Phylogeny of Green Plants Green plants “Green algae” Embryophytes Embryo (land plants) Coleochaetales Charales Chlorophytes Ref.5 Cuticle Sporopollenin Ref.4 Ref.6 Ref.7 Pop Quiz According to the phylogenetic tree shown in the previous slide, the group “green algae” is: A. Monophyletic B. Paraphyletic C. Polyphyletic D. I have no idea Phylogeny of Land Plants Embryophytes (land plants) “Bryophytes” Tracheophytes (vascular plants) Mosses Hornworts Liverworts tracheids in vascular Ref.10 Ref.8 Ref.9 tissue Ref.12 stomata Ref.11 Phylogeny of Tracheophytes Tracheophytes (vascular plants) Seed plants (Gymnosperms+Angiosperms) Lycophytes Ferns and fern allies seeds Ref.15 pollen Ref.14 Ref.13 Ref.16 true leaves Phylogeny of Seed Plants Seed plants Gymnosperms Angiosperms carpel endosperm bitegmic ovules Ref.20 Ref.18 Ref.17 flowers reduced female gametophyte Ref.19 Homework Integrate the information from the previous slides and draw a tree showing the relationships of the major plant groups. Also, mark the synapomorphies defining those major monophyletic groups along the branches. Life Cycle: Angiosperm (Flowering plants) Ref.1 Some Key Concept in Angiosperm Life Cycle NOTE: definitions used in lectures of this class are mainly following the textbook (Judd et al., 2008. Plant systematics: a phylogenetic approach, 3rd ed.) Meiosis: two-stage nuclear division process that reduces the chromosome number of a cell by half (from a diploid cell to 4 haploid daughter cells), followed by production of spores. Mitosis: nuclear division that maintains the parental chromosome number for daughter cells; the basis for growth in size and asexual reproduction in plants. Fertilization: fusion of the sperm nucleus and the egg nucleus. Zygote (2n): the cell formed by the fusion of the sperm (1n) and egg (1n) at fertilization, germinates to produce a multi-cellular sporophyte (2n) via mitosis. Spore (1n): the first cell of a gametophyte (1n), product of meiosis. Sporophyte (2n): diploid, spore-producing generation of the plant life cycle, produces spores via meiosis in a structure called sporangium (plural, sporangia). Gametophyte (1n): Haploid, gamete-producing generation of the plant life cycle; produces gametes via mitosis in specialized structures/sex organs—gametangia (male: antheridium, produce sperm; female: archegonium, produce eggs) Some Key Concept in Angiosperm Life Cycle (cont.) Embryo vs. Embryo sac Embryo (2n): young sporophyte, from the first cell after fertilization (zygote) until germination of the seed (in seed plants) or emergence from protective gametophytic tissues (other land plants). Embryo sac (1n): female gametophyte of the angiosperms (flowering plants). Life Cycle: Fern and Fern Allies Ref.2 Life Cycle: Bryophytes Ref.3 The sporophyte generation is dependent on the photosynthetic gametophyte for nutrition Generalized Life Cycle in Plants Alternation of generations = cycle between haploid (1n) and diploid (2n) phase Difference between plants and animals Animals: meiosis produces gametes directly. Plants: meiosis produces spores (to start gametophyte generation), and mitosis produces gametes. Variation of Life Cycle in Plants “Bryophytes” (mosses, liverworts, hornworts) - Most of life is in 1n phase, therefore, gametophyte (green leafy base) dominant life cycle; sporophyte (brown stalked capsule/sporangium) dependent on gametophyte (grows out of gametophyte and gets all nutrition from gametophyte). Sporophyte produces spores that land on ground & germinate into gametophytes. Ferns and fern allies - sporophyte dominant; gametophyte free-living, but small and short-lived. Leaves = sporophyte, free-living. Spores germinate from sporangia on underside of leaves (sori) and produce small, green, free-living heart-shaped gametophyte on ground. Gametophyte with separate structures that produce egg & sperm; lives ~1 year, reproduces, then dies. Sporophyte dominant life cycle: lives longer and larger and reproduces many years. Seed plants (Angiosperms and Gymnosperms) - sporophyte dominant; gametophyte dependent on sporophyte and very reduced and short-lived. Microsporangia in pollen-bearing structures (pollen cones or anthers) that produce male gametophyte, short-lived and inside the pollen grain, which consists of 2-3 cells, one cell becomes sperm. Megasporangia in ovules that produce female gametophyte in cone (“gymnosperms”) or ovary (angiosperms) and produces the egg. Spores grow into pretty small gametophytes which are contained within the parent plant (inside cones or flower). Pollination vs. Fertilization Distinction and Relationship of Pollination and Fertilization Pollination: transference of pollen from the anther to the stigma. Fertilization: fusion of the sperm nucleus and egg nucleus. Pollination occurs only in seed plants; Fertilization occurs in all sexually Reproducing organisms. In plants, pollination must occur before fertilization! (Without pollination, fertilization can not take place. ) Pollination Syndromes “Sexual Encounters of the Floral Kind” Handout to accompany film – Biology 117/317 Pollination syndromes Wind Pollination: 1) flowers appear before leaves are out 2) large number of flowers (especially males), often in catkins 3) individual flowers small and inconspicuous - without parts for attraction 4) Big stamens produce lots of pollen 5) Stigmas large and plumose or roughened (papillate) to catch pollen 6) Ratio of pollen to ovules VERY HIGH (up to 6,000 to 1) Many different kinds of insects function as pollinators; often these involve very different floral characteristics: Bees, butterflies, etc.: 1) flowers showy, with brightly colored petals 2) flowers usually with some food reward, two common ones are: pollen - protein rich reward nectar - rich in nutrients (e.g., amino acids and sugars) 3) flowers often with strong favorable scent during the day 4) flowers often with ultraviolet markings visible only to the insects (not to humans) Pollination Syndromes (cont.) Moths: 1) flowers often white 2) flowers open and scent released in the evening or at night 3) nectar reward 4) flowers often long and tubular to limit access only to long tongued moths Carrion flies (Blowflies): 1) flowers purple or brown or greenish-brown 2) flowers often close to the ground 3) scent strong and foul (like dead animal) “Buzz” pollination by bees: 1) no nectar reward (pollen sole reward) 2) connivent anthers (anthers held together) at center of flower 3) anthers opening by terminal pores; pollen shakes out when the bee buzzes the flower Birds often pollinate flowers, too: Hummingbirds (found in North and South America only): 1) flowers with long tubular corollas 2) flowers usually red 3) nectar reward in large quantity, rich in sugars (few other nutrients) 4) flowers often dangle away from plant so that bird can reach it while hovering In other parts of the world different birds, including Honeycreepers (Hawaii), Honeyeaters (Australia) and Sunbirds (S. Africa) act as pollinators. Flowers adapted to these birds differ from those adapted for hummingbirds by having a “landing platform” for the birds to perch on, because they cannot hover. The flowers still have long tubular corollas and lots of sugar-rich nectar. Image Source Ref.1 http://8e.devbio.com/image.php?id=525 Ref.2 http://8e.devbio.com/image.php?id=524 Ref.3 http://8e.devbio.com/image.php?id=523 Ref.4 http://content.answers.com/main/content/wp/en-commons/thumb/c/c9/250px-Haeckel_Siphoneae.jpg Ref.5 http://www.vcbio.science.ru.nl/images/stemgrowth/SGembryo-apicalmeristem.jpg Ref.6 http://www.uni-muenster.de/GeoPalaeontologie/Palaeo/Palbot/cut1a.jpg Ref.7 http://en.wikivisual.com/images/a/a4/Misc_pollen.jpg Ref.8 http://www.hiddenforest.co.nz/bryophytes/mosses/familys/racopilaceae/images/racop01bt.jpg Ref.9 http://ux.brookdalecc.edu/fac/biology/lab/102/images/liverwort1.jpg Ref.10 http://www.cartage.org.lb/en/themes/Sciences/BotanicalSciences/ClassificationPlants/Cryptogamia/Bryophyta/Nonvascular/hornwort1.JPG Ref.11 http://www.freewebs.com/jdingfel/Stomata.jpg Ref.12 http://f030091.ffpri.affrc.go.jp/image/OM_code_E/60.Tracheids.gif Ref.13 http://media-2.web.britannica.com/.../04/7604-004.jpg Ref.14 http://static.howstuffworks.com/gif/define-ferns-1.jpg Ref.15 http://home.pacbell.net/kenww/my_iris/other/I_foetidissima_seeds-web.jpg Ref.16 http://www.bioquest.org/scope/projectfiles/PollenMixb.jpg Ref.17 http://www.icbgpanama.org/website/gall_pictures/Gnetumfrutos.jpg Ref.18 http://www.dickcontino.com/images/ginkgo.jpg Ref.19 http://www.emc.maricopa.edu/faculty/farabee/BIOBK/fertil1.gif Ref.20 http://web.gccaz.edu/~lsola/Flower/capsella3.jpg.