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Evolution: Modern Synthesis

Problems

Synthesis of Darwin and Modern Genetics

Natural Selection under the Modern Synthesis

Problem : What types of ideas does the modern synthesis combine?

The modern synthesis combines Darwin's original theory of evolution with evidence from fields of study such as genetics, paleontology, mathematics and population genetics.

Problem : What contributions were made to the modern synthesis by experimental geneticists?

  1. Genotype, the genetic make-up of an individual, differs from phenotype, or the traits that individual displays.
  2. The environment may change phenotype, but it does not affect genotype.
  3. Hereditary variation is due to genes.
  4. Genes can change through mutation, which gives rise to genetic variability. This process takes place slowly.
  5. Environmental factors may affect the rate of mutation, but they do not direct mutation toward adaptation.

Problem : What contributions were made to the modern synthesis by the observation of natural populations?

  1. Selection pushes recombination further.
  2. Natural populations are genetically variable.
  3. Populations of species in different locations may vary genetically.
  4. Differences between species and populations can be experimentally shown to have a genetic component.
  5. Natural selection does occur in natural populations.
  6. Differences among populations of a species are often related to environmental differences and thus are adaptive.

Problem : What contributions were made to the modern synthesis by those studying the taxonomic relationships between organisms?

  1. Species represent different gene pools rather than groups that differ in one or more characters.
  2. There is a continuum of genetic difference and reproductive isolation among populations.
  3. Speciation occurs when geographically separate populations become genetically different.
  4. Gradations in phenotypic variation that occur between species, genera, orders, and higher divisions. These show that evolutionary change occurs gradually rather than through the sudden appearance of radically new "types".

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