The new phylogeny

Question 1

Name the 3 potential synapomorphies studied

Answer 1

protostomy/deuterostomy
coelom
segmentation
(not actually synapomorphies)

Question 2

Define ‘coelomate’

Answer 2

have a fluid-filled body cavity, most bilaterians including all vertebrates.

Question 3

Define ‘acoelomate’

Answer 3

No body cavity, semi-solid mesodermal tissues between gut and body wall. (flatworms)

Question 4

What type of sequences are used in molecular phylogenetics?

Answer 4

Nucleotide, protein and whole genome.

Question 5

Give an example of informative molecular alignment

Answer 5

Chaetognaths with protostomes.

Have deuterostome embryonic characters but now placed within traditional protostome group.

Question 6

Name 4 sources of sequences used to construct molecular phylogenies.

Answer 6

Ribosomal RNA
Mitochondrial genomes
microRNAs
Expressed sequence tags.

Question 7

Why are molecules better than morphology?

Answer 7

Gene/protein sequences change neutrally, less prone to convergent evolution.
Conservative AA changes are unlikely to alter protein function and so can occur neutrally.
Molecular clock- problems overcome by using slower evolving species in analyses. Sample additional species that break long branches in the tree.

Question 8

What are the 3 implications of the new phylogeny studied?

Answer 8

1. Protostomy is not a synapomorphy of lophotrochozoa and ecdysozoa.
2. Coelom is an example of homoplasy (convergence).
3. Origin of body segmentation is unclear.