section 3: classification & evolution - topic 2: the evolution of classification systems

Question 1

how was evidence for classification gathered before?

Answer 1

using observable features

Question 2

how is evidence for classification gathered now?

Answer 2

using observable features + embryological evidence, fossil evidence, molecular evidence

Question 3

what does gathering molecular evidence involve?

Answer 3

analysing the similarities in proteins and DNA

Question 4

what does molecular evidence tell us?

Answer 4

more closely related organisms will have more similar organisms

Question 5

what can you compare to gather molecular evidence?

Answer 5

how DNA is stored
the sequence of DNA bases
the sequence of amino acids in proteins from different organisms

Question 6

what has the 5 kingdom classification system now been replaced with?

Answer 6

the 3 domain system

Question 7

when was the 3 domain system proposed?

Answer 7

1990

Question 8

where do the 3 domains sit and what are they?

Answer 8

they are large superkingdoms that are above the kingdoms in the taxonomic hierarchy

Question 9

how is the 3 domain system different?

Answer 9

• organisms that were in the kingdom prokaryotae (no nucleus) are separated into 2 domains (archaea & bacteria)
• organisms with a nucleus are placed in the domain eukarya
• the lower hierarchy stays the same

Question 10

why was the 3 domain system proposed?

Answer 10

because of new evidence, mainly molecular

Question 11

what was the new molecular evidence?

Answer 11

• the enzyme RNA polymerase (needed to make RNA) is different in bacteria and archaea
• archaea, but not bacteria, have similar histones (proteins that bind to DNA) to eukarya

Question 12

what was the new cellular evidence/

Answer 12

• the bonds of the lipids in the cell membranes of bacteria and archaea are different
• the development and composition of flagella are also different