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Green algae: what are they, characteristics, types and examples

Green algae are a whole group of living beings that comprise more than 10,000 species spread throughout the world. These are organisms of fresh and salt water that are of great importance, as they are closely related to terrestrial plants.

Surely you have seen them many times when bathing in rivers and beaches or in nature documentaries, but if you want to learn more about these aquatic living beings, then join us in this Green Ecology article in which we talk in detail about what green algae are. , their characteristics, types and examples

What are green algae

If we refer to the taxonomy of green algae , these are part of the Plantae kingdom and the Viridiplantae sub- kingdom . Two clades or divisions are distinguished between them, among which are the Chlorophyta and the Charophyta .

  • Chlorophytes are formed by marine filamentous green algae, epiphytes, unicellular algae and flagellates, among others.
  • The charofíceas comprise mainly freshwater algae, with terrestrial environments and plants.

As far as the classification of green algae is concerned, they can be differentiated by their reproduction, their biological cycles or their types. We will see all these ways of classifying them in detail a little further down. In addition, to learn more about these organisms, we advise you to read this other article about the Classification of algae .

Characteristics of green algae

In summary, these are the main characteristics of green algae :

  • The main and most distinctive characteristic of green algae is that they present chlorophyll of type a and b in their structures. These pigments are responsible for giving them the green color by which they are usually called, although some of them may have other pigments.
  • Thanks to chlorophyll they can carry out photosynthesis , which allows them to extract biochemical energy from sunlight and water.
  • The vast majority of them are freshwater , whether you are dealing with unicellular or multicellular green algae. The habitat of green algae of this type usually consists of terrestrial areas with high humidity already covered from direct sun, as well as rocks, trees or even snow banks and, sometimes, they are also in symbiotic association, giving rise to lichens .
  • If we look at the different forms of reproduction of green algae , we find four main types: hologamy, conjugation, planogamy and oogamy.

Reproduction of green algae

  • Those that reproduce by hologamy, which are mainly unicellular green algae . In this reproduction, all the green algae acts as a gamete, and merges with another of the same.
  • Those that reproduce by conjugation, which is very common in filamentous green algae. In this type of reproduction, the subjects have two filaments in parallel, one male and the other female. Later, they give rise to tubes between the two filaments, through which the male sends the cellular material to the female, which will form a zygospore.
  • The method of reproduction by planogamy is given by gametes with mobile capacity promoted by flagella.
  • Finally, reproduction by oogamy occurs when the female gamete does not have a flagellum and is therefore immobile.

Types of green algae with examples

These are the types of existing green algae :

  • Chlorophyta.
  • Prasinophytina.
  • Chlorophytin.
  • Charophyta.
  • Coleochaetales.
  • Chlorokybophyceae.
  • Charophyceae.
  • Klebsormidiophyceae.
  • Mesostigmatophyceae.
  • Zygnematophyceae.

Chlorophyta

They are the most numerous, with around 8,000 species. They store starch in their plastids and include both multicellular and unicellular species. They inhabit both fresh and marine waters and, even, terrestrial areas of high humidity and have a haplodiploon life cycle. They are classified into two main types: the Prasinophytina and the Chlorophytina.

Prasinophytina

These are microscopic, flagellated, single-celled green algae. They are from marine environments and are currently considered primitive, very simple organisms.

Chlorophytin

These are multicellular green algae that are characterized by developing phycoplasts, their own microtubules.

As examples, some names of chlorophytic green algae are the Mamiellophyceae (Prasinophytina), the Chlorophyceae (Chlorophytina) and the Pedinophyceae (Chlorophytina).

Charophyta

These algae are the closest ancestors to land plants. They have calcified cell walls, with cellulose, chlorophyll a and b, starch, xanthophyll and carotene. They are of both fresh and brackish waters.

Coleochaetales

These are filamentous green algae of the discoidal type, which grow from the edges of the disk itself. They are aquatic and reproduce both asexually by zoospores and sexual by oogamy.

Chlorokybophyceae

These are made up of a single species of algae, Chlorokybus atmophyticus, a unicellular green algae of terrestrial habitat that can be found in alpine areas.

Charophyceae

Also commonly called caral algae, they are free-living organisms that can be found in fresh waters. They can reach sizes of up to 60 cm, being the only ones in the Charophyta that reach this size.

Klebsormidiophyceae

These carophytes comprise only 3 genera of multicellular algae with unbranched filaments. They are the Entransia, the Hormidiella and the Klebsormidium.

Mesostigmatophyceae

Here we find a single genus of unicellular algae, the Mesostigma, with a single species as well, the freshwater M. viride Lauterborn.

Zygnematophyceae

In the latter type we find both unicellular and multicellular freshwater algae. They reproduce by conjugation or by isogamy, and are closely related to land plants.

Importance of green algae

To briefly talk about the great importance of green algae , we highlight these aspects:

  • Green algae played a key role in the evolution of plant organisms , first colonizing aquatic environments to later give way to the development of terrestrial plants. Here you can learn more about the Origin and evolution of plants .
  • In addition, they are part of the base of the food chain in aquatic and some terrestrial ecosystems and, in addition, they are producers of oxygen through photosynthesis.
  • Currently, the pharmaceutical and food industries cultivate and use them both for their medicinal and nutritional properties, and they are foods of great nutritional value and with a very beneficial impact on human health.

If you want to learn more about green and other algae, as well as their relationship with plants, we recommend this other AgroCorrn article about Similarities and differences between plants and algae .

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