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Gonium Pectorale
''Gonium pectorale'' is a species of green algae in the family Goniaceae. It is a freshwater species with a cosmopolitan distribution. ''Gonium pectorale'' is the type species of the genus ''Gonium'', and is the most common species in the genus. It is a model organism for studying the evolution of multicellularity. Description ''Gonium pectorale'' is a colonial, flagellate organism 70–100 μm wide, with 16 (sometimes 8 or 32) cells. In its usual form, it consists of four cells in the center and 12 cells in the periphery, with flagella pointing outward. Cells are nearly spherical or weakly pear-shaped, and are up to 18 μm wide. They contain a single cup-shaped chloroplast with one or two basal pyrenoid and an eyespot in the anterior. Each cell has two, equal flagella. ''Gonium pectorale'' is similar to other ''Gonium'' species, especially in its 16-celled form. Eight-celled colonies of ''Gonium pectorale'' are almost always in a zig-zag arrangement of two cells per row. The ... [...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] |
Gonium Viridistellatum
''Gonium'' (Greek: γωνία ''gonia'', "angle" or "corner") is a genus of colonial green algae, a member of the order Chlamydomonadales. The genus was first described by Otto Friedrich Müller in 1773, and is among the most common types of algae found in freshwater habitats. It has a cosmopolitan distribution. Typical colonies of ''Gonium'' consist of 4 to 16 cells arranged in a flat plate. ''Gonium'' is capable of both asexual and sexual reproduction. Along with other algae such as ''Volvox'', '' Eudorina'' and ''Chlamydomonas'', it is a model organism for studying the origins and evolution of multicellularity. Description ''Gonium'' consists of flat, planar colonies of four to 32 cells, all identical with the colony having no anterior-posterior differentiation. In one species ''Gonium dispersum'', single cells may also be found. In a colony of 16 cells, four are in the center, and the other 12 are on the four sides, three each. A description by G.M. Smith (1920, p. 94): ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reproductively Isolated
The mechanisms of reproductive isolation are a collection of evolutionary mechanisms, behaviors and physiological processes critical for speciation. They prevent members of different species from producing offspring, or ensure that any offspring are sterile. These barriers maintain the integrity of a species by reducing gene flow between related species.Strickberger, M. 1978. ''Genética''. Omega, Barcelona, España, p.: 874–879. .Futuyma, D. 1998. ''Evolutionary biology'' (3ª edición). Sinauer, Sunderland. The mechanisms of reproductive isolation have been classified in a number of ways. Zoologist Ernst Mayr classified the mechanisms of reproductive isolation in two broad categories: pre-zygotic for those that act before fertilization (or before mating in the case of animals) and post-zygotic for those that act after it.Mayr, E. 1963. ''Animal species and evolution''. Harvard University Press, Cambridge. The mechanisms are genetically controlled and can appear in species w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cell Wall
A cell wall is a structural layer that surrounds some Cell type, cell types, found immediately outside the cell membrane. It can be tough, flexible, and sometimes rigid. Primarily, it provides the cell with structural support, shape, protection, and functions as a selective barrier. Another vital role of the cell wall is to help the cell withstand osmotic pressure and mechanical stress. While absent in many eukaryotes, including animals, cell walls are prevalent in other organisms such as fungi, algae and plants, and are commonly found in most Prokaryote, prokaryotes, with the exception of Mollicutes, mollicute bacteria. The composition of cell walls varies across taxonomic groups, species, cell type, and the cell cycle. In Embryophyte, land plants, the primary cell wall comprises Polysaccharide, polysaccharides like cellulose, hemicelluloses, and pectin. Often, other Polymer, polymers such as lignin, suberin or cutin are anchored to or embedded in plant cell walls. Algae exhibit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gamete
A gamete ( ) is a Ploidy#Haploid and monoploid, haploid cell that fuses with another haploid cell during fertilization in organisms that Sexual reproduction, reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. The name gamete was introduced by the German cytologist Eduard Strasburger in 1878. Gametes of both mating individuals can be the same size and shape, a condition known as isogamy. By contrast, in the majority of species, the gametes are of different sizes, a condition known as anisogamy or heterogamy that applies to humans and other mammals. The human ovum has approximately 100,000 times the volume of a single human sperm cell. The type of gamete an organism produces determines its sex and sets the basis for the sexual roles and sexual selection. In humans and other species that produce two Morphology (biology), morphologically distinct types of gametes, and in which Gonochorism, each individual produces only one type, a femal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isogamous
Isogamy is a form of sexual reproduction that involves gametes of the same morphology (indistinguishable in shape and size), and is found in most 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 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 types ( heterothallism), but sometimes can occur between two haploid individuals that are mitotic d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asexual Reproduction
Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction from either unicellular or multicellular organisms inherit the full set of genes of their single parent and thus the newly created individual is genetically and physically similar to the parent or an exact clone of the parent. Asexual reproduction is the primary form of reproduction for single-celled organisms such as archaea and eubacteria, bacteria. Many Eukaryote, eukaryotic organisms including plants, animals, and Fungus, fungi can also reproduce asexually. In Vertebrate, vertebrates, the most common form of asexual reproduction is parthenogenesis, which is typically used as an alternative to sexual reproduction in times when reproductive opportunities are limited. Some Monitor lizard, monitor lizards, including Komodo dragons, can reproduce asexually. While all prokaryotes reproduce without the fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mary Pocock
Mary Agard Pocock (31 December 1886 – 10 July 1977) was a South African phycologist. Biography Born in Rondebosch in 1886 to William Pocock and Elizabeth Dacomb, Mary Pocock attended Bedford High School and Cheltenham Ladies' College. Pocock then attended the University of London where she studied botany, receiving her degree in 1908. Following her degree Pocock taught at girls schools in London and the Cape before continuing her study in 1919; completing an additional honors degree in botany at Cambridge. She was a lecturer at Rhodes University for a year in 1924, a position which she took up occasionally again during her career. In 1925 she travelled with Dorothea Bleek from Rhodesia to Luanda collecting flowering plants which she studied at the Royal Botanical Gardens, Kew and the British Museum upon her return. Travelling back to South Africa, Pocock became interested in algae, obtaining a PhD on the subject from the University of Cape Town at the age of 46. In 1942 she e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
