Evolutionary Biology Quiz
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Questions and Answers

What is a codon composed of?

  • Three pairs of nucleotides (correct)
  • A single nucleotide
  • A pair of amino acids
  • Three base pairs of nucleotides

Which type of substitution does not result in any change in amino acid synthesis?

  • Transitional substitution
  • Replacement substitution
  • Silent site substitution (correct)
  • Conservative mutation

What is the main consequence of replacement substitutions?

  • They result in synonymous mutations
  • They are non-functional changes
  • They occur only in pseudogenes
  • They can alter the structure of proteins (correct)

Why do silent site substitutions have a higher rate of change than replacement substitutions?

<p>They do not result in phenotypic changes, avoiding natural selection (D)</p> Signup and view all the answers

How does the neutral theory of molecular evolution explain genetic variation?

<p>Differences arise purely from neutral mutations over time (D)</p> Signup and view all the answers

What process greatly influences the evolutionary path of globin chains in vertebrates?

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

What characterizes pseudogenes in evolutionary change?

<p>They do not code for proteins (B)</p> Signup and view all the answers

Which of the following correctly describes the consequence of a silent site substitution in a codon?

<p>It leads to no change in the encoded protein (C)</p> Signup and view all the answers

What is the primary process through which speciation occurs?

<p>Splitting of an evolutionary lineage (B)</p> Signup and view all the answers

Which of the following correctly defines cladogenesis?

<p>A splitting event leading to distinct species (D)</p> Signup and view all the answers

What type of reproductive barrier occurs before mating?

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

In eukaryotic species, what is phenotypic differentiation?

<p>Visible changes in physical characteristics (C)</p> Signup and view all the answers

Which type of speciation occurs as a result of geographic isolation?

<p>Allopatric speciation (D)</p> Signup and view all the answers

Which of the following is NOT a type of speciation mentioned?

<p>Trans-speciation (C)</p> Signup and view all the answers

What function do reproductive barriers serve in the process of speciation?

<p>To prevent gene flow between populations (A)</p> Signup and view all the answers

Which mechanism describes the process where species reinforce their distinctions after speciation?

<p>Natural selection (C)</p> Signup and view all the answers

What exemplifies the process of adaptive radiation among Galapagos finches?

<p>Variation in bill shapes suited to different diets (D)</p> Signup and view all the answers

What is a key characteristic of sympatric speciation?

<p>Involves reproductive isolation within a single population (A)</p> Signup and view all the answers

Which example best illustrates sympatric speciation among apple maggot flies?

<p>Flies that start laying eggs in different types of fruit (B)</p> Signup and view all the answers

What factor could contribute to sympatric speciation in African cichlid fishes?

<p>Sexual selection based on phenotypic traits (C)</p> Signup and view all the answers

Why is sympatric speciation often debated among scientists?

<p>It lacks convincing evidence of reproductive isolation (B)</p> Signup and view all the answers

In the context of cichlid fishes, what does the term 'species flocks' refer to?

<p>Individuals of the same species gathering in large groups (B)</p> Signup and view all the answers

What is the main challenge in demonstrating sympatric speciation?

<p>Species in the same area tend to interbreed freely (A)</p> Signup and view all the answers

Which of the following scenarios is least likely to result in sympatric speciation?

<p>A population of birds that migrates to a distant island (A)</p> Signup and view all the answers

What does the neutral theory of molecular evolution primarily assert about genetic variations?

<p>The majority of genetic variations are neutral. (B)</p> Signup and view all the answers

Who initially proposed the neutral theory of molecular evolution?

<p>Motoo Kimura (C)</p> Signup and view all the answers

What is meant by 'random genetic drift' in the context of the neutral theory?

<p>The unintentional spread of neutral mutations due to chance. (B)</p> Signup and view all the answers

According to the neutral theory, how do neutral mutations affect evolutionary rates?

<p>They explain the high rate of evolution more effectively than beneficial mutations. (B)</p> Signup and view all the answers

How do advantageous mutations differ from deleterious mutations?

<p>Advantageous mutations are beneficial while deleterious mutations are harmful. (A)</p> Signup and view all the answers

What role does natural selection play according to the neutral theory?

<p>Natural selection is almost irrelevant to molecular changes. (D)</p> Signup and view all the answers

What may lead to the formation of new species, according to molecular evolution?

<p>Accumulation of neutral genetic changes over time. (A)</p> Signup and view all the answers

Which of the following best describes neutral mutations?

<p>Mutations that do not significantly affect the organism's functioning. (A)</p> Signup and view all the answers

What is the main focus of molecular evolution as described?

<p>Use of molecular data to analyze geographic variation and phylogeny (A)</p> Signup and view all the answers

Which of the following statements about the neutral theory is true?

<p>It recognizes the existence of neutral mutations and that these are widespread. (C)</p> Signup and view all the answers

What was the significant contribution of the paper by Andrew Kern and Matthew Hahn published in 2018?

<p>It criticized the foundational grounds of the neutral theory. (C)</p> Signup and view all the answers

What aspect of genetic variation was debated following the publication by Kern and Hahn?

<p>The roles of positive and negative selection in genetic variation (A)</p> Signup and view all the answers

What modification regarding the neutral theory has been recently proposed?

<p>The terms used in describing neutrality could be misleading in some contexts. (D)</p> Signup and view all the answers

What is the primary assertion made by Motoo Kimura regarding the majority of base substitutions in a population?

<p>They are neutral with respect to natural selection. (B)</p> Signup and view all the answers

Which of the following best describes the role of negative mutations in Kimura's theory?

<p>They are quickly eliminated by natural selection. (B)</p> Signup and view all the answers

What method did J. McDonald and M. Kreitman use to test Kimura's theory?

<p>Comparing DNA sequences of specific genes. (B)</p> Signup and view all the answers

According to Kimura's neutral theory, the rate of fixation of neutral mutations depends on which factor?

<p>Genetic drift. (C)</p> Signup and view all the answers

What does the neutral theory serve as a null hypothesis for?

<p>Examining genetic variation against empirical data. (C)</p> Signup and view all the answers

Which finding supported the predictions of the neutral theory regarding protein sequence changes?

<p>Changes tend to be conservative and less radical. (D)</p> Signup and view all the answers

What characteristic is associated with pseudogenes according to the neutral theory?

<p>They have the highest substitution rate among genes. (B)</p> Signup and view all the answers

How does Kimura's theory contrast with classical Darwinism?

<p>It suggests neutral mutations play a major role in evolution. (C)</p> Signup and view all the answers

Flashcards

Speciation

The process of forming new, distinct species through evolution, leading to reproductive isolation of lineages.

Anagenesis

Evolutionary process where gradual changes in traits occur along a single lineage, without splitting into new species.

Cladogenesis

Splitting event in evolution where a parent species diverges into two or more distinct species, often due to geographic isolation.

Reproductive Isolation

Mechanisms preventing interbreeding between different species, leading to genetic separation and distinct lineages.

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Pre-Zygotic Mechanisms

Reproductive barriers occurring before fertilization, such as differences in mating rituals, incompatible genitalia, or gametes.

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Post-Zygotic Mechanisms

Reproductive barriers occurring after fertilization, such as zygote mortality or the production of sterile offspring.

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Genetic Separation

The division of a gene pool into two or more separate gene pools during speciation.

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Phenotypic Differentiation

The development of observable physical differences in a population in response to environmental pressures and genetic changes.

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Adaptive Radiation

The rapid evolution of many species from a single ancestor, often driven by adaptation to different environments.

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Sympatric Speciation

The formation of new species within a single population, without geographic isolation.

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Allopatric Speciation

Speciation due to geographic isolation.

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Apple Maggot Flies

A classic example of sympatric speciation, with a shift in host preference (from hawthorn to apple) leading to divergence.

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Species Flock

A group of closely related species that evolved from a common ancestor, often living in the same location.

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Cichlid Fish

A group of fish that provides examples of both allopatric and sympatric speciation, particularly in East African lakes.

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Sexual Selection

A type of natural selection where individuals with certain traits are more likely to attract mates.

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Codon

A set of three consecutive nucleotides that codes for a specific amino acid during protein synthesis.

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Silent Site Substitution

A change in the DNA sequence that doesn't alter the amino acid produced by a codon.

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Replacement Substitution

A change in the DNA sequence that results in a different amino acid being produced.

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Pseudogenes

Duplicate DNA sequences that don't code for proteins and are not subject to natural selection.

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Phenotype

The observable characteristics of an organism, influenced by its genotype and environment.

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Natural Selection

The process where organisms with advantageous traits are more likely to survive and reproduce, passing on those traits.

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Neutral Theory of Molecular Evolution

A theory explaining genetic differences between species by proposing that most molecular changes are neutral.

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Amino Acid Sequencing

A method to determine the order of amino acids in a protein, used to trace evolutionary relationships.

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Neutral Theory

A theory in evolutionary biology stating that most genetic variations within a population are neutral, meaning they do not affect an organism's fitness.

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Molecular Evolution

The study of how DNA sequences change over time, providing insights into evolutionary relationships and the origins of species.

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Positive Selection

The evolutionary process where beneficial mutations are favored and spread within a population, increasing fitness.

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Negative Selection

The evolutionary process where harmful mutations are eliminated from a population, reducing fitness.

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Kern and Hahn's Criticism

A recent research paper questioning the universality of the neutral theory, suggesting that the role of natural selection in driving genetic variation is underestimated.

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Kimura's Neutral Theory

Proposed by Motoo Kimura, this theory states that the majority of evolutionary changes at the molecular level are due to neutral mutations that are neither beneficial nor harmful.

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What is the role of natural selection in Kimura's theory?

Natural selection primarily eliminates deleterious mutations. It doesn't play a significant role in the fixation of neutral mutations, which are driven by genetic drift.

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What is the impact of the neutral theory?

It provides a 'null hypothesis' for testing evolutionary changes. This allows researchers to determine if genetic variation is truly driven by selection or simply by random drift.

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What is the prediction made by the neutral theory about protein sequence changes?

Neutral theory predicts that conservative changes (mutations that minimally affect protein function) are more likely to occur than radical changes (mutations that significantly alter protein function).

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How does the neutral theory explain differences within and between species?

It suggests that genetic drift is a major force, causing random differences in the accumulation of neutral mutations within and between populations. This leads to genetic divergence between species.

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How is the neutral theory tested?

It is tested by comparing DNA sequences between species and looking for patterns consistent with neutral evolution, like high rates of changes in pseudogenes and conservative changes in functional genes.

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Random Genetic Drift

The process by which neutral mutations become widespread in a population due to chance alone. It's like a coin toss; heads or tails can win, but it's not predictable.

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Motoo Kimura

A geneticist known for proposing the neutral theory of molecular evolution in 1968, challenging the prevailing view that natural selection was the main driver of evolution.

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What are neutral mutations?

Mutations that do not have a significant impact on an organism's function or survival, meaning they are neither beneficial nor harmful.

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What is the main difference between the neutral theory and Darwin's natural selection?

The neutral theory emphasizes the role of random genetic drift, while Darwin's theory focuses on natural selection favoring advantageous traits.

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How does the neutral theory explain evolution?

It suggests that most molecular changes, such as in DNA sequences, are caused by random processes acting on selectively neutral mutants, not necessarily adaptation through natural selection.

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What is the significance of the neutral theory?

It provides a framework for understanding the prevalence of neutral mutations in evolution and helps explain the rate of molecular evolution.

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Study Notes

Speciation

  • Speciation is the formation of new and distinct species throughout evolution
  • It involves the splitting of a single lineage into multiple lineages
  • These lineages become genetically independent
  • Speciation leads to reproductively isolated species

Types of Speciation

  • Anagenesis (phyletic evolution): Gradual changes within a single lineage; no splitting of the phylogenetic tree. Change in physical or genetic traits make new species distinct from ancestors
  • Cladogenesis (speciation): A splitting event; parent species forms two distinct species. This usually happens due to geographic isolation, or another driving force
  • Reproductive Isolation: This is crucial to the process. Genetic, behavioral, or physical differences create barriers that lead to the inability of two species to breed.
    • Pre-zygotic barriers: Occur before fertilization (courtship rituals, incompatible genitalia, incompatible gametes).
    • Post-zygotic barriers: Occur after fertilization (zygote mortality or sterile offspring)

Mechanisms of Speciation

  • Allopatric Speciation: Occurs when a population becomes geographically isolated, and genetic exchange through mating is prevented. This can result from geographic changes, changes to the habitat, or migration
  • Peripatric Speciation: Form of allopatric speciation - populations are very small and isolated resulting in a genetic bottleneck. Genes rare in the larger populations may become common in the small isolated population, causing a slight variation in behaviour or morphology
  • Parapatric Speciation: Continuous distribution, no clear geographic barriers, but individuals mate primarily with nearby individuals. This non-random mating can increase the rate of morphological differences and eventually lead to two species
  • Sympatric Speciation: Reproductive isolation within a single population without geographic separation
    • Example: apple maggot fly initially laying eggs in hawthorns, then switching to apple trees; leads to isolation of two groups due to different locations of mating.

Isolation Mechanisms

  • Pre-mating Isolating Mechanisms:

    • Temporal isolation: Different mating times (e.g., different seasons).
    • Ecological isolation: Different habitats within the same area.
    • Behavioral isolation: Different mating behaviors.
    • Mechanical isolation: Incompatible reproductive structures

  • Post-mating Isolating Mechanisms: - Gametic isolation: Incompatible gametes. - Zygotic mortality: Fertilized egg fails to develop - Hybrid inviability: Offspring is not viable. - Hybrid sterility: Offspring is sterile. - Hybrid breakdown: First-generation hybrids viable and fertile, but later generations are sterile.

Molecular Evolution

  • Molecular evolution refers to the changes in DNA or RNA sequences and amino acid sequences over generations. 
  • These changes can result from:
    • Mutations
    • Natural selection
  • Neutral Theory of Molecular Evolution: A large percentage of molecular changes, like those in DNA sequence, are neutral in terms of selection. This means that the changes don't increase or decrease an organism's chance of survival

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Description

Test your knowledge of key concepts in evolutionary biology, including codons, substitutions, and speciation. This quiz covers aspects of molecular evolution and reproductive barriers among species. Challenge yourself with questions about genetic variation and evolutionary mechanisms.

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