Most of the algae are aquatic. i.e.,
1. Fresh water : Spirogyra, Volvox, Chlamydomonas, Chlorella
2. Marine water: Fucus, Ulva, Sargarsum, Macrocystis
Different forms of Algae
- Phytoplanktons : Free floating on water surface and also pioneer colonizer of hydro sere. Spirogyra, Volvox
- Benthic: found at the bottom of ponds or lakes. Chara
- Epiphytic: Alage attached to other aquatic plants. Oedogonium
- Epizoic: Algae attached to other aquatic animals.
Characium ==> Attached to mosquitoes
- Endozoic: Found within aquatic animals.
- Edaphophytes (Terrestrial forms) : Found in damp soil. Oscillatoria
- Endophytes: Found within other plants. Azolla leaf posses Anabaena
- Cryophytes: Found in low temperature or snow
- Thermophytes : Which can resist in high temperature ut to 70 0C. Oscillatoria brevis
Range of Thallus
There exists wide variety of thalli in algae particularly in vegetative plant which is given below:
1. Unicellular form: It is most primitive plant, Unicellular and a single cell can perform vital process. It is of 2 types based on flagella i.e.
a) Unbranched filament: arranged in uniserate row. Spirogyra, Oedogonium
b) Branched filament: Cells arranged in different lateral branches. Cladophora, Pithophora
c) False branched: In this form any cells of plant breaks its cell wall that produces two individual filaments but get attached to the parent one. Sclytonema
4. Parenchymatous form: plant body is large and cells are divided into more than one plain forming different septa results the parenchymatous body. Ulva
5. Siphonoceous type: Plant body consists of attaching organ and added filament. This added filament part is expanded which is multicellular and aseptated. Botrydium, Vocheria.
6. Heterotrichous: It is most advanced form. This type of thallus consists of erect and prostate branch. Stigeoclonium
Nutrition:
Algae are autotrophic or heterotrophic in nature. Autotrohic algae posses distinct chloroplast
I. Spiral chloroplast/ ribbon : Spirogyra
II. Cup-shaped chloroplast :Chlamydomonas, Chlorella
III. Reticulate/ Net like chloroplast :Oedogonium
IV. Girdle/ Horseshoe/ Collar :Ulothrix
V. Stellate/ Star shaped :Zygnema
VI. Discoid : Chara
Chl’a’ and carotene pigments are found in all algae
Chl ‘b’ =Chlorophyceae
Chl ‘c’ =Phaeophyceae
Chl ‘d’ = Rhodophyceae
Chl ‘e’ = Xanthophyceae
Reproduction
1. Vegetative reproduction: This is the most common method of reproduction. It generally takes place by fragmentation, cell division, hormogonia, bulbils and starch stars.
2. Asexual Reproduction: it is formation of special type of spores which is uniparental. Spores may be:
· Zoospore: It is motile sexual spores. Under the favorable condition biciliated or multiciliated zoospores are formed and on bursting mother cell(zoosporangium) give rise to new plant. Ulothrix, Oedogonium.
· Aplanospores: It is thin walled non motile asexual spore. Ulothrix, Chlorella
· Hypnospores: Protoplasm of cell separates from the cell wall and collects in the centre to form non motile and thick walled hypnospores which under favorable condition give rise to new plant. Voucheria
· Akinete: entire cell become thick to form akinete and each o them develop new plant. Cladophora
3. Sexual reproduction:
· Isogamous: Fusion of gametes which is similar in size and structure or morphologically similar but physiologically different
· Anisogamous: Fusion of gametes which are different in size but similar in structure.
· Oogamous: Fusion of gametes different in size and structure. It is an advanced type of reproduction.