early forests reduced atmospheric CO[2] levels, leading to global cooling at the end of the Carboniferous.


      Multicellular eukaryotes dominate the Phanerozoic eon. The Phanerozoic is divided into three eras: the Paleozoic, Mesozoic, and the current Cenozoic. Overview: 25_T01-GeologicRecord-L.jpg-->


      Fossil fuels (coal, petroleum, natural gas) are formed from buried remains of dead organisms when compressed in sediment over time. Humans have dug up these carbon fuels to burn as energy sources, releasing excess carbon into the atmosphere. Fossil_fuels.gif-->


      1 29_Temp-CO2.gif-->
     
     
     
     
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Bio1151 Chapter 30 Plant Diversity II: The Evolution of Seed Plants
  1. Seed plants continued the evolution of smaller               in the              of generations.

      A Sampling of Medicines Derived from Seed Plants. Seed plants provide many products including food, wood, and many medicines.


      Bryophytes have life cycles dominated by gametophytes. Seedless vascular plants have sporophyte-dominated life cycles, with small, free-living gametophytes. Gametophyte reduction continued further in seed plants, becoming microscopic and dependent upon the sporophyte for nutrition and protection.
     
     
     
     
  2. Gymnosperms ( conifers ) bear “naked”        , typically on        , and include four phyla: Cycadophyta, Gingkophyta, Gnetophyta, and Coniferophyta.

      Phylum Cycadophyta. Cycads have large cones and palmlike leaves and thrived during the Mesozoic era - "Age of Cycads" ("Age of Dinosaurs").


      Gingko biloba is the only extant species of phylum Gingkophyta. Landscapers usually plant only pollen-producing male trees because the fleshy seeds smell rancid as they decay.


      Gnetophyta. Gnetophytes live in tropical and desert environments.
    • Welwitschia can absorb water through structures on its large leaves.
    • Gnetum species are tropical trees or vines.
    • Ephedra (Mormon Tea or Ma Huang) is a desert shrub. Ephedrine extracts have been used as a diet pill, but carries cardiovascular risks that may have led to deaths including Minnesota Viking Korey Stringer (2001) and Baltimore Orioles pitcher Steve Bechler (2003).


      Coniferophyta. Pseudotsuga menziesii (Douglas fir) produces more timber than any other American forest species. Pinus longaeva (Bristlecone pine) can reach ages of more than 4,600 years. This Sequoia giganteum (Giant Sequoia) weighs about 2,500 metric tons (about 24 blue whales, or 40,000 people). The "berries" of Juniperus communis (Common juniper) are ovule-producing cones consisting of fleshy sporophylls.
     
     
     
     
  3. The gymnosperm life cycle shows a dominant             generation,         grains transferring        to ovules, and the development of        from fertilized         .

      Life cycle of a conifer (a gymnosperm).
    • Sporophytes bear pollen and ovulate cones.
    • Pollen cones contain microsporangia with microsporocytes.
    • Ovulate cones contain ovules, each with one megasporangium and a megasporocyte.
    • Microsporocytes undergo meiosis to produce male gametophytes (pollen grains).
    • The megasporocyte undergoes meiosis to produce a megaspore.
    • The megaspore develops into a female gametophyte containing eggs.
    • The pollen grain germinates a sperm cell which travels down the pollen tube to fertilize an egg to produce a zygote.
    • The ovule becomes a seed: an embryo, food supply, and seed coat.
     
     
     
     
    • Megaspores develop into         which contain female gametophytes. Microspores develop into         grains which contain male gametophytes.

        Unfertilized ovule. In the ovule of a pine (a gymnosperm), a fleshy megasporangium is surrounded by a protective integument. (Angiosperms have two integuments.)


        Male gametophytes. Pollen cones contain microsporangia where microsporocytes undergo meiosis to produce microspores, which develop into male gametophytes (pollen grains).
       
       
       
       
    • When a pollen grain is transferred to the part of a plant containing the         , it can germinate and discharge        into the female gametophyte within the ovule.

        Fertilized ovule. A megaspore develops into a multicellular female gametophyte. A pollen grain (male gametophyte) enters through the micropyle, and develops a pollen tube in which the sperm can travel.
       
       
       
       
    • This process of                is called              and results in a       containing a sporophyte         .

        Gymnosperm seed. After fertilization, the ovule develops into a seed A seed consists of an embryo along with its food supply packaged in a protective seed coat derived from the integument.
       
       
       
       
    • The pollen eliminates the need to swim through water and allows for wide            by       .
     
     
     
     
  4. Angiosperms are seed plants that possess reproductive structures called          and         .
     
     
     
     
    • A flower is a specialized        with modified leaves; some are adapted for              by animals.

        The structure of a flower. Sepals enclose the flower, petals may be brightly colored to attract pollinators. Stamens produce pollen, and carpels contain ovaries. An ovary caontains several ovules which develop into seeds after fertilization. The stamens collectively are called "androecium", while the carpels are called "gynoecium". A complete flower has all four basic floral organs. A perfect flower contains both male and female structures.


        A flower pollinated by honeybees. This honeybee is harvesting pollen and nectar (a sugary solution secreted by flower glands) from a Scottish broom flower. The flower has a tripping mechanism that arches the stamens over the bee and dusts it with pollen, some of which will rub off onto the stigma of the next flower the bee visits. A flower pollinated by hummingbirds. The long, thin beak and tongue of this rufous hummingbird enable the animal to probe flowers that secrete nectar deep within floral tubes. Before the hummer leaves, anthers will dust its beak and head feathers with pollen. Many flowers that are pollinated by birds are red or pink, colors to which bird eyes are especially sensitive. A flower pollinated by nocturnal animals. Some angiosperms, such as this cactus, depend mainly on nocturnal pollinators, including bats. Adaptations of such plants include large, light-colored, highly fragrant flowers that nighttime pollinators can locate.
       
       
       
       
    • A Fruit typically consists of a mature        with seeds. Fruits are adapted for seed            by       ,        , or animals to new locations.


      The wall of the fertilized ovary thickens into layers of pericarp surrounding a fruit. Fleshy fruits, such as tomato (2 soft layers), grapefruit (firm outer layer, soft inner layer), and nectarine (soft outer, firm inner pit), attract animals which eat the fruit and aid in dispersal of the indigestible seeds. Dry fruits, such as milkweed and hazelnut, are often adapted for dispersal by wind or water, or by animal carriers.


      Fruit adaptations that enhance seed dispersal. Wings enable maple fruits to be carried by the wind. Seeds within berries and other fruits are dispersed in animal feces. The barbs of cockleburs facilitate seed dispersal by allowing the fruits to hitchhike on animals.


      The Swiss engineer George de Mestral invented Velcro in 1948 when he noticed cockleburs stuck tightly to his pants as well as to his dog's fur, due to tiny hooks on the fruit that entangled into loops of thread or fur. Velcro.jpg-->
     
     
     
     
  5. The angiosperm life cycle includes a         fertilization which produces a food-storing            in addition to the         .

      The life cycle of an angiosperm.
    • Anthers contain microsporangia; microsporocytes divide by meiosis to produce microspores.
    • Microspores form male gametophytes (pollen grains) which produce 2 sperm and a pollen tube.
    • Ovaries contain megasporangia; a megasporocyte divides by meiosis to yield 4 megaspores; one forms a female gametophyte (embryo sac).
    • 2 sperm nuclei reach an ovule and double fertilization occurs.
    • One sperm fertilizes the egg to form a zygote, the other fuses with 2 nuclei of the cetral cell to form a triploid endosperm.
    • The diploid zygote develops into an embryo within a seed.
    • A seed can germinate into a sporophyte.
     
     
     
     
  6. Most angiosperms are           and           , classified by the number of             (seed leaves).

      Monocot characteristics:
    • One cotyledon
    • Parallel leaf veins
    • Stem vascular tissue scattered
    • Floral organs usually in multiples of three Eudicot characteristics:
    • Two cotyledons
    • Netlike leaf veins
    • Stem vascular tissue arranged in ring.
    • Floral organs usually in multiples of four or five
     
     
     
     
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