A Level Biology Practice Exam 2025 - Free A Level Biology Practice Questions and Study Guide

Non-random sampling involves selecting individuals based on specific criteria or convenience rather than ensuring that every member of a population has an equal chance of being chosen. Opportunistic sampling epitomizes this concept, as it involves selecting samples based on their availability or accessibility at the time, rather than through a methodical or random process.

In the context of biological research, opportunistic sampling might involve a researcher collecting samples from a location where they are easy to find rather than trying to ensure that the samples collected are representative of the entire population. This can lead to biases since the samples may not accurately reflect the overall characteristics of the population being studied.

In contrast, other methods mentioned, such as simple random selection, random stratification, and randomized block design, are all techniques that aim to achieve a random representation from the population, minimizing biases and enhancing the validity of the study's findings. Each of these methods involves systematic approaches to ensure randomness and equal representation, making them fundamentally different from opportunistic sampling.