Pre AP Biology -EVO 3.1 Mechanisms of Speciation- FRQ Exam Style Questions -New Syllabus

Humans are creating geographic barriers across landscapes that may geographically isolate populations, potentially leading to allopatric speciation. While these activities often cause extinctions, the resulting habitat fragmentation reduces gene flow, allowing populations to become genetically distinct from one another over time .

Speciation is the evolutionary process by which populations evolve to become distinct species. Human activities influence this process through two primary lenses:

• Geographical Factors: Human activities such as urbanization, farming, and tree harvesting alter the availability of niches and physical space. Construction and river diversion act as geographic separation—physical barriers that result in reduced gene flow. When a population is split, it can no longer interbreed, creating a foundation for speciation .
• Genetic Factors: Once populations are isolated, they accumulate heritable changes in their DNA sequences. Over multiple successive generations, these populations undergo phenotypic changes driven by natural selection. Mutations, which are random changes in DNA, serve as a source of the genetic variation upon which these selective pressures act. If these genetic differences become significant enough to cause reproductive separation, a new species is formed .