Question

question 1-16
a single species of squirrel evolved over time into two species, each on the opposite sides of the grand canyon.
which explanation best describes the most likely cause of this speciation event?
a geographic barrier prevented gene flow between the two squirrel populations, leading to genetic differences over time.
the squirrels chose to separate and live apart due to changes in food preferences.
environmental conditions remained exactly the same on both sides, allowing the populations to remain unchanged.
the squirrels on both sides of the canyon developed identical mutations that changed their behavior.

Explanation:

Speciation due to geographic isolation (allopatric speciation) occurs when a physical barrier (like the Grand Canyon) separates a population, preventing gene flow. Over time, genetic differences accumulate. Option A states a geographic barrier (Grand Canyon) prevented gene flow between squirrel populations, leading to genetic differences (speciation). Other options are incorrect: B claims squirrels chose separation (unlikely, as geographic barrier drives it), C says environments were identical (but isolation would lead to different selection pressures), D claims identical mutations (mutations are random, not identical across populations).

Answer:

A. A geographic barrier prevented gene flow between the two squirrel populations, leading to genetic differences over time.