Henry was studying two populations of the same species of lizards. One population lived on an island and the other lived on the mainland. Both populations were affected by a hurricane that hit the island and the mainland with equal force. A year later, Henry was testing the gene frequency and saw a decrease in genetic variation in the island species, but not in the mainland species. Which best describes a conclusion he might have reached?

The hurricane was equally strong in both places, but the island population lost genetic variation while the mainland population did not. This suggests the island population was smaller, so chance losses of individuals and their alleles had a bigger effect there. That process is genetic drift, which has a stronger effect on small populations; larger populations are more likely to retain genetic variation and recover. Therefore, the best conclusion is “Genetic drift greatly affects small populations, but large populations can recover.”

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