Post on 15-Nov-2018
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Division: Chlorophyta
I. Taxonomy
II. Unifying Characteristics
III. Distinguishing Classes
IV. Classes in Detail
16,000 species, only about 1,600marine
Easiest division of Chlorophyta from other algae: - usually bright green, grassy color
Exceptions?
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Essential Members of the Phytoplankton
I. Algal Taxonomy
Hierarchichal system of classification:Level: Suffix: Example:Domain Eukaryote Kingdom Plantae Phylum/Division - phyta Chlorophyta Class - phyceae Ulvophyceae Genus Ulva species lactuca
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Parenchymatous Siphonocladous
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Morphological Concept of Classification
- Primitive unicells evolved structural complexityover time
- Morphological divergence distinguishes groups
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Chlorophyta
Egg encasement
Embryo, starch
Chl b
Chlorophyceae
Trebouxiophyceae
Ulvophyceae
Prasinophyceae
Charophytes
Land Plants
freshwater,some marine
mostly fw/terrestrial
marine macros
marine/fwflagellates
fw, terrestrial
Prasinophyceans are unicells but…..
Chlorophyceae Ulvophyceae Ulvophyceae
Chlorophyta
Charophyta
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II. Unifying features of the Chlorophyta1. Flagellate cells = typically possess 2 flagellae, equal length
multiples of twostellate
arrangement atflagellar base
Flagellar Phototaxis1. lightsensation(stigma)
2. Ca2+influx
3. 1 moreactive, 1less
4.orientationto light
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2. Mitochondria
flattened cristae
advantages?
3. PlastidsA B
C
D
E
F
G
all contain at least 1 plastidmultiple, discoid plastids = landplantsin comparison with otherheterotrophic eukaryotes greenalgae have large variety offormsas in land plants synthesize andstore starchmain photopigments =chlorophyll a and b, !-carotene
A Chlamydomonas, B Chlorella, C Asterochloris,D Acrochaete, E Spirogyra, F Enteromorpha, GPseudocodium
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4. Pyrenoids
sites of carbon fixation often within the chloroplast of algalcells= also found in euglenoids and dinoflagellatesconcentration of carbon dioxidenot found in higher land plants
III. Bases for distinction between classes1. Cell division A. Mitotic spindle
closed metacentriccentrioles open
ChlorophyceaeTrebouxiophyceaeUlvophyceaePrasinophyceaeCharophytes
Land Plants
nucleus =dumbbellshaped
Prasinophyceae = variableTrebouxiophyceae = onlyones with unusualmetacentric= how does the spindleapparatus form?
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1. Cell division B. phycoplast vs phragmoplast
furrowing furrowing
ChlorophyceaeTrebouxiophyceaeUlvophyceaePrasinophyceaeCharophytes
Land Plants
Phycoplast: tubulesparallel to plane
Phragmoplast: tubulesperpendicular to plane
unclear in Prasinophyceae &Trebouxiophyceae= centrioles non-persistent
1. Cell division C. furrowing vs cell plate formation
Furrowing: most algae Cell plate formation =Charophytes and land plants
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2. ONE basal body per flagellum, located at the flagellar base,anchoring into the cell- basal body pairing may vary
opposedparallel clockwise counterclockwise
ChlorophyceaeTrebouxiophyceaeUlvophyceaePrasinophyceaeCharophytes
Land Plants
ChlorophyceaeTrebouxiophyceaeUlvophyceaePrasinophyceaeCharophytes
Land Plants
3. Cell coveringScales - made of complexpolysaccharides, secreted fromgolgi, Prasinophyceae
Cell wall - usually cellulose,other green algae and landplants
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Some new concepts and review of old ones1. Levels of Complexity - Chlorophyta are most diverse ingrowth forms, some microscopic (unicellular), some up to 8mlongA. Unicellular formsChlamydomoas, Chlorella, Dunaliella, desmids
B. Colonial formsUnicells form large interconnected groupsPandorina, Pediastrum, Volvox
C. Filamentous formsColonial form where single algal cells formlong visible chains, threads, Cladophora,Ulothrix
D. Thallous formsComposed of plates or cells arranged intotree-like forms, Ulva
1. Levels of Complexity - Chlorophyta are most diverse ingrowth forms, some microscopic (unicellular), some up to 8mlongE. Coenocytic formsA multinucleate mass enclosed in a single cell wallCaulerpa, Codium
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2. Sexual Fusion
Isogamy - fusion betweenflagellated gametes thatare similar in size andshape
Anisogamy - fusionbetween flagellatedgametes of distinctlydifferent sizes
Oogamy - fusion betweena flagellated and non-flagellated gamete
3. Generations
Sporophyte - diploid (2n),multicellular, produces sporesthrough meiosis=> releases spores duringalternation of generations
Gametophyte - haploid (n),multicellular, may be microscopic,produces gametes through mitosis,generally the visibly dominantform
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IV. Classes in Detail - The ChlorophyteDiversity
Chlorophyceae
Trebouxiophyceae
Ulvophyceae
Prasinophyceae
Charophytes
Land Plants
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Class Prasinophyceae
Unicellular, may be flagellar
open or closed cell division phycoplast or phragmoplast division by furrowing
basal bodies opposite large golgi body b/w basal bodies
Cell covering
OstreococcusPyramimonas
extrusomes
Reproduction mainly asexual - may produceresting stages or “cysts” (nucleus-mitosis-flagellate cells-wall rupture)
Mostly marine, some freshwater
one chloroplast (cup shaped),single pyrenoid
least advanced of the Chlorophyta
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Chlorophyceae
Trebouxiophyceae
Ulvophyceae
Prasinophyceae
Charophytes
Land Plants
Class ChlorophyceaeUnicellular, colonies, filaments, coenocytes
closed cell division phycoplast division by furrowing
basal bodies clockwise
cell wall out of cellulose
mostly freshwater, some marine species
anisogamous, isogamous and oogamous
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Genus: ChlamydomonasUnicellular, terrestrial, fw, marine, even in snow
Cup-shaped chloroplast, orange eyespot
can grow in total darkness acetate as alternate carbon source
deprivation of nitrogen = diploid zygospore
haplontic = somatic cells with haploid cell numbers
Haplontic - sexual reproduction in unfavorable conditions only
Hypnozygote = resting stage
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Genus: Tetraspora
Colonial, cell body spherical, 2 ormore flagellae
Colony with gelatinous bag
Single chloroplast, cup-shaped withpyrenoid
Genus: DunaliellaUnicellular, cells often ovoid, distinctly mucilaginous
Chloroplast single, generally cup shaped
plastids packed with ! carotene
uses in cosmetics, food supplements, aquaculture
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Chlorophyceae
Trebouxiophyceae
Ulvophyceae
Prasinophyceae
Charophytes
Land Plants
Class TrebouxiophyceaeUnicells, filaments, blades
metacentric cell division phragmoplast division by furrowing
basal bodies counterclockwise
cell wall out of cellulose
mostly freshwater/terrestrial, some marinespecies
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Genus: ChlorellaUnicellular, generally spherical
Freshwater species may be endosymbiotic
Single chloroplast
Melvin Calvin
High in protein, minerals andvitamins
Chlorophyceae
Trebouxiophyceae
Ulvophyceae
Prasinophyceae
Charophytes
Land Plants
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Class UlvophyceaeUnicells, filaments, blades
closed cell division phycoplast division by furrowing
basal bodies counterclockwise
cell wall out of cellulose
mostly marine macroalgae
Diverse Morphologies
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Thallus Composition
no organized “distinct” parts
some analogous structures tovascular plants
holdfast = anchor
stipe = support to the blades
blades = photosynthetic
Blade-like
Often ephemeral inintertidal
Fast growing, tasty toherbivores
Some species euryhaline -tolerate freshwater
Genus: Ulva
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Genus: UlothrixFilamentous, unbranched uniserate
Cells closely adherent
Simple or rhizoidal basal cells
Single napkin ring-shaped chloroplast, partially or completelyencircling cell circumference
Pyrenoids single generally in more mature cells
Sexual reproduction by isogamous, biflagellate gametes
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Genus: Codium
Coenocytic/siphonous construction:
= Multinucleate, no divisionof cytoplasm with cell walls
“clotting compounds” toquickly repair wounds
Bryopsis
Uniaxial and multiaxial construction
Codium “dead man’s fingers”
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Utricles
GametangiumUtricles-peripheral portions of thesiphons maybe inflated & aggregated to form coherentouter surface gametangium (reproductive structure) originatefrom them
*Codium the size of an apple =~30 km of siphons
Attach and grow on scallops
Codium Scallop Interactions
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Kleptoplastids
- Sacoglossan radula adapted tohost alga (length of tooth ~thickness of siphon)
- Common in siphonous greens
- Pierce and suck out insides
- Stolen chloroplasts can last upto a month or so
uniaxial, but with trabeculae for support
trabecula = ingrowth of wall material
unicellular, coenocytic
rhizoids with specific attachmentmechanisms = vitronection
Siphons form rhizoidalholdfast, too
Genus: Caulerpa
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The CaulerpaInvasion
• native in Australia (non-native strains have invaded)• 1st introduced as a non-native in Mediterranean (1984)• introduced at 2 sites in S.California (Carlsbad, Huntington Harbor)
anisogamous, dioecious=separate sexes
Holocarpic reproduction
gametes migrate
Genus: Halimeda
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Calcification as defense againstherbivores
Calcification
(decalcify Halimeda, just a mass of enormous siphons)
Both chemical and structural defense common in tropical spp
Elysiella instead eatsyoung growth and convertstoxic compounds into itsdefenses