Modern Evolutionary Theory

[F] Modern Evolutionary Theory #

Tuesday, February 4, 2020 12:43 PM

Forces of Evolution #

• Mutation
• Segregation
• Independent assortment
• Recombination
• Gene flow
• Genetic drift
• Natural selection

Evolution: the change in allele frequencies

(Allele-frequency variation in a population is exactly what behavioral-genetics studies operationalize as heritability; the same statistic applied to clinical traits is in 2-3 genetics.)

Gene Flow #

Mixing of population genes #

• Two populations are separated ⇒ genetic difference
• These populations interbreed ⇒ causes gene flow
• Higher variation in populations

Genetic Drift #

Statistical sampling causes random selection (sampling error) #

• Meiosis results in 50/50 mixing of genes

  • Results in gamete sampling (random)

• May be more influential than natural selection!

  • Fewer offspring ⇒ gene simplification
    • Parents lose large amount of genetic variety
    • More offspring = higher chance of passing down more genes

• Opposite of gene flow = founder effect: when a small group of organisms splits from main population and makes a small gene pool

  • Observed by Darwin in Galapagos
  • If only a few individuals get isolated, bottleneck occurs and certain alleles can be completely lost

• if only a few individuals get isolated, bottleneck occurs and certain alleles can be completely lost

New Insights on Evolution #

Niche Construction: organisms modify their environment #

• changes what traits are selected for
• example: beavers build dams

Gene-Culture Coevolution: cultural innovation affects environment and evolution #

Multiple inheritance systems: epigenetics #

• environment affects genetic code of both individual and offspring