Systematics considers evolutionary relationships among organisms, alongside identification, naming and classification. In this topic, phylogenetic classification means grouping organisms with those evolutionary relationships in view.
The system did not distinguish prokaryotes from eukaryotes, unicellular from multicellular organisms, or photosynthetic organisms such as green algae from non-photosynthetic fungi. These limitations made a simple plant–animal division inadequate.
Name Whittaker’s five kingdoms and the main criteria he used to distinguish them.
Think of your answer, then reveal it.
Whittaker proposed Monera, Protista, Fungi, Plantae and Animalia. The main criteria were cell structure, body organisation, mode of nutrition, reproduction and phylogenetic relationships.
Why was a cell wall alone insufficient for grouping organisms as plants? How were prokaryotes, unicellular eukaryotes and fungi treated in the five-kingdom system?
Think of your answer, then reveal it.
A cell wall grouped organisms that differed in cell organisation and nutrition. Prokaryotes were placed in Monera, and unicellular eukaryotes in Protista. Fungi became a separate kingdom: they are heterotrophic and their walls contain chitin, whereas green plants have cellulosic walls.