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ChlorophytaI. Characteristics of Eukaryotic AlgaeII. CharacteristicsIII. Classes• Prasinophyceae• Chlorophyceae

Evolutionary LinesFlagellated SpeciesNon-flagellated SpeciesColoniesFilaments

• Ulvophyceae• Charophyceae

Phylum Chlorophyta

General Characteristics:• chlorophylls a&b• storage product is starch• cellulose cell walls; (organic scales)• 2 (4)smooth flagella (whiplash)• 2 chloroplast membranes (1° plastids)• marine, freshwater, aerial, symbiotic• unicell to parenchymatous

Four Classes

1.

Prasinophyceae

Chlorophyceae2.

Ulvophyceae3.

4.

Charophyceae

• least advanced (ancestral ?)• unicellular• organic scales for cell coverings• Scales on smooth flagella (1 - 4)• haplontic life history• marine and freshwater• e.g Micromonas

Class Prasinophyceae

Pyramimonas• organic scales• 4 flagella• fibrous root

Micromonas• < 2µM• 1 flagellum• naked cell

Four Classes

1.

Prasinophyceae

Chlorophyceae2.

Ulvophyceae3.

4.

Charophyceae

2

• large group• single cells to colonies to

filaments• cellulose cell wall• freshwater and terrestrial

(mostly)• haplontic• zygote is overwintering (harsh

times) structure

Class Chlorophyceae

Three evolutionary lines (from flagellated ancestor)

Class Chlorophyceae cont.

Flagellated ancestor

Flagellated colonies

Non-flagellated cellsand colonies

Filamentous species

Flagellated Chlorophytes1. flagellated cells and colonies

(1) Chlamydomonas(a) asexual reproduction

Class Chlorophyceae cont.

palmaloid stage

mi

water

(b) sexual reproduction

mi

isogametes

+ -

2n (planozygote)

fuse

zygospore

me

n

2n

More Class Chlorophyceae

Flagellated Chlorophytes cont.

Volvocine series:• increasing colony complexity• increasing reproductive complexity• evolutionary model for multicellularity?

single cell Chlamydomonas

4 - 32flat

Gonium

4 - 32Sphere

PandorinaIsogamousno polarity

Anisogamouspolarity

16 - 64Eudorina

50- 50,000Volvox

3

Class Chlorophyceae

Flagellated ancestor

Flagellated colonies

Non-flagellated cellsand colonies

Filamentous species

Pediastrum

2. Non-flagellated Chlorophytes(Chlorococcales)

• mostly freshwater group• unicells to colonies• no flagella (or remnants of flagellar

apparatus)• however, zoospores are produced

for asexual reproduction

colony form is Pediastrum(Coenobium - reproductive colony inside mother colony - cell number fixed)

Non-flagellated Chlorophytes cont.

coenocytes - colonies formed by mitosis without cell division i.e. multinucleated.eg. Hydrodictyon

Non-flagellated Chlorophytes cont.

Colony form cont.

Flagellated ancestor

Flagellated colonies

Non-flagellated cellsand colonies

Filamentous species

Oedogonium

Class Chlorophyceae

• filamentous algae occur in several Orders :

Microsporales - simple, ancestralChaetophorales - heterotrichousOedogonales - specialized branches

• Growth is by cell division and enlargement

3. Filamemtous Chlorophytes

Class Chlorophyceae cont.

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Unbranched Filaments(simplest)

Order Microsporales

• uninucleate cells• single chloroplasts• no intercellular connections• less advanced cell wall (H-pieces)• growth by interpolation

Filamemtous Chlorophytes cont. Heterotrichous filaments filamentouserect

Compactprostrate

e.g. Chaetophora

(Order Chaetophorales)

Specialized Branches(Order Oedogoniales)

• specialized cell division (forms distinctive “cap”)

• stephanokontouszoospores(flagellar crown)

• oogamous (advanced)

Filamemtous Chlorophytes cont.

• sexual reproduction

Filamemtous ChlorophytesOedogoniales cont.

antheridiaegg

oogonia

me

zygote(2n)

macandrous

nannandrous

dwarfmale

macandrous nannandrous

d.m.

an.

Four Classes

1.

Prasinophyceae

Chlorophyceae2.

Ulvophyceae3.

4.

Charophyceae

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Class Ulvophyceae• most are macrophytes (can be

seen with naked eye)• most are marine (a few are

freshwater)• morphology is variable:

parenchymatous, filamentous, siphonous, unicellular (coenocytic)

Chlorophyta cont..

Ulva fasciata

Codium reedii

Siphonous (coenocytic)• Codium• mass of thread-like tubes

(siphons)• multinucleate - mitosis and

cell division occurs but no crosswall are formed

• forms spongy thallus(Psedoparenchmyatous)

• movement required to maintain pseudoparenchymatous thallus

• in still culture filaments form• shake the culture the more complex thallus forms

• siphons form loose inner medulla and outer cortex

• cortex is primarily swollen Utricle

• utricle are site of photosynthesis

• medulla often without chloroplasts

Siphons cont.

medulla cortex

Parenchymatousforms

Ulva sp. & Enteromorpha sp.

• cellulose cell wall• marine diplohaplonic

• isomorphic Ulva

n

2nme

zygote

gametophyte

sporophyte

• isomorphic

• isogamous

gametes

zoospores

Ulva life history: isomorphic

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zoosporeformation

Four Classes

1.

Prasinophyceae

Chlorophyceae2.

Ulvophyceae3.

4.

Charophyceae

Class Charophyceae• cellulose cell walls• freshwater• haplontic life history• most closely related to

Bryophytes and vascular plants?

Chlorophytes cont..

• molecular evidence• similar introns• tufA gene in nucleus (not chloroplast)

• biochemical• lignin in cell walls

• developmental• retaining egg + zygote on gametophyte• cells covering zygote• more than 4 spores from zygote• similar flagellated sperm (Bryophytes)

Charophyceae cont. Class Charophyceae

4 Orders

1. Klebsormidiales (unbranched)2. Coleochaetales (heterotrichous)3. Zygnemetales

• Spirogyra, Zygnema, Mougeotia• Desmids

4. Charales• Chara• Nitella

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ZygnemaSpirogyraDesmids

filamentous, unicellularno flagellar stages

Spirogyra spiral chloroplastZygnema - stellate chloroplastMougeotia - plate chloroplasts

Charophyceae cont.Order Zygnemateles

Plate-likeMougeotia

SpiralSpirogyra

StellateZygnema

Sexual reproduction -conjugation

Reproduction

• no zoospores• fragmentation

Spirogyraholdfast

Scalariform conjugation• filaments line up• mucilage is excreted• protoplast balls and becomes

amoeboid gamete• papillae form towards each

other• meet, cell wall degrades and

conjugation tube forms• gametes fuse into dormant

Zygote• Zygote germinates - one cell

becomes new filament

zygo

te2n

me

Scalariform Lateral

Desmids

Two groups1. Saccoderm Desmids

• simple• unicellular• resemble filamentous forms

2. Placoderm Desmids• eloborate cells• usually two halve (semi-cells)• contain two chloroplasts

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Placoderm DesmidSaccoderm Desmid

Netrium Closterium

Desmid reproduction

asexual

Charophyceae cont.Order Charales

• large• oogamous• corticated• CaCO3 encrusted• enclosed egg• no zoospores