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Chapter 2 Summary

Key Takeaways

  • Modern Synthesis and Population Genetics: The modern synthesis combines Darwin’s theory of natural selection with Mendelian genetics. Evolution is understood as a change in allele frequencies in a population over time (microevolution). Variation in alleles arises through mutation and sexual reproduction, providing the raw material for natural selection to act upon.
  • Hardy-Weinberg Principle: The Hardy-Weinberg equilibrium provides a mathematical model to study genetic stability in populations. In the absence of evolutionary forces, allele and genotype frequencies remain constant. The equation p^2 + 2pq + q^2 = 1 allows scientists to predict genotype frequencies and assess whether evolution is occurring.
  • Biological Species Concept: A species is defined as a group of organisms that can interbreed and produce fertile offspring. While useful for sexually reproducing organisms, this concept has limitations (e.g. for asexual species or fossils). Physical appearance alone does not always indicate species boundaries.
  • Reproductive Isolation: Reproductive barriers prevent gene flow between species and are crucial for maintaining species boundaries. They include:
    • Prezygotic barriers: temporal, habitat, behavioral, mechanical, gametic isolation.
    • Postzygotic barriers: hybrid inviability, hybrid sterility, hybrid breakdown.
  • Types of Speciation: Speciation occurs when populations become reproductively isolated:
    • Allopatric speciation: involves geographic separation (e.g., mountains, rivers).
    • Sympatric speciation: happens without geographic separation, driven by behavioral, ecological, or genetic factors (e.g., habitat use within the same area).
  • Rate of Speciation: Speciation can follow different temporal patterns:
    • Gradualism: slow, continuous evolution over long periods.
    • Punctuated equilibrium: rapid bursts of change followed by long periods of stability, often triggered by environmental shifts.

OpenAI. (2025). ChatGPT. [Large language model]. https://chat.openai.com/chat
Prompt: Summarize the following content into six key takeaways.

Flashcards

Text Description
Front of card:
  1. Allele
  2. Population genetics
  3. List 2 rates of speciation
  4. p
  5. List 2 types of speciation
  6. Zygote
  7. List 5 Prezygotic Barriers
  8. Habitat isolation
  9. Postzygotic barrier
  10. Gradualism
  11. 2pq
  12. Microevolution
  13. Prezygotic barrier
  14. Hardy-Weinberg principle of equilibrium
  15. p2
  16. Reproductive barriers
  17. q
  18. Mechanical isolation
  19. Biological species concept
  20. Genetic diversity
  21. Gametic isolation
  22. Modern synthesis
  23. Genotype
  24. Allele frequency
  25. Sexual reproduction
  26. Main sources of genetic diversity
  27. Reproductive isolation
  28. Blending inheritance
  29. Phenotype
  30. Hybrid inviability
  31. Allopatric speciation
  32. List 3 Postzygotic Barriers
  33. Gene pool
  34. Temporal isolation
  35. Speciation
  36. Mutation
  37. q2
  38. Punctuated equilibrium
  39. Behavioral isolation
  40. Hybrid sterility
  41. Sympatric speciation
  42. Hardy-Weinberg equation
  43. Hybrid breakdown
  44. Fertile
  45. Viable
Back of card:
  1. A version of a gene; different alleles can produce variations in the trait controlled by the gene
  2. A branch of biology that studies allele frequency changes in populations over time and the evolutionary forces that cause these changes
  3. gradualism and punctuated equilibrium
  4. frequency of the dominant allele, Y
  5. allopatric speciation and sympatric speciation
  6. The single cell formed when a sperm fertilizes an egg
  7. Temporal isolation, habitat isolation, behavioural isolation, mechanical isolation, gametic isolation
  8. A prezygotic reproductive barrier where species live in different habitats and thus do not meet to reproduce
  9. A reproductive barrier that occurs after fertilization, resulting in non-viable or sterile offspring
  10. A pattern of evolution characterized by the slow, continuous accumulation of small genetic changes over long periods of time
  11. frequency of individuals with the heterozygous genotype (Yy)
  12. Small-scale changes in allele frequencies within a population over time
  13. A reproductive barrier that prevents fertilization from occurring
  14. A principle stating that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of evolutionary forces
  15. frequency of individuals with the homozygous dominant genotype (YY)
  16. Biological features or behaviors that prevent different species from interbreeding and producing fertile, viable offspring
  17. frequency of the recessive allele, y
  18. A prezygotic reproductive barrier where structural differences in reproductive organs prevent mating between species
  19. A definition of species stating that a species is a group of organisms that can interbreed and produce fertile, viable offspring
  20. The total variety of genetic characteristics in the genetic makeup of a population
  21. A prezygotic reproductive barrier where the sperm of one species cannot fertilize the egg of another species due to incompatibilities
  22. The integration of genetics with Darwin’s theory of natural selection, forming a unified theory of evolution that explains how evolutionary processes affect genetic variation
  23. The genetic makeup of an organism; determines the phenotype
  24. The proportion of a specific allele among all alleles of a gene in a population
  25. The process of combining genetic material from two parents to produce genetically unique offspring
  26. mutation and sexual reproduction
  27. A state in which two populations can no longer interbreed and produce fertile offspring, maintaining species boundaries
  28. An outdated theory of inheritance where offspring were thought to be a uniform blend of parental traits, making it difficult to understand how traits persist across generations
  29. The observable physical or physiological traits of an organism; determined by its genotype and environmental influences
  30. A postzygotic reproductive barrier where hybrid offspring fail to develop properly or die at an early stage
  31. The formation of new species due to geographic separation of populations, which prevents gene flow between them
  32. Hybrid inviability, hybrid sterility, hybrid breakdown
  33. The total set of alleles present in a population
  34. A prezygotic reproductive barrier where species reproduce at different times, preventing mating
  35. The evolutionary process by which populations evolve to become distinct species
  36. A change in DNA sequence that can introduce new genetic variation into a population
  37. frequency of individuals with the homozygous recessive genotype (yy)
  38. A pattern of evolution where species undergo rapid changes in short periods, followed by long periods of stability
  39. A prezygotic reproductive barrier where differences in behavior, such as mating calls or courtship rituals, prevent mating between species
  40. A postzygotic reproductive barrier where hybrid offspring are healthy but sterile and cannot reproduce
  41. The formation of new species within a shared habitat, without geographic separation
  42. p2 + 2pq + q2 = 1
  43. A postzygotic reproductive barrier where first-generation hybrids are fertile, but their offspring are weak, sterile, or less fit
  44. Able to produce offspring
  45. Capable of surviving; a viable offspring is one that can grow, develop, and potentially reproduce

OpenAI. (2025). ChatGPT. [Large language model]. https://chat.openai.com/chat
Prompt: Provide definitions for all the bolded terms in the shared content and list all the terms in alphabetical order.

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