Protistan taxonomy: a modern view

Traditional classification of the protists was on the basis of physical features such as the possession of flagella, chloroplasts and other structures. This had the effect of plac-ing into separate groups organisms that, at the molecular level, are closely related. The kinetoplastids and the euglenophytes, for example, although both flagellate forms, were distantly separated because the latter contained chloroplasts. They are now known to be closely related in phylogenetic terms (Figure 9.18). On the other hand, the kineto-plastids were previously placed together with choanoflagellates as zooflagellates, but molecular analysis now shows the two groups to have little in common in evolutionary terms.