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Algae are ubiquitous throughout the waters of the world. Particular characteristics simultaneously unite and differentiate the three primary algal lineages. Analysis of representative Deleted: T taxa within the green, red, and brown algae—as well as related diatoms—introduces a unique Deleted: y are distinct from one another and simultaneously united by particular characteristics Deleted: s of perspective on this observation. In particular, analysis of cell characteristics, life histories, zygote Deleted: algae Deleted: algae traits, and the general ecological success of these representatives illuminates common and emergent trends. Furthermore, stepping back to review the overall patterns within these lineages, reveals information related to oogamy and the relative ages of these algae. Such dissection and observation are, thus, a way of binding together knowledge and creating greater understanding from constituent pieces. Phylum Chlorophyta, green algae, arose approximately 1.6 billion years ago. Included in the chlorophytes is Volvox, a colonial genus regarded as an example of the evolutionary succession which lead to the advent of multicellularity. A Volvox colony is known as a coenobium, wherein the number of cells within each colony is set at the time of its formation. As Deleted: algae Deleted: , Deleted: and Deleted: Deleted: e unity of these organisms while still highlighting their differences Deleted: Comparisons between Deleted: each group Deleted: these observations Deleted: Likewise, trends in oogamy can also be observed and analyzed. The traits hitherto discussed are also good indicators of relative age. Deleted: t Deleted: its Deleted: organism Deleted: which scientists look to Deleted: that such, the only way a colony’s size can increase or decrease is changes in size of the individual cells via turgor pressure. Housing upwards of 50,000 cells, impressive alterations to colony size Deleted: These colonies can be formed by upwards of are still possible. In accordance with a zygotic meiosis life history, Volvox usually reproduces Deleted: and, surprisingly, observe a zygotic meiosis life history. asexually. A gonidium initiates formation of the daughter colony. Sexual reproduction does Deleted: A Deleted: majority of the time, occur, but only in times of environmental stress. Special reproductive cells form eggs and sperm. Male gametes are released, using flagella to find their way to the female gametes. Fusion results in zygospores, which remain dormant until the death of the parent colony and their subsequent release into the environment. Sexual reproduction is the nondominant reproductive form of Volvox. As such, the zygospores are designed simply to withstand environmental stresses and allow for the continuation of the lineage with some genetic recombination and variation. Deleted: The number of cells within each colony of Volvox is set at the time of its formation. Known as a coenobium, the only way alterations in size of the colony can be achieved is the individual expansion or reduction of cells via turgor pressure. Deleted: occurs Deleted: , which are oogomous Deleted: release upon Volvox’s divergence from its unicellular ancestors 200 million years ago was relatively quick (Herron et al. 2009). This may be a result of colonial living, which allows for increased acquisition and concentration of resources (Kirk 2005, Koufopanou and Bell 1993). Alongside green algae arose the red algae, belonging to phylum Rhodophyta. A few features unite all members of this phylum. Proteinaceous deposits, or pit connections, are formed between cells as a result of incomplete cytokinesis. All cells also lack flagella, including reproductive cells, leading to novel reproductive strategies. Porphyra lays the framework for the Deleted: . This Deleted: s basic sporic meiosis life history, observed by all subsequent rhodophyte taxa. Of particular note within the life history of this genus, the female gametophyte’s surface is covered in bumps. These slightly raised surface increase the chances of a rare fertilization event. In later taxa, this Deleted: many Deleted: approaches to reproduction Deleted: possesses slightly raised surfaces Deleted: is Deleted: morphology takes the form of a trichogyne and forms a procarpic system of reproduction that is characterized Deleted: s by a close spatial relationship. Porphyra exhibits another character diversified upon by other rhodophytes: amplification of the zygote. In the event of a fertilization, several copies of the Deleted: rare e zygote are made; the division and arrangement of these copies is species specific (Nelson, Brodie, and Guiry 1999). The goal of reproduction in this case is quantity of zygotes rather than quality. This is arguably in response to the difficulties posed by lack of motility. It is difficult to accurately assess the ecological success of Porphyra, as the genus has been reassessed within recent years (Sutherland et al. 2011). This has led to much uncertainty in terms of taxonomy. While more than 250 species have been described, only 78 are currently accepted (Guiry and Deleted: ; while Deleted: are currently Guiry 2016). While green and red algae lie within the kingdom Plantae, brown algae, or phaeophytes, are included in kingdom Chromista. Comparatively, phaeophytes are also a much younger lineage, emerging about 500 million years old. A striking feature of these organisms is the Deleted: at Deleted: only presence of a secondarily acquired membrane, the cytoplasmic endoparasitic reticulum, which Deleted: ( Deleted: ) surrounds the chloroplast and nucleus. Sargassum is a genus found within order Fucales. All Deleted: that members of this order observe a gametic meiosis life history. Phaeophyte sperm are heterokont, possessing one leading chemosensory flagellum and a trailing motile flagellum. Sargassum has added to this design with a proboscis, thought to serve an additional chemosensory role. It is important to note that other alterations to the male gamete exist within brown algae and are Deleted: This is not the only a Deleted: n arguably common. In order Dictyotales, for example, the the trailing flagellum of the male gamete has been lost entirely. Theoretically, this presents an advantage related to settlement (Phillips and Clayton 1991). Sargassum reproduction takes a particular focus on quality of the zygote. Within each female conceptacle, eight nuclei are formed. Seven of those a reabsorbed Deleted: . Deleted: O Deleted: has lost Deleted: , which t Deleted: Alterations to the heterokont structure are arguably common. and are known as disentegrating nuclei. This leaves more energy to be devoted towards the development of the remaining nucleus. Sargassum is a massively successful organism that is a key aspect of healthy marine environments (Széchy and Paula 2000). They form important sanctuaries for various species from predators and are key primary producers (De Wreede 1976, Wanders 1976). Deleted: ddd Diatoms, while still within kingdom Chromista, are found in the phylum Bacillariophyta. Diatom cell walls are of particular note. The frustule formation is rigid and unable to flex, making cell division a unique process. Reproduction occurs via gametic meiosis. Diatoms are characterized by two body forms. Genera such as Navicula are pennate and bilaterally symmetric; others, like Chaetoceros, are centric, possessing radial symmetry. Only one or two zygotes results from each individual (Sommer 1992). Diatoms are hugely successful organisms. In a given drop of sea water, upwards of over a million individuals may be present (Gundersen et al. 1976). Deleted: . O The taxa hitherto discussed, save for Navicula, all display oogamy. This feature covers all three life history types. While oogamy does create a tendency towards distinct male and female types, it does not preclude a particular life history type, so long as a sexual stage is present Deleted: it possesses some form of Deleted: life cycle (Dusenbery 2002). Just within the algae discussed, there exists a wide variance in lifestyle, morphology, and even taxonomic classification, but all representative taxa are united by the Deleted: ; however, each organism is commonality of oogamy. As a final point of discussion for the chlorophytes, rhodophytes, and phaeophytes, it should be noted which of these groups is the most derived. Analysis of genetic data and fossil evidence has put diatoms at the forefront of these groups, only appearing 200 million years ago. If this information was not present, however, there are other indicators of this group’s youth. Red Deleted: its Deleted: within the lineages and green algae share one of the membranes observed in brown algae, despite brown algae Deleted: Despite belonging to separate kingdoms, r belonging to a separate kingdom. The appearance of a second, new membrane within the brown algae is conceivable as having been acquiesced after the first membrane system. This places the brown algal lineage at a younger age than the other two lineages. Diatoms could be thought of as Deleted: conceived early brown algae, until one considers the novel cell walls. The absence of such a structure in all phaeophytes indicates diatoms as newly evolved relative to the other algae discussed. Without Deleted: , in Deleted: terms knowing absolute ages, the same conclusion is reached: diatoms are the most recently derived. Chlorophytes, rhodophytes, phaeophytes, and diatoms are all unique organisms designed for particular niches in marine ecosystems. From colonial Volvox to the world-dominating, Deleted: to Deleted: ill recently derived diatom, oogamy is one of the greatest unifiers of these diverse creatures. Cell characters, life history traits, zygote trends, and ecological placement are not only useful for Deleted: tools of analysis within algal lineages, but also between them. Observations of these attributes are tools Deleted: e Deleted: ; o for understanding on large and small scales, from the most minute organism to the most complex. De Wreede, R. E. 1976. The Phenology of Three Species of Sargassum (Sargassaceae, Phaeophyta) in Hawaii. Phycologia 15(2):175-183. Dusenbery, D. B. 2002. Ecological Models Explaining the Success of Distinctive Sperm and Eggs (Oogamy). Journal of Theoretical Biology 219(1):1-7. Guiry, M.D, and G. M. Guiry. 2016. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. 9 May 2016. Gundersen, K. R., J. S. Corbin, C. L. Hanson, M. L. Hanson, R. B. Hanson, D. J. Russell, A. Stollar, and O. Yamada. 1976. Structure and Biology Dynamics of the Oligotrophic Ocean Photic Zone off the Hawaiian Islands. Pacific Science 30(1):45-68. Herron, M. D., J. D. Hackett, F. O. Aylward, and R. E. Michod. 2009. Triassic Origin and Early Radiation of Multicellular Volvocene Algae. Proceedings of the National Academy of Sciences 106(9):-. Wanders, J. B. W. 1976. The Role of Benthic Algae in the Shallow Reef of Curaçao (Netherlands Antilles) II: Primary Productivity of Sargassum Beds on the NorthEast Coast Submarine Plateau. Aquatic Botany 2:327-35. Kirk, D. L. 2005. Volvox: A Search for the Molecular and Genetic Origins of Multicellularity and Cellular Definition. Cambridge University Press, Cambridge. Koufopanou, V., and G. Bell. 1993. Soma and Germ: An Experimental Approach Using Volvox. Proceedings: Biological Science-):107-113. Nelson, W. A., J. Brodie, and M. D. Guiry. 1999. Terminology Used to Describe Reproduction and Life History Strategies in the Genus Porphyra (Bangiales, Rhodophyta). Journal of Applied Phycology 11:407-410. Phillips, J. A., and M. N. Clayton. 1991. Biflagellate Spermatozoids in the Dictytotales: The Structure of Gametes and Gametangia in Zonaria angustata (Dictyotales, Phaeophyta). Phycologia 30(2):205-214. Sommer, U. 1992. Growth and Survival Strategies of Planktonic Diatoms. Pages 227-260 in C. D. Sangren, ed. Growth and Reproductive Strategies of Freshwater Phytoplankton. Camridge University Press, Cambridge. Sutherland, J. E., S. C. Lindstrom, W. A. Nelson, J. Brodie, M. D. Lynch. M. S. Hwang, H. Choi, M. Miyata, N. Kikuchi, M. C. Oliveira, T. Farr, C. Neefus, A. Morls-Mortensen, D. Milstein, K. M. Müller. 2011. A New Look at an Ancient Order: Generic Revision of the Bangiales (Rhodophyta). Journal of Phycology 47(5):-. Széchy, M. T. M, and É. J. Paula. 2000. Padrões estruturais quantitativos de bancos de Sargassum (Phaeophyta, Fucales) do litoral dos estados do Rio de Janeiro e São Paulo, Brasil. Brazilian Journal of Botany 23:121–132.