GEOL 3213 MICROPALEONTOLOGY

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GEOL 3213MICROPALEONTOLOGY

• Diatoms
• Introduction Classification

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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
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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
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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

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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

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Diatom Skeletons

• Range
• 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

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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.

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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.

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Diatom Morphology

• Striae line of punctae
• Costae raised ridge parallel to striae

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Centrales
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Examples of Centrales
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Pennales
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Examples of Pennales
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Diatom Diversity Through Time

• Centric forms
• Cretaceous to Recent
• Dominate the plankton
• Pennate forms
• Paleocene to Recent
• Dominate the benthos

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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

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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.

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End of File

• Which of these diatoms are pennate diatoms
  which are centric diatoms?

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Diatom Lab Exercise
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• Examine the slides with marine diatoms
• 2. Examine the slides with freshwater diatoms
• 3. Determine which of the unknowns is from a
  freshwater deposit and which is from a marine
  deposit. State your reasons

Unknown Marine? Nonmarine? Reason(s)
Name ______________
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Heterokonts different flagella

• 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.

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• 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.

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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.

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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