Algae is a highly diverse class of organisms capable to adapt and grow in a variety of ecosystems. They are  aquatic organisms able to synthesize their own food through photosynthesis. However, they are not the plants in a true sense because they do not contain an organized system of leaves, stems or green parts as we see in plants. Although some algae is useful, excessive growth of algae in the food, drinks and many baking items are potentially dangerous. There are approximately 7000 algae species that dwell in a variety of habitats across the world.  This article intends to delineate the structure, functions, uses and types of algae.


Definition of algae

The word algae- plural form of alga resembling plants in many ways, however, they are not the real plants.  “Algae is a term that describes a large and incredibly diverse group of eukaryotic photosynthetic life forms. These organisms do not share a common ancestor hence, they are not related to each other (polyphyletic).” Most of the algae are unicellular flagellates or amoeboids, but many complex colonial and nonmotile forms have been evolved independently into several groups. Different algae is characterized by their wide variation in the morphological features.

Types of algae 

The algae is classified based on their structure, colonization, and other characteristics. Colonial algae are spread across small and regular groups of motile cells. Capsid ones are individual, non-motile cells embedded in coat of mucilage(a polysaccharide substance extracted as a viscous or gelatinous solution from algae). Coccoid type of algae are the individual non-motile cells enclosed by their cell walls. On the other hand, palmelloid algae are nonmotile cells embedded within the mucilaginous substance. Filamentous algae  contains a string of non-motile cells connected together with or without branching. Parenchymatous algae are the cells forming a thallus with partial differentiation of tissues.


Characteristic features of algae

  1. One of the unique differences between the plants and algae is that they lack typical roots, stems, leaves, and a proper vascular system to circulate water and nutrients , but still they are photosynthetic organisms as they contain chlorophyll.

  2. There are innumerable variations in the species of algae as they range from single-celled organisms to giant kelps measuring up to 60 meters.

  3. Specific types of algae are bred in a range of both freshwater and saltwater aquatic habitats.

  4. Algae possess the morphology of both prokaryotic organisms (like cyanobacteria) and also eukaryotic organisms (blue-green algae).

  5. Algae has an ability to photosynthesize like many other plants. Photosynthesis is supported by the fact that they have the necessary photosynthetic organelles and most algae are photoautotrophs (as they use light energy to generate nutrients).

  6. Algae can be found in both unicellular and multicellular forms.

  7. Reproduction in algae occurs by both asexual and sexual modes where Asexual reproduction happens through spore formation.

  8. Algae are independent and free-living organisms, however, some of them can develop a symbiotic relationship with the other organisms.


Classification of Algae

Although Algae is classified in many ways, the principal classification is based on their color due to their pigments. Based on the pigments, 3 main varieties of algae are Chlorophyceae, Phaeophyceae, and Rhodophyceae.



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  1. Chlorophyceae is also known as green algae, as they contain green pigments with  chlorophyll-a and b, a classical  example for yhese is, Chlamydomonas and Spirogyra,

  2. Phaeophyceae are also known as brown algae exist in the marine ecosystems. They have chlorophyll- a, and c, carotenoids and xanthophyll pigments. For example, Dictyota, Laminaria, and Sargassum.

  3.  Rhodophyceae are the red algae because of their red -coloured pigment. For example, Porphyra, Gracilaria, and Gelidium.


Importance of Algae

Algae is richly used  in food industry, however, they are also useful to manufacture fodder, pisciculture products, and fertilizers. Uses of algae in different settings are ;

  1. Food industry: Algae are the rich source of many nutrients as they can provide a balanced food containing carbohydrates, fats, proteins, and vitamins A, B, C, and E. Micronutrients such as iron, potassium, magnesium, calcium, manganese, and zinc are also abundantly found in many algae. In many countries, algae have been used as a supplement in the form of powders and snacks. However, the risk of food poisoning is high as most of these are prepared by artificially processing and packing.

  2. Fertilizers: Algae are rich in minerals and vitamins hence they are also used as liquid fertilizers that fix nitrogen present in the soil.

  3. Reclaiming Alkaline: Blue-Green Algae helps in balancing the alkalinity of the soil so that  it can enhance the productivity.

  4. Binding Agent: Algal biomass has proved to be an effective binding agent for Miscanthus, with a significant increase in the compressive strength with discs composed of at least 20 % algae. At this percentage, the calorific value or glucose content of algae doesn't decrease.

  5. Biological indicator: Algae are so sensitive organisms that they are capable of reacting to even slight pollution . Therefore, they are used to keep a check on water pollution (ex, Algae like Euglena and Chlorella).

  6. Fodder: Many algae are preferred to feed livestock such as cattle and chickens.

  7. Pisciculture: In fish farming, feeding with algae helps in the mass production process. They also help in maintaining the health of the marine ecosystem as they have the ability to naturally absorb the carbon dioxide to return the oxygen into the water.



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Check your understanding

  1. Why do we call an alga is a biological indicator?

  2. Name any 4 common algae types.

  3. Explain the structure of a typical alga.

  4. Where is algae commonly found in trees?




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