1

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?

2

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

3

!"#$%&'()*+*,-(./-"01*23341

Parenchymatous Siphonocladous

!&'0'$*56*78/9:*;8<=/9:1

Morphological Concept of Classification

- Primitive unicells evolved structural complexityover time

- Morphological divergence distinguishes groups

4

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

5

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

6

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

7

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?

8

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

9

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

10

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

11

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

12

IV. Classes in Detail - The ChlorophyteDiversity

Chlorophyceae

Trebouxiophyceae

Ulvophyceae

Prasinophyceae

Charophytes

Land Plants

13

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

14

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

15

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

16

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

17

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

18

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

19

Class UlvophyceaeUnicells, filaments, blades

closed cell division phycoplast division by furrowing

basal bodies counterclockwise

cell wall out of cellulose

mostly marine macroalgae

Diverse Morphologies

20

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

21

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

22

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”

23

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

24

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

25

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

26

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