Domains Of Life - Topic 1

Question 1

What are the three domains of life?

Answer 1

Archaea
Bacteria (prokarya)
Eukarya

Question 2

What is the evidence for the common thought that all life on earth has a unique common ancestor?

Answer 2

Biochemical components - eg: L amino acids and D carbohydrates
Shared metabolic pathways
Universal genetic code (nucleotide bases)

Question 3

Give an example of a shared metabolic pathway

Answer 3

Acetyl CoA is oxidised to CO2 in the Krebs cycle of aerobic respiration.

Question 4

Why is the universal genetic code evidence of a common ancestor?

Answer 4

Because it is efficient and degenerative. This means the different triplet nucleotides code for the same amino acid.

Question 5

What does the universal genetic code tell us?

Answer 5

All known living organisms use the same genetic code. This is evidence that all organisms share a common evolutionary history and common ancestor.

Question 6

If there were multiple possible common ancestors, why did the one with the current universal genetic code “win”?

Answer 6

It is highly conserved (doesn’t change much over long periods of time, allowing tracking of evolutionary history)
Degenerative (limiting chance of mutations)
Unambiguous (Each codon codes for exactly one amino acid, start, or stop.

Question 7

What did Woese and co-workers compare to understand relationships across all living organisms?

Answer 7

16S ribosomes RNA sequences (rRNA)

Question 8

Why was 16S rRNA compared?

Answer 8

To look at deep relationships between all organisms because it is present in all of them and the pattern is highly conserved. Mroe difference in pattern = less relaxed

Question 9

What did Woese and others discover after comparing 16S rRNA?

Answer 9

There are 3 major groups of organisms with one common ancestor - the 3 domains of archea, bacteria and eukaryota

Question 10

What is speculated about the origin of archea?

Answer 10

That it originated from archea rather than the one universal ancestor all 3 domains were initially thought to come from

Question 11

What is the major difference between prokaryotes and eukaryotes?

Answer 11

Eukaryotes have internal membranes (membrane bound organelles), meaning they are more complex and form multicellular organisms

Question 12

Fill in the blanks

Answer 12