DreiDomänenTheorie

The DreiDomänenTheorie, or Three Domains Theory, is a classification system for living organisms. Proposed by Carl Woese and his colleagues in the late 1970s, it divides all life into three fundamental groups: Bacteria, Archaea, and Eukarya. This was a significant departure from the previous five-kingdom system, which primarily relied on morphological characteristics.

The key innovation of the DreiDomänenTheorie was its use of ribosomal RNA (rRNA) gene sequences for phylogenetic analysis. Woese observed that certain types of RNA, particularly those found in ribosomes, evolved at a slow and steady rate, making them excellent molecular clocks for tracing evolutionary relationships. Analysis of rRNA sequences revealed that Archaea, previously grouped with Bacteria, represented a distinct and ancient lineage.

Bacteria are prokaryotic organisms that lack a nucleus and membrane-bound organelles. They are found in virtually every environment on Earth and play crucial roles in ecosystems, from decomposition to nutrient cycling.

Archaea are also prokaryotic but share some similarities in their molecular biology with eukaryotes, despite their distinct evolutionary history. Many Archaea are extremophiles, thriving in harsh conditions like hot springs, salt lakes, and deep-sea vents.

Eukarya encompasses all organisms whose cells contain a nucleus and other membrane-bound organelles. This domain includes protists, fungi, plants, and animals. The Eukarya domain is believed to have evolved from an archaeal ancestor. The DreiDomänenTheorie has become the widely accepted framework for understanding the diversity and evolutionary history of life.