Name: green algae: forms, habitats, and roles
Uploaded: 2025-06-13T06:15:05.000Z
Duration: 1 min 21 s
Channel: JoVE

As algas verdes pertencem ao filo Chlorophyta no reino Archaeplastida.Sua tonalidade verde se deve aos cloroplastos contendo clorofila a e b.Eles habitam solo úmido, água doce e ambientes marinhos ou existem como simbiontes em líquenes.Algumas espécies de Trebouxia da Antártida são fototróficos endolíticos capazes de viver dentro de rochas porosas contendo quartzo.As algas verdes são morfologicamente diversas. Eles são categorizados em dois grupos principais - clorofitas, como as microscópicas Chlamydomonas, e carófitas, os parentes mais próximos das plantas terrestres, como a macroscópica Chara.Outros exemplos notáveis incluem Ostreococcus unicelular, Micrasterias multilobadas unicelulares, Dunaliella flagelada e Spirogyra filamentosa.As espécies de Scenedesmus existem como pacotes de quatro células, enquanto as espécies de Ulva formam grandes estruturas multicelulares semelhantes a algas marinhas.As espécies de Volvox formam colônias compreendendo várias células flageladas.Curiosamente, Botryococcus braunii é conhecido por produzir biocombustível. Mas, a produção em larga escala ainda é um desafio.

principais filos de algas

Green Algae

As algas verdes, tamb&#233;m conhecidas como clor&#243;fitas, diferenciam-se das algas vermelhas por possu&#237;rem cloroplastos com clorofilas a e b, que lhes conferem a colora&#231;&#227;o verde caracter&#237;stica. No entanto, elas n&#227;o possuem ficobiliprote&#237;nas, o que impede o desenvolvimento da pigmenta&#231;&#227;o vermelha ou azul-esverdeada observada nas algas vermelhas. Em termos de composi&#231;&#227;o de pigmentos fotossint&#233;ticos, as algas verdes se assemelham bastante &#224;s plantas e compartilham uma rela&#231;&#227;o evolutiva pr&#243;xima com elas. Taxonomicamente, as algas verdes pertencem ao filo Chlorophyta, dentro do reino Archaeplastida.
As algas verdes s&#227;o divididas em dois grupos principais: as clor&#243;fitas, como as microsc&#243;picas Chlamydomonas e Dunaliella, e as car&#243;fitas, como Chara, que s&#227;o macrosc&#243;picas e muitas vezes se assemelham a plantas terrestres. Este &#250;ltimo grupo &#233; considerado o parente mais pr&#243;ximo das plantas terrestres. A maioria das algas verdes &#233; encontrada em ambientes de &#225;gua doce, embora algumas habitem solos &#250;midos ou at&#233; cres&#231;am na neve, conferindo uma tonalidade rosada ao ambiente. Outras existem como simbiontes em l&#237;quens. Morfologicamente, as clor&#243;fitas apresentam uma ampla variedade de formas, desde organismos unicelulares at&#233; estruturas filamentosas, onde as c&#233;lulas est&#227;o dispostas linearmente, e arranjos coloniais, onde as c&#233;lulas se agregam. Algumas algas verdes atingem formas multicelulares, como a alga marinha Ulva. O ciclo de vida da maioria das algas verdes &#233; complexo, incorporando est&#225;gios reprodutivos tanto sexuados quanto assexuados.
Entre os menores eucariontes conhecidos est&#225; a alga verde Ostreococcus tauri, uma esp&#233;cie unicelular comum no fitopl&#226;ncton marinho. Com di&#226;metro celular de aproximadamente 2 micr&#244;metros, O. tauri possui o menor genoma conhecido entre os eucariontes fototr&#243;ficos, com cerca de 12,6 milh&#245;es de pares de bases. Devido ao seu conte&#250;do gen&#244;mico m&#237;nimo, Ostreococcus tem sido usado como organismo modelo para o estudo da redu&#231;&#227;o e especializa&#231;&#227;o gen&#244;mica em eucariontes.
No n&#237;vel colonial de organiza&#231;&#227;o, destacam-se algas verdes como Volvox, que formam col&#244;nias compostas por v&#225;rias centenas de c&#233;lulas flageladas. Algumas dessas c&#233;lulas atuam principalmente na fotoss&#237;ntese, enquanto outras se especializam na reprodu&#231;&#227;o. As c&#233;lulas individuais da col&#244;nia de Volvox permanecem conectadas por finas faixas citoplasm&#225;ticas, permitindo o movimento coordenado da col&#244;nia como um todo. Volvox &#233; amplamente estudado como organismo modelo para compreender os mecanismos gen&#233;ticos envolvidos na multicelularidade e na divis&#227;o de trabalho entre c&#233;lulas em organismos multicelulares.
Certas algas verdes coloniais mostram potencial promissor como fontes de biocombust&#237;vel. A esp&#233;cie Botryococcus braunii, por exemplo, secreta hidrocarbonetos de cadeia longa (C30&#8211;C36) com consist&#234;ncia semelhante &#224; do petr&#243;leo bruto. Aproximadamente 30 % do peso seco celular de B. braunii consiste desses hidrocarbonetos, gerando grande interesse em seu potencial como fonte renov&#225;vel de petr&#243;leo. Pesquisas com biomarcadores sugerem que algumas reservas de petr&#243;leo existentes podem ter se originado de antigas algas verdes, como B. braunii, que se depositaram em leitos de lagos pr&#233;-hist&#243;ricos. Se os desafios associados &#224; produ&#231;&#227;o comercial em larga escala de petr&#243;leo de algas forem superados, as algas verdes poder&#227;o contribuir para o suprimento global de petr&#243;leo por meio da fotoss&#237;ntese.
Algumas algas verdes s&#227;o capazes de viver dentro de rochas, uma caracter&#237;stica que as classifica como fototr&#243;ficas endol&#237;ticas. Esses organismos habitam rochas porosas, especialmente aquelas que cont&#234;m quartzo, e geralmente formam camadas pr&#243;ximas &#224; superf&#237;cie da rocha. Comunidades fototr&#243;ficas endol&#237;ticas s&#227;o comuns em ambientes extremos, como desertos ou regi&#245;es frias e &#225;ridas da Ant&#225;rtica. Nos Vales Secos de McMurdo, onde temperaturas e n&#237;veis de umidade s&#227;o extremamente baixos, a vida dentro das rochas oferece vantagens significativas. O sol aquece a rocha, enquanto o derretimento da neve fornece uma fonte confi&#225;vel de umidade. Al&#233;m disso, quando as rochas porosas absorvem &#225;gua, tornam-se mais transparentes, permitindo maior penetra&#231;&#227;o de luz para sustentar as camadas de algas em seu interior.
Uma variedade diversificada de organismos fototr&#243;ficos pode formar comunidades endol&#237;ticas, incluindo cianobact&#233;rias e diversas algas verdes. Al&#233;m de existirem como fototr&#243;ficos de vida livre, as algas verdes e as cianobact&#233;rias frequentemente formam rela&#231;&#245;es simbi&#243;ticas com fungos, contribuindo para comunidades de l&#237;quens endol&#237;ticos. A atividade metab&#243;lica e o crescimento dessas comunidades microbianas que habitam rochas contribuem para o intemperismo gradual das superf&#237;cies rochosas. Com o tempo, pequenas fissuras se formam, permitindo a entrada de &#225;gua, que ao congelar expande, provocando o rachamento adicional da rocha. Esse processo cria novos habitats para a coloniza&#231;&#227;o microbiana e contribui para a degrada&#231;&#227;o da rocha em solo primitivo, que, sob condi&#231;&#245;es favor&#225;veis, pode sustentar o desenvolvimento da vida vegetal e animal.

Principais filos de algas

As algas verdes, tamb&#233;m conhecidas como clor&#243;fitas, diferenciam-se das algas vermelhas por possu&#237;rem cloroplastos com clorofilas a e b, que ...

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Microbial Diversity

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green algae: forms, habitats, and roles

Green algae are photosynthetic organisms with chlorophylls a and b in their chloroplasts. These pigments give them a green color. They differ from red algae because they lack phycobiliproteins, the pigments that produce red or blue-green tones in red algae. In pigment makeup, green algae are close to plants, and they share a close evolutionary relationship with them.

Green algae belong to Phylum Chlorophyta in the Kingdom Archaeplastida. They are usually divided into two main groups: chlorophytes and charophytes. Chlorophytes include microscopic species such as Chlamydomonas and Dunaliella. Charophytes, such as Chara, are often larger and can look like land plants. Charophytes are considered the closest relatives of land plants.

Most green algae live in freshwater, but some grow in moist soil or even in snow, where they can tint the surroundings pink. Others live as symbionts in lichens. Their body forms vary widely. Some are unicellular, some are filamentous with cells arranged in a line, and some form colonies. A few, such as Ulva, are multicellular.

The life cycle of most green algae includes both sexual and asexual stages. Ostreococcus tauri is one of the smallest known eukaryotes. It is a unicellular marine phytoplankton species with a cell diameter of about 2 micrometers. It also has the smallest genome of any known phototrophic eukaryote, at about 12.6 million base pairs. Because of its small genome, Ostreococcus is used to study genome reduction and specialization in eukaryotes.

Volvox is a well-known colonial green alga. Its colonies contain several hundred flagellated cells. Some cells focus on photosynthesis, while others specialize in reproduction. Thin cytoplasmic strands connect the cells and help the colony move together. Volvox is a model organism for studying multicellularity and the division of labor among cells.

Some colonial green algae may also be useful as biofuel sources. Botryococcus braunii produces long-chain hydrocarbons, from C30 to C36, that are similar to crude oil. About 30 percent of its dry cell weight is made of these hydrocarbons. This has led to interest in green algae as a possible renewable petroleum source. Biomarker studies also suggest that some petroleum reserves may have come from ancient green algae such as B. braunii that settled in prehistoric lakebeds.

Some green algae live inside rocks, where they are called endolithic phototrophs. They are often found in porous rocks, especially quartz-containing rocks, and usually grow in layers near the surface. These communities are common in harsh places such as deserts and the cold, dry regions of Antarctica. In the McMurdo Dry Valleys, rocks can provide warmth, moisture from snowmelt, and, when wet, more light for the algae inside.

Endolithic communities can include cyanobacteria, green algae, and fungi that form lichens. As these rock-dwelling microbes grow and carry out metabolism, they slowly weather the rock surface. Small gaps form, water enters, freezes, and expands. This cracks the rock further and creates new spaces for colonization. Over time, the rock breaks down into primitive soil that can support later plant and animal life.

Green Algae: Forms, Habitats, and Roles

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Chlamydiae are bacteria that live inside eukaryotic host cells. The phylum Chlamydiae, also called Chlamydiota, contains a single order, Chlamydiales. These bacteria are obligate intracellular parasites, which means they must enter host cells to survive and grow. Members of this group are usually very small cocci, about 0.5 μm across. They also have reduced genomes, usually between 0.55 and 1 Mbp. This limited genome fits their highly specialized way of life and their dependence on host...

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Planctomycetes Cell Structure and Life Cycle

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bacterial phylum verrucomicrobiota

Verrucomicrobiota Cell Structure and Traits

Verrucomicrobiota are a bacterial phylum with several recognized orders, and most species belong to Verrucomicrobiotales. Many members are aerobic or facultatively aerobic, which means they can use oxygen but may also grow without it. They can also ferment sugars. One exception is the genus Methylacidiphilum, which contains aerobic methanotrophs, bacteria that use methane and oxygen. These bacteria live in many different places. They are found in freshwater, marine habitats, forest soils, and...

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Cyanobacteria and Oxygenic Photosynthesis

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bacterial phylum actinobacteria

Actinobacteria: Soil Bacteria and Cheese

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bacterial phylum firmicutes

Firmicutes: Bacteria, Fermentation, and Spores

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bacterial phylum bacteroidota

Gut and Environment Bacteria in Bacteroidota

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Sulfur-Using Bacteria That Harvest Light

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hyperthermophilic bacteria

Heat-Loving Bacteria and Their Enzymes

Hyperthermophilic bacteria live in extreme heat and show unusual adaptations that help them survive. Several of these species come from the Domain Bacteria and are found in hot springs and hydrothermal vents. Their biology helps explain how life can function in very hot environments. Thermotoga species are rod-shaped, gram-negative, non-sporulating hyperthermophiles. They form a sheath-like outer layer called a toga. These bacteria ferment sugars or starch and produce lactate, acetate, carbon...

bacterial phylum tenericutes

Mycoplasmas and Wall-Less Bacteria

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other unique bacteria

Magnetotactic and DNA-Resistant Bacteria

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Archaea Cell Structure and Metabolism

Archaea are a unique domain of life with cell structures and metabolic strategies that set them apart from bacteria and eukaryotes. They were named after the Archaean eon and are important for understanding both early life and modern biotechnology. One key feature of archaea is their membrane chemistry. Their membranes contain ether-linked isoprenoid lipids, which help them stay stable in extreme conditions such as high heat and chemical stress. Archaea also have RNA polymerases that are more...

diversity of archaea i

Archaea Extremes: Euryarchaeota

Euryarchaeota is a major phylum of Archaea, a domain of single-celled microorganisms. Archaea are grouped into five major phyla based on genetic and biochemical traits: Euryarchaeota, Crenarchaeota, Thaumarchaeota, Korarchaeota, and Nanoarchaeota. Among them, Euryarchaeota stands out for its wide range of shapes, metabolism, and habitat use. Members of this phylum can have rod or cocci shapes. Their metabolism may be strictly aerobic or strictly anaerobic, which lets them live in both...

diversity of archaea ii

New Archaea Phyla and Their Roles

Archaea are one of the three domains of life, and their diversity includes species that live in both extreme and moderate environments. For a long time, most known archaea were grouped into two major phyla: Euryarchaeota and Crenarchaeota. Recent molecular studies have added three more phyla to this picture: Thaumarchaeota, Nanoarchaeota, and Korarchaeota. Thaumarchaeota are mesophilic archaea, which means they live in moderate conditions. They are found in soils, lakes, and marine regions. A...

diversity of archaea iii

Crenarchaeota in Extreme Hot Springs

Crenarchaeota are a major group of Archaea known for living in extreme heat and acidity. They are found in sulfur-rich hot springs, volcanic systems, and submarine hydrothermal vents. Many of these habitats reach temperatures above 100°C. Their survival in these conditions gives clues about life on early Earth. Crenarchaeota also show a wide range of cell shapes. Some form filaments, while others have irregular discs or lobed cocci, which are round cells with lobes. Scientists place them in...

diversity of archaea iv

How Hyperthermophilic Archaea Survive Heat

Hyperthermophilic archaea are heat-loving extremophiles that live at temperatures above 80°C. They are often found in hydrothermal vents and volcanic soils, where the heat can be higher than the boiling point of water. At these temperatures, the proteins, membranes, and DNA of most organisms would break down. These archaea survive because their cell membranes are built differently. Their membranes contain a monolayer of biphytanyl tetraether lipids, which helps resist thermal damage. This...

overview of fungi

Fungi Structure, Reproduction, and Roles

Fungi are eukaryotes that are more closely related to animals than to other eukaryotes. Their cell walls contain chitin, a polysaccharide that gives strength, and glucans, which add flexibility and support. Some fungi also use mannans and galactosans in place of, or along with, chitin. These features help fungi live in acidic places and survive high osmotic pressure. Fungi can be unicellular, like yeasts, or multicellular. In multicellular fungi, the body forms a mycelium, which is a branching...

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Zygomycota: Spores, Hyphae, and Roles

Zygomycota are a former fungal group made up mostly of terrestrial molds that act as decomposers. Recent phylogenetic studies now place them in two major clades: Mucoromycota and Zoopagomycota. Mucoromycota includes many symbiotic species, while Zoopagomycota is made up mainly of parasitic and pathogenic fungi. These fungi have coenocytic hyphae, which are filaments without septa, or cross walls. That structure allows cytoplasm and organelles to move through the hyphae in one continuous stream.

fungal phylum microsporidia

Microsporidia Spores and Host Infection

Microsporidia are unicellular fungi that live as obligate intracellular parasites. They were first classified as protists, but phylogenetic, molecular, and structural evidence later linked them to the Chytridiomycota. These non-motile organisms infect many animal hosts, including humans, and depend heavily on the host cell to survive. Their cells are very small, usually 2 to 5 micrometers wide. Microsporidia form spores with a chitin shell, which helps them resist the outside environment. The...

fungal phylum ascomycota

Ascomycota: Sac Fungi and Their Spore Cycle

Ascomycota are sac fungi with a wide range of forms and roles. This fungal phylum includes unicellular yeasts and filamentous molds such as Aspergillus and Penicillium. They live in aquatic and terrestrial habitats and have major ecological and economic importance. A key feature of ascomycetes is the ascus, a sac-like structure that contains haploid ascospores. These fungi can reproduce sexually and asexually. Sexual reproduction starts with plasmogamy, the fusion of cytoplasm from two...

fungal phylum basidiomycota

Basidiomycota: Mushrooms, Spores, and Ecological Roles

Basidiomycota is a major group of fungi that includes mushrooms, puffballs, decomposers, symbionts, plant pathogens, and some edible species. These fungi matter in ecosystems, agriculture, and medicine. A key feature of this phylum is the basidium, a small club-shaped structure that makes basidiospores. Many basidiomycetes form visible fruiting bodies called basidiocarps. The life cycle starts when a haploid basidiospore germinates into monokaryotic mycelium. When two compatible mycelia fuse,...

overview of algae

Algae Structure, Habitats, and Reproduction

Algae are simple eukaryotic photoautotrophs that live in many habitats and show a wide range of body forms. They contain chlorophyll and carry out oxygenic photosynthesis. They belong to the kingdom Archaeplastida, which also includes red and green algae and land plants. Unlike other protists with chloroplasts from secondary endosymbiosis, red and green algae came from primary endosymbiotic events. Algae can look very different from one another. Some are large brown kelp in coastal waters,...

red algae

Red Algae Pigments, Shapes, and Uses

Red algae are phototrophic organisms found mostly in marine environments. Some species also live in freshwater or on land. They may be unicellular or multicellular, and some multicellular forms grow large enough to be seen easily. These algae contain chlorophyll a, but their chloroplasts do not contain chlorophyll b. Instead, they use phycobiliproteins, which are light-harvesting pigments like those found in cyanobacteria. The red color seen in many species comes from phycoerythrin, an...

green algae

Green algae are photosynthetic organisms with chlorophylls a and b in their chloroplasts. These pigments give them a green color. They differ from red algae because they lack phycobiliproteins, the pigments that produce red or blue-green tones in red algae. In pigment makeup, green algae are close to plants, and they share a close evolutionary relationship with them. Green algae belong to Phylum Chlorophyta in the Kingdom Archaeplastida. They are usually divided into two main groups:...

other algae

Stramenopile Algae: Diatoms, Golden, Brown

Stramenopile algae include diatoms, golden algae, and brown algae. These phototrophic microorganisms have flagella with many short, hairlike extensions. That feature gave the group its name, which comes from Latin words meaning “straw” and “hair.” Diatoms are unicellular, photosynthetic eukaryotes, and more than 200 genera are known. They are important parts of plankton in both marine and freshwater ecosystems. Their most distinctive feature is a silica-based cell wall called a frustule. This...

overview of protists

Protist Diversity, Movement, and Survival

Protists are diverse eukaryotic microorganisms with many ways to move, eat, and survive. They do not have the specialized tissues of plants and animals or the chitinous cell walls of fungi. Their early split within Eukarya led to major structural, functional, and ecological diversity. Scientists group protists into supergroups based on genetic analysis and shared structures. These groups include Archaeplastida, Excavata, Amoebozoa, Rhizaria, Alveolata, and Stramenopiles. This classification...

diversity of protists i

Excavata Protists and Their Adaptations

Excavata protists show many different ways of living, from photosynthesis to parasitism. This group includes organisms that can use chemical energy, light, or both. Some also live in low-oxygen, or anaerobic, environments where they survive without normal oxygen-based metabolism. Among the main Excavata groups are diplomonads and parabasalids. These are flagellated protists, meaning they move with whip-like tails, and they lack mitochondria and chloroplasts. They often live in anoxic habitats,...

diversity of protists ii

Alveolates: Ciliates, Dinoflagellates, Apicomplexans

Alveolates are protists with tiny sacs called alveoli beneath the cell membrane. These sacs may help control water balance by limiting how much water moves in and out of the cell. In dinoflagellates, alveoli may also act like armor plates. The three main alveolate groups are ciliates, dinoflagellates, and apicomplexans. Ciliates move with cilia, which are short hair-like structures that can cover the whole cell or appear in rows or tufts. One well-known ciliate is Paramecium, which uses cilia...

diversity of protists iii

Rhizaria: Pseudopods, Tests, and Skeletons

Rhizaria are unicellular protists with threadlike pseudopodia, which are thin cytoplasmic extensions used for movement and feeding. Their amoeboid shape once caused taxonomic confusion, but molecular phylogenetics has since shown where they fit on the evolutionary tree. This group includes Chlorarachniophyta, Radiolaria, and Foraminifera, and each lineage has adapted to a different ecological niche and metabolic strategy. Chlorarachniophyta are unicellular phototrophic protists found in marine...

diversity of protists iv

Amoebozoa: Movement and Life Cycles

Amoebozoa are a diverse group of terrestrial and aquatic protists. They move and feed with lobe-shaped pseudopodia. This feature sets them apart from Rhizaria, which have threadlike pseudopodia. The group includes gymnamoebas, entamoebas, and the plasmodial and cellular slime molds. Phylogenetic evidence also shows that Amoebozoa split from a lineage that later gave rise to fungi and animals. Gymnamoebas are free-living protists that live in water and soil. They move by amoeboid movement,...

key terms and concepts

Explore green algae in freshwater, rocks, and lichens, plus key examples like Volvox, Ostreococcus, and Botryococcus in a student-friendly summary.

Green Algae: Forms, Habitats, and Roles | JoVE K12

JoVE Core Microbiology provides an engaging introduction to the microbial world and its influence on health, industry, and the environment. This comprehensive collection covers key concepts such as microbial structure, metabolism, genetics, and ecology. It introduces essential laboratory techniques and microscopy methods through visually engaging animations. Corresponding scientist-in-action videos bridge classroom concepts with real-world research and applications.

microbiology

Green Algae: Forms, Habitats, and Roles

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