* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download video slide - Des Moines Area Community College, Iowa
Survey
Document related concepts
Pollination wikipedia , lookup
Plant tolerance to herbivory wikipedia , lookup
Venus flytrap wikipedia , lookup
Plant use of endophytic fungi in defense wikipedia , lookup
Cultivated plant taxonomy wikipedia , lookup
History of botany wikipedia , lookup
History of herbalism wikipedia , lookup
Plant physiology wikipedia , lookup
Fertilisation wikipedia , lookup
Plant morphology wikipedia , lookup
Ornamental bulbous plant wikipedia , lookup
Historia Plantarum (Theophrastus) wikipedia , lookup
Sustainable landscaping wikipedia , lookup
Evolutionary history of plants wikipedia , lookup
Flowering plant wikipedia , lookup
Transcript
Chapter 29 Plant Diversity I How Plants Colonized Land Land Ho! The Greening of Earth • • • • For the first 3 billion years of Earth’s history, the land was lifeless Cyanobacteria existed on land about 1.2 billion years ago ~500 million years ago plants, fungi and animals joined them DiversificationOver 290,00 species of plants inhabit Earth today Plant Evolution • Land plants evolved from green algae • Charophyceans (a type of green algae) are the closest relatives of land plants Accumulation of adaptations to the terrestrial environment allowed the first land plants to live permanently above the waterline (a) Chara, a pond organism 10 mm 40 µm (b) Coleochaete orbicularis Defining the Plant Kingdom • Systematists – Are currently debating the boundaries of the plant kingdom Viridiplantae Streptophyta Plantae Red algae Chlorophytes Charophyceans Embryophytes Ancestral alga Derived Traits of Plants • Five key traits appear in nearly all land plants but are absent in the charophyceans – Apical meristems – Alternation of generations – Walled spores produced in sporangia – Multicellular gametangia (gametes produced here) – Multicellular dependent embryos Apical meristems and alternation of generations APICAL MERISTEMS Localized regions of cell division at tips of roots and shoots Apical meristem of shoot Developing leaves . Apical meristem of root Shoot 100 µm Root 100 µm Haploid multicellular organism (gametophyte) Mitosis Mitosis n n n ALTERNATION OF GENERATIONS Spores n n Gametes Generations Gametophyte (haploid) Sporophyte (diploid) MEIOSIS FERTILIZATION 2n 2n Zygote Mitosis Diploid multicellular organism (sporophyte) Alternation of generations: a generalized scheme Walled spores; multicellular gametangia; and multicellular, dependent embryos WALLED SPORES PRODUCED IN SPORANGIA Spores Sporangium Sporophyte and sporangium of Sphagnum (a moss) Longitudinal section of Sphagnum sporangium Sporophyte Gametophyte MULTICELLULAR GAMETANGIA (where gametes are produced) Female gametophyte Archegonium with egg Antheridium with sperm Archegonia and antheridia of Marchantia (a liverwort) Female gametangia (archegonia) Male gametangia (antheridia) Male gametophyte MULTICELLULAR, DEPENDENT EMBRYOS Land plants are also known as EMBRYOPHYTES Embryo retained within tissues of female parent. The parental tissues provide the developing embryo with nutrients. Embryo Maternal tissue Embryo and placental transfer cell of Marchantia Wall ingrowths Placental transfer cell Fossilized spores and tissues – Have been extracted from 475-million-yearold rocks Fossilized spores. Unlike the spores of most living plants, which are single grains, these spores found in Oman are in groups of four (left; one hidden) and two (right). Fossilized sporophyte tissue. The spores were embedded in tissue that appears to be from plants. Diversity of Modern Plants Land plants can be informally grouped based on the presence or absence of vascular tissue An overview of land plant evolution Land plants Vascular plants Angiosperms Origin of seed plants (about 360 mya) Origin of vascular plants (about 420 mya) Origin of land plants (about 475 mya) Ancestral green alga Seed plants Gymnosperms Pterophyte (ferns, horsetails, whisk fern) Seedless vascular plants Lycophytes (club mosses, spike mosses, quillworts) Mosses Hornworts Liverworts Charophyceans Bryophytes (nonvascular plants) Bryophytes • The life cycles of mosses and other bryophytes are dominated by the gametophyte stage • Bryophytes are represented today by three phyla of small herbaceous (nonwoody) plants – Liverworts, phylum Hepatophyta – Hornworts, phylum Anthocerophyta – Mosses, phylum Bryophyta Bryophytes…the video clip Plant Classifications: Bryophytes." Online . Encyclopædia Britannica Online. 14 Jan. 2008 <http://www.britannica.com/eb/art-68471>. Bryophyte Gametophytes • In all three bryophyte phyla – Gametophytes are larger and longer-living than sporophytes Moss Life Cycle…The Movie The life cycle of a moss Raindrop 1 Spores develop into threadlike protonemata. Key Male gametophyte Haploid (n) Diploid (2n) Sperm “Bud” 2 The haploid protonemata produce “buds” that grow into gametophytes. Protonemata 4 A sperm swims through a film of moisture to an archegonium and fertilizes the egg. Antheridia 3 Most mosses have separate male and female gametophytes, with antheridia and archegonia, respectively. “Bud” Egg Spores Gametophore Female Archegonia spores develop in the sporangium gametophyte of the sporophyte. When the Rhizoid sporangium lid pops off, the peristome “teeth” regulate 6 The sporophyte grows a gradual release of the spores. long stalk, or seta, that emerges Seta from the archegonium. 8 Meiosis occurs and haploid Peristome Sporangium MEIOSIS Mature Mature sporophytes sporophytes Capsule (sporangium) FERTILIZATION (within archegonium) Calyptra Zygote Embryo Foot Archegonium Young sporophyte Capsule with peristome Female gametophytes 7 Attached by its foot, the sporophyte remains nutritionally dependent on the gametophyte. 5 The diploid zygote develops into a sporophyte embryo within the archegonium. Bryophyte gametophytes • Bryophyte gametophytes – Produce flagellated sperm in antheridia – Produce ova in archegonia – Generally form ground-hugging carpets and are at most only a few cells thick • Some mosses – Have conducting tissues in the center of their “stems” and may grow vertically Bryophyte Sporophytes • Bryophyte sporophytes – Grow out of archegonia – Are the smallest and simplest of all extant plant groups – Consist of a foot, a seta (an elongated stalk), and a sporangium • Hornwort and moss sporophytes – Have stomata (like vascular plants) (an opening for gas exchange) Bryophyte diversity Gametophore of female gametophyte LIVERWORTS (PHYLUM HEPATOPHYTA) Plagiochila deltoidea, a “leafy” liverwort Foot Seta Marchantia sporophyte (LM) HORNWORTS (PHYLUM ANTHOCEROPHYTA) An Anthoceros hornwort species Sporophyte Sporangium 500 µm Marchantia polymorpha, a “thalloid” liverwort MOSSES (PHYLUM BRYOPHYTA) Polytrichum commune, hairy-cap moss Sporophyte Gametophyte Gametophyte Ecological and Economic Importance of Mosses • Sphagnum, or “peat moss” – – Forms extensive deposits of partially decayed organic material known as peat Peatlands play an important role as carbon reservoirs an help stabilize atmospheric carbon dioxide levels. (a) Peat being harvested from a peat bog (b) Closeup of Sphagnum. Note the “leafy” gametophytes and their offspring, the sporophytes. Gametophyte (c) Sphagnum “leaf” (LM). The combination of living photosynthetic cells and dead water-storing cells gives the moss its spongy quality. (d) “Tolland Man,” a bog mummy dating from 405–100 B.C. The acidic, oxygen-poor conditions produced by Sphagnum can preserve human or other animal bodies for thousands of years. Sporangium at tip of sporophyte Living photo- Dead watersynthetic storing cells 100 µm cells Origin and Diversity of Vascular Plants • Ferns and other seedless vascular plants formed the first forests • Bryophytes and bryophyte-like plants – Were the prevalent vegetation during the first 100 million years of plant evolution • Vascular plants – Began to evolve during the Carboniferous period – Fossils of the forerunners of vascular plants date back about 420 million years Seedless Vascular Plants • These early tiny plants – Had branching sporophytes that weren’t dependent on gametopyhtes for growth, but lacked other derived traits of vascular plants Dichotomous (Y-shaped) branching made possible multiple sporangia. This evolutionary development allowed for greater spore production. Also increased survival in the face of herbivory. If some sporangia were eaten others might survive. Life Cycles with Dominant Sporophytes • In contrast with bryophytes – Sporophytes of seedless vascular plants are the larger generation, as in the familiar leafy fern – The gametophytes are tiny plants that grow on or below the soil surface Tracheophytes-Pterophyta (ferns) …the video clip fern." Encyclopædia Britannica. 2008. Encyclopædia Britannica Online. 13 Jan. 2008 <http://www.britannica.com/eb/article-9110635>. Fern Life Cycle…The Movie The life cycle of a fern 1 Sporangia release spores. Most fern species produce a single type of spore that gives rise to a bisexual gametophyte. Key 2 The fern spore develops into a small, photosynthetic gametophyte. 3 Although this illustration shows an egg and sperm from the same gametophyte, a variety of mechanisms promote cross-fertilization between gametophytes. Haploid (n) Diploid (2n) Antheridium Spore MEIOSIS Young gametophyte Sporangium Archegonium Mature sporophyte New sporophyte Sperm Egg Zygote Sporangium FERTILIZATION Sorus 6 On the underside of the sporophyte‘s reproductive leaves are spots called sori. Each sorus is a cluster of sporangia. Gametophyte Fiddlehead 5 A zygote develops into a new sporophyte, and the young plant grows out from an archegonium of its parent, the gametophyte. 4 Fern sperm use flagella to swim from the antheridia to eggs in the archegonia. Transport in Xylem and Phloem • Vascular plants have two types of vascular tissue – Xylem and phloem • Xylem – Conducts most of the water and minerals – Includes dead cells called tracheids. Their cell walls remain to provide the internal ‘pipe system’. – Cell walls are strengthened by the polymer lignin. This allows vascular plants to grow to greater heights than bryophytes • Phloem – Distributes sugars, amino acids, and other organic products – Consists of living cells Evolution of Roots • Roots – Are organs that anchor vascular plants – Enable vascular plants to absorb water and nutrients from the soil – May have evolved from subterranean stems Evolution of Leaves • Leaves – Are organs that increase the surface area of vascular plants, thereby capturing more solar energy for photosynthesis • Leaves are categorized by two types – Microphylls, leaves with a single vein – Megaphylls, leaves with a highly branched vascular system Evolution of Leaves • According to one model of evolution – Microphylls evolved first, as outgrowths of stems Vascular tissue (a) Microphylls may have originated as small stem outgrowths supported by single, unbranched strands of vascular tissue. (b) Megaphylls, which have branched vascular systems, may have evolved by the fusion of branched stems. Sporophylls and Spore Variations • Sporophylls – Are modified leaves with sporangia (may look like a “photosynthetic leaf” may not) • Most seedless vascular plants – Are homosporous, producing one type of spore that develops into a bisexual gametophyte – All seed plants and some seedless vascular plants are heterosporous, having two types of spores that give rise to male and female gametophytes Classification of Seedless Vascular Plants • Seedless vascular plants form two phyla – Lycophyta, including club mosses, spike mosses, and quillworts. Are small herbaceous plants – Pterophyta, including ferns, horsetails, and whisk ferns and their relatives. Ferns are the most diverse seedless vascular plants Groups of seedless vascular plants LYCOPHYTES (PHYLUM LYCOPHYTA) Selaginella apoda, a spike moss Isoetes gunnii, a quillwort Strobili (clusters of sporophylls) Diphasiastrum tristachyum, a club moss Psilotum nudum, a whisk fern PTEROPHYTES (PHYLUM PTEROPHYTA) Equisetum arvense, field horsetail Vegetative stem Athyrium filix-femina, lady fern Strobilus on fertile stem WHISK FERNS AND RELATIVES HORSETAILS FERNS Significance of Seedless Vascular Plants • The ancestors of modern lycophytes, horsetails, and ferns grew to great heights during the Carboniferous, forming the first forests The growth of these early forests may have helped produce the major global cooling that characterized the end of the Carboniferous period. They decayed and eventually became coal