Halliday & Matthiessen (1999: 85-6, 7):
The ideation base embodies not only folk taxonomies but also a range of taxonomic models such as those used by experts and by scientists. These are all variants within the overall ideational system. …
The move from folk taxonomies towards scientific ones involves both an increase in steps in delicacy and a change in the criteria used for classification. Wignell, Martin & Eggins (1990) give examples from the classification of roses and of birds of prey. … For birds of prey, they contrast a folk taxonomy with a "birdwatchers' vernacular taxonomy". We superimpose these to give a sense of the difference; see Figure 2-14.
These examples show the difference in degree of delicacy quite clearly; an increase in delicacy reflects the move in the direction of scientific knowledge. At the same time, the criteria for categorisation also change, from overt criteria that are accessible to the naked eye to covert criteria available only through the application of scientific techniques. The change in taxonomic criteria is very clear from a review of the early taxonomic stage of science in Europe in the 16th and 17th centuries: see Slaughter (1986).