How did evolution get it right?

[Tres Juicy]

i can back this up with simple logic

 

we have 2 creatures

one is an amoeba small single celled tiny

the other is a elephant

 

we take a hammer and hit both with said hammer repeatedly

the amoeba survives the first 25 hits, but eventually goes "splat"

the elephant survives the first 38 hits then gores and tramples out intrepid research intern

(the elephant is relevantly unharmed, the inters was weak, it has a small bruise in its side)

the intern also survives after 22 surgeries, and an extended hospital stay

 

yes it is an extreme example

but dose this get the point across

big things are harder to kill, because they are big,

as in bigger then you are, as in if you attach them you go "splat"

 

also you know what i meant, dont be petty, we can compare the fitness of two species, not mathematically, but conceptually

 

This is possibly the single worst strawman I've ever seen

[dmaiski]

Take your elephant to the edge of a 15' cliff, along with a mouse instead of an amoeba. They both scare each other and fall off the cliff. The mouse not only survives the fall but scampers off practically immediately. The elephant is broken and crippled, if not dead outright, because he is larger. And that's a more realistic natural occurrence than being beaten by a hammer.

 

true, but that is a one off scenario

in most cases the larger creature will survive more damage to its body then a smaller creature

there is more body to damage, but less can cause any significant damage to the body

 

ok and to simplify the analogy (this makes the analogy realistically infeasible, and imposible)

 

 

one creature is a tine microscopic amoeba

the other horrendously mutated amoeba the size of a bus

 

 

there these 2 creatures can be compared in fitness because they are the same species

unfortunately AMOEBA DO NOT SCALE PROPERLY TO THAT SIZE, they suffer metabolic failure from being too big

thus we must use another species(say an elephant, an intern, and an amoeba),

 

and use a test that allows a comparison of damage resistance of the organisms without accounting for their natural environments (a savannah, a basement, and a petridish (note the lack of cliffs))

this is exactly what i meant by being petty...

 

 

 

 

also take your wonderfully resistant amoeba, put it on a DRY counter, under a uv lamp for a minute

 

im sure an elephant and a lab tech would survive that

 

 

 

 

[Moontanman]

I'd like to address the fish transition to land part of this thread, is anyone aware that fish that can and do survive on land exist and have evolved from fish that could not do so?

 

Walking catfish for instance can survive for long periods out of water as they use their fins to crawl from one body of water to another. Lung fish have evolved the trait to allow them to survive the complete drying up of their ponds, both of these fish have evolved the very same traits that allowed the ancestors of modern land vertebrates to make the transition to land. Mudskippers are yet another example of fish that have evolved the necessary traits to allow them to make short forays onto land. One catfish only lives on land in the leaf litter on the floor of jungles...

 

 

Most people who do not understand the concept of evolution think that a fish evolved all the traits necessary to become an amphibian in one fell swoop but the reality is that it happened in small steps over thousands if not millions of generations generally using traits that had evolved for another purpose to their advantage.

 

Eyes are probably the most often evolved trait on animals, eyes have evolved independently in several groups, vertebrates, arthropods, cephalopods, quite possibly more than once in arthropods. Other groups have lost their eyes and re-evolved them, eyes are a huge advantage in most environments but in some they are a disadvantage and so eyes are lost over time.

 

This idea that an animal somehow evolves a particular trait because they need it is totally bogus... And evolution hasn't gotten anything right, everything is a transition to something else, evolution is not only a blind watch maker it has no goal, no direction, and no control...

[dmaiski]

i have to say moonman got it right

it took over 1.2 billion years for life to evolve from bacteria to humans

that’s roughly 2*10^13 generations

it was basically a very long process of trial and error

no guiding force, no decisions to be made

just who lived to make children and who died 10^13 times over

i amused one generation takes 30 minutes (yes it is arbitrary, no it is not important)

 

 

[Ronald Hyde]

This is another great topic. I was reading an anti-evolution tract with a friend and it showed that a horse was unlikely to have evolved. It used a statistical argument

( lying with statistics is an established art form ) based on the number of genes the horse had and the possibility that that particular horse would appear. It gave some

fantastic odds of the happening. We both said in one voice, 'that's false reasoning', the correct reasoning would be what are the odds of a horse like animal appearing.

The odds of that would be much better, in the scheme of things.

 

I'm beginning to think that Nature is a 'self organizing system' with a few simple organizing principles, you can search for that phrase. And that life and evolution

are practically inevitable in entropically favoritable circumstances.

[jp255]

evolution hasn't gotten anything right, everything is a

transition to something else, evolution is not only a blind watch maker it has

no goal, no direction, and no control...

 

It might not have any foresight, but it is possibly capable of improvement over time. What I mean is, the evolution of particular traits or features has the potential to improve evolution so that the number of generations it takes to adapt to a change in the environment is lower.

 

Examples of such traits:

 

1) natural selection of mutation rates. Evolution would be too slow with an extremely slow mutation rate and with an extremely high mutation rate.

 

2) Stress due to changes in environment can result in higher mutation rates. http://www.ncbi.nlm.nih.gov/pubmed/21236268 whilst this has not explicitly been shown to be advantageous, one can imagine that times of stress where survivability might be reduced the increased mutation rate could be worthwhile.

 

3) non-random meitoic recombination is controlled by PRDM9 in humans. This can accelerate variability in populations in regions of the genome which have large fitness gains with heterozygosity (such as MHC region). The different recombination patterns themselves can vary and be under massive selection, which suggests that some patterns of recombination result in greater fitness. PRDM9 is also one of the fastest evolving genes http://www.sciencedirect.com/science/article/pii/S0168952511000175 doesn't show the full article but still interesting to read the shown parts.

 

Due to the potential for the rate of evolution to change over time due to some of these mechanisms (and probably others too), maybe evolution could be describe as capable of real-time learning (in a sense).

[Tres Juicy]

true, but that is a one off scenario

in most cases the larger creature will survive more damage to its body then a smaller creature

there is more body to damage, but less can cause any significant damage to the body

 

ok and to simplify the analogy (this makes the analogy realistically infeasible, and imposible)

 

 

one creature is a tine microscopic amoeba

the other horrendously mutated amoeba the size of a bus

 

there these 2 creatures can be compared in fitness because they are the same species

unfortunately AMOEBA DO NOT SCALE PROPERLY TO THAT SIZE, they suffer metabolic failure from being too big

thus we must use another species(say an elephant, an intern, and an amoeba),

 

and use a test that allows a comparison of damage resistance of the organisms without accounting for their natural environments (a savannah, a basement, and a petridish (note the lack of cliffs))

this is exactly what i meant by being petty...

 

 

also take your wonderfully resistant amoeba, put it on a DRY counter, under a uv lamp for a minute

 

im sure an elephant and a lab tech would survive that

 

You seem to have misunderstood the use of the word "fit".

 

Not only that, your arguement is flawed:

 

in most cases the larger creature will survive more damage to its body then a smaller creature

there is more body to damage, but less can cause any significant damage to the body

 

Let's say we have an elephant and an ant. If we hit them both with the same hammer and the same force this is not a fair test of who can withstand the most damage.

 

Scale the hammer and force down proportionally to the size of the ant and you will find that proportionally the ant has a far greater damage resistance than the elephant.

Edited September 21, 2012 by Tres Juicy

[akh]

It might not have any foresight, but it is possibly capable of improvement over time. What I mean is, the evolution of particular traits or features has the potential to improve evolution so that the number of generations it takes to adapt to a change in the environment is lower.

 

Examples of such traits:

 

1) natural selection of mutation rates. Evolution would be too slow with an extremely slow mutation rate and with an extremely high mutation rate.

 

2) Stress due to changes in environment can result in higher mutation rates. http://www.ncbi.nlm....pubmed/21236268 whilst this has not explicitly been shown to be advantageous, one can imagine that times of stress where survivability might be reduced the increased mutation rate could be worthwhile.

 

3) non-random meitoic recombination is controlled by PRDM9 in humans. This can accelerate variability in populations in regions of the genome which have large fitness gains with heterozygosity (such as MHC region). The different recombination patterns themselves can vary and be under massive selection, which suggests that some patterns of recombination result in greater fitness. PRDM9 is also one of the fastest evolving genes http://www.sciencedi...168952511000175 doesn't show the full article but still interesting to read the shown parts.

 

Due to the potential for the rate of evolution to change over time due to some of these mechanisms (and probably others too), maybe evolution could be describe as capable of real-time learning (in a sense).

 

 

 

Its an interesting thought, but I think we do need to have caution here. To suggest that evolution can "improve" upon itself, brings into question what is actually an improvement. Also, evolution shows that "improvement" under one set of conditions may not be an "improvement" in another. So improving upon itself may be an "improvement", but change the conditions, and it is no longer an "improvement".

 

Increasing mutation rates are more likely to cause deleterious results than positive results. So, in an scenario of increased stress, does an increase in mutation rate make sense? How does this relate to fitness? When exposed to increased stress, does the increase in mutation rate simply reveal a weakness in a particular biological system?

[dmaiski]

Scale the hammer and force down proportionally to the size of the ant and you will find that proportionally the ant has a far greater damage resistance than the elephant.

 

unfortunately, life doesn’t scale hammers... dose it?

when was the last time the proverbial "falling brick" magically scaled down in size to make it survivable?

thus you have to scale up to survive the falling bricks (tada! the magic of evolution)

 

that’s exactly why it is a fair test, because nature doesn’t care if you are big or small, and drops rocks on people

 

 

 

 

 

redundancy is useful

size allows redundancy

simply put

if you have 1 of something and it fails, you die

if you have 2 of something and it fails, you survive

that’s why being bigger is an advantage over being smaller

 

 

[Tres Juicy]

unfortunately, life doesn’t scale hammers... dose it?

when was the last time the proverbial "falling brick" magically scaled down in size to make it survivable?

thus you have to scale up to survive the falling bricks (tada! the magic of evolution)

 

that’s exactly why it is a fair test, because nature doesn’t care if you are big or small, and drops rocks on people

 

 

 

 

 

redundancy is useful

size allows redundancy

simply put

if you have 1 of something and it fails, you die

if you have 2 of something and it fails, you survive

that’s why being bigger is an advantage over being smaller

 

You're still missing the point. You can't use one scenario to decide what's best for all organisms.

 

Not only that but pretty much any way you measure it ants are far more successful than elephants.

 

Also, life does scale the "hammer". How often does an Ant take massively disproportionate damage?

Edited September 22, 2012 by Tres Juicy

[akh]

unfortunately, life doesn't scale hammers... dose it?

when was the last time the proverbial "falling brick" magically scaled down in size to make it survivable?

thus you have to scale up to survive the falling bricks (tada! the magic of evolution)

 

that's exactly why it is a fair test, because nature doesn't care if you are big or small, and drops rocks on people

 

 

 

 

 

redundancy is useful

size allows redundancy

simply put

if you have 1 of something and it fails, you die

if you have 2 of something and it fails, you survive

that's why being bigger is an advantage over being smaller

 

 

 

Can we stop with the useless analogies? They are so full of flawed logic that it is useless to continue to discuss them.

 

You still have not shown how size relates to redundancy or survivability, or fitness for that matter. Do you have specific examples? Do you have specific examples of "redundancy" and how it relates to fitness? A mouse has two kidneys and so does an elephant, yet they are very different in size. Vertebrates, vary greatly in size, yet all of them have the same body plan. There are some redundancies in vertebrates (two kidneys, two lungs) but they are shared across all species. Arguably, kidneys and lungs are not truly redundant. You seem to be suggesting that a elephant, because it is bigger, will have 10 kidneys while the mouse is stuck with two. As with your hammer analogy, none of these thought processes are actually observed in nature. So it is useless, baseless conjecture to give examples of things that don't exist.

 

Vertebrates have bilateral symmetry. The only organisms I can think of that have true functional redundancy are radially symmetric with distributed brain. These organisms are universally "smaller".

Edited September 22, 2012 by akh

[assholio420]

Dinosaurs did great the most successful animals the planet has ever seen they lived for 230 million years and still going, we call them birds today but technically still dinosaurs,

http://en.wikipedia.org/wiki/Dinosaur

And humans have been roaming around ( depending on what you want to call human ) about 4 million yearshttp://humanorigins.si.edu/evidence/dating

We may be smarter then dinosaurs but they lived a lot longer then we will

 

 

[jp255]

Its an interesting thought, but I think we do need to have caution here. To suggest that evolution can "improve" upon itself, brings into question what is actually an improvement. Also, evolution shows that "improvement" under one set of conditions may not be an "improvement" in another. So improving upon itself may be an "improvement", but change the conditions, and it is no longer an "improvement".

 

An improvement is something which causes a reduction in the number of generations it takes to find the fittest allele after a change to the environment. The it is no longer an improvement point is definitely a possibility, which is why the term learning was used. Anything which causes an increase in the number of generations it takes to find the fittest allele should be selected against and eliminated. The easiest way to show that evolution is capable of self improvement is by using simple mathematical models, it would be extremely difficult to show using real examples.

 

Maybe this has been done, but the model needs to make a random fitness landscape for some genes, keep the population number constant, reproduction rates constant, assume random mating and random cross over. Then run the model at differential mutation rates many times.

 

 

Increasing mutation rates are more likely to cause deleterious results than positive results. So, in an scenario of increased stress, does an increase in mutation rate make sense? How does this relate to fitness? When exposed to increased stress, does the increase in mutation rate simply reveal a weakness in a particular biological system?

 

I'll use a relatively simple example to show that higher mutation rates can be better in times of stress. consider two populations A and B. They each consist of the same progeny(identical), but just under different conditions. Assume that deleterious mutation = death. Assume beneficial mutation rate is deleterious mutation rate/10. Assume that the deleterious mutation rate and death rate are population averages (can be applied to all individuals).

 

Pop A has a deleterious mutation rate of 30%, and a death rate of 50%, 30 will die from deleterious mutation and 50 from stress (e.g predation). Pop B has a deleterious mutation rate of 2%, and a death rate of 50%.

 

In pop A, 30 individuals will have a denovo deleterious mutation and die but some of these individuals might have died themselves from stress had they not have had a mutation (15% chance, on average 15 individuals). In pop B, 2 individuals will have a denovo mutation and die, but some of these might have died from stress had they not have had a mutation(1% chance, on average 1 individual).

 

In pop A, 15 died from deleterious mutation 35 from the death rate and 15 would have had both occurrences. 35 individuals remain alive. Probability an alive individual carries a beneficial mutation is 1.05.

 

In pop B, 1 died from deleterious mutation, 49 from death rate and 1 would have had both occurrences. 49 individuals remain alive. Probability an alive individual carries a beneficial mutation is 0.098.

 

Overall, Pop A has a 15 times higher mutation rate than pop B. The probability an alive individual carries a beneficial mutation is 10.7 times higher. My math is probably wrong somewhere! When the death rate is high, it can be advantageous to increase the mutation rate because some individuals would have died even if they had not received a deleterious mutation. Therefore, the cost of deleterious mutations is dramatically reduced in times of high death rate. Also, even when the death rate is 0, there will still be more beneficial mutations for Pop A, the point is that increased mutation rate can be elevated to search the fitness landscape quickly as a short term solution to a problem (stress).

 

This is example is purely trying to convey the potential for an increase in mutation rate increase to be advantageous. In reality it is of course, much more complicated than that. I have no idea if this mechanism has been shown to relate to fitness in any studies, otherwise I would have posted links. I personally think it is advantageous, it makes sense to me to make more attempts at exploring the fitness landscape for fitness gains when stressed as a short term solution(I believe I recall from a paper that the mutation rates rise the more stress the organism is under, need to look for that link). That is just a hunch though, this example assumes that stress is an indicator of death rate or at least a reduction of the individual's probability of surviving (and also progeny's likely reduction in survival probability also).

Edited September 22, 2012 by jp255

[akh]

An improvement is something which causes a reduction in the number of generations it takes to find the fittest allele after a change to the environment. The it is no longer an improvement point is definitely a possibility, which is why the term learning was used. Anything which causes an increase in the number of generations it takes to find the fittest allele should be selected against and eliminated. The easiest way to show that evolution is capable of self improvement is by using simple mathematical models, it would be extremely difficult to show using real examples.

 

Maybe this has been done, but the model needs to make a random fitness landscape for some genes, keep the population number constant, reproduction rates constant, assume random mating and random cross over. Then run the model at differential mutation rates many times.

 

I understand what you are saying, and I think there was some degree of caution in your initial post. I think we both agree that this is something that may be very difficult to prove. But accepting this thought would suggest that evolution today is somehow superior to evolution 250 million years ago. I just don't think there is a good case for that assertion.

 

 

This is example is purely trying to convey the potential for an increase in mutation rate increase to be advantageous. In reality it is of course, much more complicated than that. I have no idea if this mechanism has been shown to relate to fitness in any studies, otherwise I would have posted links. I personally think it is advantageous, it makes sense to me to make more attempts at exploring the fitness landscape for fitness gains when stressed as a short term solution(I believe I recall from a paper that the mutation rates rise the more stress the organism is under, need to look for that link). That is just a hunch though, this example assumes that stress is an indicator of death rate or at least a reduction of the individual's probability of surviving (and also progeny's likely reduction in survival probability also).

 

Again, I see myself leaning slightly in favor of the other side of the argument. I can see how this might work for an organism with an extreme high fecundity rate and low generation time, but the outcome is statistically poorer for organisms that do not fall under those categories. It seems to me, that it is a tremendous gamble for an organism that is placed under stress to respond by introducing more stress into the system (e.g. increased mutation rates).

Edited September 22, 2012 by akh

[dmaiski]

evolution is a random process,

it evolves creatures in all directions at once

most of these possible creatures die out, simply because they are not feasible, have disadvantageous traits for the environment, or are out competed

 

what is observable:

3600 million years ago earlies known bacteria

1200 million years eukaryotes

600 million years ago multicellular animals

500 million invertebrates, early vertebrates

360 million winged insects

300 million lizards

200-100 million dinosaurs(you know? frigging big things)

100-present mammals dominate ---> humans(again humans are realy smart frigging big things)

i would say that if there was no pressure, or advantage, to being bigger, and more complex

then we would have never evolved from bacteria

i lay no claim as to knowing what the advantage is, how it got there, or where its leading too

(if i did you a. wouldn't understand it b. deny it even exists c. it would be a guess at best)

 

but it dose exist, as shown by the last 4 billion years of history

 

there you go, a firmly supported argument(unless you plan to say the fossil record is all wrong and everything started 5000 ears ago when some extremely powerful, theistic deity farted)

 

if you don’t call a 1*10^17 times size increase in under 3 billion years statistical significant, im not sure what would count and would be in favour of hitting you with the evolution brick (take a brick, write evolution on its side with a sharpie)

 

Edited September 22, 2012 by dmaiski

[dimreepr]

evolution is a random process,

it evolves creatures in all directions at once

most of these possible creatures die out, simply because they are not feasible, have disadvantageous traits for the environment, or are out competed

 

what is observable:

3600 million years ago earlies known bacteria

1200 million years eukaryotes

600 million years ago multicellular animals

500 million invertebrates, early vertebrates

360 million winged insects

300 million lizards

200-100 million dinosaurs(you know? frigging big things)

100-present mammals dominate ---> humans(again humans are realy smart frigging big things)

i would say that if there was no pressure, or advantage, to being bigger, and more complex

then we would have never evolved from bacteria

i lay no claim as to knowing what the advantage is, how it got there, or where its leading too

(if i did you a. wouldn't understand it b. deny it even exists c. it would be a guess at best)

 

but it dose exist, as shown by the last 4 billion years of history

 

there you go, a firmly supported argument(unless you plan to say the fossil record is all wrong and everything started 5000 ears ago when some extremely powerful, theistic deity farted)

 

if you don't call a 1*10^17 times size increase in under 3 billion years statistical significant, im not sure what would count and would be in favour of hitting you with the evolution brick (take a brick, write evolution on its side with a sharpie)

 

 

Size, in the way you suggest, is primarily a result of predation.The elephant is the size it is as a result of the prey/predator arms race. It has no relation to environmental fitness. When you have dug yourself into a hole the general rule of thumb is, stop digging.

 

Edited September 22, 2012 by dimreepr

[dimreepr]

Is double posting some sort of disease? If so, I'm infected...

 

 

Edited September 22, 2012 by dimreepr

[akh]

but larger is better fitting

 

if your larger, you can:

eat the smaller ones,

are less susceptible to destruction due to damage,

have space for redundant systems,

simply put have more of everything

MEANING you will out compete the smaller organisms

 

its like the arms race:

bigger is better

smarter is better

tougher is better

 

thus it is inevitable if you think about it in terms of natural selection

the "fittest" individual will become dominant

and being bigger is fitter, simply because the little things cant harm you as much

 

 

 

Just wanted to quote your original statement, in case you have forgotten. Again, you have not shown in any way that your assertions are correct.

 

 

 

 

evolution is a random process,

it evolves creatures in all directions at once

most of these possible creatures die out, simply because they are not feasible, have disadvantageous traits for the environment, or are out competed

 

what is observable:

3600 million years ago earlies known bacteria

1200 million years eukaryotes

600 million years ago multicellular animals

500 million invertebrates, early vertebrates

360 million winged insects

300 million lizards

200-100 million dinosaurs(you know? frigging big things)

100-present mammals dominate ---> humans(again humans are realy smart frigging big things)

 

Nothing ever got smaller? All this shows is how evolution takes advantage of ecological niches. This may result in being larger or "more complex", but it is not an absolute condition of evolution.

i would say that if there was no pressure, or advantage, to being bigger, and more complex

then we would have never evolved from bacteria

 

 

Again, all this shows is evolution taking advantage of ecological niches.

(if i did you a. wouldn't understand it b. deny it even exists c. it would be a guess at best)

 

Moved onto insults? Good stuff. All I ever asked was for you to provide evidence as to your assertions. Where are your examples of the redundancy assertion?

but it dose exist, as shown by the last 4 billion years of history

 

there you go, a firmly supported argument(unless you plan to say the fossil record is all wrong and everything started 5000 ears ago when some extremely powerful, theistic deity farted)

 

if you don't call a 1*10^17 times size increase in under 3 billion years statistical significant, im not sure what would count and would be in favour of hitting you with the evolution brick (take a brick, write evolution on its side with a sharpie)

 

No, not supported at all sorry.

 

I don't even understand your last point. Was it even a point, or just another insult?

Edited September 22, 2012 by akh

[zapatos]

Size, in the way you suggest, is primarily a result of predation.The elephant is the size it is as a result of the prey/predator arms race. It has no relation to environmental fitness. When you have dug yourself into a hole the general rule of thumb is, stop digging.

 

So predator/prey relationships are not part of environmental fitness? Why not? Aren't predators part of the environment?

 

You still have not shown how size relates to redundancy or survivability, or fitness for that matter.

 

The following link seems to indicate that 'bigger is better' when it comes to predator/prey relationships. Since this is not my field I may be misreading the document (or it may not apply here), but I thought I would add this to the discussion. Of course if predator/prey relationships are not part of the environment then my point is moot.

 

The number of links with smaller predator than prey is much less than would be expected if the ordering of species in webs were independent of body size. ... Thus in most webs the role of size is dominant. In no case is it small.

 

http://www.rockefeller.edu/labheads/cohenje/PDFs/204Cohenpimm.pdf

Edited September 23, 2012 by zapatos

[Ringer]

So predator/prey relationships are not part of environmental fitness? Why not? Aren't predators part of the environment?

 

They very much are, but I assume from what was said it was meant without regard to interspecies predation.

 

 

The following link seems to indicate that 'bigger is better' when it comes to predator/prey relationships. Since this is not my field I may be misreading the document (or it may not apply here), but I thought I would add this to the discussion. Of course if predator/prey relationships are not part of the environment then my point is moot.

 

 

The link just talks about being higher up in the food web. Just because something is a predator does not mean it does well in other areas of fitness. On many levels of fitness smaller organisms tend to score much better, but on some larger organisms do better. In the end there are many ways to fill ecological niches, sometimes it's worth it to be being bigger and sometimes being larger is detrimental. To say one is better than the other doesn't really make sense in an evolutionary sense, though I do tend to side with single celled organisms.

[dimreepr]

So predator/prey relationships are not part of environmental fitness? Why not? Aren't predators part of the environment?

 

 

 

The following link seems to indicate that 'bigger is better' when it comes to predator/prey relationships. Since this is not my field I may be misreading the document (or it may not apply here), but I thought I would add this to the discussion. Of course if predator/prey relationships are not part of the environment then my point is moot.

 

 

 

http://www.rockefell...04Cohenpimm.pdf

 

My post was intended as a rebuttal of dmaiski’s post #15 andcontinued assertion, bigger is automatically better. In some circumstancesbigger is the evolved method of defence but this is by no means the only methodof defence in the predator/prey arms race: Speed agility vigilance foul tastingpoison armour spikes, the list goes on. Also with large size comes inherentvulnerability in extreme situations such as drought and food shortages, forinstance how many large animals survived the PT extinction event?

 

As for the link you’ve provided I think Ringer’s explanationpretty much covers it, far more eloquently than could I.

 

[dimreepr]

So predator/prey relationships are not part of environmental fitness? Why not? Aren't predators part of the environment?

 

 

 

The following link seems to indicate that 'bigger is better' when it comes to predator/prey relationships. Since this is not my field I may be misreading the document (or it may not apply here), but I thought I would add this to the discussion. Of course if predator/prey relationships are not part of the environment then my point is moot.

 

 

 

http://www.rockefell...04Cohenpimm.pdf

 

My post was intended as a rebuttal of dmaiski's post #15 and continued assertion, bigger is automatically better. In some circumstances bigger is the evolved method of defence but this is by no means the only method of defence in the predator/prey arms race: Speed agility vigilance foul tasting poison armour spikes, the list goes on. Also with large size comes inherent vulnerability in extreme situations such as drought and food shortages, for instance how many large animals survived the PT extinction event?

 

As for the link you've provided I think Ringer's explanation pretty much covers it, far more eloquently than could I.

 

Edited September 23, 2012 by dimreepr

[zapatos]

So then if I've got this right;

 

Bigger is often better because it obviously eliminates some of the predators who are smaller than prey. (e.g. A fox is not a threat to a deer.) On the other hand, a predator prey relationship could just as well drive the animals to smaller size, if say the animals lived in areas where the prey likes to hide in small nooks and crannies. In this case, smaller is better.

And size is only one aspect of adapting for the environment. For example, it wouldn't matter if you were bigger than any predators if you were in an area of limited resources and couldn't find enough sustenance to support your size.

 

Is that about right?

[akh]

So then if I've got this right;

 

Bigger is often better because it obviously eliminates some of the predators who are smaller than prey. (e.g. A fox is not a threat to a deer.) On the other hand, a predator prey relationship could just as well drive the animals to smaller size, if say the animals lived in areas where the prey likes to hide in small nooks and crannies. In this case, smaller is better.

And size is only one aspect of adapting for the environment. For example, it wouldn't matter if you were bigger than any predators if you were in an area of limited resources and couldn't find enough sustenance to support your size.

 

Is that about right?

 

I think you got the basic idea. I would change "bigger is often better..." to "bigger can be better...". Without question bigger is not always better, as was asserted by dmaiski. Obviously, this is not the case. If it was, all organism would get forever larger.

 

Its not just the resources that limit size http://www.pnas.org/.../14518.abstract , there are physical barriers to unlimited size. This is why you do not see land animals the size of blue whales. Tree height is limited, but not by available resources http://www.nature.co...ature02417.html .

Edited September 23, 2012 by akh

[dmaiski]

Without question bigger is not always better, as was asserted by dmaiski.

 

might i ask?

where did you pull the always out from?

 

 

 

to explain to everyone what i mean in my original post, since it has obviously hijacked and misinterpreted

 

it was an answer to the question "how did evolution get it right" ie "how did these big ugly things called humans manage to evolve"

it was stating that there is a trend where larger, more complex creatures, evolve if given the chance to

it was also an explanation of why this is so

 

nowhere did i say that size is the only driving force behind evolution

nor did i say that it cant work backwards, sideways, and rimwards, if it particularly deigns to do so

 

all i did say was:

"evolution likes to build bigger things, until they eventually collapse due to structural failure(like leg bones being too thin to support 100tone bodies)

so development of larger organisms is inevitable"

(note the distinct lack of always, never, and only)