Population Variation and Speciation

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Questions and Answers

What role do mutations play in the population?

  • They allow for the preservation of allele frequencies.
  • They remove genetic variation from the gene pool.
  • They increase genetic drift within the population.
  • They introduce changes in genetic material that serve as the raw material for evolutionary change. (correct)

How does the Founder Effect contribute to genetic variation?

  • It results in genetic drift having no impact on allele frequencies.
  • It guarantees more alleles from the original population are maintained.
  • It leads to a gene pool that is more diverse than the original population.
  • It causes the gene pool to be unrepresentative due to a small number of founding members. (correct)

What is genetic drift primarily associated with?

  • Consistent migration patterns into the population.
  • Systematic changes due to natural selection.
  • Random changes in allele frequencies due to chance events. (correct)
  • Deliberate alterations to the environment by the species.

Which of the following isolation mechanisms leads to speciation primarily due to physical barriers?

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

Which option best explains the concept of directional selection?

<p>It favors one extreme in a range of phenotypes. (A)</p> Signup and view all the answers

What is a common result of polyploidy in flowering plants?

<p>It completely prevents breeding with non-polyploid organisms. (D)</p> Signup and view all the answers

Which statement about gene flow is true?

<p>It can introduce new alleles into a population. (D)</p> Signup and view all the answers

In the context of natural selection, what can be said about the selecting force?

<p>It is influenced by fitness advantages in different environments. (D)</p> Signup and view all the answers

Which is the most probable conclusion for the clams’ shell color distribution in the intertidal zone?

<p>The population is experiencing disruptive selection, with the gray clams having no camouflage in their environment. (A)</p> Signup and view all the answers

According to the biological species concept, any populations that do not share future offspring could be considered what?

<p>Separate species. (C)</p> Signup and view all the answers

To which type of organism can the definition of species under the biological species concept not be applied?

<p>Those that reproduce asexually or are known only as fossils. (C)</p> Signup and view all the answers

When a species begins to occupy more than one niche, what is this process called?

<p>Adaptive radiation. (C)</p> Signup and view all the answers

Why is accidental polyploidy in an individual considered a form of reproductive isolation?

<p>It cannot pair gametes with others from the original population. (B)</p> Signup and view all the answers

How can geography lead to reproductive isolation?

<p>A physical barrier may arise, preventing interbreeding. (C)</p> Signup and view all the answers

When a species fails to produce any more descendants, it is said to be what?

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

The wings of the bird and wings of the bee are examples of what type of structures?

<p>Analogous structures. (D)</p> Signup and view all the answers

What type of natural selection is demonstrated by smaller squirrels surviving better than larger squirrels?

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

What does the separation of wildebeests by a river correspond to?

<p>Divergent evolution. (D)</p> Signup and view all the answers

Which pattern of evolution applies to kangaroos, koalas, and other marsupials emerging from a common ancestor?

<p>Divergent evolution. (A)</p> Signup and view all the answers

What is meant by the term 'fittest' in Charles Darwin's description of natural selection?

<p>Organisms capable of reproducing successfully. (A)</p> Signup and view all the answers

Which of the following is not a cause for deviations from Hardy-Weinberg equilibrium?

<p>The genetic stability of the population. (A)</p> Signup and view all the answers

The arm of the monkey and the flipper of the whale are examples of what type of structures?

<p>Homologous structures. (A)</p> Signup and view all the answers

Flashcards

Mutation

Changes in the genetic material that are the source of variation in populations. This can be a change in a DNA sequence or a change in the number of chromosomes.

Genetic Drift

The change in the gene pool of a population due to random chance. This is a more significant factor in small populations where chance events can drastically alter the gene frequencies.

Bottleneck Effect

A type of genetic drift that occurs after a population bottleneck, such as a natural disaster. The surviving population is smaller and may not be representative of the original population.

Founder Effect

A type of genetic drift that occurs when a small group of individuals colonizes a new area. The colonizers may not represent the full genetic diversity of the original population.

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Gene Flow

The movement of alleles into or out of a population as a result of migration of fertile individuals or gametes.

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Speciation

The process by which two populations become reproductively isolated, leading to the formation of new species. This can occur due to geographic isolation or other forms of isolation.

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Geographic Isolation

A type of isolation that occurs when two populations are geographically separated. This can be caused by mountains, rivers, or other physical barriers.

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Directional Selection

Selection that favors individuals with traits that are at one extreme of a phenotypic range. This can lead to a shift in the population towards that particular phenotype.

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Disruptive Selection

A type of natural selection that favors individuals with extreme phenotypes at the expense of those with intermediate traits.

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Biological Species Concept

Organisms that reproduce sexually are considered different species if they cannot breed and produce fertile offspring.

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Stabilizing Selection

A type of natural selection that favors individuals with intermediate phenotypes, eliminating extreme phenotypes from the population.

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Adaptive Radiation

One species rapidly diversifies into many new species with different adaptations.

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Polyploidy

A mechanism of reproductive isolation where an individual has double the normal number of chromosomes.

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Homologous Structures

Structures that share a common ancestry but have different functions.

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Analogous Structures

Structures that have similar functions but different origins.

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Vestigial Structures

Structures that have lost their original function due to evolution.

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Coevolution

The evolutionary process by which two or more species evolve in response to each other.

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Convergent Evolution

Evolutionary change where two or more species evolve similar characteristics in response to similar environmental pressures.

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Parallel Evolution

Evolutionary change where two or more species evolve in similar directions despite being geographically separated.

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Adaptive Radiation

Evolutionary pattern where one species gives rise to multiple species, each adapted to a different environment.

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Study Notes

Population Variation

  • Sources of variation: Mutation, genetic drift, gene flow are the primary sources of variation in populations.
  • Mutation: Changes in genetic material, providing raw material for evolutionary change.
  • Genetic Drift: Random changes in allele frequencies within a population.
    • Bottleneck Effect: Dramatic reduction in population size due to environmental events (e.g., natural disasters). The resulting population is often not representative of the original, with some alleles overrepresented or underrepresented.
    • Founder Effect: When a small group of individuals colonizes a new area. The new population's allele frequencies may differ significantly from the source population.
    • Gene Flow: Movement of alleles between populations. Can occur via migration of fertile individuals or gametes. Examples include wind-carried pollen.

Isolation and Speciation

  • Causes of Speciation: Six types of isolation can lead to the formation of new species:
    • Geographic Isolation (Allopatric Speciation): Physical barriers (mountains, rivers, lakes) separate populations, preventing gene flow.
    • Polyploidy: A type of mutation from errors during meiosis. Common in flowering plants. Polyploids cannot interbreed with non-polyploids, leading to isolation.

Natural Selection

  • Relationship between concepts: Natural selection is not directly linked to gene flow. Genetic drift affects allele frequencies. Reproductive isolation prevents interbreeding. Population size influences natural selection's impact.
  • Identifying the selector: Environmental changes, not fitness advantages or phenotypes, drive natural selection.
  • Types of selection:
    • Directional selection: Favors one extreme phenotype leading to a shift in the average.
    • Stabilizing selection: Favors intermediate phenotypes, reducing variation and maintaining the average.
    • Disruptive selection: Favors both extreme phenotypes, reducing the intermediate phenotype.

Species Concepts

  • Biological Species Concept: Populations that can interbreed and produce viable, fertile offspring are considered the same species. Cannot be applied to asexual reproducers or extinct species.
  • Reproductive isolation: Populations are considered separate species when they do not share future offspring.

Adaptive Radiation

  • Adaptive radiation occurs when one species diversifies into multiple species. This can happen when a species occupies various niches, leading to the evolution of different traits.

Population Genetics & Hardy-Weinberg

  • Population genetics: Study of genetic variations in populations.
  • Hardy-Weinberg equilibrium: A model where allele frequencies in a population remain constant if certain conditions are met (no mutations, random mating, no gene flow, no genetic drift, no natural selection). Deviations from equilibrium suggest evolutionary processes are operating.

Vestigial Structures

  • Vestigial structures: Structures in an organism that no longer serve an apparent function. Examples include appendix and tailbone in humans.

Evolutionary Patterns

  • Homologous structures: Similar structures with different functions, indicating shared ancestry. Examples include arm of monkey and flipper of a whale.
  • Analogous structures: Different structures with similar functions, but not from a shared ancestry. Examples include bird and bee wings.
  • Divergent evolution - when two or more populations of an ancestral species develop and diverge substantially from one another.
  • Convergent evolution - when two or more unrelated populations evolve similar traits in response to similar, or repeated, environmental selection pressures.
  • Adaptive radiation: When an ancestral species evolves into multiple new forms, adapted to different ecological niches.
  • Coevolution: Evolution of two or more species that influences each other.
  • Parallel evolution: When two populations of an ancestral species evolve in a similar manner, leading to similar traits.

Other concepts

  • Extinction: When a species ceases to exist.

  • Natural Selection: The process where organisms better adapted to their environment tend to survive and produce more offspring.

  • Fitness: An organism's ability to survive and reproduce in a particular environment.

Multiple Choice Questions (Answers not included)

  • Questions 22-32 cover various concepts related to population genetics, natural selection, speciation, and evolutionary patterns. Refer to the provided text and study notes to answer these.

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