scholarly journals NATURAL SELECTION: THE IMPACT OF SEMANTIC IMPAIRMENT ON LEXICAL AND OBJECT DECISION

2004 ◽  
Vol 21 (2-4) ◽  
pp. 331-352 ◽  
Author(s):  
Timothy T. Rogers ◽  
Matthew A. Lambon Ralph ◽  
John R. Hodges ◽  
Karalyn Patterson
Keyword(s):  
Natural Selection ◽  
Object Decision ◽  
The Impact ◽  
Semantic Impairment

Interactions Between Natural Selection, Recombination and Gene Density in the Genes of Drosophila

Genetics ◽  
2002 ◽  
Vol 160 (2) ◽  
pp. 595-608 ◽  
Author(s):  
Jody Hey ◽  
Richard M Kliman
Keyword(s):  
Gene Expression ◽  
Natural Selection ◽  
Recombination Rate ◽  
Codon Bias ◽  
Gene Density ◽  
Drosophila Genome ◽  
Functional Variation ◽  
Subtle Effect ◽  
Efficiency Of Selection ◽  
The Impact

AbstractIn Drosophila, as in many organisms, natural selection leads to high levels of codon bias in genes that are highly expressed. Thus codon bias is an indicator of the intensity of one kind of selection that is experienced by genes and can be used to assess the impact of other genomic factors on natural selection. Among 13,000 genes in the Drosophila genome, codon bias has a slight positive, and strongly significant, association with recombination—as expected if recombination allows natural selection to act more efficiently when multiple linked sites segregate functional variation. The same reasoning leads to the expectation that the efficiency of selection, and thus average codon bias, should decline with gene density. However, this prediction is not confirmed. Levels of codon bias and gene expression are highest for those genes in an intermediate range of gene density, a pattern that may be the result of a tradeoff between the advantages for gene expression of close gene spacing and disadvantages arising from regulatory conflicts among tightly packed genes. These factors appear to overlay the more subtle effect of linkage among selected sites that gives rise to the association between recombination rate and codon bias.

Fatal asymmetries

2021 ◽  
pp. 1-15
Author(s):  
Luis Sánchez
Keyword(s):  
Natural Selection ◽  
Artificial Selection ◽  
Political Institutions ◽  
Charles Darwin ◽  
The Impact ◽  
Descent Of Man

Abstract In Descent of Man, Charles Darwin noted the impact of political institutions on natural selection. He thought that institutions such as asylums or hospitals may deter natural selection; however, he did not reach a decisive answer. Questions remain as to whether the selective impacts of political institutions, which in Darwin’s terms may be referred to as “artificial selection,” are compatible with natural selection, and if so, to what extent. This essay argues that currently there appears to be an essential mismatch between nature and political institutions. Unfitted institutions put exogenous and disproportionate pressures on living beings. This creates consequences for what is postulated as the condition of basic equivalence, which allows species and individuals to enjoy similar chances of survival under natural circumstances. Thus, contrary to Darwin’s expectations, it is sustained that assumed natural selection is not discouraged but becomes exacerbated by political institutions. In such conditions, selection becomes primarily artificial and perhaps mainly political, with consequences for species’ evolutionary future.

scholarly journals Intragenomic variation in mutation biases causes underestimation of selection on synonymous codon usage

2021 ◽  
Author(s):  
Alexander L Cope ◽  
Premal Shah
Keyword(s):  
Population Genetics ◽  
Natural Selection ◽  
Codon Usage ◽  
Codon Bias ◽  
Synonymous Codon ◽  
Synonymous Codon Usage ◽  
Mutation Bias ◽  
Biased Gene Conversion ◽  
Intragenomic Variation ◽  
The Impact

Patterns of non-uniform usage of synonymous codons (codon bias) varies across genes in an organism and across species from all domains of life. The bias in codon usage is due to a combination of both non-adaptive (e.g. mutation biases) and adaptive (e.g. natural selection for translation efficiency/accuracy) evolutionary forces. Most population genetics models quantify the effects of mutation bias and selection on shaping codon usage patterns assuming a uniform mutation bias across the genome. However, mutation biases can vary both along and across chromosomes due to processes such as biased gene conversion, potentially obfuscating signals of translational selection. Moreover, estimates of variation in genomic mutation biases are often lacking for non-model organisms. Here, we combine an unsupervised learning method with a population genetics model of synonymous codon bias evolution to assess the impact of intragenomic variation in mutation bias on the strength and direction of natural selection on synonymous codon usage across 49 Saccharomycotina budding yeasts. We find that in the absence of a priori information, unsupervised learning approaches can be used to identify regions evolving under different mutation biases. We find that the impact of intragenomic variation in mutation bias varies widely, even among closely-related species. We show that the overall strength and direction of selection on codon usage can be underestimated by failing to account for intragenomic variation in mutation biases. Interestingly, genes falling into clusters identified by machine learning are also often physically clustered across chromosomes, consistent with processes such as biased gene conversion. Our results indicate the need for more nuanced models of sequence evolution that systematically incorporate the effects of variable mutation biases on codon frequencies.

scholarly journals The Impact of 'Anthropotechnology' on Human Evolution

2010 ◽  
Vol 14 (2) ◽  
pp. 72-87 ◽  
Author(s):  
Sylvia Blad ◽  
Keyword(s):  
Natural Selection ◽  
Human Evolution ◽  
Common Ancestor ◽  
Biological Evolution ◽  
Genetic Effects ◽  
Evolutionary Path ◽  
Peter Sloterdijk ◽  
The Impact

From the time that they diverged from their common ancestor, chimpanzees and humans have had a very different evolutionary path. It seems obvious that the appearance of culture and technology has increasingly alienated humans from the path of natural selection that has informed chimpanzee evolution. According to philosopher Peter Sloterdijk any type of technology is bound to have genetic effects. But to what extent do genomic comparisons provide evidence for such an impact of ‘anthropotechnology’ on our biological evolution?

scholarly journals Malthus for kids: The impact of exploring Malthus’ principle on elementary school students’ understanding of evolution by natural selection

2021 ◽  
Author(s):  
Xana Sá-Pinto ◽  
Alexandre Pinto ◽  
Joana Ribeiro ◽  
Inês Sarmento ◽  
Patrícia Pessoa ◽  
...  
Keyword(s):  
Elementary School ◽  
Natural Selection ◽  
Elementary School Students ◽  
Positive Impact ◽  
Evaluation Framework ◽  
Fine Tuning ◽  
Educational Activity ◽  
School Students ◽  
Evolution By Natural Selection ◽  
The Impact

While several researchers have suggested that evolution should be explored from the initial years of schooling, little information is available on effective resources to enhance elementary school students’ level of understanding of evolution by natural selection (LUENS). For the present study, we designed, implemented and evaluated an educational activity planned for fourth graders to explore concepts and conceptual fields that were historically important for the discovery of natural selection. Observation field notes and students’ productions were used to analyse how the students explored the proposed activity. Additionally, an evaluation framework consisting of a test, the evaluation criteria and the scoring process was applied in two fourth-grade classes to estimate elementary school students’ LUENS before and after engaging in the activity. Our results suggest that our activity allowed students to effectively link all of the key concepts in the classroom and produced a significant increase in their LUENS. These results indicate that our activity had a positive impact on students’ understanding of natural selection. They also reveal that additional activities and minor fine-tuning of the present activity are required to further support students’ learning about the concept of differential reproduction. We also observed a low level of teleological predictions for both pre- and post-tests.

scholarly journals Conceptual Characterization of Threshold Concepts in Student Explanations of Evolution by Natural Selection and Effects of Item Context

2020 ◽  
Vol 19 (1) ◽  
pp. ar1 ◽  
Author(s):  
Andreas Göransson ◽  
Daniel Orraryd ◽  
Daniela Fiedler ◽  
Lena A. E. Tibell
Keyword(s):  
Natural Selection ◽  
Spatial Scale ◽  
Biology Education ◽  
Threshold Concepts ◽  
Differential Survival ◽  
Evolutionary Mechanisms ◽  
Biological Phenomena ◽  
Wide Range ◽  
Evolution By Natural Selection ◽  
The Impact

Evolutionary theory explains a wide range of biological phenomena. Proper understanding of evolutionary mechanisms such as natural selection is therefore an essential goal for biology education. Unfortunately, natural selection has time and again proven difficult to teach and learn, and students’ resulting understanding is often characterized by misconceptions. Previous research has often focused on the importance of certain key concepts such as variation, differential survival, and change in population. However, so-called threshold concepts (randomness, probability, spatial scale, and temporal scales) have also been suggested to be important for understanding of natural selection, but there is currently limited knowledge about how students use these concepts. We sought to address this lack of knowledge by collecting responses to three different natural selection items from 247 university students from Sweden and Germany. Content analysis (deductive and inductive coding) and subsequent statistical analysis of their responses showed that they overall use some spatial scale indicators, such as individuals and populations, but less often randomness or probability in their explanations. However, frequencies of use of threshold concepts were affected by the item context (e.g., the biological taxa and trait gain or loss). The results suggest that the impact of threshold concepts, especially randomness and probability, on natural selection understanding should be further explored.

scholarly journals Deregulated Semantic Cognition Follows Prefrontal and Temporo-parietal Damage: Evidence from the Impact of Task Constraint on Nonverbal Object Use

2011 ◽  
Vol 23 (5) ◽  
pp. 1125-1135 ◽  
Author(s):  
Faye Corbett ◽  
Elizabeth Jefferies ◽  
Matthew A. Lambon Ralph
Keyword(s):  
Conceptual Knowledge ◽  
Case Series ◽  
Semantic Knowledge ◽  
Regulatory Control ◽  
Task Constraint ◽  
Semantic Cognition ◽  
Object Use ◽  
Task Conditions ◽  
The Impact ◽  
Semantic Impairment

Semantic cognition, which encompasses all conceptually based behavior, is dependent on the successful interaction of two key components: conceptual representations and regulatory control. Qualitatively distinct disorders of semantic knowledge follow damage to the different parts of this system. Previous studies have shown that patients with multimodal semantic impairment following CVA—a condition referred to as semantic aphasia (SA)—perform poorly on a range of conceptual tasks due to a failure of executive control following prefrontal and/or temporo-parietal infarction [Jefferies, E., & Lambon Ralph, M. A. Semantic impairment in stroke aphasia versus semantic dementia: A case-series comparison. Brain, 129, 2132–2147, 2006]. Although a deficit of core semantic control would be expected to impair all modalities in parallel, most research exploring this condition has focused on tasks in the verbal domain. In a novel exploration of semantic control in the nonverbal domain, therefore, we assessed eight patients with SA on two experiments that examined object use knowledge under different levels of task constraint. Patients exhibited three key characteristics of semantic deregulation: (a) difficulty using conceptual knowledge flexibly to support the noncanonical uses of everyday objects; (b) poor inhibition of semantically related distractor items; and (c) improved object use with the provision of more tightly constraining task conditions following verbal and pictorial cues. Our findings are consistent with the notion that a neural network incorporating the left inferior prefrontal and temporo-parietal areas (damaged in SA) underpins regulation of semantic activation across both verbal and nonverbal modalities.

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