CD's Evolution Through Natural Selection

• There are 5 key components to evolution through Natural Selection

  1. Natural Variation
  2. Struggle for existence (competition)
  3. Favorable Variations - Adaptations
  4. Survival of the Fittest/Natural Selection
  5. Favorable traits become more common in a population
• Natural Selection (1)

  • Key! Members of each species have differences in phenotypes called variations
  • Darwin was surprised by the MANY different variations of plants and animals that he observed on the Galapagos Islands. He noticed that similar organism on neighboring Islands had subtle differences in their phenotypes and he wondered if they may somehow be related.
• Natural Selection (2)

  • Darwin witnessed artificial selection which is when humans selection organism to get desired variation in offspring
  • Ex. dog breeding
  • Darwin thought that maybe nature could "select" organisms for survival and reproductive success based on their beneficial traits like artificial selection
• Struggle for existence (competition)

  • Nature presents challenges for organisms' survival
  • Because of high birth rates and a shortage of basic needs, organisms would be forced to compete for resources
• Favorable Variations - Adaptations

  • Darwin hypothesized that some variations (phenotypes) are beneficial (favorable) and make an organism more fit - these favorable variations are called adaptations
  • Some variations are not favorable or beneficial for success
• Survival of the Fittest/Natural Selection

  • The ability of an individual to survive and reproduce in its environment is fitness
  • Individuals with more favorable adaptations are more fit and thus will survive and reproduce more that those individuals without the favorable adaptation
  • Individuals that are not well suited to their environment either die or leave few offspring
  • This process is call survival of the fittest
• Favorable traits become more common in a population

  • Individuals who are fit will have more offspring with favorable variations that provide fitness for their particular environmental pressures
  • Over time that variation will become more common in the population over time (generations)
  • Natural Selection produces species that have different adaptations over time
  • Descent with modification: each living species has descended with changes from other species over time