What are adaptations?

  • Adaptations: a process of change in genotype/phenotype that occurs over several generations that increases the fitness of the individuals undergoing the process.
  • Adaptations have to be better than an alternative trait in order for the trait to be considered an adaptation. This does not mean that the trait is perfect. The benefit to fitness must be greater than the cost to their fitness. Traits with highest benefits become the adaptation as these genes are the ones that survive  and are passed onto the following generations.
    • Example: the panda has five fingers but no thumb so the wrist bone had adapted to help them grasp bamboo.

      “Panda” by steews4 (CC BY-NC-ND 2.0)

  • Maladaptive traits: the benefit out-weighed the cost of the behavior due to past environmental conditions, however,  a  novel environment can cause the trait to be less beneficial.
  • Pleiotropy: one gene cause multiple phenotypic effects
  • Genetic drift: random changes in gene frequencies within a population over time. More likely to occur in smaller populations because changes are more dramatic if certain individuals are eliminated and their genes removed from the population.
  • Gene Flow: Intermixing of two different populations, individuals move from one population to another and breed.
    • Can be maladaptive if the environments of each population are drastically different. An individual moving into the other population and breeding would be passing on genes that are not suited to the new environment.
      • Agelenopsis aperta a spider in Texas live in two different areas and have two different behavioral phenotypes.
        • The dessert grassland population are in harsh environment with low predators so musytbe aggressive to catch prey.
        • The Riparian population are in a more favorable environment, there are more predators in this favorable environment so this spider population are more cautious. More variety of prey so they are more selective in the prey they go after.
        • Either one moving to the other location will have an unfit aggressive response.
        • Arizona has similar populations but there is more gene flow so the Riparian population is more aggressive and less cautious than predicted from the Texas observations.

“Funnel Web Spider” by Renee (CC by 2.0)

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