General characteristics of divisions of Algae

1. General characteristics of Cyanophyta,
Chlorophyta, Phaeophyta & Rhodophyta
Sankrita Gaonkar
Assistant Professor in Botany
sankrita002@gmail.com

2. Contents
• Cyanophyta
• Chlorophyta
• Phaeophyta
• Rhodophyta
• references

3. Cyanophyta
Division: Cyanophyta=Cyanophycophyta
Class: Cyanophyceae
1. Order: Chroococcales – Chroococcus, Synechocystis,
Microcystis, Synechococcus, Gloeothece
2. Order: Oscillatoriales – Oscillatoria, Lyngbya, Spirulina
3. Order: Nostocales – Nostoc, Anabaena, Aulosira

4. General characteristics:
• Small primitive group – 2,500 species – 150 genera
• Only known oxygen producing prokaryotes
• Simplest living autotrophs
• Cellular organization – prokaryotic
• Absence of well defined nucleus
• Absence of cell organelles
• Flagella absent

5. • Thallus organization
1. Unicellular forms – spherical or oval (Chroococcus, Synechococcus)
2. Colonial forms
o Non-filamentous – Coelosphaerum, Gomphophaera, Microcystis
o Filamentous (trichome) – branched (Westiella, Hapalisiphon), unbranched
(Oscillatoria, Lyngbya)
• Flagella – absent
• Movement – gliding motion, jerky type
• Photosynthetic pigments – Chlorophyll a, β-carotene, unique – Phycobilins
(phycocyanin and phycoerythrin), xanthophylls (myxoxanthin and
mycoxanthophyll)

6. • No membrane bound chromatophores
• Storage products – myxophycean starch, proteinaceous material-
cyanophycin
• Filamentous blue-greens – heterocysts
• Nutrition – photoautotrophs

7. • Sexual reproduction – absent
• Asexual reproduction
• i) vegetative methods – fission (septum formation), fragmentation,
hormogones formation
• ii) spore formation – akinetes, endospores, exospores, nannocytes
Fission
Fragmentation

8. Chlorophyta
Division: Chlorophyta = Chlorophycophyta
Class: Chlorophyceae
1. Order: Volvocales: Pyramimonas, Chlamydomonas, Gonium,Volvox
2. Order: Tetrasporales: Tetraspora
3. Order: Chlorococcales: Chlorococcum, Pediastrum, Hydrodictyon
4. Order: Chlorellales: Chlorella, Ankistrodesmus, Oocystis, Scenedesmus
5. Order: Ulotrichales: Ulothrix, Microspora
6. Order: Cladophorales: Cladophora
7. Order: Zygnematales: Spirogyra, Closterium, Zygnema

9. General characteristics:
• Large number of species – 20,000
• Eukaryotic – membrane bound nucleus and organelles
• Thallus – green – chlorophyll – chloroplast
• Thallus organization
1. Unicellular – motile (Chlamydomonas), non-motile (Chlorella)
2. Colonial – motile (Volvox), non-motile (Hydrodictyon)
3. Coenocytic or siphonaceous – Acetabularia
4. Multicellular filamentous – Spirogyra

10. • Cell wall – inner layer – cellulose, outer layer – pectose
• Siphonales – callose
• Photosynthetic pigments – Chlorophyll a, b, carotene, xanthophyll
• Chloroplast shapes – cup-shaped, reticulate, collar, discoid, axile plate, ribbon,
stellate, band-like
Cup-shaped
Reticulate
Collar
Ribbon-shaped
Stellate

11. • Pyrenoids – proteinaceous bodies embedded
in chloroplast – storage product
• Eye-spot or stigma – associated with
chloroplast – photoreceptive
• Flagella – whiplash

12. • Reproduction
1. Vegetative – cell division (fission), fragmentation, akinetes
2. Asexual – asexual spores – zoospores (motile, bi- or quadri-flagellate),
aplanospores (non-motile autospores) – thick-wall formation (hypnospores)
3. Sexual – homothallic (monoecious), heterothallic (dioecious)
i) Isogamy – gametes are alike – size, structure, behaviour
ii) Anisogamy – dissimilar gametes
iii) Oogamy – distinct sex organs – antheridium (male), oogonium (female)

13. Phaeophyta
Division: Phaeophyta = Phaeophycophyta (brown algae)
Class: Phaeophyceae
1. Order: Ectocarpales – Ectocarpus
2. Order: Dictyotales – Dictyota
3. Order: Laminariales – Laminaria
4. Order: Fucales – Fucus, Sargassum

14. General characteristics:
• 1500-2000 species are known. most complex forms of algae
• Mostly found in deep seas and oceans, only a few
phaeophyta are freshwater species. Commonly adapted to
marine environment
• Range from a microscopic length to several meters. giant
kelp can reach to about 70 meters in length
• autotrophic, multicellular organisms
• Pigments: xanthophyll (fucoxanthin, lutein, flavoxanthin,
violaxanthin), chlorophyll a, c, carotene
Kelp

15. • Thallus organization
• All are multicellular and sessile
• General construction – holdfast, stipe, blade
• have air bladders, meant for floating photosynthetic parts
on or near the water surface for harvesting light.
• Cell wall – inner cellulosic, outer gelatinous and pectic
(algin or fucoidin)
• Food reserve – sugars
Giant kelp
Sargassum

16. • Reproduction
• Asexual – vegetative (fragmentation, propagula) and spore formation
(zoospores)
• Sexual – Isogamy, anisogamy, oogamy
Propagule

17. Fucus

18. Rhodophyta
Division: Rhodophyta = Rhodophycophyta (red algae)
Class: Rhodophyceae
1. Order: Bangiales - Porphyra
2. Order: Nemalionales - Batrachospermum
3. Order: Ceramiales - Polysiphonia

19. General characteristics:
• Sea weeds – marine
• Fresh water forms – 200 species
• Thallus – non-motile, unicellular (Porphyridium), most are multicellular,
filamentous (Goniotrichum), ribbon-like (Porphyra)
1. Uniaxial – one axial filament
2. Multiaxial - tuft of axial filament
Uniaxial Multiaxial
Porphyridium
Porphyra

20. • Cell wall – outer mucilaginous, slimy, contains sulphated galactans (agar-
agar, porphyran, furcellaran) and inner cellulosic - polysulphate esters
• Cell wall – pits – protoplasmic continuity – phylogenetic significance
• Pyrenoids – reserve proteins
• Absence of flagella
• Photosynthetic pigments – chlorophyll ‘d’, carotenoid – taraxanthin,
bilioproteins- R-phycocyanin, R-phycoerythrin
• Food storage products – floridean starch, galactoside floridoside
• Sexual reproduction – oogamous – spermatangium (spermatia),
carpogonium (egg)
• Source of Agar-- Gracilaria

21. References
• Vashishta B.R., Sinha A.K. and Singh V.P. 2012. Botany for
degree students: Algae. S. Chand & company ltd.
• Fritsch, F.E.,(1956). The structure and reproduction of the
Algae; Volume I and II. Cambridge University Press.