3 domains

How did scientists split life into domains before?

Split life into 2 domains: prokaryotes and eukaryotes

What did Woese change?

Divided Prokaryotae into 2 groups: bacteria and archaea

What are the 3 domains?

Bacteria

Archaea

Eukarya

Eukarya Features

- 80S ribosomes

- Nucleus

- DNA with histones present

- Linear DNA

Bacteria features

- Cell wall (peptidoglycan)

- Have less complex RNA polymerases than eukaryotes

- The 1st amino acid during protein synthesis is formylmethionine

- DNA is mostly circular chromosome and plasmids

- No histones

- No organelles

- 70S ribosomes

Archaea features

- Cell wall (not peptidoglycan)

- Have more complex RNA polymerases than eukaryotes

- The 1st amino acid during protein synthesis is methionine

- DNA is circular chromosome and plasmids

- Histones present

- No organelles

- 70S ribosomes

Name the cell component that appears in organisms of all 3 domains

Ribosomes

What are the main reasons that life is now classified into 3 domains?

The difference in rRNA (ribosomes)

The difference in RNA polymerase

The difference in protein synthesis

Why is the 3 domains better than the 5 kingdoms?

- 3 domains fit phylogeny better

- There are many fundamental differences between prokaryotes and the 4 other kingdoms (eukaryotes)

- Eukaryotes all have a nucleus / membrane bound organelles

- There are many fundamental differences between bacteria and archaea

- Bacteria and archaea have different RNA polymerase

How do the scientific community validate Woese's work?

Peer review

Carry out the same study to see if they get similar results

What does this tell you about the nature of scientific work?

It is constantly changing and evolving