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Related Concept Videos

Frequency-dependent Selection01:21

Frequency-dependent Selection

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When the fitness of a trait is influenced by how common it is (i.e., its frequency) relative to different traits within a population, this is referred to as frequency-dependent selection. Frequency-dependent selection may occur between species or within a single species. This type of selection can either be positive—with more common phenotypes having higher fitness—or negative, with rarer phenotypes conferring increased fitness.
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Diploid organisms have two alleles of each gene, one from each parent, in their somatic cells. Therefore, each individual contributes two alleles to the gene pool of the population. The gene pool of a population is the sum of every allele of all genes within that population and has some degree of variation. Genetic variation is typically expressed as a relative frequency, which is the percentage of the total population that has a given allele, genotype or phenotype.
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Types of Selection01:46

Types of Selection

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Natural selection influences the frequencies of particular alleles and phenotypes within populations in several different ways. Primarily, natural selection can be directional, stabilizing, or disruptive. Directional selection favors one extreme trait and shifts the population towards that phenotype while selecting against individuals displaying alternate traits. Stabilizing selection favors an intermediate trait with a narrow range of variation. Deviation from the optimal phenotype towards an...
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Mechanistic Models: Compartment Models in Individual and Population Analysis01:23

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Mechanistic models are utilized in individual analysis using single-source data, but imperfections arise due to data collection errors, preventing perfect prediction of observed data. The mathematical equation involves known values (Xi), observed concentrations (Ci), measurement errors (εi), model parameters (ϕj), and the related function (ƒi) for i number of values. Different least-squares metrics quantify differences between predicted and observed values. The ordinary least...
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Incomplete Dominance01:43

Incomplete Dominance

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Gregor Mendel's work (1822 - 1884) was primarily focused on pea plants. Through his initial experiments, he determined that every gene in a diploid cell has two variants called alleles inherited from each parent. He suggested that amongst these two alleles, one allele is dominant in character and the other recessive. The combination of alleles determines the phenotype of a gene in an organism.
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Related Experiment Video

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Why Quantification Matters: Characterization of Phenotypes at the Drosophila Larval Neuromuscular Junction
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DENSITY-DEPENDENT SELECTION ON CONTINUOUS CHARACTERS: A QUANTITATIVE GENETIC MODEL.

Yoshinari Tanaka1

  • 1Department of Biology, McGill University, 1205 Docteur Penfield Avenue, Montreal, Quebec, H3A 1B1, Canada.

Evolution; International Journal of Organic Evolution
|June 1, 2017
PubMed
Summary

This study models density-dependent selection, showing that r- and K-selection depend on population density fluctuations. Genetic traits can evolve rapidly, influenced by synergistic interactions, but strong r-selection requires continuous population disturbance.

Keywords:
Density-dependent selectionlife historyquantitative geneticsreaction normselection gradient

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Area of Science:

  • Quantitative genetics
  • Evolutionary biology
  • Ecology

Background:

  • Density-dependent selection influences population dynamics and evolutionary trajectories.
  • The concepts of r-selection and K-selection describe different adaptive strategies related to population growth rate and carrying capacity.
  • Understanding the genetic basis of these strategies is crucial for predicting evolutionary responses.

Purpose of the Study:

  • To develop a quantitative genetic model of density-dependent selection.
  • To formulate the ecological concepts of r- and K-selection in terms of selection gradients on phenotypic traits.
  • To analyze the evolutionary rates of r and K under varying population densities.

Main Methods:

  • Development of a quantitative genetic model incorporating density-dependent fitness.
  • Decomposition of selection gradients into components influencing r and K.
  • Parameterization of the model using data from laboratory selection experiments.
  • Numerical simulations to assess evolutionary dynamics and rates.

Main Results:

  • The relative importance of r- and K-selection components is determined by temporal fluctuations in population density.
  • Moderate genetic variances in underlying traits lead to rapid evolution of r and K.
  • Synergistic interactions between traits can influence the evolutionary rate.
  • Strong r-selection necessitates severe and continuous population disturbances to maintain low densities.

Conclusions:

  • The model provides a framework for understanding the interplay between ecological conditions and genetic evolution in density-dependent systems.
  • Evolutionary rates of r and K are sensitive to genetic architecture and environmental variability.
  • The conditions for strong r-selection are restrictive, highlighting the importance of sustained environmental challenges.