We know that an organism or species can adapt to environmental change or a novel environment. But this can happen due to one or a combination of several adaptive mechanisms. What are these mechanisms and what do we know them as? My current classification, based on reviewed literature, is genetics (evolution by natural selection), phenotypic plasticity, and behavioral adaptation.
Darwin's theory has a thermodynamic basis. Thermodynamics establishes a common genetic code in the universe. Biological diversity is a result of thermodynamic differences of environment !
http://endeav.net/news/27-evolution.html
http://endeav.net/news/17-thermodynamic-mechanisms-sculpting-living-organisms.html
Dr. Gladyshev, forgive me for being naïve, but if thermodynamics establishes a common genetic code in the universe, shouldn't all life forms in a similar thermodynamic environment across the globe be identical?
Daniel, I think you are quite right! Genetic selection is true for every organism. If we speak about plants, behavioral adaptation is less evident. But, there are some reports about inherited epigenetic adaptation and induced mutations via transposone move (see works of Haifa University on barley around 1998-2000). Bacteria are the most interesting case. They can do fast change of GC/AT ratio in adaptation to new life style. Plant pathogens can delete some wrong genes (like avirulence genes= T3SS effectors) in resistant plant, and live happy without them...
Dear Peter,
There are different forms of life. These forms are dependent on the environment. Genetic code, I believe, must be the common. This is a consequence of hierarchical thermodynamics.
Best,
Georgi
As I know, genes for adaptation to some specific environment already exist in the individuals of a species. One of the possible mechanisms is that on entering into a new environment, the genes in the individual turn on and start to synthesize the product in the body required for adaptability of that environment.
I think genetic adaptation (evolution by natural selection) is a between generational form of adaptation, which in long lived organisms is very long term adaptation. What about short term (within generational) adaptation? Avoidance of suboptimal conditions, gradient tracking, etc, etc?
I think this is what you were suggesting with the epigenetics Alex.
Daniel,
The short-term adaptation can be caused by pure biochemical reasons, like accumulation of cold/frost/heat/drought/pathogen protecting compounds: sugars, proline, polyphenols, phytoalexins, flavonoids, glucozynolates, etc. One stress will cause accumulation of chemicals protective to other stresses. Epigenenic adaptation can be caused by small RNA, DNA methylation, alternative splicing/processing of genes/proteins, and by certain DNA fragments proliferation. Somatic mutations stimulated by stress could be a kind of such adaptation, and some potato genotypes, apple plants were obtained by such way.. As I said, bacterial genome is more rich for such events, but mechanisms are not studied yet, despite all methods available...
”My current classification, based on reviewed literature, is genetics (evolution by natural selection), phenotypic plasticity, and behavioral adaptation. ”
Well, this is (roughly) enough.
Do you seek for something else, too?
Thank you, Alex, your suggestions basically fall under phenotypic adaptation (i.e. plasticity) correct? I am merely trying to organize a way to search for literature that is relevant to the broader types or mechanisms of adaptation.
Zsolt, I was just wondering if there were any other broad categories in addition to those three I already have.
Daniel, I almost forgot! Polyploids are very important for cold adaptation. Plants simply increase chromosome number, some fungi increase number of nucleus
Daniel,
Genetic, epigenetic and behavioral variants can all be subject to natural (or sexual) selection, so in the end, the process is the same, as long as we have variation, heredity and fitness differences in phenotypic traits.
Plasticity allows morphological, physiological and behavioral "in-life adaptations" that can be faithfully inherited or assimilated genetically. In this case, they will be equally subject to selection as genetic variation is, and the difference is that plasticity can broader the spectrum of possible phenotypes (norm of reaction) that selection will "find" in a population. But not all results of plasticity (including learned behaviors) can be transmitted between generations, in this case, being confined to short-time adaptations and without long-term phylogenetic consequences.
That's a great way of putting it Daniel. I think where I am making the distinction between natural selection, plasticity, behavior, epigenetics, etc, is the time-scale. Obviously natural selection will act at a rate consistent with population turnover, whereas plasticity can act in one or more instances in a single generation. Then in terms of behavior, a fish might cope with unfavorable conditions by physiological adaptation, through lowered metabolism or active avoidance of currents of excessive velocity or switching to different food sources. The latter might not require going through any long-term adaptive change that will significantly reflect on progeny or subsequent generations. It may just be a habitual change, that enables the organism to continue as it would in previous or alternate environments, assuming nothing else is placing a selective pressure on it.
I got your idea Daniel, and as you, I also find very useful to distinguish between those short-time, in-life adaptations, from the phylogenetic ones - through selection, as two different, but also connected processes.
The interesting current research on epigenetics and social learning results are showing that this short time adaptations can potentially "pave the way" for a phylogenetic adaptation through plasticity that is re-established or inherited through consecutive generations.
In the other direction, is also very interesting understand the process of selection of plastic traits, being plasticity itself a phylogenetic adaptation of organisms to survive and reproduce in changing environments.
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