A new classification of complex life

The tree of life needs to be revised again. Photo courtesy of Photocase.com

When life evolved 4 billion years ago, it consisted of a simple prokaryotic cell enclosing single circular DNA molecules. However, some 4 billion years later, some cells started enclosing other cells and thus the eukaryotic cells with all their complicated membrane bounded organelles such as a nucleus for storing the DNA as chromosomes, a Golgi apparatus and a mitochondria among others. Eukaryotic cells form the building block of all multi-cellular life on Earth. However, how the eukaryotes evolved and gave rise to algae, plants, fungi and animals remains elusive. A new theory divides the eukaryotes into 5 or 6 super-groups. More knowledge of the evolution is though needed for many of these groups.

Scientists from the University of Geneva in Switzerland and from the University of Oslo in Norway have attempted to unravel the evolutionary history of one these groups, the Rhizaria, comprising unicellular eukaryotes such as amoebae. They have done this by sequencing genes from members of the Rhizaria and analysing amino acid positions in 49 predominantly unicellular mechanisms from all super-groups. They find that the Rhizaria are closely related to other super-groups also consisting mainly of unicellular eukaryotes and therefore suggest that these three should be classified as one super assemblage of eukaryotes. 

Source: Burki F, Shalchian-Tabrizi K, Minge M, Skjæveland A, Nikolaev SI, et al (2007) Phylogenomics Reshuffles the Eukaryotic Supergroups. PLoS ONE 2(8): e790.

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