1. Universal physical and chemical principles: All non-life and life are governed by universal mathematical, physical, and chemical principles.
Examples: Of major importance to organismal biology are: thermodynamics, transport processes (diffusion, fluid flow, electricity, and heat transfer), oxidation-reduction, scaling, material properties, and mechanics.
2. Deep molecular homology: All living organisms are descended from a common ancestor (or common ancestral community). Thus, they share a common genomic tool kit encoding for homologous molecules that utilize the physical and chemical principles cited above for regulating the molecular activities of life.
Examples: The genes encoding for bioenergetics, metabolism, structure, information processing, and transmembrane transport.
3. Divergent structure-function relationships: Major lineages of living organisms have exploited universal physicochemical principles and common genomic toolkits in order to evolve divergent structure-function relationships in unrelated lineages for carrying out certain physiological processes.
An example: The common roles of electrochemical gradients, P-type cation pumps, and homologous transporters in the different nutrient-assimilating structures that have evolved in various multicellular lineages. Other examples of physiological processes having common molecular mechanisms in analogous cells or structures in different lineages include: hydroregulation/osmoregulation/excretion, electrical signaling, and motility.
4. Convergence –
4A) Molecular convergence - unrelated lineages of unicellular organisms (and multicellular lineages to a lesser extent) are routinely involved in the horizontal transfer of genetic material, which has had profound evolutionary, physiological, and pathogenic consequences for these lineages.
Examples: a few of many possible examples include: the evolution of pre-LUCA organisms, the transfers of pathogenic ability and of antibiotic resistance in bacteria, the transfer of thermotolerance between thermophilic prokaryotes, plastid endosymbiosis, etc.
4B) Physico-chemical convergence – due to universal physico-chemical constraints, multicellular lineages have evolved convergent solutions for carrying other physiological processes.
An example: same mechanical constraints govern the design of support structures in various multicellular lineages. Other examples include the physico-chemical constraints operating on analogous structures carrying out: gas exchange, intercellular transport, and multicellular development.
5. Symbiosis: An organism often interacts with other organisms in order to carry out its physiological processes, to reproduce its progeny, and/or to evolve better-adapted solutions to life’s challenges.
Examples: numerous symbiotic relationships of extant organisms ranging from mutualism to pathogenesis/parasitism. Evolutionary examples include: endosymbiotic origins of eukaryotic energy-transforming organelles, and plant/fungal symbiosis of early multicellular terrestrial organisms.
6. Environmental transformation: Since the origins of life, organisms have continually transformed the physical, chemical, and biological characteristics of their environments. Thus, life is continually generating new selection pressures and new opportunities influencing its evolution.
Examples; a few of many possible examples include: nutrient cycles, carbon dioxide fixation, oxygen evolution, biological nitrogen fixation, calcium carbonate deposition, soil formation, anthropogenic greenhouse gases, alien plant invasions, current mass extinction, etc.
Comments (6)
michael.klymkowsky@... said
at 4:02 pm on Nov 23, 2011
There are a number of serious misstatements here. For example, convergence is not due to horizontal gene transfer, and is common among higher organisms (think bats and birds and pterodactyls).
Joe Redish said
at 11:14 am on Jul 12, 2016
See 4B
michael.klymkowsky@... said
at 4:06 pm on Nov 23, 2011
michael.klymkowsky@... said
at 4:07 pm on Nov 23, 2011
1. Biological systems differ from other systems in that they are also governed by their history; they are the products of evolution, a process involving both natural selection of genomic variation and random events, such as genetic drift and bottlenecks.
Julia Gouvea said
at 4:28 pm on Nov 23, 2011
I guess this is an old page, but since Michael is commenting on it I would just like to add that these principles are why I favor a model-based as opposed to a principle-based conceptualizations of disciplines. These statements are sort of a bunch of "true-ish" statements. Most of them broad descriptive statements (e.g. symbiosis happened; we share common DNA; sometimes we see convergence). But these statements themselves have relatively little utility in a list like this, and by utility I mean useful for reasoning. If I see some pattern in the world, I can't just use one of these statements to make sense of it. I would really need to group of constructs and relationships (the model) to do any useful reasoning. Namely, models of natural selection, genetic drift etc. These are the cognitively powerful ideas in biology in my opinion. I can't just invoke say, "the principle of environmental transformation" to explain anything. It's too vague.
Joe Redish said
at 11:17 am on Jul 12, 2016
This comment makes incorrect assumptions as to how the principles would be used. In physics for example we have Newton's laws as principles, but those principles provide no specific guidance in particular cases before the construction of models. The principles are intended to provide "broad descriptivE" guidance in the construction of models -- to remind us of elements to not forget in our construction of those models. They are not in the least intended to pre-empt model building.
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