Naked Science Forum
General Science => General Science => Topic started by: Giles Farnaby on 16/10/2017 10:19:54
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Dear gymnosophists:
I googled extensively, but to no avail, and I was then told this was the place to ask my questions, so here they go:
I) is there a model of the maximization of biological replication at different levels? (ie, how much and how fast genes/individuals/species could reproduce in an ideal, albeit real, environment.)
II) given that some genetic traits are a must for reproduction to occur (eg, a moth’s ability to metamorphosize), is there a model of how said traits may have appeared, proliferated and finally become sine qua non in a species?
Any help from you will help more than you think.
And many thanks in advance!
Giles
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These are very good questions.
I) is there a model of the maximization of biological replication at different levels? (ie, how much and how fast genes/individuals/species could reproduce in an ideal, albeit real, environment.)
The question would be how ideal? With unlimited living space, unlimited resources, and nothing around to kill individuals, the reproductive rate could easily be calculated using basic math. The growth rate would be exponential and quickly overwhelm any real environment on Earth. Under more realistic circumstances, you could theoretically use the available energy from the Sun to calculate how much metabolic activity could be supported by it. Just keep in mind that every notch you move up the food chain you lose about 90% of available energy in the form of waste heat. Plants aren't 100% efficient either, so you'd need to account for that as well.
II) given that some genetic traits are a must for reproduction to occur (eg, a moth’s ability to metamorphosize), is there a model of how said traits may have appeared, proliferated and finally become sine qua non in a species?[/color][/i]
This is a little more difficult to answer. Some traits are much more complicated than others so the events which brought them about would also be more complicated and difficult to predict. Evolution is a bit chaotic because you never know which mutations are going to occur nor do you know which mutations will be lost to chance events. However, there are overarching patterns. Take a look at this: https://www.quantamagazine.org/can-scientists-predict-the-future-of-evolution-20140717/ (https://www.quantamagazine.org/can-scientists-predict-the-future-of-evolution-20140717/)
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Far too many adjectives- and science doesn't deal with adjectives! And the questions are actually back to front.
Species have evolved to fill real ecological niches There being more than one species on a finite planet with both physical constraints and biological competition, it can be said that at any moment, every species is optimised for its niche. Thus some prey species survive by outnumbering their predators whilst some predator species survive by limiting their numbers to the availability of prey.
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The question would be how ideal? With unlimited living space, unlimited resources, and nothing around to kill individuals, the reproductive rate could easily be calculated using basic math. The growth rate would be exponential and quickly overwhelm any real environment on Earth. Under more realistic circumstances, you could theoretically use the available energy from the Sun to calculate how much metabolic activity could be supported by it. Just keep in mind that every notch you move up the food chain you lose about 90% of available energy in the form of waste heat. Plants aren't 100% efficient either, so you'd need to account for that as well.
Propelled by your comment re bacteria I quickly found the paper "Growth Rate and Generation Time of Bacteria, with Special Reference to Continuous Culture" by E. O. Powell (from 1956 no less) which models exactly what I wanted for those tiny creatures, so thanks! Now, there is also the gene level, the species level, etc, and a maximization of any one of those does not coincide with the simultaneous maximization of the others (ie, creating amoebas may maximize the number of genes, creating beetles may maximize the number of species since they are known for their quick speciation, etc), so does someone know models regarding those levels too?
This is a little more difficult to answer. Some traits are much more complicated than others so the events which brought them about would also be more complicated and difficult to predict. Evolution is a bit chaotic because you never know which mutations are going to occur nor do you know which mutations will be lost to chance events. However, there are overarching patterns. Take a look at this: ...
Convergent evolution may or may not affect the subject of my question. Regardless of the chaos therein, we retrospectively know there are sine qua non traits for every species: those may have evolved relatively quick or slow (I don't know yet) but ultimately take a portion of the genome of every potentially feasible organism. In any case, given the reception my question has got among professional biologists I gather that this is not a topic hitherto discussed (but you are welcome to prove me wrong!).
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I'll see if I can find some references to help. There will almost certainly be different models for different vital traits. Metabolism itself is an important one.
- http://journals.plos.org/ploscompbiol/article?id=10.1371/journal.pcbi.1001137 (http://journals.plos.org/ploscompbiol/article?id=10.1371/journal.pcbi.1001137)
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1852415/ (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1852415/)
- http://www.jstor.org/stable/pdf/10.1086/671184.pdf?refreqid=excelsior:0e7ee31815b63c476137eafdf5824cd5 (http://www.jstor.org/stable/pdf/10.1086/671184.pdf?refreqid=excelsior:0e7ee31815b63c476137eafdf5824cd5)
- https://www.nature.com/articles/ncomms2958 (https://www.nature.com/articles/ncomms2958)
- http://onlinelibrary.wiley.com/doi/10.1111/2041-210X.12263/full (http://onlinelibrary.wiley.com/doi/10.1111/2041-210X.12263/full)
- https://stevefrank.org/reprints-pdf/97AmNat-Symb.pdf (https://stevefrank.org/reprints-pdf/97AmNat-Symb.pdf)
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4558865/ (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4558865/)
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creating amoebas may maximize the number of genes, creating beetles may maximize the number of species since they are known for their quick speciation, etc), so does someone know models regarding those levels too?
Do you mean maximization of the number of distinct genes (diversity/complexity of the genetic code) or do you mean maximization of the amount of genetic material (total global mass of RNA and DNA)?
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I think I have found that what I was asking in II) already has a name; I will delve right now into it and make sure:
The quantitative genetic view begins by emphasizing, as above, that fitness is a trait. It further emphasizes, however, that this trait is special. Of the potentially infinite number of traits that make up an organism, one trait— fitness— is unique in that it is the only trait that allows us to predict how much any other trait will change under natural selection from one generation to the next. This idea is captured in a result that was derived surprisingly late in the history of evolutionary biology. In late 1960s and early 1970s, Alan Robertson and George Price independently showed that the amount by which any trait, X, changes from one generation to the next is given by the genetic covariance between the trait and relative fitness. (The relevant covariance here is the “additive genetic covariance,” a statistic that disentangles the additive from dominance and epistatic effects of alleles) If a trait strongly covaries with relative fitness, it will change a good deal from one generation to the next; if not, not. This result is now known as the Secondary Theorem of Natural Selection
Re:
I'll see if I can find some references to help. There will almost certainly be different models for different vital traits. Metabolism itself is an important one.
That adds another level to the bacterial one I already had: thank you! I will do my homework reading all the links you quoted.
Do you mean maximization of the number of distinct genes (diversity/complexity of the genetic code) or do you mean maximization of the amount of genetic material (total global mass of RNA and DNA)?
I meant the maximization of the number of distinct genes. Sorry for the ambiguity in my former message.