Euglenids (euglenoids, or euglenophytes, formally Euglenida, ICZN, or Euglenophyceae, ICBN) are one of the best-known groups of flagellates, which are Excavate Eukaryotes of the phylum Euglenophyta and their cell structure is typical of that group. This means that they lack traditional mitochondria. They are commonly found in freshwater, especially when it is rich in organic materials, with a few marine and endosymbiotic members. Most euglenids are unicellular. Many euglenids have chloroplasts and produce their own food through photosynthesis, but others feed by phagocytosis, or strictly by diffusion. This group is known to contain the carbohydrate paramylon.
Euglenids are said to descend from an ancestor that took up green algae by secondary endosymbiosis.[1]
Structure and locomotion
editEuglenids are distinguished mainly by the presence of a pellicle (periplast). Within its taxon, the pellicle is one of the euglenids' most diverse features from a morphological standpoint.[2] The pellicle is composed of proteinaceous strips underneath the cell membrane, supported by dorsal and ventral microtubules. This varies from rigid to flexible, and gives the cell its shape, often giving it distinctive striations. In many euglenids the strips can slide past one another, causing an inching motion called metaboly. Otherwise they move using their flagella.
History and classification
editThe euglenids were first defined by Otto Bütschli in 1884 as the flagellate order Euglenida, as an animal. Botanists subsequently created the algal division Euglenophyta; thus they were classified as both animals and plants, as they share characteristics with both. Conflicts of this nature are exemplary of why the kingdom Protista was adopted. However, they retained their double-placement until the flagellates were split up, and both names are still used to refer to the group. Their chlorophyll are not masked with accessory pigments. I would move this sentence down to your section on osmotrophic euglenids, otherwise add some background on the chlorophyll other flagellates have-aburn
-These sentences do not really flow, they are choppy but have good information.
Nutrition
editThe classification of euglenids is still variable, as groups are being revised to conform with their molecular phylogeny. Classifications have fallen in line with the traditional groups based on differences in nutrition and number of flagella; these provide a starting point for considering euglenid diversity. Different characteristics of the euglenids' pellicles can provide insight into their modes of movement and nutrition[3].
As with other Euglenozoa, the primitive mode of nutrition is phagocytosis. Prey such as bacteria and smaller flagellates are ingested through a cytostome, supported by microtubules. These are often packed together to form two or more rods, which function in ingestion, and in Entosiphon form an extendable siphon. Most phagotrophic euglenids have two flagella, one leading and one trailing. The latter is used for gliding along the substrate. In some, such as Peranema, the leading flagellum is rigid and beats only at its tip.
Reproduction
editAlthough euglenids share several common characteristics with animals, which is why they were originally classified as so, there is no evidence of euglenids ever using sexual reproduction. This is one of the reasons they could no longer be classified as animals.
For euglenids to reproduce, asexual reproduction takes place in the form of binary fission, and the cells replicate and divide during mitosis and cytokinesis. This process occurs in a very distinct order. First, the basal bodies and flagella replicate, then the cytostome and microtubules (the feeding apparatus), and finally the nucleus and remaining cytoskeleton. Once this occurs, the organism begins to cleave at the basal bodies, and this cleavage line moves towards the center of the organism until two separate euglenids are evident. [4] Because of the way that this reproduction takes place and the axis of separation, this is called longitudinal cell division or longitudinal binary fission.[5]
Osmotrophic euglenids
editOsmotrophic euglenids are euglenids which have undergone osmotrophy.
Due to a lack of characteristics which are useful for taxonomical purposes, the origin of osmotrophic euglenids is unclear. Though, certain morphological characteristics reveal a small fraction of osmotrophic euglenids are derived from phototrophic and phagotrophic ancestors.[6]
A prolonged absence of light or exposure to harmful chemicals may cause atrophy and absorption of the chloroplasts without otherwise harming the organism. There are a number of species where a chloroplast's absence was formerly marked with separate genera such as Astasia (colourless Euglena) and Hyalophacus (colourless Phacus). Due to the lack of a developed cytostome, these forms feed exclusively by osmotrophic absorption.
References
edit- ^ Keeling PJ (2009). "Chromalveolates and the evolution of plastids by secondary endosymbiosis". J. Eukaryot. Microbiol. 56 (1): 1–8. doi:10.1111/j.1550-7408.2008.00371.x. PMID 19335769.
- ^ Leander, Brian S.; Farmer, Mark A. (2001-03-01). "Comparative Morphology of the Euglenid Pellicle. II. Diversity of Strip Substructure". Journal of Eukaryotic Microbiology. 48 (2): 202–217. doi:10.1111/j.1550-7408.2001.tb00304.x. ISSN 1550-7408.
- ^ Leander, Brian Scott (May 2001). "Evolutionary morphology of the euglenid pellicle". University Of Georgia Theses and Dissertations.
- ^ "Euglenida". tolweb.org. Retrieved 2017-03-30.
- ^ "Reproduction". Euglena. Retrieved 2017-03-31.
- ^ http://www.microbiologyresearch.org/docserver/fulltext/ijsem/53/2/617.pdf?expires=1490904090&id=id&accname=guest&checksum=3D9D3E7FAC9F12B6225DBB596F264428
Bibliography
editExternal links
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Wikipedia Evaluation
edit'Botany'
Is each fact referenced with an appropriate, reliable reference?
Yes, I find that the facts presented are referenced with reliable resources. In fact, there are no “[citation needed]” references.
Is everything in the article relevant to the article topic? Is there anything that distracted you?
Yes, everything presented is relevant. Also, I find that the organization and order of the information given is logical and flows, not taking away or distracting in any way.
Is the article neutral? Are there any claims, or frames, that appear heavily biased toward a particular position?
I find no bias towards a particular position. The article appears neutral at all times.
Where does the information come from? Are these neutral sources? If biased, is that bias noted?
While the list of references was lengthy and could not realistically be entirely reviewed, I found that nearly all the articles appeared very scholarly and credible.
Are there viewpoints that are overrepresented, or underrepresented?
I find that some of the later sections in Botany, such as “Genetics”, are overly represented, or at the least mistitled. Although, it is difficult for me to judge fully, as I am not well versed in the history and importance of botany.
Check a few citations. Do the links work? Is there any close paraphrasing or plagiarism in the article?
After clicking several links, they all appear to be working. I found no evidence of close paraphrasing, but I am not ruling it out as a possibility given the scientific nature of the topic.
Is any information out of date? Is anything missing that could be added?
Most all the articles appear to be at least moderately contemporary. I find this article to be more than sufficient in terms of what is needed, and nothing is missing. I would even be inclined to argue that there is more than necessary in this article.
Check the talk page. What kinds of discussion is going on in the Wikipedia community about how to represent this topic?
There does not seem to be much discussion on this Talk page surprisingly. The majority of the talk page consists of external link modifications.
'Cyanobacteria'
Is each fact referenced with an appropriate, reliable reference?
There are several instances where citations are needed.
Is everything in the article relevant to the article topic? Is there anything that distracted you?
Everything in the article appears to be relevant. The content and overall flow of the article make sense and are not distracting.
Is the article neutral? Are there any claims, or frames, that appear heavily biased toward a particular position?
Overall, the article appears to be neutral. Although, there are certain instances where claims are made such as cyanobacteria being the “most successful group of microorganisms”. This quote, though taken from an outside source, seems to be a matter of opinion.
Where does the information come from? Are these neutral sources? If biased, is that bias noted?
The sources appear neutral and scholarly, though there is an extensive list of sources and exploring all would be exhaustive.
Are there viewpoints that are overrepresented, or underrepresented?
Being someone who is not an expert on cyanobacteria, it is difficult for me to judge how much attention each subsection should be given relative to others. That being said, the general representation of each section seems to be at least moderately similar, so I do not feel there is any under or overrepresentation.
Check a few citations. Do the links work? Is there any close paraphrasing or plagiarism in the article?
After clicking several links, the links appear to be working. I did not find any close paraphrasing or plagiarism in the article.
Is any information out of date? Is anything missing that could be added?
In general, all the information cited seems to be from contemporary sources. There is an article dated as late as 1979, although a 40 year disparity is not immense in the science world, depending on the field.
Check the talk page. What kinds of discussion is going on in the Wikipedia community about how to represent this topic?
This talk page is very active. There are discussions directly in regards to content, such as whether or not there is a certain type of chlorophyll in cyanobacteria, and there are discussions simply about grammar, as well as personalized updates on what contributors did to the page.
Pinophyta
Is each fact referenced with an appropriate, reliable reference?
There are several instances in this article where “[citation needed]” appears, although generally speaking the facts in this article are referenced. In terms of the actual credibility of the references, every reference is one that seems trustworthy and accurate. The only reference that appears semi-unscholarly is a reference to the Guinness Book of World Records.
Is everything in the article relevant to the article topic? Is there anything that distracted you?
Everything in the article is relevant, and I find that the order and flow of the information flows smoothly. In terms of pinpointing the least relevant sections of this particular article, I would cite the sections about seed dispersal for conifers, and the economic impact. That being said, I still find value in these sections, and I would not remove them.
Is the article neutral? Are there any claims, or frames, that appear heavily biased toward a particular position?
Certain statements in the article appear slightly biased towards the prowess of conifers. For example, one such statement in the article claims that conifers are the “economically most important group of the gymnosperms”. While this statement may in fact be true, I believe it could be worded in a more neutral manner, perhaps with some citation to the economic prowess of conifers and other types of trees/plants. That being said, I find the article to be generally neutral and fact-based.
Where does the information come from? Are these neutral sources? If biased, is that bias noted?
The source of the information appears to be from neutral and unbiased sources.
Are there viewpoints that are overrepresented, or underrepresented?
I find that the information that is most talked about is the information that should be given the most attention. Although, I feel there are several sections that are underrepresented. For example, the invasive species and predators sections, (i.e. causes of death to the plant) are given a very small amount of coverage. I believe this information is important from an encyclopedic standpoint.
Check a few citations. Do the links work? Is there any close paraphrasing or plagiarism in the article?
The first link I clicked, “South Island wilding conifer strategy” did not work. I did not find any close paraphrasing in the links I clicked that did work.
Is any information out of date? Is anything missing that could be added?
Several citations are from the 1990s, 1980s, and even some from the 1970s and 1960s. Without knowing how much knowledge and research about the conifer has changed, it is difficult to say if the information is out of date. In terms of something missing that I could see being added, I would first suggest linking to all the cited articles, if possible. The majority of the citations have no link to select. In terms of content that could be added, I think there could be an expansion from the “Conditions for growth” section to a subsection about where these said conditions can be found, and in turn, geographic locations where conifers are most likely to be found/not be found.
Check the talk page. What kinds of discussion is going on in the Wikipedia community about how to represent this topic?
Interestingly enough, a section that I cited as being underrepresented in the article is discussed in the Talk page. One contributor adds that they cannot find much for invasive species, as I noticed it was small, and seeks assistance from others in expanding this section. In terms of other discussion, there is discussion of both content related topics, as well as topics such as editing links the correct way (format-based comments).