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A Sourcebook for the Worldwide Discovery of a Creative Organic Universe
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V. Life's Corporeal Evolution Develops, Encodes and Organizes Itself: An EarthWinian Genesis Synthesis

4. Multicellular Fauna and Flora Organisms in Transition

Hammerschmidt, Katrin, et al. Life Cycles, Fitness Decoupling and the Evolution of Multicellularity. Nature. 515/75, 2014. Massey University, Auckland, and University of Washington, Seattle, researchers including Paul Rainey continue to quantify and explain how relative unicellular stages proceed to merge into organism forms of benefit both to member and the new individual. By so doing it is said that Darwinian selection processes shift by way of collective reproduction to this higher level. The surmise is a natural persistence for life to combine into whole nested entities by a ratcheted repetition.

Cooperation is central to the emergence of multicellular life; however, the means by which the earliest collectives (groups of cells) maintained integrity in the face of destructive cheating types is unclear. One idea posits cheats as a primitive germ line in a life cycle that facilitates collective reproduction. Here we describe an experiment in which simple cooperating lineages of bacteria were propagated under a selective regime that rewarded collective-level persistence. Collectives reproduced via life cycles that either embraced, or purged, cheating types. When embraced, the life cycle alternated between phenotypic states. Selection fostered inception of a developmental switch that underpinned the emergence of collectives whose fitness, during the course of evolution, became decoupled from the fitness of constituent cells. Our findings capture key events in the evolution of Darwinian individuality during the transition from single cells to multicellularity. (Abstract)

Herron, Matthew, et al. Genetics of a de Novo Origin of Undifferentiated Multicellularity. Royal Society Open Science. August, 2018. Georgia Tech biologists Herron, William Ratcliff, Jacob Boswell and Frank Rosenzweig post one more quantification of how inevitable and insistent life’s evolutionary emergence from single eukaryote cells to complex organisms seems to be. And this scalar step may be the most significant advance, since all subsequent organisms including us followed from its occasion.

The evolution of multicellularity was a major transition in evolution and set the stage for unprecedented increases in complexity, especially in land plants and animals. Here, we explore the genetics underlying a de novo origin of multicellularity in a microbial evolution experiment carried out on the green alga Chlamydomonas reinhardtii. We show that large-scale changes in gene expression underlie the transition to a multicellular life cycle. These results suggest that the genetic basis for the experimental evolution of multicellularity in C. reinhardtii has both lineage-specific and shared features, and that the shared features have more in common with C. reinhardtii's relatives among the volvocine algae than with other multicellular green algae or land plants. (Abstract)

Herron, Matthew, et al, eds. The Evolution of Multicellularity. Boca Raton, FL: CRC Press, 2022. As this major evolutionary transitions model from 1995 steadily gains credible acceptance, Georgia Tech biologists MH, William Ratcliff and Peter Conlin edit a first comprehensive volume about life’s prime cell to organism emergent ramification. An initial Theory and Philosophy section has papers by Margaret O’Malley, Corina Tarnita, Richard Michod; see next Aggregative Multicellularity (David Queller); then Clonal Multicellularity; onto Life Cycles and Complex Multicellularity (Eric Libby); finally Syntheses and Conclusions (see quote). Certain chapters are Life Cycles as a Central Organizing Theme, Group Transformation, Life History, Division of Labor, and Individuality Transitions aand Single-Celled Ancestors of Animals. See

Among the most important innovations in the history of life is the transition from single-celled organisms to more complex, multicellular organisms. Multicellularity has evolved repeatedly across the tree of life, resulting in the evolution of new kinds of organisms that collectively constitute a significant portion of Earth’s biodiversity and have transformed the biosphere. This volume examines the origins and subsequent evolution of multicellularity, reviewing the types of multicellular groups that exist, their evolutionary relationships, the processes that led to their evolution, and the conceptual frameworks in which their evolution is understood. (Publisher)

The goal of this book is to provide an overview of the evolution of multicellularity by way of the types of groups that exist, their evolutionary relationships, processes that led to their origins and advance, and the conceptual frameworks in which they can be understood. In four main sections, veteran contributors review the philosophical issues and theoretical approaches as life arose and came altogether as myriad organisms by way of the evolution of aggregations, clonal assemblies, and developmental unities. (Editors Introduction)

In this chapter, we view future research on the evolution of multicellularity from a range of philosophy, natural history, phylogenetics, biophysics and astrobiology perspectives. We consider further issues such as multicellular life cycles, organismal size and complexity, the origin of development, environmental drivers and niche construction over geological timescales. So there has not been a better time to learn all we can about life’s florescent collective emergence. (Editors: Syntheses and Conclusions)

Hiebert, Laurel, et al. Coloniality, Clonality, and Modularity in Animals. Journal of Experimental Zoology B. April, 2021. In this special issue, University of Sao Paulo, University of Colorado, and Sorbonne University biologists describe how the pervasive presence of these cooperative tendencies across diverse invertebrates achieve a beneficial recurrence of common, viable principles.

Nearly half of the animal phyla contain species that propagate asexually via agametic reproduction, often forming colonies of genetically identical modules, that is, ramets, zooids, or polyps. Clonal reproduction, colony formation, and modular organization have important consequences for many aspects of organismal biology. In this review, we present an overview of the study of colonial and clonal animals, from the historic interests in this subject to modern research in a range of topics, including immunology, stem cell biology, aging, biogeography, and ecology. (Abstract)

Hiebert, Laurel, et al. From the Individual to the Colony: Marine Invertebrates as Models to Understand Levels of Biological Organization. Journal of Experimental Zoology B. April, 2021. An introduction to a special Evolution of Animal Coloniality and Modularity issue of papers, as the abstract says, from a two week tutorial on these vital qualities of communal creatures. The eight research biologist authors including Carl Simpson and Federico Brown cite postings in Brazil, France, and the USA. See also herein Coloniality, Clonality, and Modularity in Animals (below) and Dynamical Patterning Modules and Network Motifs as Joint Determinants of Development.

The developmental and evolutionary principles of coloniality in marine animals remains a largely unexplored area. In late 2018, the inaugural course on the Evolution of Coloniality and Modularity took place at the Center for Marine Biology of the University of São Paulo. Its subject matter discussed past hypotheses and ways to test these using extant and paleontological data, along with observations of animal colonies in the different colonial phyla. Topics related to multi‐level selection, modular miniaturization, polymorphism, brooding, allorecognition and more were covered. (Course abstract)

Major transitions in evolution have been associated with nested hierarchical levels of biological organization. Transitions that occur in animals (multicellularity, sociality, coloniality) offer a unique opportunity to understand how evolutionary processes affect each of these nested levels of organization because the transitions are common and repeat in different lineages. If a hierarchical organization represents an innate property of vertical complexity—i.e. nested levels of biological organization—in biological systems, organisms may evolve and transition among the distinct levels of organization using some common underlying evolutionary principles. (192)

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)

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