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Conjugatae
The Zygnematales ( (''zygós'') and νῆμα (''nḗma'') ( nom.), νήματος (''nḗmatos'') ( gen.)), also called the Conjugatales, are an order of green algae, comprising several thousand different species in two families. The larger family Zygnemataceae, with well-known genera such as ''Zygnema'' and ''Spirogyra'', includes members that grow as unbranched filaments, which grow longer through normal cell division. This group includes the desmids. Most members of both families live in freshwater, and form an important component of the algal scum that grows on or near plants and rocks. Systematically they fall within the division Charophyta/Streptophyta, in which the land plants (Embryophyta) emerged. Sexual reproduction in Zygnematales takes place through a process called ''conjugation''. Here filaments of opposite gender line up, and tubes form between corresponding cells. The male cells then become amoeboid and crawl across, or sometimes both cells crawl into the tube. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spirogyra
''Spirogyra'' (common names include water silk, mermaid's tresses, and blanket weed) is a genus of filamentous charophyte green algae of the order Zygnematales, named for the helical or spiral arrangement of the chloroplasts that is characteristic of the genus. ''Spirogyra'' species, of which there are more than 500, are commonly found in freshwater habitats. ''Spirogyra'' measures approximately 10 to 150 micrometres in width (though not usually more than 60) and may grow to several centimetres in length. Distribution ''Spirogyra'' can be been found on every continent on Earth, including Antarctica. It is freshwater algae, found rivers, ponds, and other such bodies of water. Taxonomy The genus Spirogyra was named by German naturalist Johann Heinrich Friedrich Link in 1820. The lectotype, ''Spirogyra'' ''porticalis'' was designated in 1952 by Paul C. Silvia. Reproduction ''Spirogyra'' can reproduce both sexually and asexually. In vegetative reproduction, fragmentation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Streptophyta
Streptophyta (), informally the streptophytes (, from the Greek ''strepto'' 'twisted', for the morphology of the sperm of some members), is a clade of plants. The composition of the clade varies considerably between authors, but the definition employed here includes land plants and all green algae except the Chlorophyta and the more basal Prasinodermophyta. Classifications The composition of Streptophyta and similar groups (Streptophytina, Charophyta) varies in each classification. Some authors include only the Charales and Embryophyta (e.g., Streptophyta, Streptophytina); others include more groups (e.g., Charophyta, Streptophyta, Streptobionta); some authors use this broader definition, but exclude the Embryophyta (e.g., Charophyta, Charophyceae, Streptophycophytes). The clade Streptophyta includes both unicellular and multicellular organisms. Streptophyta contains the freshwater charophyte green algae and all land plants that reproduce sexually by conjugation. ''Mesostigma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zygnema
''Zygnema'' is a genus of freshwater filamentous thalloid alga comprising about 100 species. A terrestrial species, ''Z. terrestre'', is known from India. ''Zygnema'' grows as a free-floating mass of filaments, although young plants may be found anchored to streambeds with a holdfast. The filaments form a yellow-green to bright green colored tangled mat, and are composed of elongate barrel-shaped cells, each with two star-shaped (stellate) chloroplast A chloroplast () is a type of membrane-bound organelle, organelle known as a plastid that conducts photosynthesis mostly in plant cell, plant and algae, algal cells. Chloroplasts have a high concentration of chlorophyll pigments which captur ...s arrayed along the axis of the cell. Species Some species include: * ''Z. atrocoeruleum'' * ''Z. binuclearioides'' * ''Z. carinthiacum'' * ''Z. carteri'' * ''Z. circumcarinatum'' * ''Z. coeruleum'' * ''Z. conspicuum'' * ''Z. cruciatum'' * ' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Netrium
''Netrium'' is a genus of algae belonging to the family Mesotaeniaceae The Mesotaeniaceae are a small family of unicellular green algae known as the "saccoderm desmids". The Mesotaeniaceae appear to be sister or ancestral to the Zygnemataceae. The desmids are a deep branching group of Zygnemataceae. ''Spirotaenia'' .... The species of this genus are found in Europe, America and Australia. Species: *'' Netrium digitus'' *'' Netrium interruptum'' *'' Netrium lamellosum'' *'' Netrium naegelii'' *'' Netrium obesus'' *'' Netrium oblongum'' References {{Taxonbar, from=Q1231838 Zygnematales Charophyta genera ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Desmidiales
Desmidiales, commonly called the desmids (''Gr.'' ''desmos'', bond or chain), are an order in the Charophyta, a division of green algae in which the land plants ( Embryophyta) emerged. Desmids consist of single-celled (sometimes filamentous or colonial) microscopic green algae. Because desmids are highly symmetrical, attractive, and come in a diversity of forms, they are popular subjects for microscopists, both amateur and professional. The desmids belong to the class Zygnematophyceae. Although they are sometimes grouped together as a single family Desmidiaceae, most classifications recognize three to five families, usually within their own order, Desmidiales. The Desmidiales comprise around 40 genera and 5,000 to 6,000Brook, Alan J., 1981. ''The Biology of Desmids'', page 1. (Berkeley: University of California Press). species, found mostly but not exclusively in fresh water. In general, desmids prefer acidic waters (pH between 4.8 and 7.0), so many species may be found in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spirotaenia
''Spirotaenia'' is a genus of basal unicellular green algae that may be sister to the Chlorokybophyceae. It was previously considered to be part of the Zygnemataceae. It is sexually Isogamy#Conjugation, conjugating, a mode of reproduction that was previously only known in the Zygnemataceae/Mesotaeniaceae, the sister groups to the land plants. This is surprising, as ''Spirotaenia'' is much more basal. The conjugating process is substantially aberrant. ''Spirotaenia'' may actually be more than one distinct lineage which may not be closely related. Phylogeny References Charophyta {{green alga-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chloroplast
A chloroplast () is a type of membrane-bound organelle, organelle known as a plastid that conducts photosynthesis mostly in plant cell, plant and algae, algal cells. Chloroplasts have a high concentration of chlorophyll pigments which capture the Radiant energy, energy from sunlight and convert it to chemical energy and release oxygen. The chemical energy created is then used to make sugar and other organic molecules from carbon dioxide in a process called the Calvin cycle. Chloroplasts carry out a number of other functions, including fatty acid synthesis, amino acid synthesis, and the immune response in plants. The number of chloroplasts per cell varies from one, in some unicellular algae, up to 100 in plants like ''Arabidopsis'' and wheat. Chloroplasts are highly dynamic—they circulate and are moved around within cells. Their behavior is strongly influenced by environmental factors like light color and intensity. Chloroplasts cannot be made anew by the plant cell and must ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Meiosis
Meiosis () is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, the sperm or egg cells. It involves two rounds of division that ultimately result in four cells, each with only one copy of each chromosome (haploid). Additionally, prior to the division, genetic material from the paternal and maternal copies of each chromosome is crossed over, creating new combinations of code on each chromosome. Later on, during fertilisation, the haploid cells produced by meiosis from a male and a female will fuse to create a zygote, a cell with two copies of each chromosome. Errors in meiosis resulting in aneuploidy (an abnormal number of chromosomes) are the leading known cause of miscarriage and the most frequent genetic cause of developmental disabilities. In meiosis, DNA replication is followed by two rounds of cell division to produce four daughter cells, each with half the number of chromosomes as the original parent cell. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zygote
A zygote (; , ) is a eukaryote, eukaryotic cell (biology), cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individual organism. The sexual fusion of haploid cells is called karyogamy, the result of which is the formation of a Ploidy#Haploid and monoploid, diploid cell called the zygote or zygospore. History German zoologists Oscar Hertwig, Oscar and Richard Hertwig made some of the first discoveries on animal zygote formation in the late 19th century. In multicellular organisms The zygote is the earliest developmental stage. In humans and most other Anisogamy, anisogamous organisms, a zygote is formed when an egg cell and sperm, sperm cell come together to create a new unique organism. The formation of a cell potency, totipotent zygote with the potential to produce a whole organism depends on epigenetics, epigenetic reprogramming. DNA demethyla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isogamy
Isogamy is a form of sexual reproduction that involves Gamete, gametes of the same Morphology (biology), morphology (indistinguishable in shape and size), and is found in most Unicellular organism, unicellular eukaryotes. Because both gametes look alike, they generally cannot be classified as male or female. Instead, organisms that reproduce through isogamy are said to have different Mating type, mating types, most commonly noted as "+" and "−" strains. Etymology The etymology of isogamy derives from the Greek adjective ''isos'' (meaning equal) and the Greek verb ''gameo'' (meaning to have sex/to reproduce), eventually meaning "equal reproduction" which refers to a hypothetical initial model of equal contribution of resources by both gametes to a zygote in contrast to a later evolutional stage of anisogamy. The term isogamy was first used in the year 1891. Characteristics of isogamous species Isogamous species often have two Mating type, mating types (heterothallism), ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sexual Reproduction
Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete ( haploid reproductive cells, such as a sperm or egg cell) with a single set of chromosomes combines with another gamete to produce a zygote that develops into an organism composed of cells with two sets of chromosomes ( diploid). This is typical in animals, though the number of chromosome sets and how that number changes in sexual reproduction varies, especially among plants, fungi, and other eukaryotes. In placental mammals, sperm cells exit the penis through the male urethra and enter the vagina during copulation, while egg cells enter the uterus through the oviduct. Other vertebrates of both sexes possess a cloaca for the release of sperm or egg cells. Sexual reproduction is the most common life cycle in multicellular eukaryotes, such as animals, fungi and plants. Sexual reproduction also occurs in some unicellular eukaryotes. Sexual reproduction does not occur in pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Embryophyte
The embryophytes () are a clade of plants, also known as Embryophyta (Plantae ''sensu strictissimo'') () or land plants. They are the most familiar group of photoautotrophs that make up the vegetation on Earth's dry lands and wetlands. Embryophytes have a common ancestor with green algae, having emerged within the Phragmoplastophyta clade of freshwater charophyte green algae as a sister taxon of Charophyceae, Coleochaetophyceae and Zygnematophyceae. Embryophytes consist of the bryophytes and the polysporangiophytes. Living embryophytes include hornworts, liverworts, mosses, lycophytes, ferns, gymnosperms and angiosperms (flowering plants). Embryophytes have diplobiontic life cycles. The embryophytes are informally called "land plants" because they thrive primarily in terrestrial habitats (despite some members having evolved secondarily to live once again in semiaquatic/ aquatic habitats), while the related green algae are primarily aquatic. Embryophytes are complex ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
