Algae, Biology tutorial

Introduction to Algae:

Algae exhibit great variety in size and structure. They are Colonical, unicellular, filamentous and thalloid in form. Few are microscopic, where as others are very big in size. They don't form complicated organs or tissues. The study of the ultra structure under electron microscope illustrates that blue-green algae have prokaryotic kind of cell like that of bacteria where as all other algae are eukaryotes.

Algal Morphology:

Morphologically, algae can be differentiated as unicellular, colonial, filamentous, heterotrichus, thalloid and polysiphoid forms. Instances of each of the kinds of algae are provided below.

Various Forms of Algae:

1. Unicellular Algae: Example Anacystis, Microcystis

2. Colonial Algae Microcystic, Volvox

3. Filamentions Algae Nostoc} blue-green algae Ulothrix, Oedogonium

4. Heterotrichous Algae Draparnaldiopsis Coleochaete, Ectocarpus

5. Thalloid Ulva Fucus} Brown algae

6. Polysiphonoid Polysiphonia (Red algae)

Distinctive Forms of Algae:

They are plain plants with no roots, stems and leaves. They possess Chlorophyll. Few have blue, yellow, brown and red pigments with chlorophyll. Majority are uni-cellular where as few are multicellular. Few sea weeds are large. They are mostly aquatic, with the few on damp soils and shady places instances are spirogyra, anabaena and Sargassum. Cell wall of algae is made up of true celloulose. Reserve carbohydrates are generally starch and not glycogen as in fungi.

Classification of Algae:

Categorization signifies grouping of organisms according to simulating in the characters. It is not farfetched but true that organisms illustrating similar life cycle, morphology, physiology and biochemistry are hereditarily associated from evolutionary point of view. Thus, Algae are categorized in classes. These are:

  • Cyanophyta (prokaryotic algae) or blue-green algae eg. Comprising Nostoc, An abaena, Oscillatoria.
  • Chlorophyta (algae) like Chlamydomonas, Spirogyra, Chlorella
  • Phaeophyta (brown algae) like Sargassum,Fucus, laminaria.
  • Xantophyta (yellow -green algae) like Vaucheria, Botrydium
  • Chrysophyta (Golden-Brown algae) eg. Synura, Mallomonas, Chromalina.
  • Euglenophyta (Euglenoids) eg. Euglena, Trachelommas.
  • Dinophyta (Dinoflagellates) e.g. Ceratium, Peridinum.
  • Crytophyta(Crytomanads) e.g. Crytomones, Chroomonas.
  • Bucillariophyta (Diatoms) eg. Diatoma, fragilaria.


Spirogyra the green algae belongs to family Chlorophyceae and order conjulaes or Zygnematales. It is cosmopolitan plant that forms tangled mass of filaments floratiny on inactive fresh water, particularly in ditches, ponds, springs and streams. Few species develop in running water. These species produce the short unicellular organ of attachment, known as hapteron, for anchorage on Sea weeds.

Structure of a Spirogyra:

Mature filament is unbranched and comprises of single row of identical cylindrical cells joined end to end. Cell wall is composed of Cellulose and pectin External cell wall is enclosed by mucilage, creating it shinny. Cyloplasm is the thin layer with spiral bands of chloroplast. Nucleus is suspended at centre by strands of Cytoplasm. Chloroplast has small nodular protoplasmic bodies known as pyrenoids. Starch grains are deposited around each pyrenoid.

External Features of Spirogyra:

Ecological Adaptation:

Algae range from Unicellar (microscopic) to large (macroscopic) thalloid forms creating in diversity of habitats approximately all over surface of earth. Wherever there is water, little moisture or water vapours, and light, though feeble. Algae are sure to come out as green, brown patch or yellow. When many kinds of algae grow together under alike natural situations identify as communities. Composition of the community is finds out by physical and chemical nature of habitat. In several cases, algal community points to us about nature of habitat, whether, it is rich or poor in nutrients or polluted etc., or we can say it serves as the ecological indicator.

Aquatic Algae:

Most of the algae grow in water; though, there are also sub-aerial algae. Depending on concentration of salts there are different types of water bodies, like sea water, fresh water brackish water, brine-salt lakes and salt pans. Their habitats these days may have several kinds of pollutants, such as extreme organic metal, pesticides, and heavy metals, industrial effluents that are created and dumped into them by man. This really affects algae and other organisms present in water.

Fresh Water Habitats:

Fresh water habitats include lakes, mountains streams, rivers, and temporary rainwater puddles. Examples of Algae find here comprise green algae such as diatoms, oedogonium, desmids, etc. In slow flowing rivers with rocky shores, one may discover several filamentous algae such as spirogyra, oedogonium. Surface of submerged rocks also illustrates epiphytic algae such as desmids and Cyanobacteria.

Marine Habitats:

Sea occupies largest number of algae together called as seaweed. Seacoast is sometimes flooded and exposed to sun due to feeds. Area between high tide and low tide level is called intertidal zone. Seaweed which grows in intertidal zone face alternate drying and wetting. They are also firmly joined to underlying rocks by means of hold fasts. Sometimes they may get disconnected and found flowing in open sea as in case of Sargasso Sea. Instance of seaweed comprise Sargassum wightii (brown algae), Turbinaria, gracilaria edulis

Special Attributes:

Algae are also located in special habitats where environmental situations are in severe like Brines and salt lakes where cyano bacteria (Anabaeria) and Unicellulal green alga Dunaliella can be situated; Thermal Regions (not water) thermal springs having temperatures ranging from 40º to 70 ºc) have alga such as Mastigocladus oscillareria, and Cyanobacteria; Polar Regions (very cold climate conditions) where Nostoc, oscillatoria, can be situated.

Soil and Sub aerial Algae:

Surface layers of soils give the favorable substratum when wet for development of several kinds of algas. Terrestrial algae such anabaena, play the major role as main colonizers on recently exposed areas. Subaerial algae get their water from moisture in air and grow if moisture is accessible. They are able of enduring drought like soil algae. One can see dark brown patches, at times with the velvety carpet such as cushions covering widely exposed surfaces of, finances, walls, asbestos, buildings roofs, rock surfaces and also tree trunks.

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