Genetics and Reaction Norms Quiz
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Questions and Answers

What is the primary purpose of the reaction norm in genetics?

  • To track evolutionary changes in species
  • To model genetic mutations
  • To analyze phenotypic variations across populations
  • To serve as a theoretical tool for genetic studies (correct)

What concept did Schmalhausen replace 'organic selection' with?

  • Sexual selection
  • Directional selection
  • Natural selection
  • Stabilizing selection (correct)

What is the Baldwin Effect primarily associated with?

  • The introduction of new species
  • The interaction of phenotype and environment
  • The elimination of maladaptive traits
  • The integration of genetic mutations (correct)

Which statement best describes the adaptive norm of reaction?

<p>It involves genetic mutations leading to stable phenotypic changes. (A)</p> Signup and view all the answers

What did Dobzhansky and Schmalhausen's work emphasize in evolutionary biology?

<p>The importance of stabilizing selection for adaptive responses. (C)</p> Signup and view all the answers

What does the non-adaptive norm of reaction refer to?

<p>Phenotypic changes that do not enhance fitness. (B)</p> Signup and view all the answers

What role does genetic mutation play in the adaptive norm of reaction according to the discussed theories?

<p>They enable the phenotypic effect to be stabilized for future generations. (C)</p> Signup and view all the answers

Which publication is attributed to Waddington regarding modern genetics?

<p>An Introduction to Modern Genetics (D)</p> Signup and view all the answers

What distinguishes adaptive phenotypic plasticity from non-adaptive plasticity?

<p>It is genetically controlled. (A)</p> Signup and view all the answers

What role does non-adaptive plasticity play in relation to adaptive phenotypic plasticity?

<p>It can favor the development of adaptive phenotypic plasticity. (A)</p> Signup and view all the answers

How is non-adaptive phenotypic plasticity characterized?

<p>It is independent of genetic control. (A)</p> Signup and view all the answers

What controversy was addressed regarding the nature of plasticity?

<p>Plasticity can be both a trait and an epiphenomenon of natural selection. (B)</p> Signup and view all the answers

What is the relationship between genetic control and non-adaptive plasticity?

<p>Non-adaptive plasticity can express independently from genetic control. (A)</p> Signup and view all the answers

Which type of plasticity is influenced by natural selection?

<p>Only adaptive phenotypic plasticity. (D)</p> Signup and view all the answers

What factor contributes to the variability of non-adaptive phenotypic plasticity?

<p>Both genetic and environmental factors. (A)</p> Signup and view all the answers

Which describes the nature of plasticity as proposed by Sara Via?

<p>It is a complex interaction of traits subject to change. (B)</p> Signup and view all the answers

What does West-Eberhard propose as the starting point for explaining traits' evolution?

<p>Phenotypic variations (C)</p> Signup and view all the answers

What does Via argue regarding the independence between the trait mean and plasticity?

<p>It remains to be confirmed. (B)</p> Signup and view all the answers

How does West-Eberhard define 'development'?

<p>Any phenotypic change during an individual's life (C)</p> Signup and view all the answers

What is 'developmental plasticity' according to West-Eberhard?

<p>The capacity to change in response to internal or external signals (A)</p> Signup and view all the answers

In the context of genetic variability, what does the term 'grand mean' refer to?

<p>The average of a trait across multiple environments. (D)</p> Signup and view all the answers

Which of the following best describes the example of dwarf elephants?

<p>Natural selection favored smaller elephants that could find food more easily. (A)</p> Signup and view all the answers

What is a characteristic of the approach mentioned in the content regarding plasticity?

<p>It relies on observable types rather than real causes. (B)</p> Signup and view all the answers

Which model does the content suggest is not mutually exclusive?

<p>Phenotypic plasticity. (B)</p> Signup and view all the answers

What does West-Eberhard consider to be a physical component in shaping an organism?

<p>The genome (C)</p> Signup and view all the answers

What issue does Via raise about measuring the trait mean?

<p>It can be determined for a single environment as well. (A)</p> Signup and view all the answers

Which statement regarding the 'phenotype' is accurate based on West-Eberhard's framework?

<p>The phenotype is a result of both genetic and environmental interactions. (C)</p> Signup and view all the answers

What key factor influenced the development of the dwarf elephant trait?

<p>Famine leading to atrophy (D)</p> Signup and view all the answers

What is often used to study models in quantitative genetics according to the content?

<p>Statistical studies. (D)</p> Signup and view all the answers

Which term describes an organism's ability to change in response to stimuli?

<p>Developmental plasticity (D)</p> Signup and view all the answers

What was the primary focus of the polynomial approach that Via's position rejected?

<p>The independence of the trait mean from plasticity. (D)</p> Signup and view all the answers

What does the concept of environmental tolerance relate to?

<p>The ability to adapt to external conditions. (D)</p> Signup and view all the answers

What is the main controversy surrounding genetic control for plasticity?

<p>The definition of genetic control is still uncertain. (D)</p> Signup and view all the answers

According to Scheiner and Lyman, how many distinct categories correspond to the genetic bases of plasticity?

<p>Three (A)</p> Signup and view all the answers

What does the term 'overdominance' describe in the context of genetic plasticity?

<p>An inversely proportional relationship between heterozygosity and plasticity. (C)</p> Signup and view all the answers

What characteristic of phenotypic response does a homozygotic genotype exhibit according to the context?

<p>Less plasticity in reaction norms. (C)</p> Signup and view all the answers

Which statement accurately reflects the current understanding of 'plasticity genes'?

<p>They are associated with a polynomial relationship model. (C)</p> Signup and view all the answers

What did Scheiner and Lyman's assessment aim to establish regarding genetic expression?

<p>The basis of genetic expression related to plasticity. (B)</p> Signup and view all the answers

What method did Scheiner and Lyman use to classify genetic bases of plasticity?

<p>Systematic categorization. (B)</p> Signup and view all the answers

Why is the expression 'plasticity genes' considered plural?

<p>It implies multiple genetic influences on plasticity. (C)</p> Signup and view all the answers

What is phenotypic plasticity described as in the context of changing environments?

<p>An epiphenomenon resulting from the selection of different averages. (A)</p> Signup and view all the answers

According to Schlichting and Pigliucci, what are 'plasticity genes' defined as?

<p>Regulatory loci that control structural gene expression in relation to the environment. (B)</p> Signup and view all the answers

What do Schlichting and Pigliucci suggest about the relationship between plasticity genes and plasticity as a by-product of selection?

<p>They can coexist and are not mutually exclusive. (C)</p> Signup and view all the answers

What example is cited as proof of the existence of plasticity genes?

<p>Phytochromes coding for plant responses. (A)</p> Signup and view all the answers

What is a key issue in the controversy discussed by Via and other researchers?

<p>The complexity of interaction between different environmental variables. (D)</p> Signup and view all the answers

What concept did Via maintain regarding phenotypic plasticity?

<p>It’s not a specific trait, but influenced by averages. (C)</p> Signup and view all the answers

What did the researchers categorize their disagreements as?

<p>Semantic wrangling rather than true problems. (C)</p> Signup and view all the answers

How do Via's ideas on phenotypic plasticity contribute to evolutionary discussions?

<p>They complicate understanding by invoking multiple variables. (B)</p> Signup and view all the answers

Flashcards

Norm of reaction

A theoretical tool in genetics that models phenotype-environment interactions, showing how a genotype produces different phenotypes in different environments.

Adaptive norm of reaction

A norm of reaction that results from organic selection, where a modified phenotype is assimilated through a genetic mutation, leading to similar phenotypes in future generations.

Non-adaptive norm of reaction

A norm of reaction that doesn't result from organic selection or genetic change.

Organic selection

The assimilation of a modified phenotype by the integration of a genetic mutation that leads to a similar phenotype.

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Baldwin Effect

A theory popularized by Ivan Schmalhausen about organic selection, emphasizing how adaptive phenotypic responses become genotypic responses.

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Stabilizing selection

A type of selection that emphasizes the stabilization of an adaptive phenotypic response, essentially making it genetic.

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Phenotype

The observable traits and characteristics of an organism

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Genotype

The genetic makeup of an organism

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Plasticity Genes

The genes involved in an organism's ability to change its traits in response to environmental factors.

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Genetic Basis of Plasticity

The underlying genetic mechanisms that allow for phenotypic plasticity.

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Overdominance

A genetic situation where a heterozygous genotype has a trait value between those of the two homozygous genotypes

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Heterozygosity

Having two different alleles of a gene.

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Reaction Norm

A range of phenotypic values expressed by a genotype across various environments.

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Homozygosity

Having two identical alleles of a gene.

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Phenotypic Plasticity

The ability of a genotype to produce different phenotypes in response to environmental changes.

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Polynomial Model

A model that accounts for the complex interactions between multiple genes when predicting phenotypes from genes.

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Genetic Variability

The variation in genes within a population that often arises from interactions with the environment.

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Genotype-environment interaction

The effect of a genotype depends on the environment it is in.

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Trait Mean

The average expression of a trait across all environments.

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Grand Mean

Average trait expression across a range of environments.

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Quantitative Genetics

The study of the genetic basis of traits without examining the genes directly.

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Environmental Tolerance

A species' ability to cope with variations in the environment.

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Evolution of Plasticity

The evolution of a species' ability to alter its traits in response to environmental differences.

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Developmental Plasticity

An organism's ability to change its traits in response to environmental factors during its development.

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Plasticity

An organism's ability to react to internal or external signals by changing its shape, state, movement, or activity level.

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Development

Any phenotypic change during an individual's life or any other unit of higher organization, including irreversible changes like muscle growth.

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Why study Phenotypic Variations?

It is more sound to study how an organism's traits change in response to environment to explain evolution rather than focusing only on single genetic variations.

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Dwarf Elephants as an Example

Dwarf elephants on islands evolved due to a famine that caused atrophy and natural selection favoring smaller elephants that were easier to feed.

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What is the source of a new trait?

New traits often arise from a combination of environmental influences causing phenotypic change and natural selection acting on those changes.

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Adaptive Plasticity

Phenotypic plasticity that is advantageous for survival and reproduction in a particular environment. This occurs when organisms evolve to exhibit beneficial, environmentally-induced changes in their phenotypes.

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Non-Adaptive Plasticity

Phenotypic plasticity that does not provide any reproductive or survival benefit. This occurs when a specific environmental condition influences a phenotype, but this change is not beneficial for the organism.

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What does Via's model of plasticity suggest?

Via's model suggests that plasticity is not a specific trait, but rather a by-product of selection favoring different average phenotypes in different environments. Selection acts on the varying responses, effectively producing plasticity as an outcome.

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How do Schlichting and Pigliucci view plasticity?

Schlichting and Pigliucci propose that plasticity can be both a byproduct of selection and also directly controlled by specific genes (plasticity genes). They believe that these two explanations are not mutually exclusive.

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What are phytochromes, and how do they relate to plasticity?

Phytochromes are light-sensitive proteins in plants that play a crucial role in regulating plant growth and development in response to light conditions. They provide a clear example of how genes can directly control plasticity.

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Why is studying plasticity important?

Understanding phenotypic plasticity is essential for comprehending how organisms interact with and adapt to their environment. It helps us predict how species will respond to changing environmental conditions and understand the evolutionary mechanisms driving adaptations.

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Plasticity as a Trait

The concept that plasticity itself can be influenced by genes, meaning some organisms are more adaptable than others.

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Plasticity vs. Selection

While plasticity allows for immediate adaptation to changes, natural selection acts over generations to favor those traits best suited for survival.

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Plasticity and Controversy

The idea that plasticity might not be a trait, but a result of natural selection, led to debates about how it should be defined and studied.

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Non-Adaptive Plasticity's Role

Although it doesn't directly benefit survival, non-adaptive plasticity can provide the raw material for adaptive change through natural selection.

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Genetic Control of Plasticity

The degree of plasticity an organism can exhibit is often influenced by its genetic makeup, meaning some individuals are more 'flexible' than others.

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Plasticity as an Evolutionary Tool

Plasticity is a mechanism that allows organisms to adapt to changing environments - sometimes quickly - which is crucial for survival and evolution.

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Study Notes

Phenotypic Plasticity: From Microevolution to Macroevolution

  • Phenotypic plasticity is a common concept in life sciences.
  • The term has two meanings: active—the capacity to shape or form (e.g., egg cell development); and passive—susceptibility to multiple form expressions (e.g., phenotypic plasticity).
  • Darwin discussed plasticity in terms of external conditions affecting the expression of various traits.
  • Darwin did not attribute environmental change to direct causation of variation.
  • More and Cudworth connected "plastic nature" to the Aristotelian view of ontogenesis and structural forces in biological organization.
  • The Soviet school refined the concept with the "reaction norm".
  • The norm of reaction (Reaktionsnorm) describes the range of phenotypes a single genotype can express across varying environments.
  • Schmalhausen and Dobzhansky developed the "adaptive norm".
  • This norm describes the transformation of phenotypic response into a genotypic response, highlighting its inheritance.
  • Bradshaw proposed the idea of genetic control of phenotypic plasticity, arguing that plasticity is a specific genetic trait, not a characteristic of the entire genome, and that genetic control over a character is separate from the trait control mechanism.
  • Lande and Via established quantitative genetic models to study the evolution of phenotypic plasticity.
  • Lande and Via demonstrated natural selection operating on expressed traits within specific environments.
  • The evolution of adaptive reaction norms occurs via phenotypic traits.
  • Schlichting and Pigliucci proposed "plasticity genes" as regulatory loci in charge of environmental control over structural gene expression.
  • Pigliucci revised the concept of "plasticity genes" in 1996, describing them as regulatory loci directly responding to environmental stimuli.
  • West-Eberhard, in her "developmental plasticity hypothesis", linked morphological and behavioral plasticity and saw development as a key aspect of understanding speciation and macroevolutionary changes.
  • Phenotypic plasticity plays a key role in microevolution and macroevolution, including speciation, niche diversification, and adaptive evolutionary changes.
  • Macroevolution is the evolutionary change, or the formation of new species, above the species level.
  • Phenotypic plasticity is central to adaptive evolution, and the concept of genetic variation and its evolution are important for resolving ongoing questions in evolutionary biology.

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Test your understanding of reaction norms in genetics, including concepts like adaptive and non-adaptive plasticity. This quiz covers significant contributions by key figures in evolutionary biology like Dobzhansky and Schmalhausen. Explore the implications of genetic mutations and the role of natural selection in phenotypic plasticity.

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