Originally Posted By: Orac
I don't buy that they are stronger on the bacterium at all I believe they have less mechanisms with which to adjust to enviroment changes or competition ... hence they die out as a species faster. If you go forward to humans we can even control our enviroment to a high degree.

There is no other answer to this other than "you are wrong". The degree of selection we see is a direct measure of the degree of selective forces experienced by the organism. "Compensatory mechanisms" like the ones you claim we use to somehow be stronger than bacteria are evolved - and often selected - traits and thus show the same evolutionary fingerprints as those observed in bacteria. One is not separate from the other.

As a "rule" (because there are exceptions), bacteria are much more hardy than us, and can survive much wider swings in environmental conditions. And yes, they have compensatory mechanisms just like ours that allow them to do that. Take the lowly e coli - it can survive temperatures from well below freezing to ~40C - a far wider range than most multicellular organisms including ourselves. It can survive transient exposure to pH's as low as 1 and as high as 10, and can thrive in pH 4-8.5; most metazoans are stuck with 7 to 8; above/below that and we die. Same it true of salt concentrations, exposure to heavy metals & other environmental toxins, radiation exposure, etc, etc, etc.

And e coli is average as bacteria go. Some survive & thrive over much broader temperature, pH, radiation, etc ranges.

By any measure - whether its directly quantifying selection's impact on the genome, or by measuring resiliency to environmental stressors/competition/etc, bacteria generally show a degree of fitness far beyond that of metazoans.

Originally Posted By: Orac
This was what I was getting at a complex organism has more things to attack and normal science entropy logic says it should be weaker BUT IT ISN'T that means something is important going on here .. so you missed my point.

No, I didn't miss your point. Nor did I say that 'nothing important' occurred in the development of multicellularity. However, you did just display a further misunderstanding of what science actually says about evolution, and you continue to over-estimate the relative importance - and difficulty - of multicellularity.

Entropy says nothing about the susceptibility of systems to interruption; all it describes is energy flow in a system. So there is no expectation that 'complex' organisms should be more or less susceptible to selective forces (which I assume is what you mean by 'weaker'). Secondly, the number of 'things' you have to 'attack' has no bearing on your evolutionary fitness - for several reasons:

Firstly, more does not always mean more targets for attacks(and thus, greater susceptibility) - or vice-versa. In some cases additional traits allow compensatory responses, thereby decreasing your susceptibility relative to a less 'complex' organism. But more complexity can equal more potential targets for selection. 'Complexity' is a double-edged sword, rather than a universal panacea.

Secondly, the number of "things" (genes) an organism has has no bearing on its susceptibility to selective forces. Selective forces are largely beyond the control of the organism experiencing it.

Originally Posted By: Orac
You need to look at how a complex thing can be more robust than a simple thing because in the real world they never are unless they are engineered ... and no I don't believe in inteligent design smile

Firstly, you cannot equate human-designed objects to life - there is no semblance and the same rules do not apply.

Secondly, you are falsely assuming that we have more 'parts' to break than simple organisms, and thus are more susceptible. The 'parts' evolution acts upon are genes - of which the "lowly" choanoflagellate has ~10,000 genes, and the "lowly amoeba has ~50,000. We have somewhere between 18,000 to 23,000 genes - less than some of those organisms you dismiss as 'simple'.

Thirdly, you assume that 'complexity' solely leads to suceptablity. This is false - indeed, increased complexity often provides additional 'options' for dealing with stressors - i.e. given the same selective force, the change in fitness (and thus th degree of selection experience) is less in a 'complex' organism than in a 'simple' one.

Originally Posted By: Orac
Originally Posted By: ImagingGeek

The first thing to keep in mind is the vast majority of organisms - whether measured as total number of individuals, total number of species, or total biomass - are single-celled organisms (on a scale of 100:1 to trillions:1, depending on your choice of measurement). Meaning that multicellularity, as a survival mechanism, is not overly successful. The question isn't so much why it came about, but rather why it is such a rare evolutionary path.

I would have thought that it is obvious why it is rare go back to all your own comments above.

Its rare because it requires very specific conditions to occur, and those conditions must occur over a long enough period for the multicellularity to become obligate - i.e. the conditions amiable to its formation are rare. Even so, those conditions have poccured - independently - at least three time in lifes history (plants, animals, fungi).

Its rarity has nothing to do with its suceptability to selection - otherwise, there would be no - as in zero - multicellular species.

Originally Posted By: Orac
And I totally agree with the above which when you put your own answers together it tells you why the complex organisms are considered advanced or higher.

No it doesn't. Hubris tells us why they are considered higher or advanced. A basic understanding of evolution tells us those terms are fundamentally flawed.

Originally Posted By: Orac

Using your own logic statements my argument goes like this

- The simple organisms having only simple attack and defensive abilities could not out compete some complex organisms which developed and forced out a survival niche.

The attack and defensive abilities of most unicellular organisms are as complex and deadly as those we have, so your first assumption is false.

Originally Posted By: Orac
- These early simple organisms had plasticity that was the key to there success but it also put some limits on enviroment which more complex organisms could adapt to with more complex structures, behaviours etc.

Quite the opposite - the formation of multicellular organisms was contingent on the environment created by the unicellular ones.

Originally Posted By: Orac

- Ultimately more complex organisms tend to survive as a species longer because they have more ways to solve the survival issues.

Nope. Multicellular organisms evolved to deal with a single selective force; it was one route of many to deal with predation.

Originally Posted By: Orac
All of that defines complex organisms as being more advanced because they forced there way into survival against all the odds and now survive longer as a species than simple organisms.

Again, wrong. All extant organisms were forced to survive against the same odds; the only difference is the strategy used. That is the point you continually miss - anything alive today had ancestors which survived the same sets of environmental conditions. The e coli in your gut and you have run the evolutionary gamut, in the same environment, for the same amount of time.

And you've also made a fatal error/fell into a trap. Measuring the success of an organism in years is meaningless, as years are not the 'scale' by which evolution measures time. In the 'units' of evolutionary time, unicellular species tend to last longer...

...lets see if you can figure out what those units of time are...

Originally Posted By: Orac

If you take this back to simple cars a Model T ford and the latest ferrari are equally successful they both exist today but trying to deny the Ferrari is not more advanced than the Model T is denying the obvious.

There are a number of flaws in your argument. Firstly, cars do not evolve, so the comparison is mute. Secondly, evolutionarily speaking the model t is extinct - no longer in production (reproducing) and thus dead as a species. Of course an extant species still thriving would be considered more advanced/better than an extinct one. And thirdly, your argument for 'advanced' is purely subjective - one could argue the ferrari is less 'advanced' due to its lesser utility, or shorter apparent species "lifespan" than the model 'T'.

The later is a perfect example of why those of us in the biosciences avoid terms like 'advanced', 'higher', etc - whether something is 'advanced' or 'higher' is purely subjective, and depends on the criteria by which you base your measurements. By measure of top speed, humans are more advanced than yeast. As measured by alcohol tolerance, yeast are far more advanced than humans.