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New Estimate Suggests 5.5M Species On Earth, Not 30-100M
An anonymous reader writes "How many species share our planet? According to a recalculation by an international research team, the number is significantly lower than we thought — only around 5.5 million."
Please turn in your geek badge at the door. http://en.wikipedia.org/wiki/Gray_code
in the submitted blurb that it's because they didn't include bacteria in this study.
Yes, they removed a whole group and then the number was less..I'm shocked it tell you, Shocked!
The Kruger Dunning explains most post on
But what definition of species does this estimate use? It may seem odd, but there really isn't a scientific consensus of how to define a "species". That's not to say there aren't strong opinions out there, but it tends to vary from field to field depending on what questions a particular group of biologists is trying to answer. When you actually dig down and look carefully, there are shades of gray and blurring of lines all over the place (as would be expected for a world that is constantly evolving - there's no clear day on which one species becomes two).
(If you're trying to count species from the point of view of a billionaire with a Pokemon mindset, you're going to be disappointed because there will never have a perfect checklist for you to collect)
Let me see if I understand their methods. If we take some sort of statistical sample with trees common to the deserts in Africa (let's say two Beatles named Ringo and Paul live in all of them), we can also determine the number of species on Earth? What happens if we pick a tree species where no Beatles or any species lives? Hell, what if we start with a desert with no trees or life at all? How about the poles? How many Beatles live in them apple trees?
The statistical likelihood of BS seems very high.
Living in Chile
The study doesn't take into account bacteria, archaea nor unicellular eukaryotes. That's where by far most of biodiversity (species count and number of genes and metabolic pathways) and biomass (carbon and nutrients) lie. Typical macroworld arrogance :(
Mules most certainly can mate, and occasionally the female versions get pregnant and have foals. The usual fertility issues with horse/donkey mules are because they have an odd number of genes (63) rather than 62 (donkeys) or 64 (horses) which results in difficulties pairing up genetic material. At least that's what Wikipedia tells me. Would Jamie Wailes lie to me? http://en.wikipedia.org/wiki/Mule
You can't see ANYTHING from a car, You've got to get out of the goddamned contraption and walk...Edward Abbey
How many species share our planet? According to a recalculation by an international research team, the number is significantly lower than we thought - only around 5.5 million...
Cue the science deniers in 3...2...1...
...breathlessly observing that, "Once again, science has proven that it can't be trusted..."
They did not "remove a whole group". The previous estimates of 30 to 100 million species also did not include bacteria.
Support Right To Repair Legislation.
The only definition of a species is that two organisms that cannot mate are, by definition, different species.
To illustrate the subtleties in the actual definition(s) used by biologists, a prof in a class I was in wrote a definition very much like the above, and asked the class "What's wrong with this definition?" He was impressed when I spoke up and said "According to that definition, you and I are not the same species." We were (and probably still are ;-) both male, so he just grinned and said "Ya got it." Funny thing was that a good percentage of the class still had a puzzled looks on their faces, so he had to explain to them what I'd just said.
He later mentioned that there are other important problems with such definitions. One is that people generally want "the same X as" to be a transitive relation. But Ma Nature throws monkey wrenches into such things. Thus, the domestic dog Canis familiaris can interbreed with wild wolves and jackals, but wolves and jackals can't interbreed (or rather, they can, but the few offspring are sterile). So dogs are the same species as wolves and jackals, but wolves and jackals are different species. There are many examples like this.
A more subtle sort of example is what are sometimes called "range species", in which matings of critters not too far apart are fertile, but when the distance gets above some threshold, fertile hybrids are no longer possible. This happens in a lot of shoreline species.
We've had a couple of centuries to work out such ideas, and biologists have been fairly successful at dealing with this fairly important concept. But you need more carefully worded definitions than the above.
If you want to read about an especially difficult "species" distinction, google for the results of mating lions with tigers. That should convince anyone how tricky it is to get the definition right.
Those who do study history are doomed to stand helplessly by while everyone else repeats it.
And beavers build dams in order to change their environment to their liking.
Termites build habitats for themselves with an internal environment to their liking.
Ants, ditto.
Your point was?
"I do not agree with what you say, but I will defend to the death your right to say it"
OP is right, in that there are lots of different definitions of "species" and none of them is unambiguous. "Can mate" doesn't seem to be used much amongst taxonomists, not just because of bacteria but also because of things like ring species.
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It's one possible solution to the problem of classifying Ring Species. For the simplest case, where populations (A+B) could be classified as a species, and populations (B+C) could as well, but (A+C) could not, how many species do you have? I could make strong arguments for one, two, two-point-five, and three.
It gets even trickier with longer rings/chains. If (A+B), (B+C), and (C+D) all meet a definition of "species", but (A+D) doesn't (requirement of "ring species"), that still leaves open questions about (A+C) and (B+D). One possible solution is to use larger or smaller fractions depending on the answers to those pairings.
Of course, there's also the issue of defining "species"--what Wikipedia calls the "Species Problem". Note that I was careful to say above, "could be classified as a species", or "meet a definition of species". The common definition, "able to produce fertile offspring" is almost meaningless to microbiologists (where sex--genetic sharing--is separate from reproduction) and unanswerable by paleontologists, since extinct species rarely reproduce.
As Dawkins argues, the whole concepts of species and families and kingdoms seems to stem from an attempt to inflict Platonic idealism on a messy and ambiguous reality. Life is chaotic. Should we be surprised if it turns out to have a fractal nature and fractional dimension? :)