Search results for "Biological evolution"
showing 10 items of 522 documents
Phylogenomic evidence for the presence of a flagellum and cbb(3) oxidase in the free-living mitochondrial ancestor.
2011
The initiation of the intracellular symbiosis that would give rise to mitochondria and eukaryotes was a major event in the history of life on earth. Hypotheses to explain eukaryogenesis fall into two broad and competing categories: those proposing that the host was a phagocytotic proto-eukaryote that preyed upon the free-living mitochondrial ancestor (hereafter FMA), and those proposing that the host was an archaebacterium that engaged in syntrophy with the FMA. Of key importance to these hypotheses are whether the FMA was motile or nonmotile, and the atmospheric conditions under which the FMA thrived. Reconstructions of the FMA based on genome content of Rickettsiales representatives-gener…
Reliability of mitochondrial DNA in an acanthocephalan: The problem of pseudogenes
2006
The utility of mitochondrial DNA as a molecular marker for evolutionary studies is well recognized. However, several problems can arise when using mitochondrial DNA, one of which is the presence of nuclear mitochondrial pseudogenes, or Numts. Pseudogenes of cytochrome oxidase I were preferentially amplified from Acanthocephalus lucii (Acanthocephala) using a universal PCR approach. To verify the presence and abundance of pseudogenes, length heterogeneity analysis of the PCR fragments was performed. PCR products obtained with universal primers often contained fragments of different sizes. Cloned sequences from universal PCR products nearly always contained sequence abnormalities such as inde…
Anatomical networks reveal the musculoskeletal modularity of the human head
2015
AbstractMosaic evolution is a key mechanism that promotes robustness and evolvability in living beings. For the human head, to have a modular organization would imply that each phenotypic module could grow and function semi-independently. Delimiting the boundaries of head modules and even assessing their existence, is essential to understand human evolution. Here we provide the first study of the human head using anatomical network analysis (AnNA), offering the most complete overview of the modularity of the head to date. Our analysis integrates the many biological dependences that tie hard and soft tissues together, arising as a consequence of development, growth, stresses and loads and mo…
Evolving mobile robots in simulated and real environments.
1995
The problem of the validity of simulation is particularly relevant for methodologies that use machine learning techniques to develop control systems for autonomous robots, as, for instance, the artificial life approach known as evolutionary robotics. In fact, although it has been demonstrated that training or evolving robots in real environments is possible, the number of trials needed to test the system discourages the use of physical robots during the training period. By evolving neural controllers for a Khepera robot in computer simulations and then transferring the agents obtained to the real environment we show that (a) an accurate model of a particular robot-environment dynamics can …
Evolution of molluscan hemocyanin structures
2013
AbstractHemocyanin transports oxygen in the hemolymph of many molluscs and arthropods and is therefore a central physiological factor in these animals. Molluscan hemocyanin molecules are oligomers composed of many protein subunits that in turn encompass subsets of distinct functional units. The structure and evolution of molluscan hemocyanin have been studied for decades, but it required the recent progress in DNA sequencing, X-ray crystallography and 3D electron microscopy to produce a detailed view of their structure and evolution. The basic quaternary structure is a cylindrical decamer 35nm in diameter, consisting of wall and collar (typically at one end of the cylinder). Depending on th…
Insights into virus evolution and membrane biogenesis from the structure of the marine lipid-containing bacteriophage PM2.
2008
Recent, primarily structural observations indicate that related viruses, harboring no sequence similarity, infect hosts of different domains of life. One such clade of viruses, defined by common capsid architecture and coat protein fold, is the so-called PRD1-adenovirus lineage. Here we report the structure of the marine lipid-containing bacteriophage PM2 determined by crystallographic analyses of the entire approximately 45 MDa virion and of the outer coat proteins P1 and P2, revealing PM2 to be a primeval member of the PRD1-adenovirus lineage with an icosahedral shell and canonical double beta barrel major coat protein. The view of the lipid bilayer, richly decorated with membrane protein…
Infanticide in the evolution of reproductive synchrony: effects on reproductive success.
2007
Synchronous breeding in animals and plants has stimulated both a theoretical and empirical examination of the possible benefits of active synchronization. The selective pressures of predation and infanticide are the strongest candidates proposed to explain the evolution of reproductive synchrony. Alternatively, breeding asynchronously with conspecifics may ensure a greater availability of resources per breeder. However, the possible fitness benefits resulting from active asynchronization have not yet received attention in evolutionary ecology. Here we present a hypothesis, based on a graphical model, illustrating the costs and benefits of the two modes of reproduction. We tested the hypothe…
Self-organized modularization in evolutionary algorithms.
2005
The principle of modularization has proven to be extremely successful in the field of technical applications and particularly for Software Engineering purposes. The question to be answered within the present article is whether mechanisms can also be identified within the framework of Evolutionary Computation that cause a modularization of solutions. We will concentrate on processes, where modularization results only from the typical evolutionary operators, i.e. selection and variation by recombination and mutation (and not, e.g., from special modularization operators). This is what we call Self-Organized Modularization. Based on a combination of two formalizations by Radcliffe and Altenber…
Interspecies comparison of neuroglobin, cytoglobin and myoglobin: Sequence evolution and candidate regulatory elements
2003
Neuroglobin and cytoglobin are two novel members of the vertebrate globin family. Their physiological role is poorly understood, although both proteins bind oxygen reversibly and may be involved in cellular oxygen homeostasis. Here we investigate the selective constraints on coding and non-coding sequences of the neuroglobin and cytoglobin genes in human, mouse, rat and fish. Neuroglobin and cytoglobin are highly conserved, displaying very low levels of non-synonymous nucleotide substitutions. An oxygen supply function predicts distinct modes of gene regulation, involving hypoxia-responsive transcription factors. To detect conserved candidate regulatory elements, we compared the neuroglobin…
Characterization of the hemoglobin of the backswimmer Anisops deanei (Hemiptera).
2012
Abstract While O 2 -binding hemoglobin-like proteins are present in many insects, prominent amounts of hemoglobin have only been found in a few species. Backswimmers of the genera Anisops and Buenoa (Notonectidae) have high concentrations of hemoglobin in the large tracheal cells of the abdomen. Oxygen from the hemoglobin is delivered to a gas bubble and controls the buoyant density, which enables the bugs to maintain their position without swimming and to remain stationary in the mid-water zone where they hunt for prey. We have obtained the cDNA sequences of three Anisops deanei hemoglobin chains by RT-PCR and RACE techniques. The deduced amino acid sequences show an unusual insertion of a…