Biology Chapter on Speciation and Species Concepts
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Questions and Answers

What is the primary characteristic of ecological speciation?

  • It results only from genetic mutations.
  • It leads to hybrid vigor.
  • It involves reproductive isolation as a by-product of adaptation. (correct)
  • It requires geographical isolation.

    • Which of the following statements about polyploidization is true?

  • It increases the number of chromosomes from the same species. (correct)
  • It results in the complete failure of fertilization.
  • It can instantly create reproductive isolation.
  • It only occurs in animal species.

    • What does reinforcement in the context of speciation refer to?

  • The strengthening of postzygotic barriers only.
  • The enhancement of prezygotic barriers by natural selection. (correct)
  • The promotion of hybrid formation.
  • The weakening of species boundaries.

    • How is speciation studied experimentally in a laboratory setting?

    <p>By testing various mechanisms and conditions affecting speciation.</p> Signup and view all the answers

    What is expected from ecological speciation regarding postzygotic isolation?

    <p>It predicts reduced hybrid fitness in the absence of intermediate environments.</p> Signup and view all the answers

    What is the main characteristic that defines speciation?

    <p>Splitting of a species into two or more distinct species</p> Signup and view all the answers

    Which species concept is focused on reproductive compatibility?

    <p>Biological Species Concept</p> Signup and view all the answers

    What type of reproductive barrier occurs before mating?

    <p>Temporal isolation</p> Signup and view all the answers

    What disadvantage does the Biological Species Concept face?

    <p>It is complex to test reproductive barriers.</p> Signup and view all the answers

    Under what conditions does sympatric speciation typically occur?

    <p>In the presence of strong disruptive selection</p> Signup and view all the answers

    Which of the following is NOT a prezygotic reproductive barrier?

    <p>Mechanical isolation</p> Signup and view all the answers

    What best describes allopatric speciation?

    <p>Speciation resulting from geographical barriers interrupting gene flow</p> Signup and view all the answers

    Which statement about postzygotic reproductive barriers is true?

    <p>They result in reduced viability or fertility of hybrid offspring.</p> Signup and view all the answers

    What does the biological species concept define species as?

    <p>Groups that interbreed and produce fertile offspring in nature.</p> Signup and view all the answers

    Natural selection can maintain divergence despite gene flow.

    <p>True</p> Signup and view all the answers

    Which of these is NOT a prezygotic barrier?

    <p>Gametic isolation</p> Signup and view all the answers

    What process can lead to speciation in the absence of a geographic barrier?

    <p>Sympatric speciation</p> Signup and view all the answers

    Which type of polyploidy involves the doubling of chromosomes within a single species?

    <p>Autopolyploidy</p> Signup and view all the answers

    What does the term 'reinforcement' refer to in the context of speciation?

    <p>The strengthening of prezygotic barriers by natural selection.</p> Signup and view all the answers

    Which of these is NOT a common technique used in the study of speciation?

    <p>Astrophysical observation</p> Signup and view all the answers

    Ecological speciation can be tested by comparing the degree of behavioral isolation between populations in different environments.

    <p>True</p> Signup and view all the answers

    What is the primary method of testing for ecologically-dependent postzygotic isolation?

    <p>Reciprocal transplantation</p> Signup and view all the answers

    Cladistics is an approach to systematics that uses homologies to define clades.

    <p>True</p> Signup and view all the answers

    What type of group comprises an ancestral species and ALL of its descendants?

    <p>Monophyletic group</p> Signup and view all the answers

    What type of character is unique to a group and shared by all members due to descent from a common ancestor?

    <p>Derived character</p> Signup and view all the answers

    Analogous traits, which are similar due to convergent evolution, are highly useful in constructing accurate phylogenies.

    <p>False</p> Signup and view all the answers

    What principle states that the most likely phylogenetic tree is the one that involves the fewest number of evolutionary transitions?

    <p>The principle of parsimony</p> Signup and view all the answers

    What do cladograms depict?

    <p>Branching patterns only</p> Signup and view all the answers

    What is the primary method of dating branching points (nodes) on a phylogeny?

    <p>Molecular clock analysis</p> Signup and view all the answers

    What does the molecular clock assume about the rate of nucleotide substitutions?

    <p>It's constant for a given gene</p> Signup and view all the answers

    Study Notes

    Speciation & Species Concepts

    • Speciation is the process where a species splits into two or more species
    • Daughter species share characteristics with a common ancestor
    • Irreversible endpoint; two species cannot form fertile hybrids

    Species Concepts

    • Biological species concept (BSC): Groups that interbreed and produce fertile offspring in nature. Same species if reproductively compatible, different species if reproductively isolated
    • Morphological similarity: species are similar in appearance, but misses cryptic species
    • Ecological niche: species occupy different niches. Requires conditions to apply to fossils; subjective

    Reproductive Barriers

    • Prezygotic barriers occur before mating
      • Habitat isolation
      • Temporal isolation
      • Behavioral/pollinator isolation
      • Mechanical isolation
      • Gametic isolation (including sperm competition & preference)
    • Postzygotic barriers occur after mating
      • Genetic incompatibilities: gene interaction reduces viability/fertility of offspring
      • Ecologically-dependent isolation: reduction in hybrid fitness due to phenotype/environment mismatch between parents

    Mechanisms of Speciation

    • Allopatric speciation: geographic isolation (gene flow interrupted); populations evolve independently and accumulate reproductive barriers (e.g., different mating calls).

    • Sympatric speciation: speciation in the same geographic area; hard to overcome unrestricted gene flow. Can occur from:

      • Polyploidization (increase in chromosome sets, creating instant postzygotic isolation)
      • Disruptive selection (strong selection for traits, leading to assorative mating) and positive assortive mating

    • Ecological speciation: reproductive isolation arises as a by-product of adaptation to different environments. Selection for diverging traits leads to reproductive isolation regardless of geographical barriers

    • Reinforcement: strengthening of prezygotic barriers, often post-initiation of speciation, in sympatry leads to stronger prezygotic isolation (e.g., selection for different mating calls)

    • Polyploidization: increase in chromosome sets; postzygotic isolation can be instant; common in flowering plants, two types:

      • Autopolyploid: chromosomes from a single species
      • Allopolyploid: chromosomes from two or more different species

    Studying Speciation

    • Laboratory studies: testing feasibility of various speciation mechanisms; exploring conditions for speciation to occur.
    • Experimental evolution: multiple populations derived from a common ancestor, evolution tracked under controlled conditions; useful for verifying mechanisms of divergence.
    • Ecological speciation: predicts stronger behavioural isolation between different-environment populations.

    Speciation in Nature

    • Postzygotic isolation: hybrid fitness is reduced; occurs in the absence of intermediate environments; occurs when ecological speciation is expected.
    • Tested via reciprocal transplant of parental species and hybrids in both habitats

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    Related Documents

    Speciation & Species Concepts PDF
    Systematics: Definitions & Phylogenetic Trees PDF

    Description

    Explore the processes of speciation and the various species concepts in this quiz. Delve into reproductive barriers, both prezygotic and postzygotic, and how they contribute to the formation of new species. Test your understanding of biological, morphological, and ecological classifications.

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