chapter 19 and 21

• What are the two main ideas developed by Darwin?

  Descent with modification and natural selection
• What does natural selection cause in evolution?

  It causes certain heritable characteristics to survive
• How is evolution defined in the context of populations?

  Change over time of genetic composition
• What is the relationship among all organisms according to Darwin?

  All organisms are related through descent
• What is the significance of heritable characteristics in natural selection?

  They allow individuals to survive and reproduce better
• What is Observation #1 in Darwin's theory?

  Members of a population vary greatly in traits
• What causes variation in traits according to Darwin?

  Sexual recombination during meiosis
• What is Observation #2 in Darwin's theory?

  Traits are inherited from parents to offspring
• What is Observation #3 in Darwin's theory?

  All species can produce more offspring than the environment supports
• What does the struggle for existence refer to?

  Competition for limited resources among individuals
• What is Observation #4 in Darwin's theory?

  Many offspring do not survive due to resource scarcity
• What is Inference #1 from Darwin's observations?

  Individuals with favorable traits leave more offspring
• What does differential reproduction mean?

  Some individuals reproduce more due to advantageous traits
• What is Inference #2 from Darwin's observations?

  Unequal survival leads to accumulation of favorable traits
• What does natural selection increase in organisms?

  Adaptation to their environment over time
• What happens if an environment changes over time?

  Natural selection may lead to new species
• Who evolves according to the theory of evolution?

  Populations evolve over time
• What does fitness describe in evolutionary terms?

  Success in living and reproduction
• What are the four types of data supporting evolution?

  Direct observations, homology, fossil record, biogeography
• What does the fossil record provide evidence for?

  Extinction, origin of new groups, changes over time
• What are homologous structures?

  Anatomical resemblances from a common ancestor
• What does convergent evolution refer to?

  Similar features evolve in distantly related groups
• What is biogeography?

  The geographic distribution of species
• What did Darwin observe about island species?

  They are often closely related to mainland species
• What was Pangaea?

  A single large continent that existed in the past
• How does genetic variation arise?

  Through mutation and sexual reproduction
• What is microevolution?

  Evolution on a small scale within a population
• What are the three main mechanisms causing allele frequency change?

  Natural selection, genetic drift, gene flow
• What is the role of genetic variation in evolution?

  It is necessary for natural selection to occur
• What are mutations?

  Changes in the nucleotide sequence of DNA
• What is the significance of sexual reproduction in evolution?

  It shuffles alleles into new combinations
• What is the founder effect?

  Isolation of a few individuals from a larger population

  
• What is the bottleneck effect?

  A sudden reduction in population size due to environmental change

  
• What is gene flow?

  Movement of alleles among populations
• How does gene flow affect populations?

  It reduces differences between populations over time
• What is the relationship between natural selection and allele frequencies?

  Natural selection alters allele frequencies in populations
• What happens to allele frequencies in genetic drift?

  They fluctuate unpredictably from generation to generation
• What is the impact of genetic drift on genetic variation?

  It tends to reduce genetic variation
• What is the effect of the bottleneck on genetic variation?

  It reduces genetic variation in a population

  
• How does human activity relate to the bottleneck effect?

  It can lead to reduced genetic variation in species