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Volvox
''Volvox'' is a polyphyletic genus of chlorophyte green algae in the family Volvocaceae. ''Volvox'' species form spherical colonies of up to 50,000 cells, and for this reason they are sometimes called globe algae. First reported by Antonie van Leeuwenhoek in 1700, it is distinctive and easily identified in the microscope. It occurs in variety of freshwater habitats, and has a widespread, cosmopolitan distribution. ''Volvox'' diverged from unicellular ancestors approximately . Colonies of ''Volvox'' are differentiated into somatic and reproductive cells, and are capable of both sexual and asexual reproduction. Additionally, its close relatives are diverse in body plan and reproductive strategy, ranging from unicellular organisms such as '' Chlamydomonas'' to simple colonial organisms such as '' Pandorina'' and '' Eudorina''. Because of this, ''Volvox'' and its relatives are used as model organisms in the classroom and laboratory to study biological processes such as cellular move ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Volvocaceae
The Volvocaceae are a family of unicellular or colonial biflagellates algae, including the typical genus ''Volvox'', and are collectively known as the volvocine algae. The family was named by Ehrenberg in 1834, and it is known in older classifications as the Volvocidae. All species are colonial and typically inhabit freshwater environments. They are particularly useful as model organisms for study the evolution of multicellularity, the evolution of sex, and cellular motion and mechanics. Description Volvocine algae consist of multiple, biflagellate cells. Each cell has a cell membrane, a central nucleus, multiple mitochondria, and one large chloroplast with an associated stigma (also known an eyespot). The stigma is reddish due to the presence of rhodopsin. The apical end of the cell has two equal-length flagella; the flagella beat in a manner similar to a breaststroke. Cellular organization The simplest of the Volvocaeans are ordered assemblies of cells, each similar to the r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eudorina
''Eudorina'' is a genus of green algae in the family Volvocaceae, containing about seven species. It has a cosmopolitan distribution in freshwater habitats. Description ''Eudorina'' colonies typically consist of 16, 32 or 64 cells, each of which is similar to '' Chlamydomonas reinhardtii''. These cells are bedded within an extracellular matrix composed of glycoproteins. Colonies are spherical and motile, with motility derived from the flagellated individual cells. Cells are ovoid or spherical, each with two equal flagella. (In one species '' Eudorina compacta'', the cells essentially touch each other, and are strikingly angular due to mutual compression.) There is a single cup-shaped chloroplast with one (basal) or multiple pyrenoids) and a stigma. Multiple contractile vacuoles are scattered throughout the cytoplasm. ''Eudorina'' is facultatively sexual, meaning colonies can reproduce either sexually or asexually. During development, each ''Chlamydomonas''-like cell undergoe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chlorophyte
Chlorophyta is a division (botany), division of green algae informally called chlorophytes. Description Chlorophytes are eukaryotic organisms composed of cells with a variety of coverings or walls, and usually a single green chloroplast in each cell. They are structurally diverse: most groups of chlorophytes are unicellular, such as the earliest-diverging prasinophytes, but in two major classes (Chlorophyceae and Ulvophyceae) there is an evolutionary trend toward various types of complex colonial organism, colonies and even multicellularity. Chloroplasts Chlorophyte cells contain green chloroplasts surrounded by a double-membrane envelope. These contain chlorophylls ''chlorophyll a, a'' and ''chlorophyll b, b'', and the carotenoids carotin, lutein, zeaxanthin, antheraxanthin, violaxanthin, and neoxanthin, which are also present in the leaves of land plants. Some special carotenoids are present in certain groups, or are synthesized under specific environmental factors, such ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Green Algae
The green algae (: green alga) are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ( Embryophytes) have emerged deep within the charophytes as a sister of the Zygnematophyceae. Since the realization that the Embryophytes emerged within the green algae, some authors are starting to include them. The completed clade that includes both green algae and embryophytes is monophyletic and is referred to as the clade Viridiplantae and as the kingdom Plantae. The green algae include unicellular and colonial flagellates, most with two flagella per cell, as well as various colonial, coccoid (spherical), and filamentous forms, and macroscopic, multicellular seaweeds. There are about 22,000 species of green algae, many of which live most of their lives as single cells, while other species form coenobia (colonies), long filaments ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multicellularity
A multicellular organism is an organism that consists of more than one cell, unlike unicellular organisms. 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''. Multicellular organisms arise in various ways, for example by cell division or by aggregation of many single cells. Colonial organisms are the result of many identical individuals joining together to form a colony. However, it can often be hard to separate colonial protists from true multicellular organisms, because the two concepts are not distinct; colonial protists have been dubbed "pluricellular" rather than "multicellular". There are also macroscopic organisms that are multinucleate though technically unicellular, such as the Xenophyophorea that can reach 20 cm. Evolutionary history Occurrence Multicellularity has evolved ind ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pandorina
''Pandorina'' is a genus of green algae in the family Volvocaceae. It is a common freshwater genus, and has a cosmopolitan distribution. Along with other algae such as '' Volvox'', '' Eudorina'' and ''Chlamydomonas'', it is a model organism for studying the origins and evolution of multicellularity. Description ''Pandorina'' is composed of 8, 16, or sometimes 32 cells, held together at their bases to form a globular or ellipsoidal colony surrounded by mucilage. The cells are ovoid or slightly narrowed at one end to appear keystone- or pear-shaped. Each cell has two flagella with two contractile vacuoles at its base, an eyespot, and a large cup-shaped chloroplast with at least one pyrenoid. The colonies co-ordinate their flagellar movement to create a rolling, swimming motion. ''Pandorina'' shows the beginnings of the colony polarity and differentiation seen in '' Volvox,'' with anterior cells having larger eyespots. Asexual reproduction is by simultaneous division of all cell ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chaos (genus)
''Chaos'' is a genus of single-celled amoeboid organisms in the family Amoebidae. The largest and most-known species, the so-called "giant amoeba" (''Chaos carolinensis''), can reach lengths up to 5 mm, although most specimens fall between 1 and 3 mm. Members of this genus closely resemble those of the genus ''Amoeba'' and share the same general morphology, producing numerous cylindrical pseudopods, each of which is rounded at the tip. However, while ''Amoeba'' have a single nucleus, ''Chaos'' can have as many as a thousand. Because of this attribute, ''C. carolinensis'' was once placed in the genus ''Pelomyxa'' alongside the giant multinucleate amoeba ''Pelomyxa palustris.'' Recently, molecular phylogenetic studies of this species have confirmed the view of some earlier researchers that it is more closely related to ''Amoeba'' than to ''Pelomyxa''. The species is now placed in the independent genus ''Chaos'', a sister group to ''Amoeba''. Dietary habits ''Chaos'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Colony (biology)
In biology, a colony is composed of two or more Biological specificity#Conspecific, conspecific individuals living in close association with, or connected to, one another. This association is usually for mutual benefit such as stronger defense or the ability to attack bigger prey. Colonies can form in various shapes and ways depending on the organism involved. For instance, the bacterial colony is a cluster of identical cells (clones). These colonies often form and grow on the surface of (or within) a solid medium, usually derived from a single parent cell. Colonies, in the context of development, may be composed of two or more unitary (or solitary) organisms or be Modularity, modular organisms. Unitary organisms have determinate development (set life stages) from zygote to adult form and individuals or groups of individuals (colonies) are visually distinct. Modular organisms have indeterminate growth forms (life stages not set) through repeated iteration of genetically identi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Somatic Cell
In cellular biology, a somatic cell (), or vegetal cell, is any biological cell forming the body of a multicellular organism other than a gamete, germ cell, gametocyte or undifferentiated stem cell. Somatic cells compose the body of an organism and divide through mitosis. In contrast, gametes derive from meiosis within the germ cells of the germline and they fuse during sexual reproduction. Stem cells also can divide through mitosis, but are different from somatic in that they differentiate into diverse specialized cell types. In mammals, somatic cells make up all the internal organs, skin, bones, blood and connective tissue, while mammalian germ cells give rise to spermatozoa and ova which fuse during fertilization to produce a cell called a zygote, which divides and differentiates into the cells of an embryo. There are approximately 220 types of somatic cell in the human body. Theoretically, these cells are not germ cells (the source of gametes); they transmit their mut ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Henry Baker (naturalist)
Henry Baker (8 May 1698 – 25 November 1774) was a British naturalist. Life He was born in Chancery Lane, London, 8 May 1698, the son of William Baker, a clerk in chancery. When he was 15, he was apprenticed to John Parker, a bookseller. At the close of his indentures in 1720, Baker went on a visit to John Forster, a relative, who had a deaf-mute daughter, then eight years old. As a successful therapist of deaf people, he went on to make money, by a system that he kept secret. His work as therapist caught the attention of Daniel Defoe, whose youngest daughter Sophia he married on 30 April 1729. In 1740, he was elected fellow of the Society of Antiquaries and of the Royal Society. In 1744, he received the Copley gold medal for microscopical observations on the crystallization of saline particles. He was one of the founders of the Society for the Encouragement of Arts, Manufactures and Commerce in 1754 (later the Society of Arts), and for some time acted as its secretary. He ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Systema Naturae
' (originally in Latin written ' with the Orthographic ligature, ligature æ) is one of the major works of the Sweden, Swedish botanist, zoologist and physician Carl Linnaeus (1707–1778) and introduced the Linnaean taxonomy. Although the system, now known as binomial nomenclature, was partially developed by the Bauhin brothers, Gaspard Bauhin, Gaspard and Johann Bauhin, Johann, Linnaeus was the first to use it consistently throughout his book. The first edition was published in 1735. The full title of the 10th edition (1758), which was the most important one, was ', which appeared in English in 1806 with the title: "A General System of Nature, Through the Three Grand Kingdoms of Animals, Vegetables, and Minerals, Systematically Divided Into their Several Classes, Orders, Genera, Species, and Varieties, with their Habitations, Manners, Economy, Structure and Peculiarities". The 10th edition of Systema Naturae, tenth edition of this book (1758) is considered the starting point of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
