Division Chlorophyta
Chlorophyta
I.
Characteristics of Eukaryotic Algae
II. Characteristics
III. Classes
•
Prasinophyceae
•
Chlorophyceae
Evolutionary Lines
Flagellated Species
Non-flagellated Species
Colonies
Filaments
•
Ulvophyceae
•
Charophyceae
General Characteristics:
• chlorophylls a&b
• storage product is starch
• cellulose cell walls; (organic scales)
• 2 (4)smooth flagella (whiplash)
• 2 chloroplast membranes
• marine, freshwater, aerial, symbiotic
• unicell to parenchymatous
Class Prasinophyceae
Four Classes
1.
Prasinophyceae
2.
Chlorophyceae
3.
Ulvophyceae
4.
•
least advanced (ancestral ?)
•
•
•
•
•
•
unicellular
organic scales for cell coverings
Scales on smooth flagella (1 - 4)
haplontic life history (zygotic meiosis)
marine and freshwater
e.g Micromonas
Charophyceae
Four Classes
1.
Prasinophyceae
Micromonas
• < 2µM
• 1 flagellum
• naked cell
Pyramimonas
• organic scales
• 4 flagella
• fibrous root
2.
Chlorophyceae
3.
Ulvophyceae
4.
Charophyceae
1
Class Chlorophyceae
• large group
• single cells to colonies to
filaments
• cellulose cell wall
• freshwater and terrestrial
(mostly)
• haplontic (zygotic meiosis)
• zygote is overwintering (harsh
times) structure
Class Chlorophyceae cont.
Three evolutionary lines (from
flagellated ancestor)
Flagellated colonies
Flagellated
ancestor
Non-flagellated cells
and colonies
Filamentous species
4 - 32
flat
Gonium
Flagellated Chlorophytes
Volvocine series:
• increasing colony complexity
• increasing reproductive complexity
• evolutionary model for
multicellularity?
single cell
Chlamydomonas
50- 50,000
Volvox
Anisogamous
polarity
4 - 32
Sphere
Pandorina
Isogamous
no polarity
16 - 64
Eudorina
Flagellated Chlorophytes cont.
Class Chlorophyceae
Palmelloid Chlorophytes (Tetrasporales)
• vegetative cells loose flagella
• retain flagellar apparatus
e.g. basal bodies and microtubule
roots
Pediastrum
Flagellated colonies
Tetraspora
Flagellated
ancestor
Non-flagellated cells
and colonies
Filamentous species
2
Non-flagellated Chlorophytes cont.
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.
Class Chlorophyceae
Colony form cont.
coenocytes - colonies formed
by mitosis without cell division
i.e. multinucleated.
eg. Hydrodictyon
Oedogonium
Flagellated colonies
Flagellated
ancestor
Non-flagellated cells
and colonies
Filamentous species
Class Chlorophyceae cont.
Filamemtous Chlorophytes
• filamentous algae occur in several
Orders :
Microsporales - simple, ancestral
Chaetophorales - heterotrichous
Oedogonales - specialized branches
• Growth is by cell division and
enlargement
Filamemtous Chlorophytes cont.
Unbranched Filaments (simplest)
Order Microsporales
• uninucleate cells
• single chloroplasts
• no intercellular connections
• less advanced cell wall (H-pieces)
• growth by interpolation
3
Filamemtous Chlorophytes cont.
Filament growth by interpolation
e.g. Microspora (Microsporales)
Branched filaments
Order Chaetophorales
Growth
via turgor
pressure
some are heterotrichous
e.g. Fritscheilla
Compact
prostrate
1
Filament differentiation
two branching systems
heterotrichy
filamentous
erect
2
filamentous
erect
Filamemtous Chlorophytes cont.
Specialized Branches
(Order Oedogoniales)
Compact
prostrate
e.g. Chaetophora
• specialized cell division
(forms distinctive “cap”)
• stephanokontous zoospores
(flagellar crown)
• oogamous (advanced)
Filamemtous Chlorophytes
Oedogoniales cont.
• sexual reproduction
androspore
macandrous
antheridia
nannandrous
oogonia
d.m.
egg
zygote
(2n)
me
dwarf
male
an.
macandrous
nannandrous
4
Chlorophyta cont..
Four Classes
1.
Prasinophyceae
2.
Chlorophyceae
3.
4.
Ulvophyceae
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)
Charophyceae
Siphons
Siphonous (coenocytic)
• Codium
• mass of thread-like tubes
(siphons)
• multinucleate - mitosis and cell
division occurs but no crosswall
are formed
• forms spongy thallus
(Psedoparenchmyatous)
Ulva fasciata
Codium reedii
Siphons cont.
Siphons cont.
• siphons form loose inner
medulla and outer cortex
• cortex is primarily swollen
Utricle
• utricle are site of
photosynthesis
• medulla often without
chloroplasts
• movement required to maintain
pseudoparenchymatous thallus
• in still culture filaments form
• shake the culture the more complex
thallus forms
medulla
cortex
5
Parenchymatous
forms
Ulva sp. &
Enteromorpha sp.
Ulva fasciata
Codium reedii
Ulva life history: isomorphic
gametophyte
gametes
• cellulose cell wall
• marine diplohaplonic
• isomorphic Ulva
• isomorphic
zygote
n
• isogamous
me
2n
sporophyte
zoospores
Four Classes
zoospore
formation
1.
Prasinophyceae
2.
Chlorophyceae
3.
Ulvophyceae
4.
Charophyceae
6
Chlorophytes cont..
Charophyceae cont.
Class Charophyceae
• cellulose cell walls
• freshwater
• haplontic life history
• most closely related to
Bryophytes and vascular
plants?
• 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.
Order Zygnemateles
Class Charophyceae
4 Orders
1. Klebsormidiales (unbranched)
2. Coleochaetales (heterotrichous)
3. Zygnemetales
• Spirogyra, Zygnema, Mougeotia
• Desmids
4. Charales
• Chara
• Nitella
Zygnema
Spirogyra
Desmids
filamentous, unicellular
no flagellar stages
Spirogyra spiral chloroplast
Zygnema - stellate chloroplast
Mougeotia - plate chloroplasts
Reproduction
• no zoospores
• fragmentation
Spirogyra
holdfast
Plate-like
Mougeotia
Spiral
Spirogyra
Stellate
Zygnema
Sexual reproduction conjugation
7
Scalariform conjugation
zy
go
2n te
me
• 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
Scalariform
Lateral
Desmids
Two groups
1. Saccoderm Desmids
• simple
• unicellular
• resemble filamentous forms
2. Placoderm Desmids
• eloborate cells
• usually two halve (semi-cells)
• contain two chloroplasts
Desmid reproduction
asexual
Netrium
Saccoderm Desmid
Closterium
Placoderm Desmid
Charophyceae cont.
Order Charales
• large
• oogamous
• corticated
• CaCO3 encrusted
• enclosed egg
• no zoospores
8