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Author Topic: Why doesn't ecological instability rapidly wipe out lots of important species?  (Read 11849 times)

Offline damocles

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OK then Martin, I am no biologist, but I am a decent logician. You are showing a lot of the signs of someone who has come to the forum with an agenda. It is rather pointless from my non-expert position to keep arguing the point with you, so I will sign off from this debate now.
 

Offline CliffordK

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One of the ways genetic shifts occur is with isolation.

Say you had 2 valleys.

Each somewhat isolated from each other.  Each has a population of deer, and a population of large cats (lions).

Now, say in both valleys, the deer reproduce at a rate of 2 fawns per female per year, leading to a "stable population" considering some mortality, food sources, etc.

Now, consider in one valley (A) where the breeding of the lions is such that the replacement population leads to a stable population...  say one cat per 500 deer. 

In the second valley (B), the breeding of the lions leads to a increasing population of lions, perhaps beginning at 1 cat per 500 deer, but doubling every year, so that over the course of a decade 10 doublings, one gets 210 cats, or 1024 cats per 500 deer, or about 2 cats per deer.

Undoubtedly all the deer get wiped out in that valley (B), and all the lions get wiped out too.  0 percent survival rate for both prey and predators.

Back in the valley (A) with a stable population of lions and deer, the survival rate remains high, and both species endure.

Perhaps some of the (B) group of lions is able to migrate elsewhere, but everywhere they go, they carry essentially a lethal mutation.  After wiping themselves out several times, they eventually just die off.

Eventually both the stable population (A) deer and the lions will make their way back to the second valley (B), but hopefully this time carrying the genetic mutations that lead to stable populations.

Certainly I didn't write the models that you are referring to.  But, undoubtedly they don't reflect all of the complexities of the natural environment which may include barriers that lead to differential survival rates of isolated groups of predators & prey.  And, subtle differences in genetics from one population to another, or perhaps even from one individual to another.  And, of course, considering the survival of the herbivore species with respect their food supplies too.

Those species that can not adapt to new survival demands go extinct, and are remembered only for the fossils they left behind.
 

Offline CliffordK

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I suppose with any model one can tinker with the parameters until one gets it to give the output that one desires. 

What we find time and again in nature is that with the absence of Humans, various eco-systems are generally stable.  That means that one can't just tinker with the numbers until one magically comes up with an uneasy stability.  I.E.  2 lion cubs per year, 33% survival to adulthood ==> overpopulation & decimation of population, so try changing it to 1.56 cubs per year...  etc.

What one needs is checks and balances on the populations, including the apex predators.  And, a simple method where beneficial genes such as number of offspring are actually selected for.

The model has to include differences between individuals, and differences between sub-populations within a species.  Perhaps also mobility from one location to another.  Territorial tendencies of various animals, and etc.  And, of course, booming and busting of certain populations. 

Island cultures with very slow exchange of populations between the islands and mainlands?

I suppose one can also say that over time, most species have either changed significantly, or gone extinct.
 

Offline Martin J Sallberg

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A "mutation that leads to stable populations" is nonsense. One specific mutation cannot balance populations in a dynamic system. And again, no predator/prey checks in the world can solve the problem that organisms do have time to overkill their food stocks when they dwindle (collective appetite provided by the population size formed during the plentiful times before the dwindling). It would simply lead to mass extinction anyway. It takes something qualitatively non-Malthusian to explain how mass extinctions can be postponed for so long as they evidently can. Just because something is empirically observed does not mean that a specific theory can explain it.
 

Offline CliffordK

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Mutations in birthrates occur all the time.

When breeding hogs, we would routinely select for larger litter sizes.  Even the number of nipples would vary, and for pigs, the survival rate of litters with more babies than nipples falls off quickly, so we would select for both large litters and lots of nipples.

Obviously selective pressures in nature are different than in a controlled environment in a barn.  And, hardiness may be more important than total numbers.  I think we had at least one litter out in the pasture, and it fared poorly.  In the wild, perhaps pigs with litter sizes of 5 or so would have a higher overall survival rate than litters of 16.

Many mammals that typically have one baby a year will occasionally have twins, and the probability of twins may have a genetic basis.  In cattle, however, fraternal, different sex twins usually leads to female sterility.  Infant survival rate, of course, is important to every species, no matter whether they have one baby, or thousands per year.

Deer in the USA often have twins.  Was that always the case, or is it due to selective pressure from human hunters?

Anyway, we know that "life" has existed on Earth for about 4 billion years.  And Earth is now shared by billions of species of bacteria, amoebas, protozoa, algae, plants, trees, insects, herbivores, and carnivores. 

Other than saying that it can't happen, what is your theory for the species diversity on Earth, and general stability of the ecosystems (including adapting to environmental changes and natural disasters).  Of course, a disaster to one species may be a benefit to another.

If you have a specific model that you wish for us to evaluate, please provide a copy of the model.  Documented source code with clear parameters may be best.  Otherwise, at least a model that can be run on different systems, and that clearly shows the parameters being evaluated.  And, it should be clear how each parameter interacts with the others, or what calculations and assumptions are being used.
 

Offline Martin J Sallberg

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Mutations in birthrates occur all the time.

When breeding hogs, we would routinely select for larger litter sizes.  Even the number of nipples would vary, and for pigs, the survival rate of litters with more babies than nipples falls off quickly, so we would select for both large litters and lots of nipples.

Obviously selective pressures in nature are different than in a controlled environment in a barn.  And, hardiness may be more important than total numbers.  I think we had at least one litter out in the pasture, and it fared poorly.  In the wild, perhaps pigs with litter sizes of 5 or so would have a higher overall survival rate than litters of 16.

Many mammals that typically have one baby a year will occasionally have twins, and the probability of twins may have a genetic basis.  In cattle, however, fraternal, different sex twins usually leads to female sterility.  Infant survival rate, of course, is important to every species, no matter whether they have one baby, or thousands per year.

Deer in the USA often have twins.  Was that always the case, or is it due to selective pressure from human hunters?

Anyway, we know that "life" has existed on Earth for about 4 billion years.  And Earth is now shared by billions of species of bacteria, amoebas, protozoa, algae, plants, trees, insects, herbivores, and carnivores. 

Other than saying that it can't happen, what is your theory for the species diversity on Earth, and general stability of the ecosystems (including adapting to environmental changes and natural disasters).  Of course, a disaster to one species may be a benefit to another.

If you have a specific model that you wish for us to evaluate, please provide a copy of the model.  Documented source code with clear parameters may be best.  Otherwise, at least a model that can be run on different systems, and that clearly shows the parameters being evaluated.  And, it should be clear how each parameter interacts with the others, or what calculations and assumptions are being used.

I never claimed that the biodiversity on Earth could not happen. It obviously happened. I am saying that gene-centered evolution models cannot explain it. The model I propose is that all organisms learn from their mistakes, and those associations lead to emergent planning which dramatically decreases the risk of mass extinctions from ecological instability. Since catalytic closure creates pathways analogous to synapses, learning from mistakes is probably exactly as old as reproduction.
 

Offline CliffordK

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I never claimed that the biodiversity on Earth could not happen. It obviously happened. I am saying that gene-centered evolution models cannot explain it. The model I propose is that all organisms learn from their mistakes, and those associations lead to emergent planning which dramatically decreases the risk of mass extinctions from ecological instability. Since catalytic closure creates pathways analogous to synapses, learning from mistakes is probably exactly as old as reproduction.

You need some kind of a mechanism.
It is difficult to anthropomorphize a blade of grass or an amoeba. 

Humans have difficulties enough with planning for the number of offspring for the population as a whole.  China has imposed a "one child" law with some success, but it has had some severe criticism and difficulties enforcing it.

One can not expect animals, insects, or simpler organisms to have such great planning, or that they would actually share the "planning" between species.

Many animals species have 1 or 2 offspring a year.  Sometimes with the dominant offspring killing or out-competing the other.  In cases such as endangered species, one might want to encourage more offspring, but it can be difficult.

Fish, of course, may have hundreds of offspring per adult fish.  However, a high mortality rate is built into the equation for a large number of eggs.

The reproduction of a species is also dependent on the fertility period and lifespan of the members.  Few choose when menopause will occur, or their own death.

Anyway, you need a better mechanism for these long-term characteristics to be passed down from generation to generation, affect all plants an animals, and great similarities to be found in a species no matter where it is around the globe.
 

Offline Martin J Sallberg

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You need some kind of a mechanism.
It is difficult to anthropomorphize a blade of grass or an amoeba. 

Using the word "anthropomorphism" is like asking association fallacies to attack one's mind. I have never heard a concrete, empirically testable definition separating so-called "true" intelligence from so-called "metaphorical" intelligence. It is just assumptions. Strictly technically, all thinking relies on interaction between particles of matter. And see "Does recent findings necessitate new theories of genetics?".


Humans have difficulties enough with planning for the number of offspring for the population as a whole.  China has imposed a "one child" law with some success, but it has had some severe criticism and difficulties enforcing it.

One can not expect animals, insects, or simpler organisms to have such great planning, or that they would actually share the "planning" between species.

Aha! The computerist fallacy. I debunked it in the thread "What is the brain basis for blame?". Irrationality is a result of justification, and animals , plants and microbes show very little justification.


Many animals species have 1 or 2 offspring a year.  Sometimes with the dominant offspring killing or out-competing the other.  In cases such as endangered species, one might want to encourage more offspring, but it can be difficult.

Fish, of course, may have hundreds of offspring per adult fish.  However, a high mortality rate is built into the equation for a large number of eggs.

And the relevance is?


The reproduction of a species is also dependent on the fertility period and lifespan of the members.  Few choose when menopause will occur, or their own death.

Again, see "What is the brain basis for blame?" and also "Do recent findings necessitate new theories of genetics?". The definition of "choosing" is weird.


Anyway, you need a better mechanism for these long-term characteristics to be passed down from generation to generation, affect all plants an animals, and great similarities to be found in a species no matter where it is around the globe.

Which is given in the same two other threads I referred to above.
« Last Edit: 12/05/2013 14:43:33 by Martin J Sallberg »
 

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