What are Algae?


Algae Definition

Algae is a term that describes a large and incredibly diverse group of eukaryotic, photosynthetic lifeforms which includes multicellular seaweeds and unicellular diatoms. These organisms do not share a common ancestor and hence, are not related to each other (polyphyletic).

Most algae require a moist or watery environment, hence, they are very common near or inside water bodies. Anatomically, they are similar to another major group of photosynthetic organisms – the land plants. However, that is where the differences end as algae lack many structural components typically present in plants, such as true stems, shoots, and leaves. Furthermore, they also do not have vascular tissues to circulate essential nutrients and water throughout their body.

Types of Algae

There are many types of algae, however, these are some of the more prominent types:

  • Blue-green Algae

One of the most well-known types of algae is blue-green algae. Also called cyanobacteria, this type of algae is most commonly observed in dams, rivers, reservoirs, creeks, lakes and etc. This class of bacteria usually acts like a plant whereby, it obtains energy through the process of photosynthesis. Ecologically, blue-green algae are very important to the environment as it fixes the nitrogen in the soil. Hence, it is also called as nitrogen-fixing bacteria.

However, this type of algae can be toxic to human beings. They can either be neurotoxic(affects the respiratory or nervous system, causing paralysis) or hepatotoxic (causes the liver to fail). This type of bacteria is found in lichens, Anthoceros, etc.

Also Read: Rhizobium – The Nitrogen Fixing Bacteria

  • Red Algae

It is also called as Rhodophyta and is a distinctive type of species that are mostly found in the freshwater lakes. This eukaryotic algae also happens to be one of the oldest plant-like fossils ever discovered, dating back to more than 1.6 billion years ago. The color of red algae is attributed to the pigments phycocyanin and phycoerythrin. The other pigments within it include chlorophyll A. They lack chlorophyll B or beta-carotene.

Extended Reading: Red Algae

  • Green Algae

It is a large group of bacteria that help other organisms to undergo photosynthesis. Green algae have primary pigments such as chlorophyll A and B, along with auxiliary pigments such as xanthophylls and beta carotene. Members are unicellular and colonial flagellates. Prominent examples of green algae include Paramecium, hydra, etc.

Extended Reading: Chloroplasts

Characteristics of Algae

Typically, general characteristics of algae are common to plants as well as animals.

For instance, algae can photosynthesize like plants, and they possess specialized structures and cell-organelles including centrioles and flagella found only in animals. Listed below are some of the general characteristics of algae.

  • Algae are photosynthetic organisms.
  • Algae can be either unicellular or multicellular organisms.
  • Algae lack a well-defined body, so, structures like roots, stems or leaves are absent.
  • Algaes are generally found in the tissues of other plants or on the rocks in the moist places.
  • Reproduction in algae occurs in both asexual and sexual forms. Asexual reproduction occurs by spore formation.
  • Most of them are generally found in water and are aquatic in nature, especially plankton. These are of a free-floating type.

Examples of Algae

Prominent examples of algae include:

  • Nostoc
  • Fucus
  • Diatoms
  • Spirogyra

Other less, well-known examples of algae include:

  • Microcystis
  • Duckweed
  • Pandorina

Algal Biofuel

Recent developments in science and technology have led to algae being used as an alternate source of fuel. Algal biofuel or algae fuel is an increasingly viable alternative to traditional fossil fuels. It is used to produce everything from “green” diesel to “green” jet fuel. It is similar to the other biofuels made from corn and sugar-cane.

Further Reading:

Difference Between Algae And Fungi



Questions on Algae

1. What are Algae?

Algae is a large, diverse group of eukaryotic, photosynthetic organisms that are not necessarily related to each other.

2. How are algae different from traditional plants?

Unlike traditional plants, algae do not have true roots, stems, and leaves. Hence, they need to be near a moist or watery environment to survive. In other words, they do not possess vascular tissue necessary for conduction of water and minerals.

3. Briefly outline the types of algae.

Algae are primarily classified into the following types:

  • Blue-green Algae
  • Red Algae
  • Green Algae

4. State the major characteristics of algae.

  • Either unicellular or multicellular organisms
  • Found in moist places.
  • Reproduction occurs sexually and sexually.
  • Asexual reproduction occurs by spore formation.
  • Lacks a well-defined body.
  • They are photosynthetic in nature.

5. State 4 examples of algae.

  • Nostoc
  • Spirogyra
  • Diatoms
  • Duckweed

For more detailed information about Algae and its characteristics features, explore BYJU’S Biology.

Practise This Question

Your elbows move similar to the opening and closing of a door. This is because of ______________ joints.

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