1.2: CONCEPT AND USES OF CLASSIFICATION SYSTEMS
SUMMARY
Classification organises the enormous variety of life into manageable groups based on shared features, with a species defined as a group of organisms that can reproduce to produce fertile offspring. The binomial system gives every species a unique two-part scientific name — genus followed by species — using an internationally agreed format that prevents confusion caused by different common names. Dichotomous keys provide a practical tool for identifying organisms through a series of two-choice questions based on observable features.
🚀 At Extended level, classification systems aim to reflect evolutionary relationships, grouping organisms by common ancestry rather than surface-level similarity alone. DNA base sequence comparison has strengthened this approach, because organisms that share a more recent common ancestor have more similar DNA — they have had less time for mutations to introduce differences. This molecular evidence can correct misclassifications based on physical features, as it reveals true genetic relationships regardless of outward appearance.