1. by :Piya Roychaudhuri For 1st semester
ALGAE
by :Piya Roychaudhuri
For 1st semester

2. The study of ALGAE is called “Phycology”
Chlorophyl- bearing plants,
Thalloid ,
Autotrophic & Aquatic.

3. HABITATS A)Aquatic ( Fresh water & marine) Moist
stones, Soils and Wood.
B) Association with Fungi e.g. Lichen and
animals e.g. Sloth bear
C) Marine forms are Sea Weeds
D) Fresh water Algae
– Microscopic, Unicellular e.g. Chlamydomonas
- Colonial forms e.g. Volvox
- Filamentous forms e.g. Ulothrix & Spirogyra.

4. REPRODUCTION Vegetative – by fragmentation. Fragments
develops into thallus.
Asexual produce different type of spores
(zoospores)
- Zoospores – Flagellated motile
and germination gives rise to new
plants.

5. Sexual Reproduction – fusion of two gemets
1. Isogamous – Flagellated similar in size
e.g. chlamydomonas
- Non-flagellated but similar in
size e.g. spirogyra.
2. Anisogamous – two gemets dissimilar in size
e.g. chlamydomonas.
3. Oogamous - Fusion between one large,
non-motile – female gemete.
smaller motile- male gamete
e.g. Volvox, Fucus.

6. Isogamous
Anisogamous
Oogamous

7. CLASSES OF ALGAE The Algae are divided into three mail Classes:
Chlorophyceae
Phaeophyceae
Rhodophyceae

8. CHLOROPHYCEAE ( Green Algae)
Plant Body unicellular, Colonial or
Filamentous
Rigid Cell Wall – Inner layer – Cellulose
- Outer layer – Pectose
Green due to chlorophyll a & b
Definite chloroplasts – Discoid, Plate-like reticulate,
cup- shaped,spiral or ribbon-shaped
Storage bodies Pyrenoids, located in the
chloroplasts. Store food in the
form of oil droplets

9. CHLAMYDOMONAS
VOLVOX
ULVA

10. Chlorophyceae -Reproduction
The Sex organs are always unicellular
Vegetative – Fragmentation(spores)
Asexual Reproduction – Flagellated zoospores
Sexual Reproducion – isogemous,
anisogemous and
oogamous

11. Phaeophyceae (Brown Algae)
Marine habitats
Plant body attached to the substratum by a Hold fast, Stalk –Stipe, Leaf Like- Photosynthetic organ – Frond
Golden brown – Xanthophyll pigment fucoxanthin in their chromotophores. Addition to chlo.a, chlo.c and carotenoids.
Accumulation of reserve food as fats and oil rather then starch.
The cellulosic wall covered by algin
Centrally located vacuole and nucleus.

12. LAMINARIA
DICTYOTA
SARGASSUM

13. Phaeophyceae- Reproduction
Vegetative reproduction – Fragmentation
Asexual Reproduction - biflagellate
zoozpores (two unequal)
Sexual Reproduction - Isogamous,
anisogamous or oogamous.
- Union of gamets takes
place in water or within the oogonium.

14. Rhodophyceae (Red Algae)
Red Pigment, r-phycoerythrin in their body
Found in the warmer areas
Red thalli – Multicellular
The food stored as floridden starch

15. GRACILARIA
PORPHYRA
GELIDIUM

16. Rhodophyceae-Reproduction
Vegetative Reproduction – Fragmentation
Asexual – Non-motile spores
Sexual Non-motile gamets (oogamous)
e.g. Polysiphonia, porphyra etc.

17. Algae- Economic Importance
Use as Food e.g. Porphyra, Laminaria &
Sargassum.
Certain marine brown & red algae produce large amount of hydrocolloids (water holding substances)
Algin – brown algae e.g. sargassum
Agar used to grow microbs and preparation of icecream and jellies e.g. Gelidium & Gracilaria.
Rich proteins – Chlorella & Spirullina

18. THANK YOU