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Results for “Evolutionary adaptability”

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PubMed1999

Emergence of homeostasis and "noise imprinting" in an evolution model.

Homeostasis, the creation of a stabilized internal milieu, is ubiquitous in biological evolution, despite the entropic cost of excluding noise information from a region. The advantages of stability seem self evident, but the alternatives are not so clear. This issue was studied by means of numerical experiments on a simple evolution model: a population of Boolean network "organisms" selected for performance of a curve-fitting task while subjected to noise. During evolution, noise sensitivity increased with fitness. Noise exclusion evolved spontaneously, but only if the noise was sufficiently unpredictable. Noise that was limited to one or a few stereotyped patterns caused symmetry breaking that prevented noise exclusion. Instead, the organisms incorporated the noise into their function at little cost in ultimate fitness and became totally noise dependent. This "noise imprinting" suggests caution when interpreting apparent adaptations seen in nature. If the noise was totally random from generation to generation, noise exclusion evolved reliably and irreversibly, but if the noise was correlated over several generations, maladaptive selection of noise-dependent traits could reverse noise exclusion, with catastrophic effect on population fitness. Noise entering the selection process rather than the organism had a different effect: adaptive evolution was totally abolished above a critical noise amplitude, in a manner resembling a thermodynamic phase transition. Evolutionary adaptation to noise involves the creation of a subsystem screened from noise information but increasingly vulnerable to its effects. Similar considerations may apply to information channeling in human cultural evolution.

Algorithms↗

PubMed2003

Life-span learning: a developmental perspective.

The article discusses learning as embedded processes of development and aging, and as social activity over the life course. The concept of life-span learning is proposed and outlined to discuss these processes as aspects of and propositions in life-span development and aging theory. Life-span learning processes arise and continuously develop in a dynamically complex body, brain, and the mind they support as essential features of development and aging over the life course. Life-span learning processes are established by evolutionary adaptive mechanisms, enriched by challenging environments, and continuously developed in supportive social structures. These ideas are derived from evolutionary biology and psychology, the cognitive sciences, life-span development and aging research, and adult development and learning studies. It is argued that life-span learning activities that challenge the body-mind-brain nexus are indispensable to optimize individual development and aging. Three global interventions and their strategies are discussed that enhance life-span learning: Learning to Learn, Learning for Growth, and Learning for Well-being.

Aging↗

PubMedDate not supplied

[Evolutionary psychiatry].

The author's perspective is that of a naturalist and ethologist. In this paper, he looks for evidences of phylogenetic components inherited from evolutionary adaptive behaviours in the etiology of psychopathological syndromes: bipolar depressions, seasonal affective disorders, obsessive-compulsive disorders, hysterical syndrome, impulsive behaviours, eating disorders, etc. Evolutionary psychiatry which sets present human pathological behaviour in the context of our species past evolution and of our ancestor's adaptations to their natural environment, leads the psychopathologist to revise certain of classic concepts in this field and resort to some of the concepts used by the ethologists, such as territory, hierarchy, allo-grooming and altruistic behaviour. It constitutes an invitation to reconsider the heredity of mental disorders in the light of phylogenetic consideration. As Freud and Lorenz have always recommended, one should not dissociate ontogeny from phylogeny in the study of human behaviour, whether normal or pathological.

Altruism↗

PubMed1994

The two faces of growth: benefits and risks to bone integrity.

Bones grow by two processes: cortical bone is made by periosteal apposition (growth in width), and cancellous bone is made by endochondral ossification (growth in length). In both the axial and appendicular skeleton, about half of peak adult bone mass is accumulated during the adolescent growth spurt, which occurs two years earlier in girls than in boys, and is under pituitary control via interactions between growth hormone and sex hormones. Throughout growth, but particularly during adolescence, the ability of bone to adapt to mechanical loading is much greater than after maturity. This is the main reason why the effects of physical activity on bone are greater in cross-sectional studies in young athletes than in longitudinal studies in previously sedentary adults. In wild animals, by the time growth has ceased, the bones must be as strong as they will ever need to be, and attainment of further strength after cessation of growth would serve no biologic purpose. Adaptation of growing bone to mechanical loading is the purpose of the mechanostat, which enables physiologic adaptation in individuals to establish and maintain a species-specific property of the bones that is determined by evolutionary adaptation in populations. But growth confers risks as well as benefits to the skeleton. The large increase in incidence of upper extremity (particularly lower forearm) fractures, coincident with the adolescent growth spurt in both sexes, is due to an increase in cortical porosity as a consequence of an increase in intracortical bone turnover, which supplies some of the calcium needed by the growing ends of the long bones. This enables an increased demand for calcium to be spread over a longer time, analogous to the cyclic physiologic osteoporosis which occurs during the antler growth cycle in deer. The subsequent decline in cortical porosity is responsible for the continued increase in radial bone density after cessation of growth, referred to as consolidation. In the present state of knowledge, an increased incidence of fracture during the adolescent growth spurt is the inescapable consequence of an appropriate level of physical activity, and is the price that has to be paid in order to maximize bone accumulation during growth and minimize fracture risk in old age.

Adolescent↗

PubMedDate not supplied

[Interaction of forward and backward conditioned connections as the neurophysiologic basis of the motivation for behavior].

Motivation is defined as a physiological mechanism of activation of traces, kept in memory (engramms) of those external objects which can satisfy the organism's need and those actions which can satisfy it. In the last years E. A. Asratyan advanced and substantiated the concept that the physiological mechanism of motivation is based on the interaction of forward and backward conditioned connections where the backward connection is an activating influence of reinforcing reflex on the structures receiving conditioned signal and achieving the action which was earlier followed by reinforcement. It is experimentally shown that the appearance and extent of the backward conditioned connections generalization depend on the degree of motivational excitation. The backward conditioned connection is a specialized Ukchtomsky's dominant in the functional structure of the consolidated conditioned reflex, which makes the behaviour goaldirected and active. Thus, fundamental phenomena lay in the basis of behaviour: dominant and conditioned reflex--discovered and introduced in the science by A. A. Ukchtomsky and I. P. Pavlov. In the individual adaptive behaviour the dominant and conditioned reflex play the same role as variability and selection in the process of evolutionary adaptation. That is why the suggestion made by K. Popper and J. Eccles (1977) to replace Pavlov's theory of conditioned reflexes by the hypotheses theory is unfounded.

Adaptation, Psychological↗

PubMed2003

Liberating genetic variance through sex.

Genetic variation in fitness is the fundamental prerequisite for adaptive evolutionary change. If there is no variation in survival and reproduction or if this variation has no genetic basis, then the composition of a population will not evolve over time. Consequently, the factors influencing genetic variation in fitness have received close attention from evolutionary biologists. One key factor is the mode of reproduction. Indeed, it has long been thought that sex enhances fitness variation and that this explains the ubiquity of sexual reproduction among eukaryotes. Nevertheless, theoretical studies have demonstrated that sex need not always increase genetic variation in fitness. In particular, if fitness interactions among beneficial alleles (epistasis) are positive, sex can reduce genetic variance in fitness. Empirical data have been sorely needed to settle the issue of whether sex does enhance fitness variation. A recent flurry of studies[1-4] has demonstrated that sex and recombination do dramatically increase genetic variation in fitness and consequently the rate of adaptive evolution. Interpreted in light of evolutionary theory, these studies rule out positive in these experiments epistasis as a major source of genetic associations. Further studies are needed, however, to tease apart other possible sources.

Alleles↗

PubMed1999

Diminishing returns from mutation supply rate in asexual populations.

Mutator genotypes with increased mutation rates may be especially important in microbial evolution if genetic adaptation is generally limited by the supply of mutations. In experimental populations of the bacterium Escherichia coli, the rate of evolutionary adaptation was proportional to the mutation supply rate only in particular circumstances of small or initially well-adapted populations. These experiments also demonstrate a "speed limit" on adaptive evolution in asexual populations, one that is independent of the mutation supply rate.

Adaptation, Physiological↗

PubMed1996

Descriptive and functional characterization of variation in the Fundulus heteroclitus Ldh-B proximal promoter.

Variation in enzyme expression may be an important mechanism for physiological and evolutionary adaptation. The Ldh-B locus in the teleost fish Fundulus heteroclitus is one of a very few loci for which an evolutionary difference in transcription rate between populations has been demonstrated. To begin to understand the molecular modifications that are responsible for altering transcription, we have characterized the Ldh-B proximal promoter using a combination of sequence analysis, transient transfection, and in vivo footprinting. The Ldh-B gene has several transcription start sites and a TATA-less, Inr (initiator of transcription motif) containing promoter with multiple Sp1-like motifs. Transfection experiments reveal that Sp1 sites, TCC repeats, and Inrs are functional components of the proximal promoter. We find substantial sequence variation between populations within the proximal promoter (250 bp from the transcription start sites) and footprinting analysis indicates that some of this sequence variation is associated with differential protein binding to the apparent TFIID binding site and Sp1 sites. Together, these data suggest that variation in the Ldh-B proximal promoter may play a role in the observed difference in transcription rates between northern and southern populations of F. heteroclitus.

Adaptation, Physiological↗

PubMed2005

Stress and adaptation in conservation genetics.

Stress, adaptation and evolution are major concerns in conservation biology. Stresses from pollution, climatic changes, disease etc. may affect population persistence. Further, stress typically occurs when species are placed in captivity. Threatened species are usually managed to conserve their ability to adapt to environmental changes, whilst species in captivity undergo adaptations that are deleterious upon reintroduction into the wild. In model studies using Drosophila melanogaster, we have found that; (a) inbreeding and loss of genetic variation reduced resistance to the stress of disease, (b) extinction rates under inbreeding are elevated by stress, (c) adaptive evolutionary potential in an increasingly stressful environment is reduced in small population, (d) rates of inbreeding are elevated under stressful conditions, (e) genetic adaptation to captivity reduces fitness when populations are reintroduced into the 'wild', and (f) the deleterious effects of adaptation on reintroduction success can be reduced by population fragmentation.

Adaptation, Biological↗

PubMed1995

[Antibiotic resistance--an ambivalence of attitudes. As of now, the bacteria are in advantage].

The value of the precious medical asset that antibiotics constitute is contimualby being eroded by the spread of resistance. For some time that bacterial world has been adapting itself to contend with the toxic assault of man-made poisons, antibiotics, by developing resistance in a very rapid process of evolutionary changes occurring before our very eyes. This evolutionary adaptation is an example of natural genetic engineering entailing an interchange between bacteria of genes conferring antibiotic resistance. Trimethoprim resistance is an example where numerous genes of unknown origin (some closely interrelated), expressing drug-resistant dihydrofolate reductases, move among human commensals and pathogens. They have been shown to move as gene cassettes in and out of the recently characterised integron structure occurring in many pathogens. They are also carried by various transposons such as Tn7, or Tn5393 originally observed in a plant pathogen, Erwinia amylovora. Betalactam resistance is another example of natural genetic engineering, where new betalactamases are continually emerging, and individual enzyme substrate specificity is modified by point mutation. At present, betalactamase mutants resistant to all commercially available betalactams, including clavulanic acid used in combination with betalactam antibiotics, are to be found in clinical isolates. Thus, currently bacteria seem to be triumphing in the running battle between the pharmaceutical industry and the bacterial world, the former introducing one new antibiotic variant after another, to which bacteria promptly develop resistance by manipulating their own genomes.

Animals↗

PubMed1979

Bootstrapping on the adaptive landscape.

Different versions of a gene or of a multigenic system may be essentially equivalent so far as the specific function of the structures which they code for or control is concerned, but very different with respect to their amenability to evolution. The structural features which increase evolutionary amenability are a disadvantage to the organism in terms of energy. Nevertheless, they accumulate in the course of evolution as a consequence of hitchhiking along with the desirable traits whose evolution they make possible. This is the bootstrap principle of evolutionary adaptability. In terms of the adaptive landscape bootstrapping corresponds to populations evolving in such a way that they occupy regions of the landscape which are more amenable to evolutionary hill climbing. The bootstrapping idea has implications for structure-function relations in a number of complex biological information processing systems, including biochemical systems, the immune system, and the brain. Bootstrapping is also discussed in connection with the origin of information processing (the origin of life) and in connection with possible designs for macromolecular computing systems.

Adaptation, Biological↗

PubMed2001

Decrease of psychomotor performance in subjects with latent 'asymptomatic' toxoplasmosis.

Toxoplasma gondii is known to induce specific behavioural changes in its intermediate hosts. This is usually considered to be an evolutionary adaptation aimed to increase the probability of transmission of the parasite into its definitive host, the cat, by predation. In rodents an increase of reaction time as well as many other specific behavioural patterns have been observed. Here we report the results of our double blind study showing the significantly longer reaction times of 60 subjects with latent toxoplasmosis in comparison with those of 56 controls. Moreover, the existence of a positive correlation between length of infection and mean reaction time suggested that slow and cumulative effects of latent toxoplasmosis rather than a one-step (and possibly transient) effect of acute toxoplasmosis disease are responsible for the decrease of psychomotor performance of infected subjects. To our knowledge, this is the first study confirming the existence of such parasite-induced changes in human behaviour that could be considered in evolutionary history of the human species as adaptive from the point of view of parasite transmission.

Animals↗

PubMed2003

Comparison of the genomes of human and mouse lays the foundation of genome zoology.

The extensive similarities between the genomes of human and model organisms are the foundation of much of modern biology, with model organism experimentation permitting valuable insights into biological function and the aetiology of human disease. In contrast, differences among genomes have received less attention. Yet these can be expected to govern the physiological and morphological distinctions apparent among species, especially if such differences are the result of evolutionary adaptation. A recent comparison of the draft sequences of mouse and human genomes has shed light on the selective forces that have predominated in their recent evolutionary histories. In particular, mouse-specific clusters of homologues associated with roles in reproduction, immunity and host defence appear to be under diversifying positive selective pressure, as indicated by high ratios of non-synonymous to synonymous substitution rates. These clusters are also frequently punctuated by homologous pseudogenes. They thus have experienced numerous gene death, as well as gene birth, events. These regions appear, therefore, to have borne the brunt of adaptive evolution that underlies physiological and behavioural innovation in mice. We predict that the availability of numerous animal genomes will give rise to a new field of genome zoology in which differences in animal physiology and ethology are illuminated by the study of genomic sequence variations.

Animals↗

PubMed2002

[Evolution of the interaction fo living systems with the environment].

Basic principles of interaction of living systems with environmental factors and different phases of the organic evolution are presented. The general strategy of adaptation of living systems on various levels of organization to changes in the environment is considered. It is shown that in the course of evolutionary adaptation the living systems not only altered their morphophysiological status but also actively adjusted the environment modifying its physical/chemical parameters. Special attention is given to the hereditary and external factors in of structural and functional evolution living organisms. Environmental factors are shown to gain significance in structural/functional and behavioral formation of living organisms as the organic world has evolved.

Biological Evolution↗

PubMed2001

Genetic shift in photoperiodic response correlated with global warming.

To date, all altered patterns of seasonal interactions observed in insects, birds, amphibians, and plants associated with global warming during the latter half of the 20th century are explicable as variable expressions of plastic phenotypes. Over the last 30 years, the genetically controlled photoperiodic response of the pitcher-plant mosquito, Wyeomyia smithii, has shifted toward shorter, more southern daylengths as growing seasons have become longer. This shift is detectable over a time interval as short as 5 years. Faster evolutionary response has occurred in northern populations where selection is stronger and genetic variation is greater than in southern populations. W. smithii represents an example of actual genetic differentiation of a seasonality trait that is consistent with an adaptive evolutionary response to recent global warming.

Adaptation, Physiological↗

PubMed1999

Molecular cloning and characterization of CD4 in an aquatic mammal, the white whale Delphinapterus leucas.

Given the importance of the cell surface recognition protein, CD4, in immune function, the cloning and characterization of CD4 at the molecular level from an odontocete cetacean, the white whale (Delphinapterus leucas), was carried out. Whale CD4 cDNA contains 2662 base pairs and translates into a protein containing 455 amino acids. Whale CD4 shares 64% and 51% identity with the human and mouse CD4 protein, respectively, and is organized in a similar manner. Unlike human and mouse, however, the cytoplasmic domain, which is highly conserved, contains amino acid substitutions unique to whale. Moreover, only one of the seven potential N-linked glycosylation sites present in whale is shared with human and mouse. Evolutionarily, the whale CD4 sequence is most similar to pig and structurally similar to dog and cat, in that all lack the cysteine pair in the V2 domain. These differences suggest that CD4 may have a different secondary structure in these species, which may affect binding of class II and subsequent T-cell activation, as well as binding of viral pathogens. Interestingly, as a group, species with these CD4 characteristics all have high constitutive expression of class II molecules on T lymphocytes, suggesting potential uniqueness in the interaction of CD4, class II molecules, and the immune response. Molecular characterization of CD4 in an aquatic mammal provides information on the CD4 molecule itself and may provide insight into adaptive evolutionary changes of the immune system.

Adaptation, Biological↗

PubMed1984

Initiation of complement activation.

The complement system is an excellent one to look at as an example of a triggered enzyme system. It is found to use almost all the strategies of enzyme cascades and for initiation which were discussed in the introduction. The classical pathway is a fine example of an active zymogen form of activation and the alternative pathway is the canonical example of a tickover. Both may also be activated by exogenous enzymes from other systems. The strategies of enzymes waiting for substrates, of substrates waiting for enzymes, and of both waiting for modifying proteins are all seen in various stages of the reaction. There is an association of a linear cascade with the positive feedback amplification loop. This degree of evolutionary adaptation is not only aesthetically pleasing but must be taken to mean that the system is of considerable biological importance and has been over a long evolutionary time span.

Complement Activation↗

PubMed2002

Autoimmunity on alert: naturally occurring regulatory CD4(+)CD25(+) T cells as part of the evolutionary compromise between a 'need' and a 'risk'.

Autoimmunity, at least in the central nervous system (CNS), is not only an outcome of immune system malfunction, but is the body's own protective mechanism against destructive self-compounds. Likewise, the naturally occurring regulatory CD4(+)CD25(+) T cells have a physiological function, and are not merely an evolutionary adaptation to suppress self-reactive T-cell clones that escaped deletion in the thymus. We postulate that the regulatory T (Tr) cells are the product of an evolutionary compromise between the need for autoimmunity on alert for tissue maintenance and the need to control autoimmunity to avoid autoimmune disease. In the event of an insult to the CNS, the balance between self-reactive (effector) T cells and Tr cells determines the time of onset, the intensity and the duration of the autoimmune response. This response might thus represent an adaptive mechanism, which is optimal for day-to-day maintenance, but insufficient in extreme cases of CNS damage or failure of regulation. Downregulation or upregulation of CD4(+)CD25(+) Tr cells might be a way to achieve better protection from neurodegenerative conditions induced by self-destruction or avoid autoimmune inflammatory disease development, respectively.

Animals↗