Transcript Ferns
Seedless Plants Chapter 30 Origin of Land Plants • All green algae and the land plants shared a common ancestor a little over 1 BYA – Kingdom Viridiplantae – Not all photoautotrophs are plants • Red and brown algae are excluded • A single species of freshwater green algae gave rise to the entire terrestrial plant lineage 2 • The green algae split into two major clades – Chlorophytes – Never made it to land – Charophytes – Sister to all land plants • Land plants … – Have multicellular haploid and diploid stages – Trend toward more diploid embryo protection – Trend toward smaller haploid stage 3 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Green plants Streptophyta Land plants Bryophytes Tracheophytes Euphyllophytes Red Algae Green algae Green algae Chlorophytes Charophytes Seed plants Liverworts Mosses Hornworts Lycophytes Ferns + Allies Gymnosperms Angiosperms Ancestral alga 4 • Adaptations to terrestrial life – Protection from desiccation • Waxy cuticle and stomata – Moving water using tracheids • Tracheophytes have tracheids – Xylem and phloem to conduct water and food – Dealing with UV radiation caused mutations • Shift to a dominant diploid generation – Haplodiplontic life cycle • Mulitcellular haploid and diploid life stages • Humans are diplontic 5 Haplodiplontic Life Cycle • Multicellular diploid stage – sporophyte – Produces haploid spores by meiosis – Diploid spore mother cells (sporocytes) undergo meiosis in sporangia • Produce 4 haploid spores • First cells of gametophyte generation • Multicellular haploid stage – gametophyte – Spores divide by mitosis – Produces gametes by mitosis – Gametes fuse to form diploid zygote • First cell of next sporophyte generation 6 Gametophyte (n) MITOSIS Spore Sperm n Egg n n n Spore n MEIOSIS 2n FERTILIZATION 2n Spore mother cell 2n 2n Sporangia Zygote Embryo Sporophyte (2n) 7 • All land plants are haplodiplontic • Relative sizes of generations vary • Moss – Large gametophyte – Small, dependent sporophyte • Angiosperm – Small, dependent gametophyte – Large sporophyte 8 Bryophytes Tracheophytes Hornworts Mosses Liverworts • Closest living descendants of the first land plants • Called nontracheophytes because they lack tracheids Charophytes Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. – Do have other conducting cells • Mycorrhizal associations important in enhancing water uptake – Symbiotic relationship between fungi and plants 9 • Simple, but highly adapted to diverse terrestrial environments • 24,700 species in 3 clades – Liverworts – Mosses – Hornworts • Gametophyte – conspicuous and photosynthetic – Sporophytes – small and dependent • Require water for sexual reproduction 10 Liverworts (phylum Hepaticophyta) • Have flattened gametophytes with liverlike lobes Female gametophyte – 80% look like mosses • Form gametangia in umbrella-shaped structures • Also undergo asexual reproduction © David Sieren/Visuals Unlimited 11 Leafy vs Thallose Liverworts 12 Leafy vs Thallose Liverwort 13 Marchantia polymorpha 14 15 Liverwort Sex… (if you are under 18, please close your eyes!) Click here for XXX rated liverwort porn 16 Mosses Moss grows on the north side of a tree… 18 “Haircap Moss”, Polytrichum 19 Hair Cap Moss 20 Apple Moss, Bartramia 21 Pin Cushion Moss, Leucobryum 23 Delicate Fern Moss, Thuidium 24 Mosses (phylum Bryophyta) • Gametophytes consist of small, leaflike structures around a stemlike axis – Not true leaves – no vascular tissue • Anchored to substrate by rhizoids • Multicellular gametangia form at the tips of gametophytes – Archegonia – Female gametangia – Antheridia – Male gametangia • Flagellated sperm must swim in water 25 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Male Gametophytes Sperm Egg Antheridia Archegonia Female Germinating spores Rhizoids Sporophyte Zygote n 2n MITOSIS MITOSIS Gametophyte Spores 2n 1n Mature sporophyte Developing sporophyte in archegonium 2n Sporangium Parent gametophyte 1n 26 Hornworts (phylum Anthocerotophyta) • • • • Origin is puzzling – no fossils until Cretaceous Sporophyte is photosynthetic Sporophyte embedded in gametophyte tissue Cells have a single large chloroplast Photosynthetic sporophyte 27 Tracheophyte Plants • Cooksonia, the first vascular land plant – Appeared about 420 MYA – Phylum Rhyniophyta • Only a few centimeters tall Sporangia – No roots or leaves – Homosporous – only 1 type of spore 28 Vascular tissues • Xylem – Conducts water and dissolved minerals upward from the roots • Phloem – Conducts sucrose and hormones throughout the plant • Enable enhanced height and size in the tracheophytes • Develops in sporophyte but not gametophyte • Cuticle and stomata also found in land plants 29 Tracheophytes • Vascular plants include seven extant phyla grouped in three clades 1. Lycophytes (club mosses) 2. Pterophytes (ferns, whisk ferns, and horsetails) 3. Seed plants • Gametophyte has been reduced in size relative to the sporophyte during the evolution of tracheophytes • Similar reduction in multicellular gametangia has occurred as well 30 31 • Stems – Early fossils reveal stems but no roots or leaves – Lack of roots limited early tracheophytes • Roots – Provide transport and support – Lycophytes diverged before true roots appeared • Leaves – Increase surface area for photosynthesis – Evolved twice • Euphylls (true leaves) found in ferns and seed plants • Lycophylls found in seed plants 32 Lycophyll Origins Stem with vascular tissue Stem, leafy tissue without vascular tissue Stem, leafy tissue with vascular tissue Single vascular strand (vein) Euphyll Origins Branching stems with vascular tissue Unequal branching Branches in Photosynthetic tissue single planes “webs” branches Branched vascular strands (veins) 33 • 400 million years between appearance of vascular tissue and true leaves – Natural selection favored plants with higher stomatal densities in low-CO2 atmosphere – Higher stomatal densities favored larger leaves with a photosynthetic advantage that did not overheat • Seeds – Highly resistant – Contain food supply for young plant – Lycophytes and pterophytes do not have seeds 34 Chlorophytes Charophytes Liverworts Mosses Hornworts Lycophytes Ferns + Allies Gymnosperms Angiosperms Flowers Fruits Seeds Euphylls Stems, roots, leaves Dominant sporophyte Vascular tissue Stomata Multicellular embryo Antheridia and archegonia Cuticle Plasmodesmata Chlorophyll a and b Ancestral alga • Fruits in the flowering plants (angiosperms) add a layer of protection to seeds and attract animals that assist in seed dispersal, expanding the potential range of the species 35 Seed Plants Ferns and Allies Lycophytes Hornworts Lycophytes • • • • • Worldwide distribution – abundant in tropics Lack seeds Superficially resemble true mosses Sporophyte dominant 36 15 PA species Princess Pine Dendrolycopodium obscurum 37 Shining Club Moss Lycopodium lucidulum 38 Ground Pine 39 Seed Plants Whisk Ferns Ferns Horsetail Ferns Ferns • Phylogenetic relationships among ferns and their relatives is still being sorted out • Common ancestor gave rise to 2 clades • All form antheridia and archegonia • All require free water for flagellated sperm Lycophytes Pterophytes 40 Whisk Ferns • Found in tropics, none locally • Sporophyte consists of evenly forking green stems without true leaves or roots (found to be monophyletic with ferns) • Some gametophytes develop elements of vascular tissue – Only gametophytes known to do so 41 Horsetails • All 15 living species are homosporous • Constitute a single genus, Equisetum; 5 species in PA • Sporophyte consists of ribbed, jointed photosynthetic stems that arise from branching rhizomes with roots at nodes • Silica deposits in cells – scouring rush 42 Ferns Ferns • Most abundant group of seedless vascular plants – About 11,000 species • Coal formed from forests 300 MYA • Conspicuous sporophyte and much smaller gametophyte are both photosynthetic 44 Antheridium Archegonium Rhizoids Archegonium Egg Sperm Gametophyte MITOSIS Antheridium Spores 1n MEIOSIS Zygote 2n n MITOSIS 2n Underside of leaf frond Mature frond Leaf of young sporophyte Adult sporophyte Mature sporangium Embryo Sorus (cluster of sporangia) Gametophyte Sporangium • Fern life cycle differs from that of a moss • Much greater development, independence, and dominance of the fern’s sporophyte • Gametophyte lacks vascular tissue Rhizome 45 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Tightly Coiled Fern Uncoiling Fern (left): © Mike Zens/Corbis; (right): © Ed Reschke • Fern morphology – Sporophytes have rhizomes – Fronds (leaves) develop at the tip of the rhizome as tightly rolled-up coils (“fiddleheads”) 46 Fern reproduction • Produce distinctive sporangia in clusters called sori on the back of the fronds • Diploid spore mother cells in sporangia produce haploid spores by meiosis • Spores germinate into gametophyte – Rhizoids but not true roots – no vascular tissue • Flagellated sperm 47 sterile frond fertile frond fiddlehead/crozier rhizome Ferns Pinnate Pinnatifid Not everything that looks like a fern is one! …and not everything that is a fern looks like one! Ostrich Fern Matteuccia struthiopteris • separate fertile and vegetative fronds 67 68 Sensitive Fern Onoclea sensibilis 69 Hay-scented Fern Dennstaedtia punctilobula 70