Microevolution and Diversity in Populations
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Questions and Answers

What is defined as the reproductive success of a genotype within a population?

  • Genetic drift
  • Absolute fitness
  • Relative fitness (correct)
  • Phenotypic fitness

In a population where 840 individuals are tongue-rollers, what is the frequency of the dominant allele (T) based on the Hardy-Weinberg principle?

  • 0.7
  • 0.4
  • 0.6 (correct)
  • 0.5

Which factor is NOT one of the five that determine allele frequencies in microevolution?

  • Population size (correct)
  • Natural selection
  • Mutation
  • Gene flow

What condition must be met for a population to remain in Hardy-Weinberg equilibrium?

<p>No mutations occurring (A)</p> Signup and view all the answers

What type of selection occurs when individuals with extreme phenotypes have advantages over others in the population?

<p>Disruptive selection (B)</p> Signup and view all the answers

What is the primary mechanism by which new genes and alleles originate in a population?

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

Which of the following represents the frequency of homozygous recessive individuals in the population, given that 160 out of 1000 individuals are homozygous recessive?

<p>$0.16$ (C)</p> Signup and view all the answers

What happens to a population that deviates from Hardy-Weinberg equilibrium?

<p>It will begin to change over time. (A)</p> Signup and view all the answers

What is the primary cause of genetic drift?

<p>Random events affecting allele frequencies (A)</p> Signup and view all the answers

What is the bottleneck effect primarily responsible for?

<p>Decreasing genetic diversity due to limited survival (B)</p> Signup and view all the answers

How does the founder effect influence genetic diversity in new populations?

<p>It reduces genetic diversity due to a small allele sample brought by founders (A)</p> Signup and view all the answers

What is one consequence of gene flow between populations?

<p>Reduction of genetic variability in the receiving population (B)</p> Signup and view all the answers

What does sexual selection typically result in within a species?

<p>Sexual dimorphism or differences between sexes (C)</p> Signup and view all the answers

Which of the following is NOT a consequence of genetic drift?

<p>Enhanced genetic diversity within a small population (C)</p> Signup and view all the answers

What effect does a bottleneck event have on allele representation in a surviving population?

<p>Some alleles may be completely lost (D)</p> Signup and view all the answers

What is the primary mechanism by which gene flow occurs?

<p>Migration of breeding individuals between populations (D)</p> Signup and view all the answers

What is the primary effect of directional selection on a population's allele frequency?

<p>It shifts allele frequencies toward one phenotypic extreme. (A)</p> Signup and view all the answers

In which scenario is disruptive selection most likely to occur?

<p>With the introduction of a new geographical barrier to a population. (D)</p> Signup and view all the answers

Which of the following best describes a potential outcome of disruptive selection?

<p>Formation of two distinct sub-populations over time. (A)</p> Signup and view all the answers

What role does artificial selection play in the context of directional selection?

<p>It mimics natural processes and can accelerate phenotypic changes. (D)</p> Signup and view all the answers

What phenomenon was observed in the Galapagos finches that illustrates directional selection?

<p>Survival of only finches with large beaks during a drought. (A)</p> Signup and view all the answers

Which trait is primarily favored in a directional selection scenario?

<p>One of the extreme traits within the population. (D)</p> Signup and view all the answers

What is a characteristic feature of disruptive selection compared to directional selection?

<p>It favors two or more distinct phenotypes. (A)</p> Signup and view all the answers

How does natural selection contribute to adaptation in populations?

<p>By enabling specific traits to become more common in response to environmental changes. (D)</p> Signup and view all the answers

What type of character varies along a spectrum within a population?

<p>Quantitative characters (C)</p> Signup and view all the answers

What is microevolution primarily concerned with?

<p>Population-level changes in allele frequency (B)</p> Signup and view all the answers

Which of the following accurately defines polymorphism?

<p>Presence of two or more discrete characters in a population (A)</p> Signup and view all the answers

What is the primary factor that leads to the adaptation of organisms to their environment?

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

In the context of microevolution, which statement is true regarding individual evolution?

<p>Populations, not individuals, are the units of evolution. (A)</p> Signup and view all the answers

Which type of selection favors a specific trait that increases fitness in an organism?

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

What is a major difference between microevolution and macroevolution?

<p>Microevolution deals with small, subtle changes while macroevolution involves large-scale changes. (A)</p> Signup and view all the answers

Which of the following is NOT a consequence of genetic diversity in a population?

<p>Stable allele frequencies over time (A)</p> Signup and view all the answers

What occurs during stabilizing selection?

<p>Selection against both phenotypic extremes (C)</p> Signup and view all the answers

Which of the following terms describes contrasting forms within a species?

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

What does fixation of an allele mean?

<p>The allele is present at a frequency of 1 (100%) (C)</p> Signup and view all the answers

Which of the following statements about intrasexual selection is true?

<p>It refers to competition among males for mating opportunities (C)</p> Signup and view all the answers

What impacts the expression of quantitative characters in organisms?

<p>Multiple genes interacting additively (C)</p> Signup and view all the answers

What is a disadvantage of stabilizing selection?

<p>Greater risk of extinction if the environment changes (B)</p> Signup and view all the answers

During sexual selection, what is the primary factor influencing mate choice?

<p>Coloration and size in males (C)</p> Signup and view all the answers

Natural selection can lead to which of the following outcomes in a population?

<p>Adaptation of organisms to their environment (D)</p> Signup and view all the answers

What is the primary focus of the Hardy-Weinberg principle?

<p>Changes in allelic frequencies over time (B)</p> Signup and view all the answers

Which equation represents the genetic equilibrium established by Hardy-Weinberg?

<p>p2 + 2pq + q2 = 1 (B)</p> Signup and view all the answers

Which of the following is NOT a condition required for Hardy-Weinberg equilibrium?

<p>Stable mutations (D)</p> Signup and view all the answers

In the Hardy-Weinberg model, what do the terms p and q represent?

<p>Proportions of dominant and recessive alleles (C)</p> Signup and view all the answers

Which genotype frequency corresponds to the homozygous recessive genotype aa?

<p>q2 (D)</p> Signup and view all the answers

What will happen to genotypic frequencies when any of the Hardy-Weinberg assumptions is violated?

<p>They will change over time (A)</p> Signup and view all the answers

What does the term 'fitness' refer to in the context of evolutionary biology?

<p>The ability of an organism to survive and reproduce (C)</p> Signup and view all the answers

Which of the following statements about Hardy-Weinberg equilibrium is true?

<p>It represents a model of genetic stability under specific conditions. (A)</p> Signup and view all the answers

Flashcards

Microevolution

Generation-to-generation change in allele frequency in a population.

Quantitative Character

Traits that vary along a spectrum within a population, often due to multiple genes.

Discrete Character

Traits that are either-or, determined mainly by a single gene.

Polymorphism

Presence of 2 or more distinct forms (morphs) within a population, often noticeable (e.g., blood type).

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Evolutionary change

Inherited change over time in traits associated with a population.

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Macroevolution

Large-scale changes in organisms observable over many generations.

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Population

All individuals of the same species in a specific location at a given time.

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Hardy-Weinberg Equilibrium

A theoretical model where allele frequencies in a population will remain constant from generation to generation in the absence of evolutionary influences.

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Allelic Frequency

The proportion of a particular allele (version of a gene) in a population.

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Genetic Equilibrium conditions

Large population, no mutation, no migration, no natural selection, random mating.

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p + q = 1

The sum of the frequencies of two alleles for a gene is always one.

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p^2 + 2pq + q^2 = 1

Equation describing the expected genotype frequencies when in Hardy-Weinberg equilibrium.

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Homozygous Dominant (AA)

Individuals with two copies of the dominant allele.

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Homozygous Recessive (aa)

Individuals with two copies of the recessive allele.

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Heterozygous (Aa)

Individuals having one dominant and one recessive allele.

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Relative Fitness

How well a genotype performs compared to others in a population, based on reproductive success.

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Most Prolific Genotype

The genotype that produces the most offspring in a population.

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Mutation

A change in the DNA sequence, the origin of new genes and alleles.

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Genetic Drift

Random fluctuation in allele frequencies within a population due to chance events.

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Gene Flow

The movement of alleles between populations due to migration or interbreeding.

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Natural Selection

Differential survival and reproduction of individuals with different genotypes.

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Bottleneck Effect

A dramatic reduction or near extinction of a population that results in a less diverse gene pool.

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Founder Effect

A new population established by a small number of individuals from a larger population, leading to a unique gene pool.

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Sexual Selection

Natural selection of traits related to mating success, often resulting in differences in appearance between males and females.

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Genetic variation

Difference in genes within a population

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Secondary Sexual Characteristics

Traits that distinguish males and females beyond those directly involved in reproduction, like size, color, or behavior.

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Intrasexual Selection

Competition among members of the same sex for mating opportunities, often involving displays of strength or dominance.

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Adaptive Evolution

The process of change in a population over time as traits that increase survival and reproduction become more common.

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Positive Selection

This occurs when a specific trait allele increases an organism's fitness, making it more likely to survive and reproduce, leading to an increase in the frequency of that allele in the population.

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Negative Selection

When a specific trait allele reduces an organism's fitness, making it less likely to survive and reproduce, causing a decrease in the frequency of that allele.

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Stabilizing Selection

Type of natural selection that favors intermediate phenotypes, reducing the population's variation, as extreme variations become less common.

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Directional Selection

A type of natural selection where one extreme phenotype is favored, shifting the allele frequency curve in one direction.

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Disruptive Selection

Natural selection favoring two extreme phenotypes while selecting against the intermediate phenotype.

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What does Directional Selection cause?

Directional selection causes adaptation to new conditions, often resulting from a changing or novel environment.

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What is an example of Directional Selection?

A classic example is bacterial resistance to antibiotics, where bacteria with resistance to the antibiotic survive and reproduce, leading to a higher prevalence of antibiotic-resistant bacteria in the population.

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Why is a new barrier important in Disruptive Selection?

A new barrier can lead to a physical separation of a population, creating distinct environments and favoring different phenotypes in each group.

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What is a result of Disruptive Selection?

Disruptive selection can lead to two distinct sub-populations, which may eventually evolve into separate species.

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What is an example of Disruptive Selection?

The three-spine stickleback fish shows disruptive selection with two morphs: one living in the open water and feeding on small plankton, and another living on the bottom and feeding on insects and crustaceans.

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What is the key feature of Disruptive Selection?

Disruptive selection favors extreme phenotypes while selecting against the average phenotype within a population.

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Study Notes

Microevolution

  • Microevolution is the generation-to-generation change in allele frequency within a population.
  • Microevolutionary changes are usually subtle.
  • Evolution happens in populations, not individuals.
  • Individuals do not evolve during their lifetime.
  • A population is all the individuals of the same species in a specific location at a specific time.
  • Traits can vary due to environmental and genetic factors.
  • Evolutionary change is inherited.

Diversity

  • Quantitative characters vary along a continuum within a population.
  • Quantitative characters are usually due to polygenic inheritance (additive effects from 2 or more genes influencing a single character).
  • Discrete characters are either-or traits.
  • Discrete characters are usually determined by a single locus with different alleles having distinct impacts on the phenotype.

Polymorphism

  • Polymorphism occurs when two or more discrete characters are present and noticeable within a population.
  • Polymorphism applies only to discrete characters, not quantitative ones.
  • Contrasting forms are called morphs.
  • Examples include red and white flowers in a wildflower population or different coloured butterflies, freckles or blood types in humans

Defining Microevolution

  • Individuals in a population have the same number and kind of genes.
  • Genes exist in different allelic forms, causing variations in traits.
  • The gene pool includes all alleles for all gene loci in a population.
  • In diploid organisms, individuals have two alleles for each gene locus.
  • Only a fraction of an organism's alleles are present in the population's gene pool.
  • Genotype frequency is the proportion of a certain genotype in a population.
  • Allele frequency refers to the proportion of specific alleles in a population.

Hardy-Weinberg

  • Genetic equilibrium exists when allele frequencies don't change from one generation to the next (no evolution).
  • This occurs when no factors are influencing allele frequencies.
  • A population not evolving at a given locus is in equilibrium.
  • Changes in allele frequency over generations indicate evolution.
  • The Hardy-Weinberg equilibrium is a mathematical model where allele and genotype frequencies remain constant from one generation to the next in a population.

Hardy-Weinberg Conditions

  • No mutation is occurring
  • Large population
  • No migration
  • No natural selection
  • Random mating

Deviating from Hardy-Weinberg Equilibrium

  • Evolution occurs when conditions for Hardy-Weinberg equilibrium are not met.
  • Five factors that might drive allele frequency change:
  • Mutation
  • Genetic drift
  • Gene flow
  • Sexual selection
  • Natural selection

1. Mutation

  • New genes and alleles originate through mutation.
  • Mutations are changes in nucleotide sequences of DNA.
  • Somatic mutations are not passed to offspring. Only gametic mutations are.
  • Mutation rates are low in most animals and plants (about 1 in 100,000 genes per generation).

2. Genetic Drift

  • Genetic drift is a random change in allele frequencies, primarily in small populations.
  • Bottleneck effects occur when a large population is reduced rapidly to a small number of individuals; subsequent population might not reflect the original population's allele frequencies.
  • Founder effects occur when a few individuals start a new population; allele frequencies in new population may not reflect the source population.

3. Gene Flow

  • Gene flow is the movement of alleles between populations.
  • Immigration or emigration of individuals can introduce new alleles and change allele frequencies in populations.
  • Gene flow tends to reduce differences among populations.

4. Sexual Selection

  • Sexual selection is when one sex shows a preference for certain traits in the other sex, leading to certain traits becoming more common in future generations.
  • Traits favoured in sexual selection may not be favoured in other respects (e.g. large feathers increase mates, but also make them more visible to predators).
  • Competition among males.

5. Natural Selection

  • Natural selection is the process where organisms with traits better suited for their environment are more likely to survive and reproduce.
  • Positive selection: beneficial traits increase in allele frequency.
  • Negative selection: traits linked to reduced fitness decrease in allele frequency
  • Stabilizing selection: averages are most fit. Individuals with average traits have the highest fitness.
  • Directional selection: one extreme is favored, leading to a shift towards that extreme in the population
  • Disruptive selection: two extremes are favored over the average, leading to a bimodal distribution.

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Topic 15: Microevolution PDF

Description

Explore the concepts of microevolution, diversity, and polymorphism within populations. Understand how allele frequencies change over generations and the impact of genetic and environmental factors on traits. This quiz will test your knowledge on these critical evolutionary biology topics.

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