The Tree of Life Consolidates

Roland Piquepaille writes "The Tree of Life is an expression first used by Charles Darwin to describe the diversity of organisms on Earth and their evolutionary history. There are only two life forms, — eukaryotes, which gather their genetic material in a nucleus, and prokaryotes, such as bacteria, which have their genetic material floating freely in the cell. Until recently, eukaryotes, which include humans, were divided into five groups. But now, based on work by European researchers, the Tree of Life has lost a branch. After doing the largest ever genetic comparison of life forms they concluded that there are only four groups of eukaryotes."

Comments

Archaea

[virology-not for com]

Let's not forget that many scientists think there are three domains (Prokaryotes, Eukaryotes and Archaea). Archaea are very similar to Prokaryotes in that they don't have a nucleus, but they also share many features with Eukaryotes, including several key enzymes. Due to their similarity to the two other lineages, it is thought that Archaea may in fact be the grand daddy of all life. http://en.wikipedia.org/wiki/Archaea

Re:Archaea

[reverseengineer]

The level of organization being discussed in the paper treats a subdivision of the eukaryotes into "superkingdoms." (There's actually not a completely agreed upon term for this level.) This would put these groups a level below the three domains (Eucarya, Eubacteria, Archaebacteria) proposed by Carl Woese. There's a high-level differentiation between the superkingdoms involved based on organization of flagella, with a high-level split between unikonts (one flagellum) and bikonts (two, naturally). This is of course based on evolutionary ancestry- humans are unikonts, but don't have many cells with flagella.

The unikonts contain the amoebae lineages in one grouping, and the animal and fungi together in another. The bikonts contain the plants and algaes in one grouping, and also a handful of other groupings which take care of the rest of the eukaryotes, most of which are unicellular organisms of various sort. It is the "various sort" that's being ironed out with this paper- the authors argue that on the basis of a common genetic heritage, a couple of the leftover groupings can be consolidated.

Ironically, this move would actually reunite groupings that were fairly recently separated by the argument that no firm evidence of relation existed. Back when the "five Kingdoms" (Animalia, Plantae, Fungi, Monera, Protista) were considered the top level of organization, Protista existed as a sort of "junk drawer" for simple organisms which did not clearly fit in the other categories. Now it looks as though some of these organisms really are related.

Rather, you haven't been keeping up.

[IdahoEv]

When I was in 9th grade (I guess about 10 years ago!), there were five "kingdoms": bacteria, protista, fungi, plantae, and animalia.

What's happened is that better information has rapidly come to the fore as genetic analysis have been done during the last 15 years. The tree has been revised several times.

The five kingdom model was already known to be wrong 10 years ago, but that information hadn't propagated to gradeschool and highschool textbooks yet. If you'd studied biology in college, your information would be more up to date.

These days there are three superkingdoms: Bacteria, Archaea, and Eukarya. (Bacteria and Archaea were formerly grouped together as "monera" or "bacteria" before it was realized that genetically they are as distinct from each other as they are from Eukarya.) Eukarya is broken into a number of kingdoms, and that number has just changed from 5 to 4. Even the 5 they were last year weren't exactly same ones that you learned in school.

Re:Three levels of truth (maybe more...)

[yali]

When religion doesn't get it right, people abandon it completely.

No they don't. They just reinterpret the primary tenets of the religion to suit their current desired conclusions.

A good demonstration of this is in the classic study When Prophecy Fails. A group of social psychologists studied a doomsday cult whose leader had predicted the end of the world. When the predicted date passed and the world didn't end, people did not leave the cult. Instead, they found reasons to explain it away (God was so impressed with their devotion that he put off the apocalypse on their behalf). The end result was that their beliefs were strengthened, not weakened, by disconfirmatory evidence.

(As a sidenote, the study was an important early test of Leon Festinger's theory of cognitive dissonance; Festinger had predicted the cult's response based on his theory.)

Re:Just hoopla over definitions

[Seiruu]

[quote]I never heard of "PLoS ONE"[/quote]

Then you have also never heard of Open Access, because then you would certainly know what PLoS ONE is. A shame you've never heard of it, because it is a very significant and rapidly growing movement within the scientific community. It puts the emphasis on opening up the access of scientific literature to everyone by switching from reader-pays to author-pays models. And with that said, it is very likely that scholars select PLoS ONE or other OA journals (peer reviewed of course) to show that they believe in the Open Access concept and let everyone with a digital connection have access to it.

Re:Just hoopla over definitions

[Anonymous Coward]

I never heard of "PLoS ONE", it claims to be a peer reviewed journal at least. If this was ground breaking I'd expect it to be published in Nature though.

I'm actually surprised you haven't heard of PLoS journals.

PLoS is an open-access publisher of science journals. Basically, the journals are free to access, and content is published under a creative-commons-type license.

PLoS journals are excellent, and rival the best journals in their content. There is no "general" science journal like Science or Nature, but there are topical journals like PLoS Biology, PLoS Medicine, etc. I'd argue that the content in these topic journals are comparable to Nature and Science publications.

PLoS One is a relatively experimental journal published by PLoS that attempts to push the open access model to its limits, by making the peer-review process completely open, where anyone is allowed to comment.

If anything, the fact that this article was published in a PLoS journal raised rather than lowered my expectations regarding its quality.