NCEA Level 3 Biology – Speciation (AS91605) Practice Exam 2025 - Free NCEA Speciation Practice Questions and Study Guide

Genetic drift refers to the random fluctuations in allele frequencies within a population from one generation to the next. This phenomenon is particularly significant in small populations, where chance events can lead to substantial changes in genetic makeup, independent of natural selection. For instance, if a few individuals survive a catastrophic event purely by chance, they may pass on their alleles to the next generation, causing a shift in the genetic structure of the population.

In larger populations, allele frequencies remain relatively stable due to the mixing of many individuals, which lessens the effects of random changes. However, in small populations, genetic drift can lead to the fixation or loss of alleles, reducing genetic diversity and potentially impacting the population's ability to adapt to environmental changes over time.

The other choices describe different biological concepts. The selection process of the fittest individuals pertains to natural selection, which involves differential survival and reproduction based on advantageous traits. Intentional breeding to produce certain traits relates to artificial selection, where humans selectively breed organisms for specific characteristics. Adaptation of species to environmental changes encompasses the broader concept of evolution through natural selection, where specific traits enhance survival in changing habitats. In contrast, genetic drift operates independently of fitness and is a product of random chance.