- Study of algae in Botany is called as Phycology (or) Algalogy.
- Thallophyta comprises undifferentiated plant body (which is not differentiated into root, stem and leaves) called as thallus.
- Fritsch is known as Father of algae.
- Algae contain chlorophyll ‘a’ with starch as a reserve food, found mostly in freshwater as well as in marine condition and also in moist soil, stone and wood.
- Algae are found in different forms
→ Unicellular (Eg: Chlamydomonas)
→ Colonies (Eg: Volvox)
→ Filaments (Eg: Vlothrix)
- All kinds of reproduction such as Vegetative (Fragmentation), Asexual (Spores) and sexual methods (Syngamy) is recorded in algae.
- Sexual reproduction is of two types – Isogamy and Heterogamy (Anisogamy and oogamy)
- Male and Female gametes are morphologically similar in Isogamy. Eg: Ulothrix
- In Anisogamy, male gametes are smaller in size and active than the female gamete Eg: Chlamydomonas
- The most advanced type is oogamy, where a female gamete is non-motile – large with a motile, smaller male gamete. Eg. Volvox and Fucus.
- Certain algal growth floats on the water surface and looks like foam (or) soap as they grow abundantly in water reservoirs where an excess of nutrients are available to them. This condition is called algal bloom Eg; Microcystis, Oscillatoria etc;
- Major 3 classification of algae is chlorophyceae (green algae), Phaeophyceae (Brown algae) and Rhodophyceae (Red algae).
- Chlorophyceae possess pigments such as Chlorophyll ‘a’ and ‘b’ with Carotenoids and Xanthophyll. Chloroplast generally contains one (or) more storage bodies called Pyrenoids which has an inner layer of cellulose and an outer layer of pectose.
- Asexual reproduction is usually through zoospores.
- Common green alga include Spirogyra, Ulothrix, Chlamydomonas, Volvox and Chara.
- Volvox is called coenobium as well as rolling alga as it rotates during swimming
- Spirogyra is unbranched filamentous algae forms floating masses called pond scum with a sheath of mucilage occurs on the outside, which gives a silly touch and hence it is also known as mermaids tresses (or) water silk.
- Thaeophyceae contains chlorophyll ‘a’ and ‘c’ with other pigments such as Fucoxanthin, Flavoxanthin and β-carotenes, that possess mannitol and laminarin as the stored food material.
- The cell wall of brown alagae possess alginic acid along with cellulose
- Unicellular forms are generally absent
- The plant body possess large lamina with air vesicles to provide buoyancy and such giant forms of a algae-called kelps.
- Commonly found types are Laminaria (devil’s apron), Dictyota, Fucus, Sargassum (gully weed) and Ectocarpus.
- Laminaria and Fucus are a rich source of Iodine.
- Brown algae is popular for its production of alginic acid, which is used in emulsions
- Sargassus, Laminaria, Alaria are used as edible brown algae and as fodder.
- Red alae has pigments such as chlorophyll ‘a’ and ‘d’ with phycoerythrin and phycocyanin.
- Floridean starch is the reserve food material with the cellulosic cell wall.
- Red algae are found both on the surface of the water and also at great depths in the oceans.
- The only fresh water algae is Batrachospermum, which is grown well in aerated water.
- Commonly found red algae are Gelidium, Gracilaria, Porphyra, Polysiphonia.
- Agar is obtained from Gelidium, Gracillaria sp, which is a bacterial food.
- Polysiphonia is considered to be the one of the sources of bromine and also has anti bacterial properties.
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Part-5: View this video for the topic from 0:09 to 11:23
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