Green Algae

Green Algae

Green algae (plural: green alga) are photosynthetic seaweed that are distinguished by the presence of chlorophylls a and b as the major pigments, giving them a green color. Food is stored as starch within plastids. The Chlorophyta (chlorophytes) and Streptophyta, notably the Charophytes, are among them.

Green Seaweed Definition

Green algae (plural: green alga) are photosynthetic seaweed that are distinguished by the presence of chlorophylls a and b as the major pigments, giving them a green color. Food is stored as starch within plastids. The Chlorophyta (chlorophytes) and Streptophyta, notably the Charophytes, are among them.

The Prasinodermophyta and its unnamed sister, which includes the Chlorophyta and Charophyte/Streptophyta, comprise the green algae (singular: green alga). The land plants (Embryophytes) originated deep inside the Charophyte alga as the Zygnematophyceae’s sibling.[1][2][3] Some authors are beginning to include Embryophytes after discovering that they evolved within green algae.[2][4][5][6][7][many citations] The full clade, which contains both green algae and embryophytes, is known as the clade Viridiplantae and the kingdom Plantae. Green algae include unicellular and colonial flagellates, the majority of which have two flagella per cell, as well as colonial, coccoid, and filamentous forms, as well as macroscopic, multicellular seaweeds. There are over 22,000 different types of green algae.[8] Many species spend the majority of their lives in the wild.

Green Algae

A few different creatures rely on seaweed. to perform photosynthesis. The chloroplasts of Lepidodinium dinoflagellates, euglenas, and chlorarachniophytes were acquired from eaten green algae[9], and the latter maintain a nucleomorph (vestigial nucleus). Green algae are also found in the ciliate Paramecium, Hydra viridissima, and flatworms as symbiotic partners. Some green algae, particularly those of the genera Trebouxoid (class Trebouxiophyceae) and Trentepohlia (class Ulvophyceae), can form lichens through symbiotic relationships with fungi. In general, the fungal species that form lichens cannot survive on their own, but the algal species is frequently seen in nature without the fungus. Trentepohlia is a filamentous green alga that may survive on moist soil and rocks.

Why is it called green algae?

Photosynthetic algae known as “seaweed.” (plural: “green alga”) are distinguished by possessing chlorophylls a and b as the major pigments, which gives them their characteristic green color.

green algae

Is seaweed a plant or bacteria?

Algae are sometimes categorized as plants and other times as “protists,” which is a catch-all term for a collection of essentially unrelated creatures that are put together because they are not animals, plants, fungus, bacteria, or archaea’s.

Cellular structure

Green algae have chloroplasts that contain the accessory pigments beta carotene (red-orange) and xanthophyll (yellow) in stacked thylakoids, which give them their vivid green color.[12][13] Green algae’s cell walls are typically composed of cellulose, and they store carbohydrates in the form of starch.[14]

Mitochondria with flat cristae are found in all green algae. When paired flagella are present, they are employed to move the cell. They are held together by a cross-shaped network of microtubules and fibrous strands. Flagella are only found in the motile male gametes of charophytes[15], bryophytes, pteridophytes, cycads, and Ginkgo, but not in Pinophytes or flowering plants.

Closed mitosis is the most prevalent mode of cell division among members of the Chlorophyceae class.


Photosynthetic eukaryotes emerged from an initial endosymbiotic event in which a heterotrophic eukaryotic cell ingested a photosynthetic cyanobacterium-like prokaryote, which got stably integrated and evolved into a membrane-bound organelle called the plastid.[18] This first endosymbiosis event gave rise to three autotrophic plastid-containing clades: (green) plants (with chloroplasts), red algae (with rhodoplasts), and glaucophytes (with mitoplasts).

Evolution and classification

Green algae and their embryophyte offspring are sometimes grouped in the green plant clade Viridiplantae (or Chlorobionta). The supergroup Primo plantae, which also includes red algae and glaucophyte algae, is sometimes known as Archaeplastida or Plantae sense alto. A unicellular flagellate was the ancestor of green algae.[20]

The Viridiplantae family split into two clades. The Chlorophyta group includes the early diverging prasinophyte lineages as well as the core Chlorophyta, which contains the vast majority of known green algae species. Charophytes and terrestrial plants are members of the Streptophyta. The following is a consensual reconstruction of green algal connections based primarily on molecular evidence.

Evolution and classification

The Mesostigmatophyceae, Chlorokybophyceae, and Spirotaenia are all more typically basal Streptophyta.

Because the algae of this paraphyletic group “Charophyte” were previously included in Chlorophyta, green algae and Chlorophyta were synonyms in this definition. As the green algae clades are resolved further, the embryophytes, a deep charophyte branch, are either incorporated into “algae”, “green algae”, and “Charophytes”, or these terms are replaced by cladistic terminology such as Archaeplastida, Plantae/Viridiplantae, and Streptophyta, respectively.


Green algae are a class of photosynthetic eukaryotic organisms with haplobiontic and diplobiontic life cycles. Diplobiontic species, such as Ulva, have a reproductive cycle known as alternation of generations, in which two multicellular forms, haploid and diploid, alternate and may or may not be isomorphic (have the same morphology). Only the haploid generation, the gametophyte, is multicellular in haplobiontic species. The fertilized egg cell, the diploid zygote, goes through meiosis, producing haploid cells that will produce new gametophytes. Diplobiontic organisms have both a multicellular haploid generation and a multicellular diploid generation, which developed from haplobiontic predecessors. In this stage, the zygote divides repeatedly through mitosis and develops into a multicellular diploid sporophyte. By meiosis, the sporophyte produces haploid spores that germinate.

Probiotic green algae can be isomorphic or heteromorphic. The morphology of isomorphic algae is same in haploid and diploid generations. The appearance and size of gametophytes and sporophytes varies in heteromorphic algae.[33]

Fertilizations of a big non-motile cell by a smaller motile cell (zoogamy) differs from fusion of similar cells (isogamy). However, these characteristics vary, most notably among the basal green algae known as prasinophytes.

Haploid algal cells (which carry just one copy of their DNA) can unite to generate diploid zygotes. When filamentous algae do this, they construct bridges between cells and leave behind empty cell walls that may be seen under a light microscope. This is known as conjugation, and it occurs in situations such as

Sex pheromone

Although only a few model organisms have been studied in depth, sex pheromone production is most likely a common feature of green algae. Volvox is a chlorophyte genus. Various species form spherical colonies with up to 50,000 cells. Volvox carter (2,000 – 6,000 cells) is a well-studied species that lives in ephemeral pools of water that tend to dry out in the late summer heat. Asexual V. carter die fast when their habitat dries up. They are able to avoid death, however, by entering the sexual phase of their life cycle soon before drying, which results in the creation of latent desiccation-resistant zygotes. A glycoprotein pheromone initiates sexual development (Hellmann et al., 1998). This pheromone is one of the most powerful biological effector chemicals known to man.


Green algae, notably characean algae, have been used as model experimental organisms to study the processes of membrane ionic and water permeability, osmoregulation, turgor regulation, salt tolerance, cytoplasmic streaming, and action potential production.

Classification and Taxonomy

Algae are a paraphyletic group of creatures distinguishable from there groupings by their watery, photosynthetic, eukaryotic nature. They comprise a vast variety of creatures, ranging from unicellular to colonial to multicellular. Algae, in general, have chlorophyll but lack the real roots, stems, and leaves found in embryophytes. Algae are categorized further depending on the primary photosynthetic pigments. Green algae are distinguished from other kinds of algae by their greenish color, as opposed to red algae (Rhodophyta), brown algae (e.g. Phaeophyte), golden algae (Cryophyte), and blue-green algae (Cyanophyte). Green algae’s greenish color and photosynthetic capacity are linked to the quantity of chlorophylls a and b in their plastids. These pigments can be found in

classification and taxonomy

Sub-groups of green algae

The chlorophytes and charophytes are two types of green algae. Charophytes are green algae found mostly in freshwater, whereas chlorophytes are found primarily in saltwater. Green algae may also be found in terrestrial settings (such as soil, rocks, and trees).

The charophytes are more closely linked to the embryophytes, which include bryophytes and tracheophytes (vascular plants). Charophytes and embryophytes, unlike chlorophytes, have enzymes such as class I aldolase, Cu/Zn superoxide dismutase, glycolate oxidase, and flagellar peroxidase. In addition, charophytes, like embryophytes, utilize phragmoplasts during cell division. Thus, the charophytes, along with the embryophytes, form the clade Streptophyta.

General Characteristics

The following are some general features of green algae:

  • Forms: Green algae have many forms: unicellular, multicellular, or colonial. Unicellular green algae are solitary, single-celled photosynthetic organisms (e.g. Micrasterias sp.). Multicellular algae are those that appear filamentous or forming leaf-like thallus (Ulva sp.). Some of them form colonies, such as Volvox species.
  • Cell wall: The cell wall of a green algal cell is comprised chiefly of celloulso
  • Pigments: The chloroplast consists predominantly of green pigments, i.e. chlorophylls a and b. Other pigments present are the accessory pigments, beta-carotene, and xanthophyll’s. (1)
  • Stored food: They store photosynthetic products in the form of starch
  • Motility: Some green algae are flagellated. The flagella are usually two to three in number, located apically or sub-apically. The flagella are used for cell movement.
  • Reproduction and alternation of generations: Green algae may reproduce asexual and sexual

Evolution and Phylogeny

The following are the general characteristics of Green algae are thought to be the forefathers of land plants (Embryophyte). According to the endosymbiotic hypothesis, green algae evolved from previous eukaryotes that absorbed photosynthetic prokaryotes. The symbiotic relationship between the two primordial living forms resulted in the prokaryote being permanently incorporated within the host cell and eventually transforming the former into an organelle, namely the plastid. This event is also thought to have triggered the evolution of other autotrophic clades, such as red algae and glaucophytes. (2) Green algae, in turn, developed and are thought to have given rise to embryophytes, notably via the Phylum Charophyte.

Biological Importance

Aquatic creatures rely heavily on green algae for nourishment. They are an important source of starch, which they generate through photosynthesis. They are also an important source of atmospheric oxygen due to their photosynthetic activities. They form symbiotic alliances with other creatures. For example, they have been discovered to be closely related to the ciliate Paramecium. Trebouxoid spp., a green algae, forms lichens with fungus. Another example is Chlorella species creating symbiotic relationships with Hydra species.

What is called green algae?

Green algae are creatures that are distinguished by the presence of chlorophylls a and b as the primary photosynthetic pigments, starch stored inside the chloroplast as the primary storage product, and whiplash (smooth) flagella (e.g., Bold and Wynne, 1985).

Where is green algae found?

Green algae can be found freely floating in fresh water. The vast majority of species are minuscule and live in lakes, ponds, and streams. Large amounts of such algae may color a whole lake, making it seem like green paint. Green algae blooms are common in the early to mid-summer months.

Why is green algae important?

They are essential in aquatic settings because they create the energy foundation of the food chain for all aquatic animals. Algae, being autotrophic organisms, use photosynthesis to convert water and carbon dioxide into sugar.

What is another name for green algae?

Cyanobacteria, formerly known as blue-green algae, are photosynthetic microscopic organisms that are technically bacteria. They were originally called blue-green algae because dense growths often turn the water green, blue-green or brownish-green.

What causes green algae?

Algae may grow rapidly in streams with an excess of nitrogen and phosphorus, especially when the water is warm and the weather is calm. This proliferation causes algae blooms, which turn the water a noticeable green color, though other colors can occur.

Importance of Green Algae

fresh green algae

Green algae are an important food source for aquatic organisms. They are an essential source of starch, which they produce via photosynthesis. Because of their photosynthetic activity, they are a vital source as well of atmospheric oxygen. They form a symbiotic interaction with other creatures.

Effects of Green Algae

Exposure to high levels of blue-green algae and their toxins can cause diarrhea, nausea or vomiting; skin, eye or throat irritation; and allergic reactions or breathing difficulties. Animals that ingest huge volumes of water with blooms, scums, or benthic mats may become unwell or die. This can happen to pets and cattle.


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