II. Algal taxonomy
Division: Chlorophyta
(green algae)
Hierarchical system of classification:
I. General Characteristics
II. Distinguishing Classes
III. Morphology
IV. Classes in Detail
Level:
Domain
Group
Division
Class
Order
Family
suffix:
Genus
species
-phyta
-phyceae
-ales
-aceae
example:
Eukaryote
Plantae
Chlorophyta
Ulvophyceae
Ulvales
Ulvaceae
Ulva
fenestrata
~ 16,000 species
~ 90% freshwater
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Groups (Kingdom)
DOMAIN
1.Bacteria- cyanobacteria (blue green algae)
2.Archae
3.Eukaryotes
2
“Algae”
Glaucophytes
1. Alveolates- dinoflagellates
2. Stramenopiles- diatoms, heterokonyophyta
Plantae
3. Rhizaria- unicellular amoeboids
Rhodophyta
Chlorophytes
4. Excavates- unicellular flagellates
5. Plantae- rhodophyta, chlorophyta, seagrasses
6. Amoebozoans- slimemolds
Chl b,
starch
Charophytes
Land Plants
7. Fungi- heterotrophs with extracellular digestion
8. Choanoflagellates- unicellular
9. Animals- multicellular heterotrophs
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Adapted from Sadava 2014
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Phylogenetics of Chlorophyta
(morphological, molecular data)
I. General Green Characteristics:
5 classes:
1) Pigments: ?
Chlorophyta
Chlorophyceae
Trebouxiophyceae
Chl b,
starch
Ulvophyceae
3) Storage product?
Prasinophyceae
Encasement
of egg
2) Chloroplast structure?:
4) Flagella?
Charophytes
Charophyceae
Embryo, cuticle
Land plants
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Classes:
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II. Distinguishing among classes based on:
Chlorophyceae = freshwater
Trebouxiophyceae = freshwater, soil and marine
1. How flagella are attached/constructed:
• basal bodies orientation
• microtubule roots
Ulvophyceae = marine macroalgae
Prasinophyceae = primarily marine flagellates, some freshwater;
modern representatives of earliest green algae
2. Cell covering:
• scales vs. cell wall
3. How cells divide:
• aspects of mitosis and cytokinesis
Charophyceae = freshwater; all terrestrial plants are derived
from Charophycean class
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8
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II. Distinguishing among classes based on:
Flagella- complex cellular projections used for movement
- bundle of nine fused pairs of microtubule doublets
surrounding two central single microtubules
"9+2"
1. How flagella are attached/constructed:
-basal bodies orientation
-microtubule roots
Basal bodies- attachment site of the flagella
- containing a microtubules 9 triplet configuration
forming a hollow cylinder
Flagella
Basal Bodies
Flagella
Microtubule roots
Basal Bodies
Cell
Microtubule roots
anterior
Cell
9
swimming direction
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Flagella
Basal Bodies: ONE per flagellum, located at base of
flagellum, anchoring into cell
-pairs of basal bodies may be
opposite
parallel
clockwise
counterclockwise
Microtubule roots:
-under the cell membrane at point of
attachment of basal bodies
- may be cruciate or broadband
Basal Bodies
Microtubule roots
Cell
Flagella
Basal Bodies
Microtubule roots
Cell
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cruciate
5
broad-band
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II. Distinguishing among classes based on:
II. Distinguishing among classes based on:
2. Cell covering- scales vs. cell wall
Scales are made of complex
polysaccharides secreted from golgi
3. How cells divide:
(aspects of mitosis and cytokinesis)
Cell wall = usually cellulose
Chlorophyceae, trebouxiophyceae,
Ulvophyceae, charophyceae
prasinophyceae
•
open vs. closed mitotic spindle
•
phycoplast vs. phragmoplast
•
furrowing vs. cell plate formation in center of cell
closed
metacentric centrioles
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II. Distinguishing among classes based on:
II. Distinguishing among classes based on:
3. How cells divide:
(aspects of mitosis and cytokinesis)
3. How cells divide:
(aspects of mitosis and cytokinesis)
•
open vs. closed mitotic spindle
•
phycoplast vs. phragmoplast
•
furrowing vs. cell plate formation in center of cell
furrowing
Phycoplast: microtubules
parallel to dividing plane
-rare in algae
Open
-during Mt nuclear
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envelope breaks down
•
open vs. closed mitotic spindle
•
phycoplast vs. phragmoplast
•
furrowing vs. cell plate formation in center of cell
furrowing
Phragmoplast: double
microtubules perpendicular
to dividing plane
-land plants
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furrowing = most algae
cell plate formation = a
few algae and land plants
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III. Morphology
III. Morphology
Chlorophyta:
Chlorophyta:
easiest division to identify visually
• usually bright, grass-green color
easiest division to identify visually
• usually bright, grass-green color
Except -
photo: M orga n Bond
Snow algae
Dunaliella
Trentepohlia parasitic
on Monterey Cypress
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For classes:
- any easy “rules” using external thallus morphology?
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Diversity in chloroplast shape: (unique to algae)
“napkin ring-shaped parietal”
“cup-shaped parietal”
- Prasinophyceans are all unicells, but…
Charophyceans
“stellate (star-shaped)”
“axial (plate-like)”
“ribbon-like”
“reticulate (net-like)”
Chlorophyceae
Ulvophyceae
Ulvophyceae
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“multiple discoid”
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V. Classes in detail - Chlorophyte Diversity:
Some new terms:
Isogamy – sexual fusion between flagellated gametes that
are similar in size and shape
5 classes:
Chlorophyceae
Anisogamy – sexual fusion between flagellated gametes of
distinctly different sizes
Trebouxiophyceae
Oogamy – sexual fusion between a flagellated gamete
(sperm) and non-flagellated gamete (egg)
Ulvophyceae
Prasinophyceae
Review:
Sporophyte: diploid, 2n, multicellular release spores in
alternation of generations
Charophyceae
Gametophyte: hapliod, 1n, multicellular release gametes in
alternation of generations
Land plants
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Class Charophyceae:
1.
Charophyceae
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Microtubule Roots: broadband
Basal Bodies: parallel
How flagella are attached/constructed:
• basal bodies orientation = parallel
• microtubule roots = broad band
Flagella
2. Cell covering:
• scales vs. cell wall = wall
3. How cells divide:
• spindle = open
• microtubule organization = phragmoplast
• division by = furrow or plate
Basal Bodies
Microtubule roots
Cell
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Class Charophyceae:
Algal Life Cycles
Genera: Desmids, Chara
 most closely related to
terrestrial plants
Haplontic- 1N thallus, the zygote is the only diploid stage
usually unicells or filaments, but
sometimes colonies and more
complex forms
Mt
 freshwater
fuse
N
N
 haplontic- 1N thallus, the zygote is
grow
the only diploid stage
oogamous reproduction
Me
1N
spores
2N
zygote
 dormant zygotes
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Class Charophyceae:
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Class Charophyceae: Order Charales Genus Chara
Order Zygnematales
Desmids
 Macroscopi c
• 2 semi-cells that are mirror
images, nucleus is in center
 Freshwater
• asexual reproduction = mitosis
 Can be partially calcified
• sexual conjugation = pairing
between cells
 Central axis with whorls
of branches at nodes
• movement through mucilage
secretion
 Often smell of garlic
 Food and nursery habitat
for waterfowl
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Class Prasinophyceae:
IV. Classes in detail - Chlorophyte Diversity:
5 classes:
Chlorophyceae
Trebouxiophyceae
1.
Ulvophyceae
Prasinophyceae
How flagella are attached/constructed:
• basal bodies orientation = variable
• microtubule roots = variable
2. Cell covering:
• scales vs. cell wall = scales
Charophyceae
Land plants
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Some Prasinophyceans
3. How cells actually divide:
• spindle = open or closed
• microtubule organization = phragmoplast or phycoplast
• division by = furrow
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Class Prasinophyceae
Genus Tetraselmis
Microtubule Roots: cruciate
Basal Bodies: opposite
modern representatives of ancestral green (most
primitive)
Flagella
unicellular flagellates
Basal Bodies
 freshwater and marine
Microtubule roots
 one plastid with one pyrenoid
Cell
mostly asexual
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V. Classes in detail - Chlorophyte Diversity:
Class Chlorophyceae:
5 classes:
Chlorophyceae
Trebouxiophyceae
1.
Ulvophyceae
Prasinophyceae
How flagella are attached/constructed:
• basal bodies orientation = clockwise
• microtubule roots = cruciate
2. Cell covering:
• scales vs. cell wall = wall
Charophyceae
Land plants
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Chlorophyceae
3. How cells divide:
• spindle = closed
• microtubule organization = phycoplast
• division by = furrowing
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Class Chlorophyceae:
Microtubule Roots: cruciate
Basal Bodies: clockwise
 7000+ spp
mostly freshwater
unicells, colonies, coenocytes, filaments,
 haplontic life history- 1N thallus, the zygote is the only diploid stage,
with “hypnozygote” = thick walled resting stage
 isogamous, anisogamous, and oogamous species
Flagella
Basal Bodies
Genera:
Chlamydomonas, Volvox, Dunaliella
Microtubule roots
Cell
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Order: Volvocales Genus: Chlamydomonas
Chlamydomonas life history:
Usually asexual
fluid conditions
Mt
moist but not
wet conditions
“palmelloid
stage”
• Cup-shaped chloroplast, orange eyespot
• Scientists sequenced and mapped genome in 2003
• Used as a model to determine how gene expression works
• Use mutations to determine where genes are on chromosomes
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Haplontic- Sexual reproduction in unfavorable conditions
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Genus: Volvox
• Spherical colonies of 500 – 40,000 cells
• Each colony contains a large number of somatic cells and a
small number of reproductive cells
• Zygotes are orange
(1/2)
(1/2)
Hypnozygote
= resting stage
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Genus: Dunaliella
Volvox life history
• Oogamous
• Gonidia = specialized cells
that divide to become
daughter colonies
• Zoospore = spore with
flagella
• Endospore = surrounds
zoospore
• Common in salt ponds: have special ion pumps
• Packed with beta-carotene to protect from UV irradiance
• Mesospore = initially
surrounds endospore +
zoospore
• Commercial value (beta-carotene) = used for food coloring and
in pharmaceuticals
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V. Classes in detail - Chlorophyte Diversity:
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Class Trebouxiophyceae:
5 classes:
Chlorophyceae
Trebouxiophyceae
1.
Ulvophyceae
Prasinophyceae
How flagella are attached/constructed:
• basal bodies orientation = counterclockwise
• microtubule roots = cruciate
2. Cell covering:
• scales vs. cell wall = wall
Charophyceae
Land plants
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3. How cells actually divide:
• spindle = closed; metacentric
• microtubule organization = phycoplast
• division by = furrow
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Trebouxiophyceae
Microtubule Roots: cruciate
Basal Bodies: counter- clockwise
Class Trebouxiophyceae:
 mostly freshwater and terrestrial algae
 unicells, filaments, blades
Genera: Chlorella, Prasiola
Flagella
Basal Bodies
Microtubule roots
Cell
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Genus:
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Genus:
Chlorella
Prasiola
- Unicellular
- Diplontic- 2N thallus, the gametes are the only haploid stage
- Endosymbiont in freshwater animals
- Single, cup-shaped chloroplast
- Found in ultra-high intertidal (spray zone) in areas with high
guano
- “Nitrophilic”
- Used by Melvin Calvin to investigate carbon fixation in plants
(Calvin cycle)
- Thalli small (< 2cm), monostromatic blades
- Marketed as a dietary supplement
- Individuals higher on shore produce asexual (2N) spores
- Individuals lower on shore produce gametes, oogamous
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Prasiola Life History
49
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