Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
GEOL 3213 MICROPALEONTOLOGY Diatoms: Introduction & Classification Photosynthetic algae : Phylum – Bacillariophyta (diatoms) *Phylum – Chrysophyta (chrysophytes) Phylum – Haptophyta (coccoliths) Phylum – Phaeophyta (brown algae) Phylum – Chlorophyta (green algae) Phylum- Rhodophyta (red algae) etc. *Diatoms and coccoliths are grouped together with the chrysophyta (includes silicoflagellates) by some workers. Other “Algae” • • • • • • • Diatoms – Biology & Ecology Unicellular &/or colonial organisms Eukaryotic Lack flagella Asexual and sexual reproduction May be single celled or in chains Photosynthetic, productive even in cold nutrient-rich water (Antarctic, etc.) Base of the food chain = “Grass of the sea” (Account for up to 25% total world primary food production by phytoplankton. Some species harvested for food for shellfish industry.) • Planktic and benthic forms Seafloor siliceous ooze composed of diatoms and radiolaria Diatoms – Biology & Ecology • Can move on & within the sediment with mucus streamers associated with a groove called the raphe • Can live heterotrophically in the dark • Occurrences: – Freshwater (lacustrine, swamp, marsh, riverine) – Marine (shoreline environments to the deep sea) – Other: • • • • Damp terrestrial Hot springs Hypersaline lakes Melt-water pools on icebergs • Diversity of benthic forms is high worldwide Diatom Classification • Diatoms are the “golden brown” algae • Some researchers classify them in the Phylum Bacillariophyta • Other workers put them, with the coccolithophores & silicoflagellates, in the Phylum Chrysophyta • Frustrule (porous valves) shapes vary greatly, so there is no simple summary of morphology • Two major subdivisions are recognized: – Centrales (centric) = circular, oblong, hemicircular, triangular, or quadrangular, with surface features arranged around a central point – radially symmetrical – Pennales (pennate) = elongate with major features at right angles to the median line (long axis). (These are further subdivided into 7 subgroups.) - bilaterally symmetrical • Range: Diatom Skeletons – Jurassic(?) marine, Mid-Cretaceous to Recent – Oldest nonmarine forms are Eocene • Skeleton called a frustrule – Overlapping bivalves • Box = hypotheca • Lid = epitheca • Overlapping sides = girdle – – – – – – • • • • Porous (called punctae); striae & costae Raphe = groove = for locomotion? Opaline Marine dominantly centric forms (Cretaceous to Recent) Nonmarine dominantly pennate forms (Paleocene to Recent) As small as 5 um and up to 500 or more um Account for 70-90% siliceous particles suspended in oceanic water Siliceous skeleton resistant to solution in deep sea sediments Diagenetic solution & reprecipitation leads to chert formation Sediments: oozes, diatomaceous earth, diatomite HOW DIATOMS REPRODUCE • Reproduction mainly asexual – occurs during mitosis. Some sexual reproduction with meiosis (when population sizes very small) • Alternation of sexual and asexual reproduction • Figure below: Girdle views of diatom valves through several reproductive phases. Note the progressive decrease in size of some forms. Diatom structure • Frustule made of polymerized opaline silica joined in two overlapping halves. Two halves fit together like Petri dish – elaborate “glass houses” • “Raphe” - Tiny slit that runs along cells – thought that tiny microfibrils extrude from this to enable locomotion • Pennate form – better movers – more common in freshwater • Centric form – more common in marine. Diatom Morphology • Striae = line of punctae • Costae = raised ridge parallel to striae Centrales Examples of Centrales Pennales Examples of Pennales Diatom Diversity Through Time • Centric forms – Cretaceous to Recent – Dominate the plankton • Pennate forms – Paleocene to Recent – Dominate the benthos Diatoms Uses • Applications of diatom studies – Used a lot by Quaternary geologists – Age-dating and correlation • Many short-ranged species • Especially for the Tertiary – Paleoenvironmental studies – O18/O16 ratios used for paleotemperature studies – Used to detect polluted water because of environmental sensitivity, e. g., to nitrate and phosphate nutrient enrichments • Natural absorbent: Diatoms from marine & freshwater deposits are mined because – Highly porous – Low density • Used to make dynamite: – Without its adsorbent character, Nobel's invention would not have been possible – Absorbing nitro-glycerin into diatomite made possible it's • Transport • Safe use • Other major industrial uses are: – Filtration • Water purification • Wine & beer industry use diatomite during filtration processes – Abrasive (fine) • Silver polish (why?) But they are not all good and beautiful…. • Big contibutors to 'natural' occurrences of toxic marine conditions. – Eutrophication: • Along coasts - Some diatom blooms have caused mass pollution, oxygen depletion, exphixiation, starvation. – Marine biotoxin ('domoic acid’) – Some diatom species that produce it are members of the planktonic genera Pseudonitzschia & Peragallo • Domoic acid is a naturally occurring amino acid and is a glutamate analogue that strongly binds to the glutamate receptors in the brain where it causes nerve cells to transmit impulses continuously until the cells die. End of File • Which of these diatoms are pennate diatoms & which are centric diatoms? End of File Examine the slides with marine diatoms Name: ______________ Diatom Lab Exercise 1. 2. Examine the slides with freshwater diatoms Reason(s) 3. Determine which of the unknowns is from a freshwater deposit and which is from a marine deposit. State your reasons: Unknown Marine? Nonmarine? 1. 2. Heterokonts = “different flagella” 1) Tinsel - Long pleuronematic flagellum, directed forward during swimming – Lining pleuronematic flagellum are two rows of special, stiff hairs, called mastigonemes (or flimmers). The mastigonemes are composed of glycoprotein and are synthesized in the cisternae of the endoplasmic reticulum. 2) Whiplash - a shorter smooth flagellum that points backwards along the cell. The smooth, backwardly directed flagellum bears a swelling near its base, which fits against the concave eyespot. The eyespot lies at the anterior of the cell, enclosed within the chloroplast, and consists of a single layer of globules containing reddish-orange pigment. The eyespot and flagellar swelling together form the photoreceptor apparatus, which is the light-perceiving organelle of the cell. Molecular studies • 1) fungus like heterokonts – diverged early • 2) pigmented heterokonts derived from a single, common ancestor • 3) early separation of the pigmented forms into two clades: diatoms vs the rest. • 3) green algae – clear ancestor of plants. Plants paraphyletic to protists. Life cycles • Zygotic meiosis – fungi and some algae – Dominant phase haploidy, transient zygotes divide meiotically and form new haploids. • Gametic meiosis – animals, water molds and some green and brown algae – Zygote produces haploid gametes that fuse and restore diploidy. Gametes do not grow. • Sporic meiosis (alternation of generations) – plants, many algae and some others • Meiosis produces spores which can divide mitotically to create multicellular haploid organism. These gametophytic cells can fuse - sporophyte