DOCSLIB.ORG

Tree of Life by Dana Visalli

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Tree of Life by Dana Visalli The Tree of Life by Dana Visalli/www.methownaturalist.com It is not known how life on earth began. Genetic and chemical evidence indicates that life was initiat- ed only once, as one species, and that all succeeding organisms are descendants of this first life, which is known as LUCA--the last universal common ancestor. The Earth is thought to be 4.5 billion years old, and life appeared approximately 3.8 billion years ago, almost as soon as the planet had stabilized ade- quately for life to be theoretically possible. Estimates for the total number of species alive today vary wildly, from around 5 million to more than 100 million. 1.8 million species have been named and catego- rized by scientists. The immediate evolutionary relationships among organisms are not universally agreed upon and so the branching of the Tree of Life has different interpretations. The one used here is one of the more straightforward versions. Life began as relatively simple, single cells resembling Bacteria, and diversified from there into 6 distinct Kingdoms: Bacteria, Archea, Protists, Plants, Fungi and Animals. A currently popular alternate tree divides life first into 3 domains--Bacteria, Archea, and Eukaryotes (see below), and then the Eukaryotes radiated into 4 kingdoms. An important evolutionary division is between prokaryotes and eukaryotes. The word prokaryote translates from the Greek as ‘before the seed,’ or ‘before the nucleus.’ Prokaryotes--Bacteria and Archea- -do not have a nucleus in their cells--a separate area with its own membrane that contains the DNA of the cell. The word eukaryote means ‘true seed’ or ‘true nucleus,’ and obviously a eukaryote does have a nu- cleus. This group includes the other 4 kingdoms of life besides Bacteria and Archea: Protists, Plants, Fun- gi and Animals. Primary Life Groups: 6 Kingdoms: Kingdom Bacteria (Greek, ‘cane,’ because the first Bacteria discovered were rod-shaped)- About 2000 species known in 11 phyla. The total number is hard to assess, guesses range from the tens of thousands to billions. Bacteria are prokaryotes; their cells have no nucleus. They are found in almost all environments, from deep underground to the stratosphere. The biomass of bacteria thought to exceed that of all animals and plants combined. Bacterial cells are about 1/10th the size of eukaryotic cells and Bacteria, magnified 1000x are typically 0.5-5.0 u (micrometers; a micrometer is 1 millionth of a meter) in length. Dana Visalli/[email protected]/www.methownaturalist.com, Kingdom Archea (Greek, ‘ancient’)- About 1000 species known in 2 phyla; the actual total existing is unknown. Like Bacteria, Archea are prokaryotes, but they have unique proper- ties that separate them from both eukaryotes and Bacteria. Most Archea are an- aerobes--they obtain their energy without using oxygen, and in fact oxygen is toxic to them. Many Archea are ‘extremeophiles,’ which means ‘lover of extreme conditions.’ They can be found thriving in extremely hot water (up to and above An Archea, Sulfolobus 212°F), in ice, in super-saturated salt water. and deep below ground. Size is 0.1-15 u. Kingdom Protista (Greek, ‘the very first’) (aka Protoctista)- 100,000-200,000 species in 36 phyla. Pro- tists have eukaryotic cells and are mostly unicellular; some are multicellular but have no specialized tissue, algae for example. They are typically divided into 3 groups, animal-like, plant-like and fungi-like protists. Size is variable; while aver- aging 0.1 mm, they vary from 0.01 mm to 65 meters (giant kelps). Paramecium, a Protist Kingdom Plantae (Latin, ‘to sprout’)- About 300,000 species in 12 phyla (often called divisions in the Plant Kingdom). Plants are thought to have evolved from certain green algae. They began to colonize land 450 million years ago, which required some means of dealing the problem desiccation (drying out). Size ranges from the duckweed-like Wolffia which is 0.5 mm long, to the largest redwood tree at 115 meters (380 feet) tall. Kingdom Fungi Flower anthers & pollen (Greek ‘sponge’)- 75,000 species in 6 phyla have been identified; total may num- ber more than a million. One of the 6 phyla of Fungi is lichens, which are mostly fungal with an algae or cyanobacteria symbiont (lives inside the fungus). Fungi are now thought to have diverged from other life 1.5 billion years ago, and colo- nized land about 500 million years ago. Most plant species have a symbiotic (beneficial) relationship with one or more fungal species. The majority of the fun- gi that we see--mushrooms--have most of their organic structure underground and can grow to enormous size. A honey mushroom (Armillaria ostoyae) in Ore- Honey mushroom gon grows over 2200 acres and is a contender for the largest organism on the plan- et. Yeast cells can be as small as 2 micrometers (2 millionths of a meter). Kingdom Animalia (Latin, ‘breath’ or ‘soul’)- The total number of animals on earth is unknown; a mil- lion have been identified and the total is probably well over 5 million (including insects and various worm phyla). 99% of all animals are invertebrates--they lack a backbone. Of the 36 phyla of animals, most are aquatic worms of one sort or an- other. Truly land-dwelling forms are found only in two phyla, Arthropoda A moss piglet, in moss (insects and their kin) and Cordata (animals with backbones). One contender for the smallest animal in the world is the water bear or moss piglet (tardigrade); di- minutive ones are 0.1 mm long. The largest animal in the world and the largest that has ever lived is the blue whale. It can grow to 100 feet in length and 400,000 pounds. Before whaling there were probably a million blue whales in the oceans; today there are about 8000. Kingdoms break down as follows: Subkingdom, Phylum, Class, Order, Family, Ge- A blue whale nus, Species. For example humans are in Phylum Chordata, Class Mammalia, Order Primates, Family Hominidae, Genus Homo, Species H. sapiens. 2 Branches on the Tree of Life Prions (The name derived from ‘protein-infection’)-A prion is an infectious agent, a pro- tein in a misfolded form. All known prion diseases in mammals affect the struc- ture of the brain or other neural tissue and all are currently untreatable and fatal. Diseases include bovine spongiform encephalapathy (mad cow disease) and Creutzfeldt-Jacob Disease. Prions are not considered living organisms but are mis- folded protein molecules which may propagate by transmitting a misfolded pro- tein state. If a prion enters a healthy organism, it induces existing, properly White spots are microscopic holes folded proteins to convert into the disease-associated, misfolded prion form. This in neural tissue caused by prions triggers a chain reaction that produces large amounts of the prion form. Prion rep- lication is subject to natural selection just like in living organisms. Viruses (Latin, ‘poison’)- About 5000 viruses are known, with another 4000 unclassified, and probably over million extant. A virus is a minute infectious agent that can reproduce only by entering a host cell in a living organism and using its cell ma- chinery. Some can crystallize like minerals and persist for years in that state. Vi- ruses can infect all types of life forms, from animals and plants to Bacteria and Archea. The smallest ones are only 20 nm (nanometers, 20 billionths of a meter, 20 millionths of a millimeter). Viruses attacking a bacteria The virus particle, or virion, in its simplest form is just nucleic acid enclosed in a protein shell. Its genome may consist of double- or single-stranded DNA or RNA. the smallest viruses have as few as four genes, while the largest have several hundred. Much smaller still are viroids, tiny molecules of naked RNA, which foul up the metabolism of plants. Prokaryotes (Greek, ‘before the seed’) Prokaryotes are organisms that have what could be considered primitive cells which have no nucleus--no membrane-bound area inside the cell containing the cell’s DNA. A second type of larger cells, the eukaryotes (‘true seed’), do have a nucleus. Two kingdoms make up the prokaryotes, Bacteria and Archea. They are the earliest life form we know of, 3.8 billion years old, and the only life-form on Earth for 2 billion years. Prokaryotes outnumber all eukaryotes combined: there are more bacteria in one human mouth than all the people that have ever lived; the human body contains more bacterial cells than human cells, and it is thought that the biomass of Bacteria and Archea outweigh the combined biomass of the other 4 kingdoms. They are pervasive, being found in salty, acidic, alkaline, and very hot and cold environments as well as what life typically considers comfortable. Bacteria are essential to the other kingdoms, as decomposers of organic material, fixers of nitrogen, and pro- ducers of atmospheric oxygen and nitrogen. If Bacteria disappeared, the other four kingdoms would soon fol- low. On the other hand half of all human disease is caused by Bacteria. Some are opportunistic- they are always present, for example Streptoccus pneumonia, which is always in the throat, and will multiply when body defenses are down. Prokaryotes are 1/10 to 1/100 the size of eukaryotic cells, have 1/1000 the DNA, and are haploid, which means they only have one strand of DNA, rather than two (diploid). Bacterial motility (movement) is by flagella or slime secretion. Reproduce occurs by binary fission--splitting in half--which progresses geometri- cally. Some cells can reproduce every 20 minutes, which would equal 1 million kg in 24 hrs. Like sex in eu- karyotes, prokaryotes do indulge in bacterial conjugation, when two organisms come into contact, a thin bridge can form, through which one of the bacteria donates a copy of some of its DNA.
Load more

Recommended publications
  • The 2014 Golden Gate National Parks Bioblitz - Data Management and the Event Species List Achieving a Quality Dataset from a Large Scale Event
    National Park Service U.S. Department of the Interior Natural Resource Stewardship and Science The 2014 Golden Gate National Parks BioBlitz - Data Management and the Event Species List Achieving a Quality Dataset from a Large Scale Event Natural Resource Report NPS/GOGA/NRR—2016/1147 ON THIS PAGE Photograph of BioBlitz participants conducting data entry into iNaturalist. Photograph courtesy of the National Park Service. ON THE COVER Photograph of BioBlitz participants collecting aquatic species data in the Presidio of San Francisco. Photograph courtesy of National Park Service. The 2014 Golden Gate National Parks BioBlitz - Data Management and the Event Species List Achieving a Quality Dataset from a Large Scale Event Natural Resource Report NPS/GOGA/NRR—2016/1147 Elizabeth Edson1, Michelle O’Herron1, Alison Forrestel2, Daniel George3 1Golden Gate Parks Conservancy Building 201 Fort Mason San Francisco, CA 94129 2National Park Service. Golden Gate National Recreation Area Fort Cronkhite, Bldg. 1061 Sausalito, CA 94965 3National Park Service. San Francisco Bay Area Network Inventory & Monitoring Program Manager Fort Cronkhite, Bldg. 1063 Sausalito, CA 94965 March 2016 U.S. Department of the Interior National Park Service Natural Resource Stewardship and Science Fort Collins, Colorado The National Park Service, Natural Resource Stewardship and Science office in Fort Collins, Colorado, publishes a range of reports that address natural resource topics. These reports are of interest and applicability to a broad audience in the National Park Service and others in natural resource management, including scientists, conservation and environmental constituencies, and the public. The Natural Resource Report Series is used to disseminate comprehensive information and analysis about natural resources and related topics concerning lands managed by the National Park Service.
    [Show full text]
  • Review of Acanthocephala (Hemiptera: Heteroptera: Coreidae) of America North of Mexico with a Key to Species
    Zootaxa 2835: 30–40 (2011) ISSN 1175-5326 (print edition) www.mapress.com/zootaxa/ Article ZOOTAXA Copyright © 2011 · Magnolia Press ISSN 1175-5334 (online edition) Review of Acanthocephala (Hemiptera: Heteroptera: Coreidae) of America north of Mexico with a key to species J. E. McPHERSON1, RICHARD J. PACKAUSKAS2, ROBERT W. SITES3, STEVEN J. TAYLOR4, C. SCOTT BUNDY5, JEFFREY D. BRADSHAW6 & PAULA LEVIN MITCHELL7 1Department of Zoology, Southern Illinois University, Carbondale, Illinois 62901, USA. E-mail: [email protected] 2Department of Biological Sciences, Fort Hays State University, Hays, Kansas 67601, USA. E-mail: [email protected] 3Enns Entomology Museum, Division of Plant Sciences, University of Missouri, Columbia, Missouri 65211, USA. E-mail: [email protected] 4Illinois Natural History Survey, University of Illinois at Urbana-Champaign, Illinois 61820, USA. E-mail: [email protected] 5Department of Entomology, Plant Pathology, & Weed Science, New Mexico State University, Las Cruces, New Mexico 88003, USA. E-mail: [email protected] 6Department of Entomology, University of Nebraska-Lincoln, Panhandle Research & Extension Center, Scottsbluff, Nebraska 69361, USA. E-mail: [email protected] 7Department of Biology, Winthrop University, Rock Hill, South Carolina 29733, USA. E-mail: [email protected] Abstract A review of Acanthocephala of America north of Mexico is presented with an updated key to species. A. confraterna is considered a junior synonym of A. terminalis, thus reducing the number of known species in this region from five to four. New state and country records are presented. Key words: Coreidae, Coreinae, Acanthocephalini, Acanthocephala, North America, review, synonymy, key, distribution Introduction The genus Acanthocephala Laporte currently is represented in America north of Mexico by five species: Acan- thocephala (Acanthocephala) declivis (Say), A.
    [Show full text]
  • "Lophophorates" Brachiopoda Echinodermata Asterozoa
    Deuterostomes Bryozoa Phoronida "lophophorates" Brachiopoda Echinodermata Asterozoa Stelleroidea Asteroidea Ophiuroidea Echinozoa Holothuroidea Echinoidea Crinozoa Crinoidea Chaetognatha (arrow worms) Hemichordata (acorn worms) Chordata Urochordata (sea squirt) Cephalochordata (amphioxoius) Vertebrata PHYLUM CHAETOGNATHA (70 spp) Arrow worms Fossils from the Cambrium Carnivorous - link between small phytoplankton and larger zooplankton (1-15 cm long) Pharyngeal gill pores No notochord Peculiar origin for mesoderm (not strictly enterocoelous) Uncertain relationship with echinoderms PHYLUM HEMICHORDATA (120 spp) Acorn worms Pharyngeal gill pores No notochord (Stomochord cartilaginous and once thought homologous w/notochord) Tornaria larvae very similar to asteroidea Bipinnaria larvae CLASS ENTEROPNEUSTA (acorn worms) Marine, bottom dwellers CLASS PTEROBRANCHIA Colonial, sessile, filter feeding, tube dwellers Small (1-2 mm), "U" shaped gut, no gill slits PHYLUM CHORDATA Body segmented Axial notochord Dorsal hollow nerve chord Paired gill slits Post anal tail SUBPHYLUM UROCHORDATA Marine, sessile Body covered in a cellulose tunic ("Tunicates") Filter feeder (» 200 L/day) - perforated pharnx adapted for filtering & repiration Pharyngeal basket contractable - squirts water when exposed at low tide Hermaphrodites Tadpole larvae w/chordate characteristics (neoteny) CLASS ASCIDIACEA (sea squirt/tunicate - sessile) No excretory system Open circulatory system (can reverse blood flow) Endostyle - (homologous to thyroid of vertebrates) ciliated groove
    [Show full text]
  • Platyhelminthes, Nemertea, and "Aschelminthes" - A
    BIOLOGICAL SCIENCE FUNDAMENTALS AND SYSTEMATICS – Vol. III - Platyhelminthes, Nemertea, and "Aschelminthes" - A. Schmidt-Rhaesa PLATYHELMINTHES, NEMERTEA, AND “ASCHELMINTHES” A. Schmidt-Rhaesa University of Bielefeld, Germany Keywords: Platyhelminthes, Nemertea, Gnathifera, Gnathostomulida, Micrognathozoa, Rotifera, Acanthocephala, Cycliophora, Nemathelminthes, Gastrotricha, Nematoda, Nematomorpha, Priapulida, Kinorhyncha, Loricifera Contents 1. Introduction 2. General Morphology 3. Platyhelminthes, the Flatworms 4. Nemertea (Nemertini), the Ribbon Worms 5. “Aschelminthes” 5.1. Gnathifera 5.1.1. Gnathostomulida 5.1.2. Micrognathozoa (Limnognathia maerski) 5.1.3. Rotifera 5.1.4. Acanthocephala 5.1.5. Cycliophora (Symbion pandora) 5.2. Nemathelminthes 5.2.1. Gastrotricha 5.2.2. Nematoda, the Roundworms 5.2.3. Nematomorpha, the Horsehair Worms 5.2.4. Priapulida 5.2.5. Kinorhyncha 5.2.6. Loricifera Acknowledgements Glossary Bibliography Biographical Sketch Summary UNESCO – EOLSS This chapter provides information on several basal bilaterian groups: flatworms, nemerteans, Gnathifera,SAMPLE and Nemathelminthes. CHAPTERS These include species-rich taxa such as Nematoda and Platyhelminthes, and as taxa with few or even only one species, such as Micrognathozoa (Limnognathia maerski) and Cycliophora (Symbion pandora). All Acanthocephala and subgroups of Platyhelminthes and Nematoda, are parasites that often exhibit complex life cycles. Most of the taxa described are marine, but some have also invaded freshwater or the terrestrial environment. “Aschelminthes” are not a natural group, instead, two taxa have been recognized that were earlier summarized under this name. Gnathifera include taxa with a conspicuous jaw apparatus such as Gnathostomulida, Micrognathozoa, and Rotifera. Although they do not possess a jaw apparatus, Acanthocephala also belong to Gnathifera due to their epidermal structure. ©Encyclopedia of Life Support Systems (EOLSS) BIOLOGICAL SCIENCE FUNDAMENTALS AND SYSTEMATICS – Vol.
    [Show full text]
  • Evidence for Selection on a Chordate Histocompatibility Locus
    ORIGINAL ARTICLE doi:10.1111/j.1558-5646.2012.01787.x EVIDENCE FOR SELECTION ON A CHORDATE HISTOCOMPATIBILITY LOCUS Marie L. Nydam,1,2,3 Alyssa A. Taylor,3 and Anthony W. De Tomaso3 1Division of Science and Mathematics, Centre College, Danville, Kentucky 40422 2E-mail: [email protected] 3Department of Molecular, Cellular, and Developmental Biology, University of California Santa Barbara, Santa Barbara, California 93106 Received June 7, 2011 Accepted July 31, 2012 Allorecognition is the ability of an organism to differentiate self or close relatives from unrelated individuals. The best known applications of allorecognition are the prevention of inbreeding in hermaphroditic species (e.g., the self-incompatibility [SI] systems in plants), the vertebrate immune response to foreign antigens mediated by MHC loci, and somatic fusion, where two genetically independent individuals physically join to become a chimera. In the few model systems where the loci governing allorecognition outcomes have been identified, the corresponding proteins have exhibited exceptional polymorphism. But information about the evolution of this polymorphism outside MHC is limited. We address this subject in the ascidian Botryllus schlosseri,where allorecognition outcomes are determined by a single locus, called FuHC (Fusion/HistoCompatibility). Molecular variation in FuHC is distributed almost entirely within populations, with very little evidence for differentiation among different populations. Mutation plays a larger role than recombination in the creation of FuHC polymorphism. A selection statistic, neutrality tests, and distribution of variation within and among different populations all provide evidence for selection acting on FuHC, but are not in agreement as to whether the selection is balancing or directional.
    [Show full text]
  • Plant Evolution an Introduction to the History of Life
    Plant Evolution An Introduction to the History of Life KARL J. NIKLAS The University of Chicago Press Chicago and London CONTENTS Preface vii Introduction 1 1 Origins and Early Events 29 2 The Invasion of Land and Air 93 3 Population Genetics, Adaptation, and Evolution 153 4 Development and Evolution 217 5 Speciation and Microevolution 271 6 Macroevolution 325 7 The Evolution of Multicellularity 377 8 Biophysics and Evolution 431 9 Ecology and Evolution 483 Glossary 537 Index 547 v Introduction The unpredictable and the predetermined unfold together to make everything the way it is. It’s how nature creates itself, on every scale, the snowflake and the snowstorm. — TOM STOPPARD, Arcadia, Act 1, Scene 4 (1993) Much has been written about evolution from the perspective of the history and biology of animals, but significantly less has been writ- ten about the evolutionary biology of plants. Zoocentricism in the biological literature is understandable to some extent because we are after all animals and not plants and because our self- interest is not entirely egotistical, since no biologist can deny the fact that animals have played significant and important roles as the actors on the stage of evolution come and go. The nearly romantic fascination with di- nosaurs and what caused their extinction is understandable, even though we should be equally fascinated with the monarchs of the Carboniferous, the tree lycopods and calamites, and with what caused their extinction (fig. 0.1). Yet, it must be understood that plants are as fascinating as animals, and that they are just as important to the study of biology in general and to understanding evolutionary theory in particular.
    [Show full text]
  • Number of Living Species in Australia and the World
    Numbers of Living Species in Australia and the World 2nd edition Arthur D. Chapman Australian Biodiversity Information Services australia’s nature Toowoomba, Australia there is more still to be discovered… Report for the Australian Biological Resources Study Canberra, Australia September 2009 CONTENTS Foreword 1 Insecta (insects) 23 Plants 43 Viruses 59 Arachnida Magnoliophyta (flowering plants) 43 Protoctista (mainly Introduction 2 (spiders, scorpions, etc) 26 Gymnosperms (Coniferophyta, Protozoa—others included Executive Summary 6 Pycnogonida (sea spiders) 28 Cycadophyta, Gnetophyta under fungi, algae, Myriapoda and Ginkgophyta) 45 Chromista, etc) 60 Detailed discussion by Group 12 (millipedes, centipedes) 29 Ferns and Allies 46 Chordates 13 Acknowledgements 63 Crustacea (crabs, lobsters, etc) 31 Bryophyta Mammalia (mammals) 13 Onychophora (velvet worms) 32 (mosses, liverworts, hornworts) 47 References 66 Aves (birds) 14 Hexapoda (proturans, springtails) 33 Plant Algae (including green Reptilia (reptiles) 15 Mollusca (molluscs, shellfish) 34 algae, red algae, glaucophytes) 49 Amphibia (frogs, etc) 16 Annelida (segmented worms) 35 Fungi 51 Pisces (fishes including Nematoda Fungi (excluding taxa Chondrichthyes and (nematodes, roundworms) 36 treated under Chromista Osteichthyes) 17 and Protoctista) 51 Acanthocephala Agnatha (hagfish, (thorny-headed worms) 37 Lichen-forming fungi 53 lampreys, slime eels) 18 Platyhelminthes (flat worms) 38 Others 54 Cephalochordata (lancelets) 19 Cnidaria (jellyfish, Prokaryota (Bacteria Tunicata or Urochordata sea anenomes, corals) 39 [Monera] of previous report) 54 (sea squirts, doliolids, salps) 20 Porifera (sponges) 40 Cyanophyta (Cyanobacteria) 55 Invertebrates 21 Other Invertebrates 41 Chromista (including some Hemichordata (hemichordates) 21 species previously included Echinodermata (starfish, under either algae or fungi) 56 sea cucumbers, etc) 22 FOREWORD In Australia and around the world, biodiversity is under huge Harnessing core science and knowledge bases, like and growing pressure.
    [Show full text]
  • Lessons from 20 Years of Plant Genome Sequencing: an Unprecedented Resource in Need of More Diverse Representation
    bioRxiv preprint doi: https://doi.org/10.1101/2021.05.31.446451; this version posted May 31, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. Lessons from 20 years of plant genome sequencing: an unprecedented resource in need of more diverse representation Authors: Rose A. Marks1,2,3, Scott Hotaling4, Paul B. Frandsen5,6, and Robert VanBuren1,2 1. Department of Horticulture, Michigan State University, East Lansing, MI 48824, USA 2. Plant Resilience Institute, Michigan State University, East Lansing, MI 48824, USA 3. Department of Molecular and Cell Biology, University of Cape Town, Rondebosch 7701, South Africa 4. School of Biological Sciences, Washington State University, Pullman, WA, USA 5. Department of Plant and Wildlife Sciences, Brigham Young University, Provo, UT, USA 6. Data Science Lab, Smithsonian Institution, Washington, DC, USA Keywords: plants, embryophytes, genomics, colonialism, broadening participation Correspondence: Rose A. Marks, Department of Horticulture, Michigan State University, East Lansing, MI 48824, USA; Email: [email protected]; Phone: (603) 852-3190; ORCID iD: https://orcid.org/0000-0001-7102-5959 Abstract The field of plant genomics has grown rapidly in the past 20 years, leading to dramatic increases in both the quantity and quality of publicly available genomic resources. With an ever- expanding wealth of genomic data from an increasingly diverse set of taxa, unprecedented potential exists to better understand the evolution and genome biology of plants.
    [Show full text]
  • The Origins of Chordate Larvae Donald I Williamson* Marine Biology, University of Liverpool, Liverpool L69 7ZB, United Kingdom
    lopmen ve ta e l B Williamson, Cell Dev Biol 2012, 1:1 D io & l l o l g DOI: 10.4172/2168-9296.1000101 e y C Cell & Developmental Biology ISSN: 2168-9296 Research Article Open Access The Origins of Chordate Larvae Donald I Williamson* Marine Biology, University of Liverpool, Liverpool L69 7ZB, United Kingdom Abstract The larval transfer hypothesis states that larvae originated as adults in other taxa and their genomes were transferred by hybridization. It contests the view that larvae and corresponding adults evolved from common ancestors. The present paper reviews the life histories of chordates, and it interprets them in terms of the larval transfer hypothesis. It is the first paper to apply the hypothesis to craniates. I claim that the larvae of tunicates were acquired from adult larvaceans, the larvae of lampreys from adult cephalochordates, the larvae of lungfishes from adult craniate tadpoles, and the larvae of ray-finned fishes from other ray-finned fishes in different families. The occurrence of larvae in some fishes and their absence in others is correlated with reproductive behavior. Adult amphibians evolved from adult fishes, but larval amphibians did not evolve from either adult or larval fishes. I submit that [1] early amphibians had no larvae and that several families of urodeles and one subfamily of anurans have retained direct development, [2] the tadpole larvae of anurans and urodeles were acquired separately from different Mesozoic adult tadpoles, and [3] the post-tadpole larvae of salamanders were acquired from adults of other urodeles. Reptiles, birds and mammals probably evolved from amphibians that never acquired larvae.
    [Show full text]
  • The Plankton Lifeform Extraction Tool: a Digital Tool to Increase The
    Discussions https://doi.org/10.5194/essd-2021-171 Earth System Preprint. Discussion started: 21 July 2021 Science c Author(s) 2021. CC BY 4.0 License. Open Access Open Data The Plankton Lifeform Extraction Tool: A digital tool to increase the discoverability and usability of plankton time-series data Clare Ostle1*, Kevin Paxman1, Carolyn A. Graves2, Mathew Arnold1, Felipe Artigas3, Angus Atkinson4, Anaïs Aubert5, Malcolm Baptie6, Beth Bear7, Jacob Bedford8, Michael Best9, Eileen 5 Bresnan10, Rachel Brittain1, Derek Broughton1, Alexandre Budria5,11, Kathryn Cook12, Michelle Devlin7, George Graham1, Nick Halliday1, Pierre Hélaouët1, Marie Johansen13, David G. Johns1, Dan Lear1, Margarita Machairopoulou10, April McKinney14, Adam Mellor14, Alex Milligan7, Sophie Pitois7, Isabelle Rombouts5, Cordula Scherer15, Paul Tett16, Claire Widdicombe4, and Abigail McQuatters-Gollop8 1 10 The Marine Biological Association (MBA), The Laboratory, Citadel Hill, Plymouth, PL1 2PB, UK. 2 Centre for Environment Fisheries and Aquacu∑lture Science (Cefas), Weymouth, UK. 3 Université du Littoral Côte d’Opale, Université de Lille, CNRS UMR 8187 LOG, Laboratoire d’Océanologie et de Géosciences, Wimereux, France. 4 Plymouth Marine Laboratory, Prospect Place, Plymouth, PL1 3DH, UK. 5 15 Muséum National d’Histoire Naturelle (MNHN), CRESCO, 38 UMS Patrinat, Dinard, France. 6 Scottish Environment Protection Agency, Angus Smith Building, Maxim 6, Parklands Avenue, Eurocentral, Holytown, North Lanarkshire ML1 4WQ, UK. 7 Centre for Environment Fisheries and Aquaculture Science (Cefas), Lowestoft, UK. 8 Marine Conservation Research Group, University of Plymouth, Drake Circus, Plymouth, PL4 8AA, UK. 9 20 The Environment Agency, Kingfisher House, Goldhay Way, Peterborough, PE4 6HL, UK. 10 Marine Scotland Science, Marine Laboratory, 375 Victoria Road, Aberdeen, AB11 9DB, UK.
    [Show full text]
  • Simple Animals Sponges and Placozoa the Twig of the Tree That Is the Animals the Tour Begins
    Animal Kingdom Simple animals Sponges and placozoa Tom Hartman Asymmetry www.tuatara9.co.uk Animal form and function 1 Module 111121 2 The twig of the tree that is the animals Animals All other animals Animals Sponges Choanoflagellates Choanoflagellates Fungi Fungi 3 4 All other animals Animals (bilateralia) Radiata Sponges Choanoflagellates Fungi The tour begins 5 6 1 Animal Kingdom The Phylum Quirky phyla • In the standard Linnean system (and taxonomic systems • There are 39 animal phyla (+/- 10!) based on it), a Phylum is the taxonomic category between Kingdom and Class. • The Micrognathozoa were • A phylum is a major ranking of organisms, defined discovered in 2000 (1 species)in according to the most basic body-parts shared by that springs in Greenland. group. But we must include the creatures and their • Xenoturbellida removed from the common ancestor. molluscs and moved to the – Chordata (animals with a notochord - vertebrates and others), – Arthropoda (animals with a jointed exoskeleton) dueterostomes when DNA – Mollusca (animals with a shell-secreting mantle), evidence was discounted due to – Angiosperma (flowering plants), and so on. what it had eaten! – A number of traditional Phyla - e.g. Protozoa, possibly Arthropoda - • Cycliophora discovered on the are probably invalid (polyphyletic). lips of lobsters in 1995. 7 8 The Class Our journey • In the Linnean system (and taxonomic systems Kingdom Group Phylum based on it), a Class is the taxonomic category Porifera between Phylum and Order. Placozoa • A class is a major group of organisms, e.g. Cnidaria Mammalia, Gastropoda, Insecta, etc that Parazoa Ctenophora contains a large number of different Radiata Platyhelminthes sublineages, but have shared characteristics in Animalia Protostome Rotifera common e.g.
    [Show full text]
  • Kinorhyncha:Cyclorhagida
    JapaneseJapaneseSociety Society ofSystematicZoologyof Systematic Zoology Species Diversity, 2002, 7, 47-66 Echinoderesaureus n. sp. (Kinorhyncha: Cyclorhagida) from Tanabe Bay (Honshu Island), Japan, with a Key to the Genus Echinoderes Andrey V.Adrianovi, Chisato Murakami2and Yoshihisa Shirayama2 iinstitute ofMarine BiotQgy, Fkir-East Branch ofRetssian Accutemp of Sciences, Palchevskly St. IZ VIadivostok 690041, Russia 2Seto Marine Btolqgical Laboratorly, Its,oto U}ziversdy, Shirahama 459, IVishimuro, Vliakayama, 649-2211 Jicipan (Received 18 May 2001; Accepted 10 December 2oo1) A new species of echinoderid kinorhynch, Echinoderes aureus, is de- scribed and illustrated using a differential interference contrast microscope with Nomarski optics. The kinorhynchs were collected from washings of a brown alga, Padina arborescens Holmes, growing in tide pools in Tanabe Bay, Honshu Island, Japan. Diagnostic characters of E. aureLts are the pres- ence of middorsal spines on segments 6-10, lateral spines/tubu}es on seg- ments4 and 7-12, a pair of remarkably large subcuticular scars in a subven- tral position on segment 3, and an ineomplete rnidventral articulation on segment 4. The positions of numerous sensory-glandular organs, the sizes of various lateral spinesltubules, and the shapes of the terminal tergal and sternal extensions are also diagnostic. Echinoderes aureus constitutes the ' 59th valid species o ± the genus Echinoderes and the 15th speeies described from the Pacific Ocean. This is the fourth representative of Pacific ki- norhynchs found only in the intertidal zone and the second Pacific Ebhin- oderes living on macroalgae in tide pools, A dichotomous key to all 59 species is provided. Key Words: kinorhynch, taxonumy, Echinoderes, key, placid, spine, tubule, setae Introduction Kinorhyncha constitutes a taxon of meiobenthic, free-living, segmented and spiny marine invertebrates, generally less than lmm in length.
    [Show full text]