Algae

algaalgalfilamentous algaeseaweedalgæmicroalgaeAlgal bedalgal growthalgologistpond scum
Algae (singular alga ) is an informal term for a large, diverse group of photosynthetic eukaryotic organisms that are not necessarily closely related, and is thus polyphyletic.wikipedia
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Diatom

diatomsBacillariophyceaeBacillariophyta
Included organisms range from unicellular microalgae, such as Chlorella and the diatoms, to multicellular forms, such as the giant kelp, a large brown alga which may grow up to 50 m in length. Throughout the 20th century, most classifications treated the following groups as divisions or classes of algae: cyanophytes, rhodophytes, chrysophytes, xanthophytes, bacillariophytes, phaeophytes, pyrrhophytes (cryptophytes and dinophytes), euglenophytes, and chlorophytes.
Diatoms (diá-tom-os 'cut in half', from diá, 'through' or 'apart'; and the root of tém-n-ō, 'I cut'.) are a major group of algae, specifically microalgae, found in the oceans, waterways and soils of the world.

Photosynthesis

photosyntheticphotosynthesizephotosynthesizing
Algae (singular alga ) is an informal term for a large, diverse group of photosynthetic eukaryotic organisms that are not necessarily closely related, and is thus polyphyletic.
Most plants, most algae, and cyanobacteria perform photosynthesis; such organisms are called photoautotrophs.

Polyphyly

polyphyleticdiphyleticpolyphyletic group
Algae (singular alga ) is an informal term for a large, diverse group of photosynthetic eukaryotic organisms that are not necessarily closely related, and is thus polyphyletic.
Other polyphyletic groups are for example algae, C4 photosynthetic plants, and edentates.

Multicellular organism

multicellularmulticellular organismsmulticellularity
Included organisms range from unicellular microalgae, such as Chlorella and the diatoms, to multicellular forms, such as the giant kelp, a large brown alga which may grow up to 50 m in length.
All species of animals, land plants and most fungi are multicellular, as are many algae, whereas a few organisms are partially uni- and partially multicellular, like slime molds and social amoebae such as the genus Dictyostelium.

Green algae

green algagreengreen algal
Green algae are examples of algae that have primary chloroplasts derived from endosymbiotic cyanobacteria. Some unicellular species of green algae, many golden algae, euglenids, dinoflagellates, and other algae have become heterotrophs (also called colorless or apochlorotic algae), sometimes parasitic, relying entirely on external energy sources and have limited or no photosynthetic apparatus.
The green algae (singular: green alga) are a large, informal grouping of algae consisting of the Chlorophyta and Charophyta/Streptophyta, which are now placed in separate divisions, as well as the potentially more basal Mesostigmatophyceae, Chlorokybophyceae and Spirotaenia.

Chloroplast

chloroplastschloroplast stromaplastoglobuli
Green algae are examples of algae that have primary chloroplasts derived from endosymbiotic cyanobacteria.
Chloroplasts are organelles that conduct photosynthesis, where the photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, and stores it in the energy-storage molecules ATP and NADPH while freeing oxygen from water in plant and algal cells.

Chlorophyll

chlorophyllschlorophyll ''aLeaf green
One definition is that algae "have chlorophyll as their primary photosynthetic pigment and lack a sterile covering of cells around their reproductive cells".
Chlorophyll (also chlorophyl) is any of several related green pigments found in the mesosomes of cyanobacteria, as well as in the chloroplasts of algae and plants.

Plastid

plastidsproplastidproplastids
Algae constitute a polyphyletic group since they do not include a common ancestor, and although their plastids seem to have a single origin, from cyanobacteria, they were acquired in different ways.
The plastid (Greek: πλαστός; plastós: formed, molded – plural plastids) is a membrane-bound organelle found in the cells of plants, algae, and some other eukaryotic organisms.

Organism

organismsflora and faunaliving organisms
Algae (singular alga ) is an informal term for a large, diverse group of photosynthetic eukaryotic organisms that are not necessarily closely related, and is thus polyphyletic.
Eukaryotic organisms are characterized by the presence of a membrane-bound cell nucleus and contain additional membrane-bound compartments called organelles (such as mitochondria in animals and plants and plastids in plants and algae, all generally considered to be derived from endosymbiotic bacteria).

Autotroph

autotrophicautotrophsautotrophy
Most are aquatic and autotrophic and lack many of the distinct cell and tissue types, such as stomata, xylem, and phloem, which are found in land plants.
They are the producers in a food chain, such as plants on land or algae in water (in contrast to heterotrophs as consumers of autotrophs).

Rhizoid

rhizoidsrhiziods
Algae lack the various structures that characterize land plants, such as the phyllids (leaf-like structures) of bryophytes, rhizoids in nonvascular plants, and the roots, leaves, and other organs found in tracheophytes (vascular plants).
Rhizoids are protuberances that extend from the lower epidermal cells of bryophytes and algae.

Phycology

phycologistalgologistalgology
Accordingly, the modern study of marine and freshwater algae is called either phycology or algology, depending on whether the Greek or Latin root is used.
Phycology (from Greek φῦκος, phykos, "seaweed"; and -λογία, -logia) is the scientific study of algae.

Asexual reproduction

asexualasexuallyreproduce asexually
Algae exhibit a wide range of reproductive strategies, from simple asexual cell division to complex forms of sexual reproduction.
Multiple fission at the cellular level occurs in many protists, e.g. sporozoans and algae.

Macrocystis pyrifera

giant kelpBladder kelpkelp
Included organisms range from unicellular microalgae, such as Chlorella and the diatoms, to multicellular forms, such as the giant kelp, a large brown alga which may grow up to 50 m in length.
M. pyrifera is the largest of all algae.

William Henry Harvey

Harv.HarveyW.H.Harvey
W.H.Harvey (1811–1866) and Lamouroux (1813) were the first to divide macroscopic algae into four divisions based on their pigmentation.
William Henry Harvey, FRS FLS (5 February 1811 – 15 May 1866) was an Irish botanist and phycologist who specialised in algae.

Purple sulfur bacteria

Chromatialespurple sulfurpurple
Algae have photosynthetic machinery ultimately derived from cyanobacteria that produce oxygen as a by-product of photosynthesis, unlike other photosynthetic bacteria such as purple and green sulfur bacteria.
Unlike plants, algae, and cyanobacteria, purple sulfur bacteria do not use water as their reducing agent, and therefore do not produce oxygen.

Golden algae

Chrysophyceaechrysophytegolden alga
Some unicellular species of green algae, many golden algae, euglenids, dinoflagellates, and other algae have become heterotrophs (also called colorless or apochlorotic algae), sometimes parasitic, relying entirely on external energy sources and have limited or no photosynthetic apparatus. Throughout the 20th century, most classifications treated the following groups as divisions or classes of algae: cyanophytes, rhodophytes, chrysophytes, xanthophytes, bacillariophytes, phaeophytes, pyrrhophytes (cryptophytes and dinophytes), euglenophytes, and chlorophytes.
The Chrysophyceae, usually called chrysophytes, chrysomonads, golden-brown algae or golden algae are a large group of algae, found mostly in freshwater.

Seaweed

macroalgaeseaweedssea weed
The largest and most complex marine algae are called seaweeds, while the most complex freshwater forms are the Charophyta, a division of green algae which includes, for example, Spirogyra and stoneworts.
Seaweed, or macroalgae, refers to several species of macroscopic, multicellular, marine algae.

Brown algae

brown algaPhaeophyceaebrown
Included organisms range from unicellular microalgae, such as Chlorella and the diatoms, to multicellular forms, such as the giant kelp, a large brown alga which may grow up to 50 m in length. Throughout the 20th century, most classifications treated the following groups as divisions or classes of algae: cyanophytes, rhodophytes, chrysophytes, xanthophytes, bacillariophytes, phaeophytes, pyrrhophytes (cryptophytes and dinophytes), euglenophytes, and chlorophytes.
The brown algae (singular: alga), comprising the class Phaeophyceae, are a large group of multicellular algae, including many seaweeds located in colder waters within the Northern Hemisphere.

Cryptomonad

cryptophytescryptomonadsCryptophyta
Throughout the 20th century, most classifications treated the following groups as divisions or classes of algae: cyanophytes, rhodophytes, chrysophytes, xanthophytes, bacillariophytes, phaeophytes, pyrrhophytes (cryptophytes and dinophytes), euglenophytes, and chlorophytes.
The cryptomonads (or cryptophytes) are a group of algae, most of which have plastids.

Cyanobacteria

blue-green algaecyanobacteriumblue green algae
Algae have photosynthetic machinery ultimately derived from cyanobacteria that produce oxygen as a by-product of photosynthesis, unlike other photosynthetic bacteria such as purple and green sulfur bacteria. Throughout the 20th century, most classifications treated the following groups as divisions or classes of algae: cyanophytes, rhodophytes, chrysophytes, xanthophytes, bacillariophytes, phaeophytes, pyrrhophytes (cryptophytes and dinophytes), euglenophytes, and chlorophytes. Although cyanobacteria are often referred to as "blue-green algae", most authorities exclude all prokaryotes from the definition of algae.
Cyanobacteria, which are prokaryotes, are also called "blue-green algae", though some modern botanists restrict the term algae to eukaryotes.

Dinoflagellate

dinoflagellatesDinoflagellataPyrrhophyta
Some unicellular species of green algae, many golden algae, euglenids, dinoflagellates, and other algae have become heterotrophs (also called colorless or apochlorotic algae), sometimes parasitic, relying entirely on external energy sources and have limited or no photosynthetic apparatus. Throughout the 20th century, most classifications treated the following groups as divisions or classes of algae: cyanophytes, rhodophytes, chrysophytes, xanthophytes, bacillariophytes, phaeophytes, pyrrhophytes (cryptophytes and dinophytes), euglenophytes, and chlorophytes.
The dinoflagellates (Greek δῖνος dinos "whirling" and Latin flagellum "whip, scourge") are a classification subgroup of protista.They are a large group of flagellate eukaryotes that constitute the phylum Dinoflagellata.

Jean Vincent Félix Lamouroux

J.V.LamourouxLamourouxJ.V. Lamouroux
W.H.Harvey (1811–1866) and Lamouroux (1813) were the first to divide macroscopic algae into four divisions based on their pigmentation.
Jean Vincent Félix Lamouroux (3 May 1779 – 26 March 1825) was a French biologist and naturalist, noted for his seminal work with algae.

Marine biology

marinemarine biologistmarine life
In 1768, Samuel Gottlieb Gmelin (1744–1774) published the Historia Fucorum, the first work dedicated to marine algae and the first book on marine biology to use the then new binomial nomenclature of Linnaeus.
In 1768, Samuel Gottlieb Gmelin (1744–1774) published the Historia Fucorum, the first work dedicated to marine algae and the first book on marine biology to use the then new binomial nomenclature of Linnaeus.

Protist

ProtistaprotistsProtoctista
With the abandonment of plant-animal dichotomous classification, most groups of algae (sometimes all) were included in Protista, later also abandoned in favour of Eukaryota.
The protists do not form a natural group, or clade, since they exclude certain eukaryotes with whom they share a common ancestor; but, like algae or invertebrates, the grouping is used for convenience.