Mechanisms of Evolution

Introduction to Evolution

• Definition: Evolution is the change in the frequency of alleles in a gene pool over time.
• Macroevolution: Large-scale changes leading to new species over long periods.
  • Example: Dinosaurs evolving into various species.
• Microevolution: Small-scale changes in gene frequency within a species, leading to macroevolution over time.

Key Concepts

• Allele Frequency: Evolution refers to any change in allele frequency within a gene pool.
• Natural Selection: Well-known mechanism where better-adapted organisms survive and reproduce.
• Focus on mechanisms of evolution beyond natural selection.

Mechanisms Beyond Natural Selection

1. Genetic Drift

   • Definition: Random changes in allele frequency, not due to adaptation.
   • Lab Example: Using beans to simulate moth populations, showing stable allele frequency in large populations but changes in small ones.
   • Real-world Example: Bottleneck effect reduces variation when a significant population reduction occurs.
   • Founder Effect: New populations started by a few individuals, leading to different allele frequencies compared to original population.

2. Gene Flow

   • Definition: Movement of alleles into or out of a population through immigration or emigration.
   • Effect: Can increase or decrease genetic variation.

3. Sexual Selection

   • Definition: Non-random mating where certain traits are preferred, affecting allele frequencies.
   • Example: Peacock tails have evolved to attract mates despite being a disadvantage for survival.

Summary

• Genetic drift, gene flow, and sexual selection contribute to evolutionary change without relying on natural selection.
• Understanding these mechanisms provides a broader view of how evolution can occur in nature.