Protists - Reflexions

Protists

In order to classify the 30 million living organisms which today exist on the Earth, biologists group them together on the basis of their relatedness over the course of evolution. They are divided into three domains and six kingdoms. The first two domains, Archea and Bacteria, gather together the prokaryotes, unicellular organisms whose cell has neither a nucleus nor any other internal compartment. Each of these domains contains just a single kingdom, the archaebacteria and the eubacteria. The third domain, the Eukarya, brings together unicellular eukaryotes (a cell with a nucleus and complex internal compartments called organelles). This domain is divided into four kingdoms: the protists, the fungi, the plants and the animals (including human beings). The protist kingdom groups together the unicellular organisms and it is thought that the three other kingdoms (whose members are generally pluricellular) come from the protists.