Chapter 26: Phylogeny and the tree of life (2)

Question 1

Differentiate between shared ancestral trait and shared derived trait.

Answer 1

• A shared ancestral character is a character that originated in an ancestor of taxon
• A shared derived character is an evolutionary novelty unique to a particular clade.

A character can be both ancestral and derived, depending on the context

Question 2

Differentiate between outgroup and ingroup.

Answer 2

An outgroup is a species or group of species from an evolutionary lineage that is known to have diverged before the lineage that includes the species we are studying (the ingroup)

Question 3

A character found in both the outgroup
and the ingroup is assumed to be ________.

Answer 3

A character found in both the outgroup
and the ingroup is assumed to be ancestral.

Question 4

How can mtDNA and rRNA be used to study evolutionary history?

Answer 4

• rRNA changes relatively slowly and is useful for investigating branching points hundreds of millions of years ago

– mtDNA evolves rapidly and can be used to explore recent evolutionary events

Question 5

Why are rRNA sequences so conserved?

Answer 5

rRNA sequences are conserved (unchanged) over time due to their crucial role in the function of the ribosome.

Question 6

What is horizontal gene transfer?

Answer 6

Horizontal gene transfer is the movement of genes from one genome to another

Question 7

How does horizontal gene transfer take place?

Answer 7

Mechanisms of Horizontal gene transfer – occurs by

– exchange of transposable elements and plasmids,
– viral infection, and
– fusion of organisms

Question 8

What is the importance of horizontal gene transfer?

Answer 8

• Disparities between gene trees can be explained by the occurrence of horizontal gene transfer
• Horizontal gene transfer has played a key role in the evolution of both prokaryotes
  and eukaryotes