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Division: Chlorophyta (green algae)

~ 16,000 species ~ 90% freshwater

I. General Characteristics II. Distinguishing Classes III. Morphology IV. Classes in Detail

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Hierarchical system of classification: Level: suffix: example: Domain Eukaryote Group Plantae Division -phyta Chlorophyta Class -phyceae Ulvophyceae Order -ales Ulvales Family -aceae Ulvaceae Genus Ulva species fenestrata

II. Algal taxonomy

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DOMAIN 1.Bacteria- cyanobacteria (blue green algae)

2.Archae 3.Eukaryotes

Groups (Kingdom) 1. Alveolates- dinoflagellates 2. Stramenopiles- diatoms, heterokonyophyta 3. Rhizaria- unicellular amoeboids 4. Excavates- unicellular flagellates 5. Plantae- rhodophyta, chlorophyta, seagrasses 6. Amoebozoans- slimemolds 7. Fungi- heterotrophs with extracellular digestion 8. Choanoflagellates- unicellular 9. Animals- multicellular heterotrophs

“Algae”

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Adapted from Sadava 2014

Glaucophytes

Rhodophyta

Chlorophytes

Charophytes

Land Plants

Plantae

Chl b, starch

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Chlorophyceae Trebouxiophyceae Ulvophyceae Prasinophyceae Charophytes Charophyceae

Phylogenetics of Chlorophyta (morphological, molecular data)

Land plants

5 classes:

Chloroph

yta

Chl b, starch

Encasement of egg

Embryo, cuticle

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I. General Green Characteristics:

1) Pigments: ?

2) Chloroplast structure?:

3) Storage product?

4) Flagella?

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Chlorophyceae = freshwater Trebouxiophyceae = freshwater, soil and marine Ulvophyceae = marine macroalgae Prasinophyceae = primarily marine flagellates, some freshwater; modern representatives of earliest green algae Charophyceae = freshwater; all terrestrial plants are derived from Charophycean class

Classes:

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1. How flagella are attached/constructed:

• basal bodies orientation • microtubule roots

2. Cell covering: • scales vs. cell wall

3. How cells divide: • aspects of mitosis and cytokinesis

II. Distinguishing among classes based on:

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1. How flagella are attached/constructed: -basal bodies orientation -microtubule roots

anterior

swimming direction

Cell

Flagella

Basal Bodies

Microtubule roots

II. Distinguishing among classes based on:

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Flagella- complex cellular projections used for movement - bundle of nine fused pairs of microtubule doublets surrounding two central single microtubules "9+2" Basal bodies- attachment site of the flagella - containing a microtubules 9 triplet configuration forming a hollow cylinder

Cell

Flagella

Basal Bodies

Microtubule roots

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opposite parallel clockwise counterclockwise

Basal Bodies: ONE per flagellum, located at base of flagellum, anchoring into cell -pairs of basal bodies may be

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Cell

Flagella

Basal Bodies

Microtubule roots

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Microtubule roots: -under the cell membrane at point of attachment of basal bodies - may be cruciate or broadband Cell

Flagella

Basal Bodies

Microtubule roots

cruciate broad-band

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2. Cell covering- scales vs. cell wall

II. Distinguishing among classes based on:

Scales are made of complex polysaccharides secreted from golgi

Cell wall = usually cellulose

prasinophyceae Chlorophyceae, trebouxiophyceae, Ulvophyceae, charophyceae

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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

closed

II. Distinguishing among classes based on:

Open -during Mt nuclear envelope breaks down

metacentric centrioles

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Phragmoplast: double microtubules perpendicular to dividing plane -land plants

Phycoplast: microtubules parallel to dividing plane -rare in algae

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

II. Distinguishing among classes based on:

furrowing furrowing

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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

II. Distinguishing among classes based on:

furrowing = most algae cell plate formation = a few algae and land plants

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III. Morphology

Chlorophyta: easiest division to identify visually

• usually bright, grass-green color

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III. Morphology

Chlorophyta: easiest division to identify visually

• usually bright, grass-green color Except -

Snow algae Dunaliella

Trentepohlia parasitic on Monterey Cypress

photo: M organ Bond

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Charophyceans

Chlorophyceae Ulvophyceae Ulvophyceae

For classes: - any easy “rules” using external thallus morphology?

- Prasinophyceans are all unicells, but…

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“napkin ring-shaped parietal”

“reticulate (net-like)”

Diversity in chloroplast shape: (unique to algae)

“cup-shaped parietal”

“axial (plate-like)”

“stellate (star-shaped)”

“multiple discoid”

“ribbon-like”

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Some new terms:

Isogamy – sexual fusion between flagellated gametes that are similar in size and shape Anisogamy – sexual fusion between flagellated gametes of distinctly different sizes Oogamy – sexual fusion between a flagellated gamete (sperm) and non-flagellated gamete (egg) Sporophyte: diploid, 2n, multicellular release spores in alternation of generations Gametophyte: hapliod, 1n, multicellular release gametes in alternation of generations

Review:

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Chlorophyceae Trebouxiophyceae Ulvophyceae Prasinophyceae Charophyceae

Land plants

5 classes:

V. Classes in detail - Chlorophyte Diversity:

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Class Charophyceae:

1. How flagella are attached/constructed:

• basal bodies orientation = parallel • microtubule roots = broad band

2. Cell covering: • scales vs. cell wall = wall

3. How cells divide: • spindle = open • microtubule organization = phragmoplast • division by = furrow or plate

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Microtubule Roots: broadband Basal Bodies: parallel

Charophyceae

Cell

Flagella

Basal Bodies

Microtubule roots

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Class Charophyceae:

most closely related to terrestrial plants

usually unicells or filaments, but sometimes colonies and more complex forms

freshwater

haplontic- 1N thallus, the zygote is the only diploid stage oogamous reproduction

dormant zygotes

Genera: Desmids, Chara

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Algal Life Cycles Haplontic- 1N thallus, the zygote is the only diploid stage

N

Me

Mt

N

fuse

2N zygote

1N spores

grow

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Class Charophyceae: Order Zygnematales Desmids

• 2 semi-cells that are mirror images, nucleus is in center

• asexual reproduction = mitosis

• sexual conjugation = pairing between cells

• movement through mucilage secretion

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Class Charophyceae: Order Charales Genus Chara

Macroscopic Freshwater

Can be partially calcified

Central axis with whorls of branches at nodes Often smell of garlic

Food and nursery habitat for waterfowl

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Chlorophyceae Trebouxiophyceae Ulvophyceae Prasinophyceae Charophyceae

IV. Classes in detail - Chlorophyte Diversity:

Land plants

5 classes:

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Class Prasinophyceae:

1. How flagella are attached/constructed:

• basal bodies orientation = variable • microtubule roots = variable

2. Cell covering: • scales vs. cell wall = scales

3. How cells actually divide: • spindle = open or closed • microtubule organization = phragmoplast or phycoplast • division by = furrow

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Microtubule Roots: cruciate Basal Bodies: opposite

Some Prasinophyceans

Cell

Flagella

Basal Bodies

Microtubule roots

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Class Prasinophyceae Genus Tetraselmis

modern representatives of ancestral green (most primitive)

unicellular flagellates

freshwater and marine

one plastid with one pyrenoid

mostly asexual

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Chlorophyceae Trebouxiophyceae Ulvophyceae Prasinophyceae Charophyceae

Land plants

5 classes:

V. Classes in detail - Chlorophyte Diversity:

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Class Chlorophyceae:

1. How flagella are attached/constructed:

• basal bodies orientation = clockwise • microtubule roots = cruciate

2. Cell covering: • scales vs. cell wall = wall

3. How cells divide: • spindle = closed • microtubule organization = phycoplast • division by = furrowing

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Microtubule Roots: cruciate Basal Bodies: clockwise

Chlorophyceae

Cell

Flagella

Basal Bodies

Microtubule roots

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Class Chlorophyceae:

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

Genera:

Chlamydomonas, Volvox, Dunaliella

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• 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

Order: Volvocales Genus: Chlamydomonas

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Chlamydomonas life history:

Usually asexual

“palmelloid stage”

Mt

fluid conditions

moist but not wet conditions

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Haplontic- Sexual reproduction in unfavorable conditions

Hypnozygote = resting stage

(1/2) (1/2) 40

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

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Volvox life history

• Oogamous

• Gonidia = specialized cells that divide to become daughter colonies

• Zoospore = spore with flagella

• Endospore = surrounds zoospore

• Mesospore = initially surrounds endospore + zoospore

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Genus: Dunaliella

• Common in salt ponds: have special ion pumps

• Packed with beta-carotene to protect from UV irradiance

• Commercial value (beta-carotene) = used for food coloring and in pharmaceuticals

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Chlorophyceae Trebouxiophyceae Ulvophyceae Prasinophyceae Charophyceae

Land plants

5 classes:

V. Classes in detail - Chlorophyte Diversity:

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Class Trebouxiophyceae:

1. How flagella are attached/constructed:

• basal bodies orientation = counterclockwise • microtubule roots = cruciate

2. Cell covering: • scales vs. cell wall = wall

3. How cells actually divide: • spindle = closed; metacentric • microtubule organization = phycoplast • division by = furrow

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Microtubule Roots: cruciate Basal Bodies: counter- clockwise

Trebouxiophyceae

Cell

Flagella

Basal Bodies

Microtubule roots

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Class Trebouxiophyceae:

mostly freshwater and terrestrial algae unicells, filaments, blades

Genera: Chlorella, Prasiola

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Genus: Chlorella

- Unicellular - Endosymbiont in freshwater animals

- Single, cup-shaped chloroplast - Used by Melvin Calvin to investigate carbon fixation in plants (Calvin cycle) - Marketed as a dietary supplement

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Genus: Prasiola

- Diplontic- 2N thallus, the gametes are the only haploid stage - Found in ultra-high intertidal (spray zone) in areas with high guano - “Nitrophilic”

- Thalli small (< 2cm), monostromatic blades - Individuals higher on shore produce asexual (2N) spores

- Individuals lower on shore produce gametes, oogamous

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Prasiola Life History