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A Sourcebook for the Worldwide Discovery of a Creative Organic Universe
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VI. Earth Life Emergence: Development of Body, Brain, Selves and Societies

5. Multicellular Fauna and Flora Organisms

Hou, Chen, et al. Energetic Basis of Colonial Living in Social Insects. Proceedings of the National Academy of Science. 107/3634, 2010. Researchers from New York, Florida, Oklahoma, and Panama find the same anatomical and physiological relations to recur for both organisms themselves, and for viable colonial groupings they may reside in. Such deep, broad recurrence then implies an unavoidable sign of life’s evolution as an inherently convergent process.

Metabolic scaling theory, based largely on the body mass scaling of metabolic rate, has successfully predicted many aspects of the physiology and life history of individual (or unitary) organisms. Here we show, using a diverse set of social insect species, that this same theory predicts the size dependence of basic features of the physiology (i.e., metabolic rate, reproductive allocation) and life history (i.e., survival, growth, and reproduction) of whole colonies. The similarity in the size dependence of these features in unitary organisms and whole colonies points to commonalities in functional organization. Thus, it raises an important question of how such evolutionary convergence could arise through the process of natural selection. (3634)

Our results also imply that colonies are groups of individuals that are functionally organized to capture and use energy in ways that are remarkably similar to those of unitary organisms. Indeed the similarity in the scaling relationships for both colonies and unitary organisms suggests that the physiology and life history of colonies and unitary organisms follow the same “rules” with respect to size. (3636)

Ingber, Donald. The Architecture of Life. Scientific American. January, 1998. A universal set of self-assembly rules hold for and give rise to a bodily anatomy “organized hierarchically as tiers of systems within systems.” The author muses in closing that through achievements such as tensegrity geometry evident in protein structures, we are finally reading the book of nature foretold by Plato and Galileo.

Ispolatov, Iaroslav, et al. Division of Labour and the Evolution of Multicellularity. Proceedings of the Royal Society B. 279/1768, 2012. University of British Columbia, and ETH Zurich, theoretical microbiologists find the common, beneficial propensity of evolving groups from microbes to neighborhoods to spontaneously divide functional tasks to be similarly present as cells join into viable multicellular assemblies.

Understanding the emergence and evolution of multicellularity and cellular differentiation is a core problem in biology. We develop a quantitative model that shows that a multicellular form emerges from genetically identical unicellular ancestors when the compartmentalization of poorly compatible physiological processes into component cells of an aggregate produces a fitness advantage. This division of labour between the cells in the aggregate occurs spontaneously at the regulatory level owing to mechanisms present in unicellular ancestors and does not require any genetic predisposition for a particular role in the aggregate or any orchestrated cooperative behaviour of aggregate cells. Mathematically, aggregation implies an increase in the dimensionality of phenotype space that generates a fitness landscape with new fitness maxima, in which the unicellular states of optimized metabolism become fitness saddle points. Evolution of multicellularity is modelled as evolution of a hereditary parameter: the propensity of cells to stick together, which determines the fraction of time a cell spends in the aggregate form. Stickiness can increase evolutionarily owing to the fitness advantage generated by the division of labour between cells in an aggregate. (Abstract)

Jacobeen, Shane, et al. Cellular Packing, Mechanical Stress and the Evolution of Multicellularity. Nature Physics. 14/3, 2018. Georgia Tech biophysicists including William Ratcliff consider these physical and structural features which seem to facilitate how bunching cell communities to could rise into beneficial composite compartments. See also Nascent Life Cycles and the Emergence of Higher-Level Individuality by Ratcliff, et al.

The evolution of multicellularity set the stage for sustained increases in organismal complexity. However, a fundamental aspect of this transition remains largely unknown: how do simple clusters of cells evolve increased size when confronted by forces capable of breaking intracellular bonds? Here we show that multicellular snowflake yeast clusters fracture due to crowding-induced mechanical stress. Over seven weeks of daily selection for large size, snowflake clusters evolve to increase their radius 1.7-fold by reducing the accumulation of internal stress. This work demonstrates how readily natural selection finds simple, physical solutions to spatial constraints that limit the evolution of group size—a fundamental step in the evolution of multicellularity. (Abstract)

Jung, Heekyung, et al. The Ancient Origins of Neural Substrates for Land Walking. Cell. 172/4, 2018. In a paper noted in the New York Science Times, an eleven member team from the USA, Australia, and Singapore, based at NYU School of Medicine, describe for the first time a rudimentary neural basis for the transition from an aquatic phase to mobile terrestrial creatures. As a surmise, it would appear that this fins to feet procession seems written into life’s oriented evolutionary advance.

Walking is the predominant locomotor behavior expressed by land-dwelling vertebrates, but it is unknown when the neural circuits that are essential for limb control first appeared. Certain fish species display walking-like behaviors, raising the possibility that the underlying circuitry originated in primitive marine vertebrates. We show that the neural substrates of bipedalism are present in the little skate Leucoraja erinacea, whose common ancestor with tetrapods existed ∼420 million years ago. Leucoraja exhibits core features of tetrapod locomotor gaits, including left-right alternation and reciprocal extension-flexion of the pelvic fins. This network encodes peripheral connectivity modules that are distinct from those used in axial muscle-based swimming and has apparently been diminished in most modern fish. These findings indicate that the circuits that are essential for walking evolved through adaptation of a genetic regulatory network shared by all vertebrates with paired appendages. (Abstract)

Kaiser, Dale. Building a Multicellular Organism. Annual Review of Genetics. 35/103, 2001. The same process of symbiosic association occurs in the formation of an organism as it did when diverse bacteria evolved and joined to form nucleated cells.

Multicellular organisms appear to have arisen from unicells numerous times. Multicellular cyanobacteria arose early in the history of life on Earth. Multicellular forms have since arisen independently in each of the kingdoms and several times in some phyla. If the step from unicellular to multicellular life was taken early and frequently, the selective advantage of multicellularity may be large….The capacity for signaling between cells accompanies the evolution of multicellularity with cell differentiation. (103)

Kapheim, Karen, et al. Genomic Signatures of Evolutionary Transitions from Solitary to Group Living. Science. 348/1139, 2015. At the frontier of joining this popular major transitions model with a consistent genetic-like basis, some 70 scientists with multiple postings in the USA, China, Denmark, Spain, Switzerland, Germany, Brazil, Canada, and Saudi Arabia, add further credibility of life’s apparent insistence to arise by iterating the same cycle and form from entity to community. This vectorial emergence proceeds in kind from biomolecular and bacterial stages onto groups within civilizations. See also Climbing the Social Ladder: The Molecular Evolution of Sociality by Sandra Rehan and Amy Toth in Trends in Ecology & Evolution (Online June 2015).

The evolution of eusociality is one of the major transitions in evolution, but the underlying genomic changes are unknown. We compared the genomes of 10 bee species that vary in social complexity, representing multiple independent transitions in social evolution, and report three major findings. First, many important genes show evidence of neutral evolution as a consequence of relaxed selection with increasing social complexity. Second, there is no single road map to eusociality; independent evolutionary transitions in sociality have independent genetic underpinnings. Third, though clearly independent in detail, these transitions do have similar general features, including an increase in constrained protein evolution accompanied by increases in the potential for gene regulation and decreases in diversity and abundance of transposable elements. Eusociality may arise through different mechanisms each time, but would likely always involve an increase in the complexity of gene networks. (Abstract)

Kaveh, Kamron, et al. Games of Multicellularity. Journal of Theoretical Biology. Online May, 2016. As the quotes advise, with Carl Veller and Martin Nowak, Harvard University, Program for Evolutionary Dynamics, researchers apply game theory models to life’s persistent transition from single cells to cellular organisms to propose a better explanation.

Evolutionary game dynamics are often studied in the context of different population structures. Here we propose a new population structure that is inspired by simple multicellular life forms. In our model, cells reproduce but can stay together after reproduction. They reach complexes of a certain size, n, before producing single cells again. The cells within a complex derive payoff from an evolutionary game by interacting with each other. The reproductive rate of cells is proportional to their payoff. We consider all two-strategy games. We study deterministic evolutionary dynamics with mutations, and derive exact conditions for selection to favor one strategy over another. Our main result has the same symmetry as the well-known sigma condition, which has been proven for stochastic game dynamics and weak selection. For a maximum complex size of n=2 our result holds for any intensity of selection. For n≥3n≥3 it holds for weak selection. As specific examples we study the prisoner's dilemma and hawk-dove games. Our model advances theoretical work on multicellularity by allowing for frequency-dependent interactions within groups.

To put it concisely, the evolution of multicellularity is often studied in a framework that does not adequately account for the interactions of cells within a group. In this paper, we place the evolution of multicellularity into an explicitly game-theoretic framework. Evolutionary game dynamics is the study of frequency dependent selection. The success of a genotype (or phenotype or strategy) depends on the frequency of different genotypes in the population. Evolutionary game dynamics was initially studied in well-mixed and infinitely large populations using deterministic differential equations. More recently it has moved to finite population sizes using stochastic dynamics. Evolutionary games are also studied in structured populations. A game-theoretic approach to the evolution of multicellularity allows us to generalize the traditional framework by accounting for frequency-dependent competition within multicellular units. The primary goal of our paper is to understand how the population structure of simple multicellularity affects the outcome of biological games. (3)

Kirk, David. A Twelve-Step Program for Evolving Multicellularity and a Division of Labor. BioEssays. 27/3, 2005. For the subject evolution of the algae genus Volvox cateri, the 12 stages run from “incomplete cytokinesis” to “bifurcated cell division program.” What is of note is that the constant process of nested differentiation and symbiotic emergence repeats once more.

The origin of multicellular organisms with a division of labor is also one of the most interesting and complex problems in the field of evolution of development, because it presumably involved – at a minimum – a transition from cellular autonomy to cellular cooperation, the invention of novel morphogenetic mechanisms, and the elaboration of novel spatial patterns of differential gene expression. (299)

Klein, Jan and Naoyuki Takahata. Where Do We Come From? Berlin: Springer, 2002. An extensive essay on the evolutionary reconstruction of molecular and phylogenetic pathways which lead to homo sapiens.

Knoll, Andrew. Life on a Young Planet. Princeton: Princeton University Press, 2003. The story of the early diversification of multicellular organisms in the Cambrian seas. Three tasks are cited: a narrative history, how this came to be known, and a look for general principles at work. These result in a view of evolution as an accumulative process which involves the coevolution of Earth and its biospheric life. Altogether this creates a special bioplanet which life proceeds to take over and molds for its own advantage.

Knoll, Andrew. The Multiple Origins of Complex Multicellularity. Annual Review of Earth and Planetary Sciences. 39/217, 2011. The Harvard paleobotanist surveys from the second decade of the 21st century how intricate organisms came into somatic form from simpler eukarotes. This advance is said to have occurred in six clades: animals, embryophytic land plants, florideophyte red algae, laminarial brown algae, and two groups of fungi. Key facilitation was provided by intercellular adhesion, communication, and a developmental program.

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