Sciencemadness Discussion Board

Balance of Nature

franklyn - 5-9-2015 at 07:53

Remarkable Discovery

www.washingtonpost.com/news/energy-environment/wp/2015/09/03...

Tsjerk - 5-9-2015 at 09:18

Why is this remarkable? It further proves what was predicted... Which is nice and definitely worth a paper. But remarkable?

Sulaiman - 5-9-2015 at 09:41

to me it is remarkable how many predator-prey cycles
must have been required to get an evolutionary balance of numbers/voracity/rates of population increase and decrease etc.
just to get Earth ready for me :P

[Edited on 5-9-2015 by Sulaiman]

Little_Ghost_again - 6-9-2015 at 18:16

seems way oversimplified to me, most/many prey have more than one predator, also alot/most predators eat more than one type of prey. So for example you get whole shoals of mackerel wiped out by say dolphins or whatever but the predator dosnt decrease because the shoal has gone it goes and eats something else.
Dunno but seems like they are trying to explain something complicated as if its a simple question of one prey and one predator. interesting to think about though, makes me think of fox's there only real predator is man and dogs, and yet both man and dogs are around in large numbers but the fox population steadily grows, I guess you could argue dogs and people are not a real predator to the fox, so that would account for an increase in numbers of fox's. However the fox has to eat so the increase in foxs should impact its prey, this happens to say a rabbit population but when rabbits get thin on the ground then the fox finds something else to eat. I just cant see that fitting a fixed ratio.
Fuck it I am off to bed :D

macckone - 7-9-2015 at 07:50

The most interesting thing about this is that predators don't increase in direct proportion to prey. They lag a good bit. This means that in an ecosystem that is overpopulated with prey animals, the predators will not actually kill off sufficient prey to bring the system back in balance. The prey animals will die off due to vegetation overgrazing rather than predation to bring the system back into balance.

aga - 7-9-2015 at 08:24

Terms like 'natural balance' are misleading, in that the natural balance as regards, say, foxes, could well be extinction rather than some arbitrary ratio of foxes to their prey species.

Nature tends to be rather more complicated.

careysub - 8-9-2015 at 06:14

The Washington Post article, and commentary here, grossly misrepresents the actual findings of this study, which makes it sound like it is just dealing with mammalian predators. What is remarkable is that it extends to all levels of biological communities across kingdoms.

Here is the full abstract:
Quote:

INTRODUCTION
A surprisingly general pattern at very large scales casts light on the link between ecosystem structure and function. We show a robust scaling law that emerges uniquely at the level of whole ecosystems and is conserved across terrestrial and aquatic biomes worldwide. This pattern describes the changing structure and productivity of the predator-prey biomass pyramid, which represents the biomass of communities at different levels of the food chain. Scaling exponents of the relation between predator versus prey biomass and community production versus biomass are often near ¾, which indicates that very different communities of species exhibit similar high-level structure and function. This recurrent community growth pattern is remarkably similar to individual growth patterns and may hint at a basic process that reemerges across levels of organization.

RATIONALE
We assembled a global data set for community biomass and production across 2260 large mammal, invertebrate, plant, and plankton communities. These data reveal two ecosystem-level power law scaling relations: (i) predator biomass versus prey biomass, which indicates how the biomass pyramid changes shape, and (ii) community production versus community biomass, which indicates how per capita productivity changes at a given level in the pyramid. Both relations span a wide range of ecosystems along large-scale biomass gradients. These relations can be linked theoretically to show how pyramid shape depends on flux rates into and out of predator-prey communities. In order to link community-level patterns to individual processes, we examined community size structure and, particularly, how the mean body mass of a community relates to its biomass.

RESULTS
Across ecosystems globally, pyramid structure becomes consistently more bottom-heavy, and per capita production declines with increasing biomass. These two ecosystem-level patterns both follow power laws with near ¾ exponents and are shown to be robust to different methods and assumptions. These structural and functional relations are linked theoretically, suggesting that a common community-growth pattern influences predator-prey interactions and underpins pyramid shape. Several of these patterns are highly regular (R2 > 0.80) and yet are unexpected from classic theories or from empirical relations at the population or individual level. By examining community size structure, we show these patterns emerge distinctly at the ecosystem level and independently from individual near ¾ body-mass allometries.

CONCLUSION
Systematic changes in biomass and production across trophic communities link fundamental aspects of ecosystem structure and function. The striking similarities that are observed across different kinds of systems imply a process that does not depend on system details. The regularity of many of these relations allows large-scale predictions and suggests high-level organization. This community-level growth pattern suggests a systematic form of density-dependent growth and is intriguing given the parallels it exhibits to growth scaling at the individual level, both of which independently follow near ¾ exponents. Although we can make ecosystem-level predictions from individual-level data, we have yet to fully understand this similarity, which may offer insight into growth processes in physiology and ecology across the tree of life.


So this relationship exists with every "predator-prey" system from microrganisms to the largest mammals, and includes the plant kingdom as well.

The existence of power law relationships like this is a manifestation of underlying principles of organization that give rise to them (generative laws). Establishing what these laws provides key insights into how living systems are organized at levels.

As an example a family of generative laws are "attachment processes", ones in which "those that have, get more". That is, the more of some "asset" an entity has, the more likely it is to get more of it; there is no leveling principle.

The speciation structure within tree-of-life families was shown to have a power law relationship back in the 1920s due to the fact that diverse genera were likely to add more species (more opportunities for speciation events) than genera with few species.

The structure of links in the Internet is also an attachment process (sites with more links tend to get even more links), giving rise to a power law structure.

So is the distribution of wealth, those that have more money get more money.

There is also a log-normal distribution that looks very similar power laws, but are distinct. If you can differentiate between them, then that provides insights into the underlying generative laws.

Here is a paper on the subject of generative laws:
http://www.stat.berkeley.edu/~aldous/Networks/1089229510.pdf

(Generative laws, and statistical distributoins in nature, are an interest of mine.)


Bert - 8-9-2015 at 18:39

Until a species that can learn how to re-write their own DNA comes along... Then all bets are off.

macckone - 9-9-2015 at 09:26

Quote: Originally posted by Bert  
Until a species that can learn how to re-write their own DNA comes along... Then all bets are off.

Infestations of aggressively destructive species are usually controlled
by the natural development of viruses targeted to the species. Or
they destroy the environment that they need to survive often wiping
out other species in the process. I think we are on the later course
of action.

careysub - 9-9-2015 at 12:16

Quote: Originally posted by Bert  
Until a species that can learn how to re-write their own DNA comes along... Then all bets are off.


Species have come up with something better - nervous systems. A natural neural network easily stores far more information than DNA, and modify that information very rapidly. Behavioral changes to a population that rely on DNA changes are far, far slower (many, many generations) than changes due to neural processing which can in much less than a single generation.

Behavioral changes, thanks to biological feedback systems, can even modestly change physical form far faster than DNA changes.

aga - 9-9-2015 at 12:24

Quote: Originally posted by Bert  
Until a species that can learn how to re-write their own DNA comes along... Then all bets are off.

All species do exactly that, all of the time.

Some do it faster than others, e.g. Flu Virus.

Whether they do it by Will or by sheer dint of their existing genetic rules is largely irrelevant when considering life systems on a planetary scale.

(Lizard aliens can of course modulate their own DNA, appearing almost human at will.)

Bert - 9-9-2015 at 13:46

Had a bit more of deliberate, planned genetic engineering in mind, Aga... Not thinking evolutionary pressures + genetic drift/horizontal gene transfer are anything different than what we've had up to this point- Which produced the pattern of inter species population flux relationships of the OP article?

Of course, I didn't tightly define my terms. Touché! Pretty good shootin' fer a drunk-

aga - 9-9-2015 at 14:47

P'kyaaaang !
... as the shot misses, and riccochets off an empty beer bottle nearby, which amazingly remains unharmed.


aga - 9-9-2015 at 14:52

Well, the notion that Us, as dwellers on This planet doing anything Un-Natural is frankly ridiculous.

We are part and parcel of it.

Whatever we think of as our Nadir, we're simply the same as Fungii and bacteria - part of the same Life System in this dirtball in space.

Personally i've recently expanded my knowledge of What We Are to include the Moon, which is Old News to human females of breeding age.

careysub - 9-9-2015 at 18:19

I should point that no genetic change is "goal directed" via gene transfer or any other natural process.

Whether a gene change has any effect at all at the somatic level, or if so, what that change is, is entirely independent of the process itself. Only if the gene change manifests itself in someway, allowing selection to act upon it, does it have any possibility of enhancing fitness (usually the reverse).

Behavioral changes *are* goal directed however, and are designed directly to enhance fitness (though they may fail to do so).

The power that nervous systems bestow in allowing species to dominate their environment is easy to see.

franklyn - 14-1-2016 at 18:49

http://news.yahoo.com/ancient-people-conquered-arctic-least-...

www.yahoo.com/tech/frozen-mammoth-injuries-place-humans-1952...

chemrox - 9-2-2016 at 14:47

Quote: Originally posted by aga  
Terms like 'natural balance' are misleading, in that the natural balance as regards, say, foxes, could well be extinction rather than some arbitrary ratio of foxes to their prey species.

Nature tends to be rather more complicated.

I agree and a lot of misleading comes from trying to analogize to human activity from nature in general. I've heard LeChatlier (sp?) quoted as an excuse to sabotage nature. Overpopulation will not be solved without sacrificing nature (read as DNA). In other words tell the bitches with SUVs to quit breeding

chemrox - 9-2-2016 at 14:50

Quote: Originally posted by franklyn  
Remarkable Discovery

www.washingtonpost.com/news/energy-environment/wp/2015/09/03...


Page Not Found
Submitted by sacrilege [1] on 09/23/2014 11:01 -0500

Any way to recover this?

@Bert: "a species" ? should be plural my friend

[Edited on 9-2-2016 by chemrox]