The three-domain classification system

What is biological classification?

The organisation of organisms into groups based on their characteristics and evolutionary relationships.

What are the three domains of life?

Bacteria, Archaea and Eukaryota.

What are the five kingdoms in the traditional classification system?

Animals, plants, fungi, protoctists and prokaryotes.

Why did genetic analysis change biological classification?

DNA and RNA comparisons revealed evolutionary relationships that were not clear from physical characteristics alone.

What are the main differences between Bacteria and Archaea?

They have important genetic and biochemical differences, despite both being prokaryotic organisms.

What organisms belong to the domain Eukaryota?

Organisms whose cells contain a nucleus, including animals, plants, fungi and protoctists.

Why is genetic evidence useful for classification?

Comparing DNA or RNA sequences helps identify evolutionary relationships between organisms.

Why was the three-domain system proposed?

Genetic evidence showed that life could be divided into three major evolutionary groups rather than relying only on the traditional five kingdoms.