Bio 201 F11 Lect 14 (True) v4nr

Bio 201 F11 Lect 14 (True) v4nr - •  mid‐semester...

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Unformatted text preview: •  mid‐semester course assessment period has begun. •  ‐you should receive an e‐mail today •  responses are completely anonymous; instructors will only see aggregated comments. Biology in the News [see folder on BB] •  •  •  •  •  •  •  •  •  chimps (Pan troglodytes) and bonobos (the pygmy chimpanzee; Pan paniscus) are very closely related species and both have 98.7% DNA sequence similarity with their next closest relaIves, Homo sapiens chimps and humans both are violent; bonobos are disInctly not (homicide is unknown in the species) chimps have both homicide and male violence against females how do bonobos deal with conflict? one major way: have sex, another way: be tolerant; they seem to be substanIally more tolerant of their fellow bonobos than chimps are of fellow chimps they share more and hug each other more than chimps studies by Brian Hare of Duke University found significant altruism; bonobos sharing prized food items with others these traits may be present in bonobos because they live in an area (Congo) with plenty of food and don't have to compete for food they also have a matriarchal society; females work together and can gang up on and dominate threatening males (in chimps, males team up to dominate females and weaker males) genomic and other studies in the near future may help us understand how bonobos evolved these traits and whether our dark and generous sides are mechanisIcally similar to those of chimps and bonobos, respecIvely hUp:// science_naIon/bonobos.jsp? WT.mc_id=USNSF_51 hUp:// 0‐5 6‐10 11‐15 16‐20 21‐25 26‐30 31‐35 36‐40 41‐45 46‐50 51‐55 56‐60 61‐65 66‐70 71‐75 76‐80 81‐85 86‐90 91‐95 96‐100 # students Bio 201 F11 mid term 1 80 70 60 50 40 30 20 10 0 score average st. dev. median 73.15 17.00 74.29 Fungi ‘ •  Like animals and chaonoflagellates, are opisthokonts (“behind”+”pole”[flagellum]) –  These 3 groups descended from a common ancestor that probably had a flagellum •  Fungi have these synapomorphies –  AbsorpIve heterotrophy –  Cell wall (disInct from bacterial, plant cell walls) •  Cell wall has chiIn (disInct from chiIn of arthropod animals) –  long polymerized carbohydrate molecule that provides structural rigidity Fungal anatomy •  Four of the five recognized groups of fungi have both unicellular and mulIcellular forms –  No unicellular forms known in the glomeromycetes –  Unicellular species are called yeasts •  In mulIcellular species –  Body (vegetaIvely growing mass) is called the mycelium –  Individual filaments are called hyphae (sing. hypha) –  Some hyphae are separated by septa (sing. septum), which are incomplete walls, others are coenocy9c (mulIple nuclei) Saccharomyces The fungal lifestyle •  InImate contact with substrate for absorpIon of nutrients •  Many species can tolerate temperature extremes and high concentraIons of nutrients (hypertonic environments) •  But, most fungi need moist environments •  Mycelia of many fungi are unseen •  Mycelia can grow quickly and a single individual can become massive in size The fungal lifestyle: nutrient sources •  Majority are saprobic ‐ feed on dead organic maUer (also called saprophyIc; term no longer used) •  Some are parasites, many on plants –  Faculta9ve can switch between saprobic and parasiIc –  Obligate are parasites 100% of the Ime •  e.g. Blumeria graminis Blumeria graminis is an obligate pathogen The fungal lifestyle: nutrient sources •  Some fungi are pathogens –  In humans, e.g. Candida albicans in immunosuppressed paIents (e.g. those with HIV) –  In plants, many crop diseases •  e.g. Ustilago maydis, corn smut fungus •  In Mexico, called huitlacoche –  A delicacy The fungal lifestyle: nutrient sources •  Even some predators: e.g. Anthrobotrys anchonia (3 cells) A worm crawling into the ring induces the cells to swell and trap the worm. Then hyphae grown in and digest the worm. Many leaf‐cuUer ant species are fungi farmers •  Ants feed chewed up leaf material to fungal mycelia in their nests •  Usually the “farm” is a single fungal individual (clone) –  Fends off other fungi with anIfungal compounds produced by the fungus •  (see pages 1185‐1186 in textbook) hUp:// Fungal life cycles LIFE 9th ed. Fig. 30.12 D •  Great diversity •  Some have alternaIng generaIons (as in previous lecture) •  Some have a dikaryon stage as part of an alternaIng generaIons life cycle The dikaryo9c stage is unique to fungi (but not all fungi have this stage) A brief view of fungal diversity The 5 major phyla of fungi •  Chytrids (Chytridiomycota) –  AquaIc –  The only fungi that have flagellae on their gametes (like animal sperm) –  <1000 species •  Most are parasites or saprobic species –  A chytrid epidemic in amphibians •  Chytridiomycosis caused by Batrachochytrium dendrobatidis A brief view of fungal diversity •  Zygomycetes (Zygomycota) –  Most are terrestrial –  Includes saprobic and parasitic species (usually animal hosts) –  >700 described species •  e.g. Rhizopus stolonifer, black bread mold –  FruiIng structures (sporangia) produce haploid sporangiospores A brief view of fungal diversity •  Glomeromycetes (Glomeromycota) –  many are arbuscular mycorrhizae •  <200 described species •  Most in soil –  Asexual reproducIon, no evidence for sexual reproducIon –  Very important for the survival of their host plants The tree-like arbuscule that forms when a glomeromycete infects a plant root. A brief view of fungal diversity •  Ascomycetes (Ascomycota) –  ~60,000 described species –  Sexual reproducIon; produce ascospores in sac‐like structures (asci; sing. ascus) –  Includes yeasts; most famous: Saccharomyces cerevisiae •  Bread making, Brewing •  Eat sugar and produce CO2 during fermentaIon –  Also produce ethanol –  Brown mold Aspergillus species •  Used to make soy sauce, sake –  Edible mushroom species •  Morels •  Truffles –  Many plant mold diseases •  Chestnut blight, Dutch elm disease, powdery mildew –  Penicillium (green mold) •  penicillin A brief view of fungal diversity •  Basidiomycetes (Basidiomycota) –  ~25,000 described species –  Produce basidiocarp fruiIng structures (“mushrooms”) •  •  Most are saprobic Common grocery story species is Agaricus bisporus • Most are saprobic • Many ectomicorrhizal • Dikaryons can live a very long time (compared to ascomycete dikaryon stage, which is very short) (or pores) • Be careful out there! Many mushrooms are poisonous! Calvatia gigantea, the Giant Puffball Animals share these synapomorphies   ulticellularity m   obility m   eterotrophy h Diversity of animal life: from unicellular life ~ 1200 – 900 mya Most phyla show up in fossil record ~ 570 mya (“Cambrian Explosion”) Most evidence of this history of life comes from the fossil record Fossil cicada from the lower Cretaceous (~130‐145 mya) How do we date fossil evidence? •  RelaIve: fossils occur in sedimentary rocks –  Older rocks occur below younger rocks •  Geologic formaIons of various ages are recognized, and oven named, by the fossils they contain •  –  Can use this to match geologic layers from different parts of the world Absolute: –  Radioisotope daIng •  E.g. carbon for fossils < 50,000 years old •  14C/12C raIo in all living organisms is roughly constant –  But when organisms die, they stop gewng 14C from the environment and 14C/12C raIo decreases »  Half‐life = 5700 years How do we date fossil evidence? Isotopes of other elements are used for longer Imeframes –  Requires igneous rocks nearby (embedded) in the sedimentary rocks »  40K/40Ar raIo used for most events in ancient evoluIon of life »  [half life =~1.25 billion yrs] –  Or if no igneous rocks nearby »  PaleomagneIc daIng »  ‐record of known reversals of Earth’s magneIc field preserved in sedimentary and igneous rocks •  Table 21.2 –  Good summary of major eras, periods, and events in Earth’s history »  DO NOT have to memorize MacroevoluIonary paUerns: Mass exIncIons Permian‐Triassic exIncIon ~ 96% of all marine species ~70% of all land species Meteror impact in Yucatan ‐ exIncIon of dinosaurs; also a period of widespread volcanic acIvity Causes of mass exIncIons •  SIll largely unknown •  65 mya Cretaceous‐TerIary –  Meteor impact –  But also major volcanic acIvity in Asia/India •  Sea level drops/rises oven implicated –  warming periods; melIng polar icecaps –  glaciaIons •  “Flood Basalt events” –  Major volcanic episodes on land masses or ocean floors –  Send large amounts of parIculates into atmosphere for extended periods •  Can cause major exIncIons of plants and collapses of food chains Climate change through Earth’s history Con9nental DriM Alfred Wegener (1880‐1930) Precambrian “The Origin of Con9nents and Oceans” (1912) Cambrian Plate tectonics Gondwanan Flora and Fauna A far more ancient superconInent: Rodinia •  ~1 billion to ~800 million years ago •  Land masses were concentrated in the tropics •  Hypothesis: this led to “Snowball Earth” Snowball Earth hypothesis •  During Cryogenian period •  (850‐630 million years ago) •  ConInents concentrated in tropics –  Absorbed less heat from sun than open ocean –  More rainfall ‐>more erosion •  Erosion removes CO2 from atmosphere •  e.g. CaSiO3 + 2CO2 + H2O → Ca2+ + SiO2 + 2HCO3- -”Anti-Greenhouse effect” •  Glaciers covered virtually the enIre Earth •  Only marine microorganisms survived The end of snowball Earth •  Volcanic acIvity eventually melted the ice and broke up Rodinia •  Ice retreated •  This set the stage for evoluIon of new life forms –  Complexity, mulIcellularity –  Cambrian Explosion Cambrian - first appearance of animals with hard skeletons Continent of Laurentia Note: this was before Pangaea (Pangaea~250 mya) The Burgess shale: the first menagerie of the Cambrian Early-mid Cambrian animals of the Burgess shale, Canada All are marine forms. Trilobite (arthropod) The first large, mobile organisms had the entire ocean world open to them -Organisms and their environments were different then? -Genomes could change easily? -Environments full of mutagens? Higher mutation rates? Or... maybe it wasnʼt an explosion (sparse fossil record) animal phylogeny: previous version of textbook th ediIon) the current view (LIFE 9 ...
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