Talk:Eukaryote

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Eukaryotes

  • arose from prokaryotes and developed into larger more complex organisms
  • both unicellular and multicellular

Sportfanatic (talk) 00:36, 5 January 2008 (UTC)

The taxobox is going to present considerable difficulty here. First, there are problems associated with top-level groups, for which see Talk:Bacteria. More importantly, however, there is no good way to divide the eukaryotes. The standard approach is of course to divde them into four kingdoms, with most forms thrown in the Protista, but this is not really standard when talking about the eukaryote groups in general, and the domain was partly established to get rid of that group. At the moment, some people recognise varying numbers of kingdoms, while others abandon ranked taxa altogether when talking about the top-level groups. There are dozens of these, ranging in size from the kingdoms to peculiar species without any known relatives, as listed on evolutionary tree.

All in all, I would be surprised if any ranked or comprehensive breakdown would be the suitable quick overview that taxoboxes are supposed to provide, and I think it might probably better to skip it. It's not like it's that important to extend the system to the domains - there are only three, of which the other two can double as kingdoms, and they are not always treated formally. The composition of the eukaryotes is already given in the second sentence of the article, and any more detailed notes on systematics would probably warrant another section (which we may want anyways).

Josh

  • I fully recognize the problems here. One way it could be handled is to put in parentheses after Protista in the taxobox something like - (metakingdom) to indicate it's not really normal, and let people go to the Protista page for further breakdown. What both classical taxonomy and cladistics do clearly share is hierarchy, and I think we should do our best to blend these. The reasons are these:
    • First, people mentally organize information logically, and when there are certain fixed categories, it's easier for people to conceptualize information.
    • Second, it makes for greater ease of navigation thru the system.
    • Third, it's adapting a system in long usage that's not about to go out of business any time soon, so forcing it to better adapt to reality is a good thing.
  • Now, the classification of the various unicellular organisms are certainly outside my area of core expertise, so I certainly welcome any good modifications to anything I've done. jaknouse 16:03 Apr 2, 2003 (UTC)

I see the taxobox on the left margin overwritten by text. Is this a formatting problem or my browser? Skeetch

It looks like the div tags around tables break them on older browsers. Since the tables can be placed on the right without them, is there any reason not to get rid of them?

That fixed it for me. I'm using a current, MS-WIN2000 version of IE. Skeetch

Ok. It looks like the tags were added to create margins, but if they don't work on even newer browsers, they should definitely be removed in all cases. I will notify the author who had put them in.

A quick note on some reverts. It was added that some eukaryotes - for instance diplomonads and microsporidia - do not have organelles. These groups are unusual in lacking mitochondria, but all eukaryotes have nuclei and an internal membrane system, and diplomonads have other organelles such as flagella. I also changed back the passage explicitly calling the protists a kingdom; not everyone classifies the eukaryotes that way, I don't think it makes things any more clear.

Also, someone changed the eukaryotes share a common origin to the eukaryotes are thought to share a common origin, and I've changed it back. There is no serious doubt on the matter, and we shouldn't treat all biology as a matter of opinion. Thanks, Josh


Question: the reproduction part mentions that eukaryotes have a *smaller* volume to surface ratio than prokaryotes. It seems to me that since they can be a thousand times as big that they should have a *larger* volume to surface ratio, or, conversely, *smaller* surface to volume ratio? Cheers, Frank.

Contents

[edit] pronunciation

how do you say it GrimRepr39 22:58, 6 September 2006 (UTC)

'You-carry-oat' Wikinterpreter

[edit] Archaea

The article needs to mention the modern three-domain system eukarya/archaea/bacteria very early on (say, in the second sentence). As it is, the article reads like the distinction between eukaryotes and prokaryotes is still thought of as the basic division of life; this view is obsolete. Archaea are more closely related to eukaryotes than to bacteria. In the article they are barely mentioned at all. --mglg(talk) 23:39, 11 September 2006 (UTC)

well, i went and revised the intro. then saw your request, so i cleared up the fact that the three domains made up all of life, with link to domain biology. Wikiskimmer 02:16, 29 June 2007 (UTC)

[edit] Crista shapes

It's impossible to tell from the illustration whether the crista folds are shaped like condoms or toadstools (such as those that grow off the side of a tree). MaxEnt 15:50, 1 July 2007 (UTC)

if your question is serious, the answer is that mitochondrial crista have DIFFERENT shapes in different groups of eukaryotes.Wikiskimmer 18:44, 1 July 2007 (UTC)

[edit] Eukaroyte intro

he following is confusing: "Finally, reproduction involves a complex way of separating the duplicated chromosomes, called mitosis, which is also mediated by arrangements of microtubules."

When seeing "reproduction" I think of sexual reproduction, which is meiotic. I would clarify and expand using the concept of cell division such as

Eukaroytes utilized two types of cell division, each starting with DNA replication and separation of Chromosome pairs within a nucleus. In mitosis one diploid cell divides to produce two genetically identical cells. In meiosis, which is required in sexual reproduction, one diploid cell undergoes two stages of cell division, resulting in four haploid cells (gametes) each of which is genetically different. Kant58 19:15, 13 July 2007 (UTC)

Be bold! Bendž|Ť 20:05, 13 July 2007 (UTC)

that was my sentence, i merely wanted to succinctly describe the diff between euks and proks for the intro. to me that involves chromosomes and complex assemblies of microtubules. do you think it should be spelled out more in the intro or put in the body? ok, i tried it. Seems too complex now!Wikiskimmer 22:54, 13 July 2007 (UTC)

[edit] Cytoskeletal Structures

The description of the structure of microtubles is both confusing and misleading. "They are supported by a bundle of microtubules arising from a basal body, also called a kinetosome or centriole" This implies all three are the same and that Basal body is the superior term, which is contradicted first by the links for basal body, centriole & kinetosome, and the later sentences on centrioles. —Preceding unsigned comment added by 212.85.13.68 (talk) 09:33, 20 October 2007 (UTC)

[edit] Animal cells

An animal cell is a form of eukaryotic cell that makes up many tissues in animals.

Well, duh? Jack the Stripper (talk) 17:14, 19 November 2007 (UTC)

[edit] An update:

This is how the Eukariote tree looks like today (only four branches):

  • Plants (red and green algae, including land plants)
  • Unikonta (Animalia, Fungi and Amoebozoa)
  • SAR (Stramenopiles+Alveolates+Rhizaria)
  • Excavata (the remaining free living and parasitic organisms)

For the moment it is not possible to place Chromalveolate in any of these four groups, but it is most likely it belongs in the SAR-group, which will probably be confirmed in just a few years time (Kamran Shalchian and Kjetill S. Jakobsen).

Just wanted to mention it. 217.68.114.116 (talk) 09:53, 28 December 2007 (UTC)

The phylogeny proposed above appears in this paper:
Burki et al. 2007. Phylogenomics Reshuffles the Eukaryotic Supergroups. PLoS ONE 2(8): e790.
By the way, chromalveolates consist mostly of stramenopiles + alveolates, so they are a major part of the "SAR" group by definition.
While some agreement has emerged recently on the membership of eukaryotic supergroups, this paper shows that there is still much disagreement on how these groups are related to each other. We may be better off leaving contentious taxa like Cabozoa, Corticata, and Bikonta out of the taxoboxes until these are better resolved.

Cephal-odd (talk) 14:13, 16 January 2008 (UTC)

Hopefully there will be some answers in not too long. A few supergroups are better then a huge number of smaller groups. If Telonemia (in the Chromalveolata) belongs in the SAR group, then perhaps SAR and Unikonta are mest closely related, as Telonemia is said to remind a lot about basic animal cells. I also notice the list already mentioned does not include the glaucophyte algae, but i guess they belongs to the plant group anyway. 217.68.114.116 (talk) 13:54, 18 January 2008 (UTC)
My reading of the Burki et al paper is that there is a lot about this stuff which isn't certain yet. If you aren't sure of the monophyly of, say, the Chromalveolata (or one of the subgroups within it, or whatever), it is hard to sample enough different species to make sure that your cladogram really makes any sense. I agree with Cephal-odd that Cabozoa and Corticata are to be treated as hypotheses (and perhaps not even the favored ones) rather than as established. I'm not sure about Bikonta; at least as far as I could tell from the Burki et al paper their data seems to support bikont versus unikont distinctions. As for glaucophytes, yes those are part of Archaeplastida (at least according to our articles). Kingdon (talk) 20:35, 23 January 2008 (UTC)

[edit] Eukaryotes and the evolution of sex

Bernt Walther has proposed that the origin of eukaryotes occured at the same time as the origin of sex. Is this something we should mention in the article?--Gunnar Mikalsen Kvifte (talk) 22:25, 3 February 2008 (UTC)

I would think that Evolution of sex would be the place for any discussion of this. It is hardly an area I know much about, but I see a lot of speculation and not so much well-established fact, which might make it difficult for us to say much about it. Kingdon (talk) 03:22, 4 February 2008 (UTC)

[edit] fossil record

A few months ago, the start of the fossil_range parameter was changed from Proterozoic to Mesoproterozoic. It's true that the Mesoproterozoic saw a big increase in eukaryote like fossils, including Bangiomorpha, the first fossil to fit into a modern group (red algae in this case). But there is some evidence of eukaryotes going back before 1600 million years ago, into the Paleoproterozoic, including acritarchs and the possible alga Grypania. Because these claims are not without controversy, I think it best to leave the starting time as Proterozoic, and have made it so in the taxobox. Cephal-odd (talk) 05:34, 18 May 2008 (UTC)

Fossil_range is for the fossil record only. We don't have a field for molecular divergence yet, but we're discussing at at WP:TOL. Perhaps you'd like to share some input there. Now the big question...you just said that the oldest fossil is from Mesoproterozoic, but in the article you indicate quite clearly the Paleoproterozoic...which one is actually the oldest fossil? Bob the Wikipedian (talk) 20:56, 18 May 2008 (UTC)
Agreed about the fossil_range value. So far I haven't even attempted to address the molecular clock estimates of divergence times between eukaryotes and whatever prokaryotes they're most closely related to. Such an estimate would probably have a huge margin of error. The Knoll et al. paper cited in the article clearly argues for the presence of Eukaryote body fossils going back to the Paleoproterozoic. The Mesoproterozoic just has a lot more such fossils, including ones that have convinced almost everyone that eukaryotes were around then. Also, the oldest fossil that can be assigned to a specific modern group of eukaryotes is Bangiomorpha from the Proterozoic.
Biomarkers are another issue again. These are quite different from molecular clock estimates of divergent times; they are chemical traces that are thought to be left by a particular kind of organism -- in this case, steranes from eukaryotes dating to 2700 Ma. These biomarkers are not usually considered fossils, but with a little stretching they could be considered trace fossils, since they are an observable remnant of the organisms' activity, in contrast with a theoretical divergence date. Cheers, Cephal-odd (talk) 22:45, 18 May 2008 (UTC)
You've inspired me to go look up the word "sterane". :) Bob the Wikipedian (talk) 12:24, 19 May 2008 (UTC)