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Download ch 29-30 plant diversity notes-2007
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Phylogeny and Systematics Ch. 25 Phylogeny • Evolutionary history of a species or group of related species • Reconstructing phylogeny is part of the scope of systematics – Systematics—the study of biological diversity in an evolutionary context Phylogenetic Trees • Diagrams that trace evolutionary relationships as best as they can be determined • Systematist use evidence from: – Fossil record • Phenotypic appearances – Molecular biology • Comparison of nucleic acid sequences/amino acid sequences • DNA sequence analysis—identifying & comparing homologous sequences • Species diverge as changes (genetic mutations) occur Taxonomy • Branch of biology concerned with naming and classifying the diverse forms of life • Scientific name of an organism = binomial system • Genus / species Phylogenetic trees reflect the hierarchical classification Cladistic Analysis Cladogram • Synonymous with phylogenetic systematics • Clade=evolutionary branch • Classifying organisms according to the order in time that branches arose along a dichotomous tree • Analyzing the taxonomic distribution of homologies enables us to identify the sequence in which derived characters evolved during vertebrate phylogeny. Fig. 25.11 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Kingdom: Plantae Plant Diversity Ch. 29 & 30 Land plants evolved from green algae • Green algae called charophyceans are the closest relatives of land plants • Four key traits in common: – Rose-shaped complexes for cellulose synthesis – Peroxisome enzymes – Structure of flagellated sperm – Formation of a phragmoplast • Supported by genetic similarites in both their nuclear and chloroplast genes Chara, a pond organism (LM). 10 mm 40 µm Coleochaete orbicularis, a disk-shaped charophycean (LM). Adaptations Enabling the Move to Land • In charophyceans a layer of a durable polymer called sporopollenin prevents exposed zygotes from drying out • The accumulation of traits that facilitated survival on land may have opened the way to its colonization by plants Land plants possess a set of derived terrestrial adaptations • Many adaptations emerged after land plants diverged from their charophycean relatives • 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 – Multicellular dependent embryos Plant Characteristics • Multicellular eukaryotes • Photosynthetic autotrophs • Chloroplasts with photosynthetic pigments – chlorophyll, carotenoids • Cell walls contain cellulose • Excess glucose stored as starch in plastids Life Cycles of Plants: Alternation of Generations • Gametophyte— multicellular individual with haploid cells – Produce haploid cells that fuse to form zygotes • Sporophyte—multicellular individual with diploid cells – Develop from the zygotes that are formed Gametophyte Phase Dark round structures are antheridia or archegonia of the fern gametophyte (x12) The fern sporophyte grows from a fertilized egg in an archegonium on the gametophyte. (x12) Fern Fiddleheads Sporophyte Phase Sori on Fern Leaf Fern Leaf with Sori Plant Phylogeny 1. Origin of plants from aquatic ancestors— Ordovician period (475mya) – – Cuticle formation and jacketed gametangia Vascular tissue with conducting cells 2. Diversification of seedless vascular plants—Devonian period (400mya) Plant Phylogeny 3. Origin of the seed—Devonian period (360mya) – – Seed = plant embryo packaged with food store and protective coat Gymnosperms—early seed plants—naked seeds 4. Emergence of flowering plants— Cretaceous period (130mya) – Angiosperms—plants bear seeds inside flower’s protective ovaries Land plants Vascular plants Seed plants Angiosperms Gymnosperms Pterophytes Seedless vascular plants Lycophytes Mosses Hornworts Liverworts Charophyceans Bryophytes Origin of seed plants (about 360 mya) Origin of vascular plants (about 420 mya) Origin of land plants (about 475 mya) Ancestral green alga Classification of Plants I •Nonvascular Plants (Bryophytes) •Division Bryophyta (mosses) •Division Hepatophyta (liverwarts) •Division Anthocerophyta (hornwarts) Characteristics: •Small herbaceous plants (nonwoody) •No vascular tissue, so relies on diffusion and capillary action to get water •Need water to reproduce •Gametophytes—larger and longer-living than sporophytes •Sporophytes—typically present only part of the time •Gametangia protect developing gametes •antheridium—produce flagellated sperm •archegonium—produce single egg Division Bryophyta (mosses) http://gallery.criticalmoss.net/cache/moss_Moss.png_400.jpg •Spongy mat—can absorb and retain water •Grips substratum with rhizoids (cellular filaments) http://www.dkimages.com/discover/previews/998/35002390.JPG http://www2.una.edu/pdavis/images/liverworts/rhizoidUlbasechipol10CM.jpg www.davidlnelson.md/Cazadero/Mosses.htm Bryophyta http://www.davidlnelson.md/Cazadero/CazImages/Moss_sporangium2.jpg • The green leafy structures are gametophytes. • The brown structures are sporophyte stalks and spore capsules. Raindrop Key Male gametophyte Life Cycle of Moss Haploid (n) Diploid (2n) Sperm “Bud” Spores develop into threadlike protonemata. A sperm swims through a film of moisture to an archegonium and fertilizes the egg. Antheridia The haploid protonemata produce “buds” that grow into gametophytes. Protonemata Most mosses have separate male and female gametophytes, with antheridia and archegonia, respectively. “Bud” Egg Gametophore Spores Female Archegonia gametophyte Meiosis occurs and haploid spores develop in the sporangium of the sporophyte. When the sporangium lid pops off, the peristome “teeth” regulate gradual release of the spores. Peristome The sporophyte grows a long stalk, or seta, that emerges from the archegonium. Sporangium MEIOSIS Mature sporophytes Rhizoid Seta Calyptra Capsule (sporangium) Foot FERTILIZATION (within archegonium) Zygote Embryo Archegonium Young sporophyte Capsule with peristome (SEM) Female gametophytes Attached by its foot, the sporophyte remains nutritionally dependent on the gametophyte. The diploid zygote develops into a sporophyte embryo within the archegonium. Division Hepatophyta (liverworts) http://www.kingsnake.com/westindian/hepaticopsida5.JPG •Sporangia have coilshaped cells that spring out and disperse spores LIVERWORT SPOROPHYTE •Sporophytes are horn-shaped, elongated capsules that grow from the mat like gametophyte •Photosynthetic cells have only one large chloroplast sporophyte www.botany.hawaii.edu/.../Cyanobacteria.htm Division Anthocerophyta (hornworts) gametophyte http://taggart.glg.msu.edu/bot335/Hornw.jpg hornwort Phaeoceros Classification of Plants •Vascular Plants Seedless Vascular Plants •Division Lycophyta (lycophytes) •Division Sphenophyta (horsetails) •Division Pterophyta (ferns) •Characteristics: •Sporophytes are the larger generation •Gametophytes are tiny plants that grow on or below the soil surface •Terrestrial Adaptations: •Roots-transport water •Cellulose (structure support) •Vascular tissue-xylem (water) and phloem (food) •Pollen-eliminates need for water in reproduction •Increased dominance of diploid sporophyte Division Lycophyta (lycophytes) Lycopodium annotinum Order Isoetales Quillworts •Low-growing plants with rhizomes and true leaves •Some are epiphytes (use another organism as a substratum Rhizome: stem like part of the plant from which the leaves grow sporangia http://hcs.osu.edu/hcs300/svp1.htm http://hcs.osu.edu/hcs300/svp1.htm Division Sphenophyta (horsetails) Sphenophytes consist of only one genus, Equisetum, with about thirty living species known worldwide Homosporous-bisexual gametophyte produces egg and sperm Division Pterophyta (ferns) • Most diverse seedless vascular plants • Fronds-compound leaves • Homosporous • Sporangia borne on underside of specialized sporophylls • Water necessary for fertilization • Sporophyte develops within archegonium http://en.wikipedia.org/wiki/Fern http://en.wikipedia.org/wiki/Image:Sa-fern.jpg 3 Variations on Alternation of Generations in Plants Evolution of Roots • Roots are organs that anchor vascular plants • They enable vascular plants to absorb water and nutrients from the soil • Roots 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 that is used for photosynthesis • Leaves are categorized by two types: – Microphylls, leaves with a single vein – Megaphylls, leaves with a highly branched vascular system • According to one model of evolution, microphylls evolved first, as outgrowths of stems Classification of Plants II • Vascular Plants • Seed Plants • Gymnosperms – – – – Division Coniferophyta (conifers) Division Cycadophyta (cycads) Division Ginkgophyta (ginkgo) Division Gnetophyta (Gnetae) Seeds Replace Spores • Relatively harsh terrestrial environment led to development of resistant structures for the dispersal of offspring • Seeds more hardy because of multicellular nature • Seed = sporophyte embryo + food supply surrounded by protective coat • Seed plants are heterosporous – Megasporangia produce megaspores female gametophyte – Microsporangia produce microspores male gametophyte • Seed plants evolved from plants with megasporangia, which produce megaspores that give rise to female gametophytes • Seed plants evolved from plants with microsporangia, which produce microspores that give rise to male gametophytes cavehill.uwi.edu/FPAS/bcs/bl14apl/pter3.htm Heterospory: The Rule Among Seed Plants Micrograph of Selaginella Ovules and Production of Eggs • An ovule consists of a megasporangium, megaspore, and one or more protective integuments • Gymnosperm megaspores have one integument • Angiosperm megaspores usually have two integuments Integument Female gametophyte (n) Seed coat (derived from integument) Spore wall Egg nucleus (n) Megasporangium (2n) Megaspore (n) Unfertilized ovule Male gametophyte (within germinating pollen grain) (n) Micropyle Fertilized ovule Discharged sperm nucleus (n) Pollen grain (n) Food supply (female gametophyte tissue) (n) Embryo (2n) (new sporophyte) Gymnosperm seed http://www.wildliferanger.com/users/www.wildliferanger.com/upload/Th e%20Pollinator%20515.JPG Pollen and Production of Sperm • Microspores develop into pollen grains, which contain the male gametophytes • Pollination—transfer of pollen to the part of a seed plant containing the ovules • Dispersal by air or animals • If a pollen grain germinates, it gives rise to a pollen tube that discharges two sperm into the female gametophyte within the ovule The Evolutionary Advantage of Seeds • A seed develops from the whole ovule • A seed is a sporophyte embryo, along with its food supply, packaged in a protective coat commons.wikimedia.org/wiki/Image:Avocado_seed... Division Coniferophyta (conifers) Araucaria cunninghamii. The hoop pine. Lake Tinaroo Falls Dam, Queensland, Australia. •Largest division of Gymnosperms -most are evergreens: pines, spruces, firs, larches, yews, junipers, cedars, cypresses, and redwoods Sequioadendron giganteum. The Giant Sequoia. Yosemite National Park, Mariposa County, California. Division Coniferophyta (conifers) Needle-shaped conifer leaves are adapted to dry conditions •thick cuticle covers the leaf •stomata are in pits, reducing water loss Division Coniferophyta (conifers) Mature ovulate cones and seeds Heterosporous- both male and female gametophytes develop from different types of spores on separate cones http://www.seinangu.ac.jp/~djohnson/natural/campusplants/023pine.cone3.JPG http://www.esu.edu/~milewski/intro_biol_two/lab_3_seed_plts/images/Male _stroboli.jpg Division Coniferophyta (conifers) Cedrus deodora. Near Placerville http://upload.wikimedia.org/wikipedia/commons/3/3b/Cycas_inflo rescence.jpg Division Cycadophyta (cycads) Leaves and male cone of Cycas revoluta • Living fossils— Jurassic Period is sometimes called the "Age of Cycads" http://a.abcnews.com/images/Technology/nc_cycads_071004_ms.jpg http://www.hort.wisc.edu/mastergardener/Features/botgardens/lotusl Division Cycadophyta (cycads) Cycas revoluta http://z.about.com/d/forestry/1/7/l/i/Ginkgo_biloba_st ueber.jpg www.science.siu.edu/.../ginkgophyta.html Ginkgo biloba Division Ginkgophyta (ginkgo) www.science.siu.edu/.../ginkgophyta.html Ephedra andina. http://wc.pima.edu/~bfiero/tucsonecology/plants/images/s w_ephe01.jpg http://upload.wikimedia.org/wikipedia/commons/thumb/d/d5/Ephedra_ andina_1.jpg/581px-Ephedra_andina_1.jpg Division Gnetophyta (Gnetae) Mormon tea Classification of Plants II •Vascular Plants Seed Plants Angiosperms Division Anthophyta (flowering plants) Reproductive adaptations of angiosperms include flowers and fruits • Angiosperms are flowering plants • These seed plants have reproductive structures called flowers and fruits • They are the most widespread and diverse of all plants Stigma Stamen Anther Carpel Style Filament Ovary California Poppy Petal Sepal Sunflower Ovule Receptacle Division Anthophyta (flowering plants) Indian Paintbrush in Grand Canyon. Fruit develop from the ovary http://www-plb.ucdavis.edu/labs/rost/Tomato/Reproductive/stages2aa.gif Fruits • A fruit typically consists of a mature ovary but can also include other flower parts • Fruits protect seeds and aid in their dispersal • Mature fruits can be either fleshy or dry Tomato, a fleshy fruit with soft outer and inner layers of pericarp Ruby grapefruit, a fleshy fruit with a hard outer layer and soft inner layer of pericarp Nectarine, a fleshy fruit with a soft outer layer and hard inner layer (pit) of pericarp Milkweed, a dry fruit that splits open at maturity Walnut, a dry fruit that remains closed at maturity Fruits • Various fruit adaptations help disperse seeds • Seeds can be carried by wind, water, or animals to new locations Wings enable maple fruits to be easily carried by the wind. Seeds within berries and other edible fruits are often dispersed in animal feces. The barbs of cockleburs facilitate seed dispersal by allowing these fruits to hitchhike on animals. The Angiosperm Life Cycle • In the angiosperm life cycle, double fertilization occurs when a pollen tube discharges two sperm into the female gametophyte within an ovule • One sperm fertilizes the egg, while the other combines with two nuclei in the central cell of the female gametophyte and initiates development of food-storing endosperm • The endosperm nourishes the developing embryo Key The Angiosperm Life Cycle Haploid (n) Diploid (2n) Microsporangium Microsporocytes (2n) Anther Mature flower on sporophyte plant (2n) MEIOSIS Microspore (n) Ovule with megasporangium (2n) Male gametophyte (in pollen grain) Generative cell Ovary Germinating seed Pollen grains MEIOSIS Stigma Pollen Megasporangium tube (n) Sperm Surviving megaspore (n) Embryo (2n) Endosperm (food supply) (3n) Seed Pollen tube Seed coat (2n) Style Antipodal cells Female gametophyte Polar nuclei (embryo sac) Synergids Eggs (n) Pollen tube Sperm (n) Zygote (2n) Nucleus of developing endosperm (3n) Eggs nucleus (n) FERTILIZATION Discharged sperm nuclei (n) Tube cell