scholarly journals The evolutionary biomechanics of locomotor function in giant land animals

2021 ◽  
Vol 224 (11) ◽  
Author(s):  
John R. Hutchinson
Keyword(s):  
Evolutionary History ◽  
Neuromuscular Control ◽  
Interspecific Variation ◽  
Current Theory ◽  
Locomotor Function ◽  
Form And Function ◽  
Maximal Speed ◽  
And Function ◽  
Giant Size ◽  
Land Vertebrates

ABSTRACT Giant land vertebrates have evolved more than 30 times, notably in dinosaurs and mammals. The evolutionary and biomechanical perspectives considered here unify data from extant and extinct species, assessing current theory regarding how the locomotor biomechanics of giants has evolved. In terrestrial tetrapods, isometric and allometric scaling patterns of bones are evident throughout evolutionary history, reflecting general trends and lineage-specific divergences as animals evolve giant size. Added to data on the scaling of other supportive tissues and neuromuscular control, these patterns illuminate how lineages of giant tetrapods each evolved into robust forms adapted to the constraints of gigantism, but with some morphological variation. Insights from scaling of the leverage of limbs and trends in maximal speed reinforce the idea that, beyond 100–300 kg of body mass, tetrapods reduce their locomotor abilities, and eventually may lose entire behaviours such as galloping or even running. Compared with prehistory, extant megafaunas are depauperate in diversity and morphological disparity; therefore, turning to the fossil record can tell us more about the evolutionary biomechanics of giant tetrapods. Interspecific variation and uncertainty about unknown aspects of form and function in living and extinct taxa still render it impossible to use first principles of theoretical biomechanics to tightly bound the limits of gigantism. Yet sauropod dinosaurs demonstrate that >50 tonne masses repeatedly evolved, with body plans quite different from those of mammalian giants. Considering the largest bipedal dinosaurs, and the disparity in locomotor function of modern megafauna, this shows that even in terrestrial giants there is flexibility allowing divergent locomotor specialisations.

scholarly journals Convergent Evolution of Claw Shape in a Transcontinental Lizard Radiation

2019 ◽  
Vol 60 (1) ◽  
pp. 10-23 ◽  
Author(s):  
Simon Baeckens ◽  
Charlotte Goeyers ◽  
Raoul Van Damme
Keyword(s):  
Habitat Use ◽  
Convergent Evolution ◽  
Interspecific Variation ◽  
Environmental Pressures ◽  
Form Analysis ◽  
Form And Function ◽  
Claw Morphology ◽  
And Function ◽  
Claw Shape ◽  
Structural Habitat

Abstract Species occupying similar selective environments often share similar phenotypes as the result of natural selection. Recent discoveries, however, have led to the understanding that phenotypes may also converge for other reasons than recurring selection. We argue that the vertebrate claw system constitutes a promising but understudied model system for testing the adaptive nature of phenotypic, functional, and genetic convergence. In this study, we combine basic morphometrics and advanced techniques in form analysis to examine claw shape divergence in a transcontinental lizard radiation (Lacertidae). We find substantial interspecific variation in claw morphology and phylogenetic comparative statistics reveal a strong correlation with structural habitat use: ground-dwelling species living in open areas are equipped with long, thick, weakly curved, slender-bodied claws, whereas climbing species carry high, short, strongly curved, full-bodied claws. Species occupying densely vegetated habitats tend to carry intermediately shaped claws. Evolutionary models suggest that claw shape evolves toward multiple adaptive peaks, with structural habitat use pulling species toward a specific selective optimum. Contrary to findings in several other vertebrate taxa, our analyses indicate that environmental pressures, not phylogenetic relatedness, drive convergent evolution of similarly shaped claws in lacertids. Overall, our study suggests that lacertids independently evolved similarly shaped claws as an adaptation to similar structural environments in order to cope with the specific locomotory challenges posed by the habitat. Future biomechanical studies that link form and function in combination with genomic and development research will prove valuable in better understanding the adaptive significance of claw shape divergence.

Introduction

2017 ◽  
Author(s):  
Mathias Clasen
Keyword(s):  
Cultural Context ◽  
Defense Mechanisms ◽  
Evolutionary History ◽  
Sociocultural Context ◽  
Critical Approach ◽  
Human Central Nervous System ◽  
Form And Function ◽  
Recent Developments ◽  
And Function ◽  
The Brain

Horror entertainment is paradoxically popular. It is one of the most consistently popular genres across media, yet it is designed to make audiences feel bad. An evolutionary perspective, one that builds on recent developments in cognitive and evolutionary psychology, can help explain the genre’s popularity as well as its form and function. This chapter argues that horror fiction is crucially dependent on evolved properties of the human central nervous system and that a nuanced and scientifically valid understanding of horror requires that we take human evolutionary history seriously. Horror targets ancient defense mechanisms in the brain. At the same time, horror changes in response to sociocultural context. Hence, the chapter argues for a biocultural critical approach to horror, one that is sensitive to cultural context as well as evolved psychological underpinnings. The chapter explains the rationale of the book and outlines its structure.

scholarly journals Phylogenetic and physiological signals in metazoan fossil biomolecules

2020 ◽  
Vol 6 (28) ◽  
pp. eaba6883 ◽  
Author(s):  
Jasmina Wiemann ◽  
Jason M. Crawford ◽  
Derek E. G. Briggs
Keyword(s):  
Evolutionary History ◽  
Phylogenetic Information ◽  
Deep Time ◽  
Form And Function ◽  
In Situ Raman ◽  
History Of ◽  
Higher Rank ◽  
And Function ◽  
Molecular Signals

Proteins, lipids, and sugars establish animal form and function. However, the preservation of biological signals in fossil organic matter is poorly understood. Here, we used high-resolution in situ Raman microspectroscopy to analyze the molecular compositions of 113 Phanerozoic metazoan fossils and sediments. Proteins, lipids, and sugars converge in composition during fossilization through lipoxidation and glycoxidation to form endogenous N-, O-, and S-heterocyclic polymers. Nonetheless, multivariate spectral analysis reveals molecular heterogeneities: The relative abundance of glycoxidation and lipoxidation products distinguishes different tissue types. Preserved chelating ligands are diagnostic of different modes of biomineralization. Amino acid–specific fossilization products retain phylogenetic information and capture higher-rank metazoan relationships. Molecular signals survive in deep time and provide a powerful tool for reconstructing the evolutionary history of animals.

scholarly journals Beyond crystals: the dialectic of materials and information

2012 ◽  
Vol 370 (1969) ◽  
pp. 2807-2822 ◽  
Author(s):  
Julyan H. E. Cartwright ◽  
Alan L. Mackay
Keyword(s):  
Evolutionary History ◽  
Materials Science ◽  
Energy Landscape ◽  
Living System ◽  
Complex Structures ◽  
Structure Form ◽  
Form And Function ◽  
Metastable Structures ◽  
Complex Topology ◽  
And Function

We argue for a convergence of crystallography, materials science and biology, that will come about through asking materials questions about biology and biological questions about materials, illuminated by considerations of information. The complex structures now being studied in biology and produced in nanotechnology have outstripped the framework of classical crystallography, and a variety of organizing concepts are now taking shape into a more modern and dynamic science of structure, form and function. Absolute stability and equilibrium are replaced by metastable structures existing in a flux of energy-carrying information and moving within an energy landscape of complex topology. Structures give place to processes and processes to systems. The fundamental level is that of atoms. As smaller and smaller groups of atoms are used for their physical properties, quantum effects become important; already we see quantum computation taking shape. Concepts move towards those in life with the emergence of specifically informational structures. We now see the possibility of the artificial construction of a synthetic living system, different from biological life, but having many or all of the same properties. Interactions are essentially nonlinear and collective. Structures begin to have an evolutionary history with episodes of symbiosis. Underlying all the structures are constraints of time and space. Through hierarchization, a more general principle than the periodicity of crystals, structures may be found within structures on different scales. We must integrate unifying concepts from dynamical systems and information theory to form a coherent language and science of shape and structure beyond crystals. To this end, we discuss the idea of categorizing structures based on information according to the algorithmic complexity of their assembly.

scholarly journals Appendicular Muscle Physiology and Biomechanics in Crocodylus niloticus

2020 ◽  
Author(s):  
Krijn B Michel ◽  
Tim G West ◽  
Monica A Daley ◽  
Vivian R Allen ◽  
John R Hutchinson
Keyword(s):  
Muscle Power ◽  
Fiber Type ◽  
Muscle Physiology ◽  
Locomotor Function ◽  
Contraction Velocity ◽  
Form And Function ◽  
Type Composition ◽  
Extant Species ◽  
And Function ◽  
Parameter Values

Abstract Archosaurian reptiles (including living crocodiles and birds) had an explosive diversification of locomotor form and function since the Triassic approximately 250 million years ago. Their limb muscle physiology and biomechanics are pivotal to our understanding of how their diversity and evolution relate to locomotor function. Muscle contraction velocity, force, and power in extinct archosaurs such as early crocodiles, pterosaurs, or non-avian dinosaurs are not available from fossil material, but are needed for biomechanical modeling and simulation. However, an approximation or range of potential parameter values can be obtained by studying extant representatives of the archosaur lineage. Here, we study the physiological performance of three appendicular muscles in Nile crocodiles (Crocodylus niloticus). Nile crocodile musculature showed high power and velocity values—the flexor tibialis internus 4 muscle, a small “hamstring” hip extensor, and knee flexor actively used for terrestrial locomotion, performed particularly well. Our findings demonstrate some physiological differences between muscles, potentially relating to differences in locomotor function, and muscle fiber type composition. By considering these new data from a previously unstudied archosaurian species in light of existing data (e.g., from birds), we can now better bracket estimates of muscle parameters for extinct species and related extant species. Nonetheless, it will be important to consider the potential specialization and physiological variation among muscles, because some archosaurian muscles (such as those with terrestrial locomotor function) may well have close to double the muscle power and contraction velocity capacities of others.

See how they ran: morphological and functional aspects of skeletons from ancient Egyptian shrew mummies (Eulipotyphla: Soricidae: Crocidurinae)

2019 ◽  
Vol 100 (4) ◽  
pp. 1199-1210
Author(s):  
Neal Woodman ◽  
Alec T Wilken ◽  
Salima Ikram
Keyword(s):  
Ancient Egypt ◽  
Locomotor Function ◽  
Form And Function ◽  
Greco Roman ◽  
Ancient Egyptian ◽  
Modern Species ◽  
Functional Aspects ◽  
Components Analysis ◽  
And Function ◽  
The Last Two Millennia

Abstract Animals served important roles in the religious cults that proliferated during the Late (ca. 747–332 BCE) and Greco-Roman Periods (332 BCE–CE 337) of ancient Egypt. One result was the interment of animal mummies in specialized necropolises distributed throughout the country. Excavation of a rock-tomb that was re-used during the Ptolemaic Period (ca. 309–30 BCE) for the interment of animal mummies at the Djehuty Site (TT 11–12) near Luxor, Egypt, was carried out in early 2018 by a Spanish–Egyptian team sponsored by the Consejo Superior de Investigaciones Científicas, Madrid. The tomb burned sometime after deposition of the mummies, leaving behind abundant disassociated skeletal remains, primarily of avians, but also including two species of shrews (Soricidae): Crocidura olivieri and C. religiosa. To investigate possible intraspecific variation in morphology and locomotor function in these two species during the last two millennia, we measured morphological features of individual postcranial bones from the two archaeological samples and calculated indices that have been used to assess locomotor function. We compared the measurements to those from modern C. olivieri, C. religiosa, and C. suaveolens using principal components analysis, and we compared locomotor indices to those we calculated for the three modern species of Crocidura and to those from nine species of myosoricine shrews. Osteological features of the postcranial skeleton of conspecific Ptolemaic and modern samples of C. olivieri and C. religiosa are generally similar in character and proportion, and, skeletally, these shrews and modern C. suaveolens are consistent with soricids having a primarily ambulatory locomotor mode. One exception is the deltopectoral crest of the humerus, which appears to be longer in modern C. religiosa. Despite general conservation of form and function, Ptolemaic C. olivieri had larger body size than modern Egyptian populations and were more similar in size to modern C. olivieri nyansae from Kenya than to modern C. olivieri olivieri from Egypt.

Scanning tunneling microscopy (STM) of DNA and RNA

1989 ◽  
Vol 47 ◽  
pp. 34-35
Author(s):  
Patricia G. Arscott ◽  
Gil Lee ◽  
Victor A. Bloomfield ◽  
D. Fennell Evans
Keyword(s):  
Molecular Structures ◽  
Inorganic Materials ◽  
Resolving Power ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Form And Function ◽  
Dna And Rna ◽  
Calf Thymus ◽  
And Function ◽  
The Relationship

STM is one of the most promising techniques available for visualizing the fine details of biomolecular structure. It has been used to map the surface topography of inorganic materials in atomic dimensions, and thus has the resolving power not only to determine the conformation of small molecules but to distinguish site-specific features within a molecule. That level of detail is of critical importance in understanding the relationship between form and function in biological systems. The size, shape, and accessibility of molecular structures can be determined much more accurately by STM than by electron microscopy since no staining, shadowing or labeling with heavy metals is required, and there is no exposure to damaging radiation by electrons. Crystallography and most other physical techniques do not give information about individual molecules.We have obtained striking images of DNA and RNA, using calf thymus DNA and two synthetic polynucleotides, poly(dG-me5dC)·poly(dG-me5dC) and poly(rA)·poly(rU).

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