Seedless Plant Quiz PDF

Chapter 25: Seedless Plants Be able to: Explain the evidence linking the ancestors of plants to multicellular algae. Describe plant adaptations key to the transition to land life. Describe the characteristics and diversity of extant Bryophytes. Describe the evolution of key adaptations of early vasc...

Chapter 25: Seedless Plants Be able to: Explain the evidence linking the ancestors of plants to multicellular algae. Describe plant adaptations key to the transition to land life. Describe the characteristics and diversity of extant Bryophytes. Describe the evolution of key adaptations of early vascular plants. Describe the characteristics and diversity of extant seedless vascular plants. 2 Land Plants (originated ~470mya)  Plants share a common ancestor with charophytes (green algae) in the archaeplastida supergroup of eukaryotes. 5 mm Chara species, a pond organism Coleochaete orbicularis, a disk-shaped charophyte that also lives in ponds 40 µm Green Algae and Plants: Shared Characteristics Chlorophytes, Charophytes & Plants share: multicellularity cell walls with cellulose chloroplasts with same pigments (chlorophyll. a & b) storage molecule is starch chlorophyte (Ulva) charophyte (Chara) plant (moss) From Water to Land Desiccation, or drying out, is a constant danger for an organism exposed to air Both gametes and zygotes must be protected from desiccation Plants need to develop structural support in a medium that does not give the same lift as water The male gametes must reach the female gametes using new strategies, because swimming is no longer possible Disadvantages: risk of desiccation (both adult & gametes) no “support” in air From Water to Land Advantages of Land: [CO2] higher light intensity higher more minerals no “herbivores” no competition From Water to Land Adaptations: Life cycle in all land plants exhibits the alternation of generations An apical meristem tissue in roots and shoots Evolution of a waxy cuticle to resist desiccation Cell walls with lignin to support structures off the ground. From Water to Land Alternation of generations many unique spores many cells do meiosis From Water to Land compare to charophyte life cycle: only multicellular is haploid zygote does meiosis to produce only 4 diverse offspring only 4 recombinant spores only one cell; does meiosis charophyte: multicellular (n) NOT alternation of generations! From Water to Land Walled haploid spores dispersal thru air: sporopollenin protects made within multicellular sporangium spore sporangium sporophyte gametophyte From Water to Land Multicellular gametangia protecting sperm w/in antheridium sperm many sperm; protected Female gametophyte From Water to Land egg protected within archegonium fertilization here: forming zygote Male gametophyte Archegonia and antheridia of Marchantia one egg, protected by tissue From Water to Land Apical Meristems continuously dividing cells roots & shoots grow toward resources light CO2 water minerals From Water to Land Waxy cuticle waxy coat stops desiccation pores needed to allow CO2/O2 exchange controllable stomata in most plants CO2 O2, H2O From Water to Land Secondary metabolites chemicals that deter, repel or poison competitors, herbivores, & parasites caffeine latex rubber From Water to Land Mycorrhizae mutualism with fungi; helps water & mineral absorption dates back to first land plants (before true roots)! Major Divisions of Land Plants Seedless, Nonvascular Plants  Collectively referred to as “Bryophytes”  Non-woody, small, ground-covering plants that require water for reproduction  Have rhizoids for attachment (not true roots)  3 Phyla: Hepaticophyta (Liverworts) Anthocerotophyta (Hornworts) Bryophyta (Mosses) “Bryophytes” – Nonvascular Plants Bryophyte Characteristics: Haploid gametophyte is dominant form: Dominant=longest lasting or largest makes eggs & flagellated sperm most are small, low growing, moist areas “Bryophytes” – Nonvascular Plants Bryophyte Characteristics: Diploid sporophyte depends on gametophyte for food & water grows within archegonium of gametophyte sporangium makes many haploid spores mature sporophyte liverwort 1. Liverworts Most have elevated gametophytes that resemble miniature trees (Marchantia) Thallus Reduced or very small sporophytes; Some “thalloid” and others “leafy” Gametophore of female gametophyte Sporophyte Foot Seta Marchantia polymorpha, a “thalloid” liverwort Marchantia sporophyte (LM) 500 µm Capsule (sporangium) Plagiochila deltoidea, a “leafy” liverwort 2. Hornworts Common name refers to horn-like long tapered shape of sporophyte Good colonizers of moist soils Symbiotic relationship with nitrogen-fixing cyanobacteria sporophyte gametophyte 3. Mosses The most numerous of the non-vascular plants Inhabit extreme environments as mountain tops, tundra, and deserts Sporophyte grows up from female gametophyte to gain elevation for spore dispersal Polytrichum commune, hairy-cap moss Capsule Sporophyte Seta Gametophyte Mosses Ecological Importance “pioneer” species in nutrient-poor soils moss are major primary producers in cold or highaltitude regions Sphagnum “peat moss” bogs: important wetlands, also harvested for fuel some peatlands have preserved corpses for thousands of years Tollund Man Seedless Vascular Plants (SVP) Until vascular tissue evolved, all land plants were short, ground cover plants Oldest seedless vascular plant fossils ~425 MYA (Club Moss) (Ferns) SVP Characteristics 1. Branched sporophytes that are independent of gametophyte for nutrition 2. Diploid sporophyte dominates life cycle 3. Transport in Xylem and Phloem (vascular system) 1. Xylem: cells specialized to move water and minerals 2. Phloem: cells specialized to move sugars, amino acids, other organic products 4. Evolution of true roots 5. Evolution of true leaves Only Lycophytes have microphylls: Small, spine-shaped leaves supported by a single strand of vascular tissue Almost all other vascular plants have megaphylls: Leaves with a highly branched vascular system Greater photosynthetic productivity than microphylls Sporophylls Leaves modified to bear sporangia - Fern sporophylls look like normal leaves but have sori that generate spores on underside - Lycophyte sporophylls modified into a cone-like structure called a strobilus 29 Sporophylls Homosporous spore production (most seedless vascular plants) Sporangium on sporophyll Single type of spore Typically a bisexual gametophyte Eggs Sperm Heterosporous spore production (all seed plants and few seedless vascular plants) Megasporangium on megasporophyll Microsporangium on microsporophyll Megaspore Microspore Female gametophyte Male gametophyte Eggs Sperm 1. Lycophytes (Club mosses and relatives) -Current species all small (1,200 spp.) - tropical and temperate Isoetes Strobili (clusters of gunnii, a quillwort sporophylls) 1 cm Selaginella apoda, a spike moss 2.5 cm Diphasiastrum tristachyum, a club moss Spike mosses and quillworts are heterosporous Club mosses are homosporous 2. Pterophytes (Ferns and relatives) Horsetails, whisk ferns, and ferns belong to the phylum Monilophyta ferns whisk ferns horsetails 2. Pterophytes (Ferns and relatives) Whisk ferns (Psilotum) dichotomous branching no true leaves or roots Homosporous Photosynthesis occurs in stem occurs in stems ~40 cm sporangia 2. Pterophytes (Ferns and relatives) Horsetails (Equisetum) jointed stems with tiny leaves Strobili Homosporous Photosynthesis occurs in stems strobilus ~60 cm 2. Pterophytes (Ferns and relatives) Ferns most widespread & diverse Monilophytes homosporous large megaphylls sori on underside of sporophylls mostly in understory or as epiphytes sori sporophyll “fiddlehead” “epiphyte” = grows on the surface of a plant Fern Life Cycle Importance of seedless plants Disappearance of mosses Ferns Biological indicator of environmental pollution Promotes weathering of rocks Accelerates topsoil formation Used as food Peat moss (Sphagnum) Used as fuel (renewable resource) Soil conditioner Extinct SVPs Coal Energy source